JP6085880B2 - Carbon quantum dot manufacturing method and carbon quantum dot - Google Patents
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- 238000004519 manufacturing process Methods 0.000 title claims description 68
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 174
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 151
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- Carbon And Carbon Compounds (AREA)
Description
本発明は、炭素材を原料とした量子ドット構造物である炭素量子ドットの製造方法及び該製造方法により製造される炭素量子ドットに関する。 The present invention relates to a method for producing a carbon quantum dot that is a quantum dot structure using a carbon material as a raw material, and a carbon quantum dot produced by the production method.
近年、一般的な有機系色素や蛍光蛋白質に比べて輝度が極めて高くかつ光褪色しにくい発光材料として、量子ドットが注目されている。量子ドットとは、直径が０．５ｎｍ〜１００ｎｍ、特に２ｎｍ〜１０ｎｍの三次元電子閉じ込め構造を持つ超微細ナノ粒子のことであり、粒子サイズを制御することにより、バンドギャップを制御し発光波長（色）を調節できる。今日、代表的な量子ドットとしては、ＩＩ−ＶＩ族のＣｄＳｅやＣｄＴｅ、Ｉ−ＶＩＩ族のＣｕＣｌ等、ＩＩＩ−Ｖ族のＩｎＡｓ等、ＩＶ族のＳｉ、Ｃ等からなる超微細ナノ粒子が挙げられる。 In recent years, quantum dots have attracted attention as light-emitting materials that have extremely high brightness and are less likely to fade when compared with common organic dyes and fluorescent proteins. A quantum dot is an ultrafine nanoparticle having a three-dimensional electron confinement structure with a diameter of 0.5 nm to 100 nm, particularly 2 nm to 10 nm. By controlling the particle size, the band gap is controlled and the emission wavelength ( Color). Today, typical quantum dots include II-VI group CdSe, CdTe, I-VII group CuCl, III-V group InAs, etc., ultrafine nanoparticles composed of group IV Si, C, etc. It is done.
しかしながら、ＣｄＳｅなどの遷移金属原子からなる量子ドットは、バイオ分野への応用に際して、毒性などに懸念が残る。また、これらの量子ドットは、コロイド化学的合成法により合成されることから、溶媒中に安定させるため、通常、その表面を界面活性剤やポリマーなどで被覆する必要があり、また、細胞などへの結合などの応用に際しては、特別な表面修飾を考慮する必要がある。更に、これらの半導体量子ドットは、有機溶媒中で調製されることが多く、親水溶媒条件の制約を受け、応用範囲が限られる。
こうした問題を解決するために、コア−シェル構造型の半導体量子ドットも提案されているが（例えば、特許文献１，２、非特許文献１参照）、合成手法が複雑になる問題がある。
However, a quantum dot made of a transition metal atom such as CdSe has concerns about toxicity and the like when applied to the bio field. In addition, since these quantum dots are synthesized by colloidal chemical synthesis, it is usually necessary to coat the surface with a surfactant or polymer in order to stabilize them in a solvent. For application such as bonding, special surface modification must be considered. Furthermore, these semiconductor quantum dots are often prepared in an organic solvent, and are limited in the application range due to restrictions on hydrophilic solvent conditions.
In order to solve such a problem, a core-shell structure type semiconductor quantum dot has also been proposed (see, for example, Patent Documents 1 and 2 and Non-Patent Document 1), but there is a problem that the synthesis method becomes complicated.
これに対し、生体への適応性や無毒性、低環境負荷、原料供給の安定性、低コスト化などの観点から炭素で構成された量子ドットが有望視され、近年、炭素量子ドットについて報告例が見られるようになっている。
例えば、炭素ターゲットをレーザーアブレーション（ｌａｓｅｒ ａｂｌａｔｉｏｎ）後、化学処理を実施して製造する手法（非特許文献２）や蝋燭の煤から製造する手法（非特許文献３）に続き、グラファイト酸化物を化学処理して製造する手法（非特許文献４）、グラファイト酸化物を前駆体とする化学反応から製造する手法（特許文献３）、フラーレンの転換反応から製造する手法（非特許文献５）、更に、炭素繊維や活性炭など、より安価な炭素原料を化学処理して製造する手法（非特許文献６〜８）が報告されるようになった。なお、これらの手法は、大別してトップダウン（ｔｏｐ−ｄｏｗｎ）の手法であるが、有機前駆体分子のポリマー化から炭素量子ドットを製造するボトムアップ（ｂｏｔｔｏｍ−ｕｐ）の手法（非特許文献９）も報告され始めている。
On the other hand, quantum dots composed of carbon are considered promising from the viewpoints of adaptability to living organisms, non-toxicity, low environmental load, stability of raw material supply, cost reduction, etc., and recently reported examples of carbon quantum dots Can be seen.
For example, following a method of manufacturing a carbon target by laser treatment after laser ablation (non-patent document 2) or a method of manufacturing from a candle jar (non-patent document 3), a graphite oxide is chemically treated. A method of manufacturing by treatment (Non-Patent Document 4), a method of manufacturing from a chemical reaction using graphite oxide as a precursor (Patent Document 3), a method of manufacturing from a fullerene conversion reaction (Non-Patent Document 5), Techniques (Non-Patent Documents 6 to 8) for producing a cheaper carbon raw material such as carbon fiber and activated carbon by chemical treatment have been reported. These methods are broadly classified as top-down methods, but a bottom-up method for producing carbon quantum dots from the polymerization of organic precursor molecules (Non-Patent Document 9). ) Is also starting to be reported.
ところで、前述の炭素繊維や活性炭を炭素原料として炭素量子ドットを製造する手法では、強酸としての硫酸、硝酸又はこれらの混酸を用いて炭素原料を化学処理することとしている。
しかしながら、このような強酸を用いる場合、製造条件が厳しいことに加え、最後に大量のアルカリで中和処理する必要があり、製造プロセスが複雑になる問題がある。
したがって、より簡便かつ効率的な方法で炭素量子ドットを製造する方法の開発が求められている。
By the way, in the method of manufacturing a carbon quantum dot using the above-mentioned carbon fiber or activated carbon as a carbon raw material, the carbon raw material is chemically treated using sulfuric acid, nitric acid or a mixed acid thereof as a strong acid.
However, when such a strong acid is used, in addition to severe manufacturing conditions, it is necessary to neutralize with a large amount of alkali at the end, resulting in a complicated manufacturing process.
Therefore, development of a method for producing carbon quantum dots by a simpler and more efficient method is demanded.
本発明は、従来における前記諸問題を解決し、以下の目的を達成することを課題とする。即ち、本発明は、簡便かつ効率的な方法で炭素量子ドットを製造可能な炭素量子ドットの製造方法及び炭素量子ドットを提供することを目的とする。 An object of the present invention is to solve the above-described problems and achieve the following objects. That is, an object of the present invention is to provide a carbon quantum dot production method and a carbon quantum dot capable of producing carbon quantum dots by a simple and efficient method.
前記課題を解決するための手段としては、以下の通りである。即ち、
＜１＞ 炭素材と濃度が５０ｗｔ％以下の過酸化水素水とを混合し、前記炭素材と前記過酸化水素水との混合液を８０℃以上の温度で加熱し、過酸化水素により前記炭素材中の炭素を分解反応させ、前記炭素材由来の炭素量子ドットを生成させた炭素量子ドット生成液を調製する炭素量子ドット生成液調製工程と、前記炭素量子ドット生成液中の前記炭素量子ドットと前記過酸化水素を分離して前記分解反応を停止させ、前記炭素量子ドットを取得する炭素量子ドット取得工程と、を含むことを特徴とする炭素量子ドットの製造方法。
＜２＞ 炭素材が、活性炭である前記＜１＞に記載の炭素量子ドットの製造方法。
＜３＞ 炭素量子ドット生成液調製工程における炭素材と過酸化水素水との混合液に対する加熱温度が、１２０℃以下である前記＜１＞から＜２＞のいずれかに記載の炭素量子ドットの製造方法。
＜４＞ 炭素量子ドット生成液調製工程及び炭素量子ドット取得工程が、炭素材と過酸化水素水との混合液に対して、過酸化水素水の沸点以上の温度で加熱処理を実施し、前記炭素量子ドットを生成させるとともに前記炭素量子ドット生成液中の過酸化水素を気化させて分解反応を停止させる一連の工程である前記＜１＞から＜３＞のいずれかに記載の炭素量子ドットの製造方法。
＜５＞ 炭素材中の炭素１モルに対して、２モル以上の過酸化水素を混合させる前記＜４＞に記載の炭素量子ドットの製造方法。
＜６＞ 炭素量子ドット取得工程が、炭素量子ドット生成液を減圧乾燥させて、過酸化水素を除去する工程である前記＜１＞から＜３＞のいずれかに記載の炭素量子ドットの製造方法。
＜７＞ 炭素量子ドット生成液調製工程及び炭素量子ドット取得工程を一連の工程として、この一連の工程を繰り返し実施する前記＜１＞から＜６＞のいずれかに記載の炭素量子ドットの製造方法。
Means for solving the problems are as follows. That is,
<1> A carbon material and a hydrogen peroxide solution having a concentration of 50 wt% or less are mixed, a mixed solution of the carbon material and the hydrogen peroxide solution is heated at a temperature of 80 ° C. or more, and the carbon A carbon quantum dot production liquid preparation step of preparing a carbon quantum dot production liquid in which carbon in the material is decomposed to produce carbon quantum dots derived from the carbon material, and the carbon quantum dots in the carbon quantum dot production liquid And a carbon quantum dot acquisition step of acquiring the carbon quantum dots by separating the hydrogen peroxide and stopping the decomposition reaction.
<2> The method for producing carbon quantum dots according to <1>, wherein the carbon material is activated carbon.
<3> The carbon quantum dot according to any one of <1> to <2>, wherein the heating temperature for the mixed liquid of the carbon material and the hydrogen peroxide solution in the carbon quantum dot production liquid preparation step is 120 ° C. or less . Production method.
<4> carbon quantum dot product liquid preparation step and a carbon quantum dots acquisition process, the mixed solution of carbon material and hydrogen peroxide was carried out heat treatment at a temperature higher than the boiling point of hydrogen peroxide, the The carbon quantum dot according to any one of <1> to <3>, which is a series of steps of generating a carbon quantum dot and vaporizing hydrogen peroxide in the carbon quantum dot production liquid to stop a decomposition reaction. Production method.
<5> The method for producing carbon quantum dots according to <4>, wherein 2 mol or more of hydrogen peroxide is mixed with 1 mol of carbon in the carbon material.
<6> The method for producing carbon quantum dots according to any one of <1> to <3>, wherein the carbon quantum dot acquisition step is a step of drying the carbon quantum dot production liquid under reduced pressure to remove hydrogen peroxide. .
<7> The method for producing carbon quantum dots according to any one of <1> to <6>, wherein the carbon quantum dot production liquid preparation step and the carbon quantum dot acquisition step are a series of steps, and the series of steps are repeatedly performed. .
本発明によれば、従来技術における前記諸問題を解決することができ、簡便かつ効率的な方法で炭素量子ドットを製造可能な炭素量子ドットの製造方法及び炭素量子ドットを提供することができる。 ADVANTAGE OF THE INVENTION According to this invention, the said various problems in a prior art can be solved, and the manufacturing method and carbon quantum dot of a carbon quantum dot which can manufacture a carbon quantum dot by a simple and efficient method can be provided.
（炭素量子ドットの製造方法）
本発明の炭素量子ドットの製造方法は、少なくとも、炭素量子ドット生成液調製工程と、炭素量子ドット取得工程と、を含み、必要に応じて、その他の工程を含む。
(Method for producing carbon quantum dots)
The manufacturing method of the carbon quantum dot of this invention contains a carbon quantum dot production | generation liquid preparation process and a carbon quantum dot acquisition process at least, and includes another process as needed.
＜基本原理＞
過酸化水素による炭素の分解反応は、よく知られている。通常、前記炭素（固体）を前記過酸化水素に接触させると、下記式（１），（２）の化学量論式で前記分解反応が進められ、前記炭素が分解して、最終的にＣＯ、ＣＯ２として放出される。
<Basic principle>
The decomposition reaction of carbon with hydrogen peroxide is well known. Usually, when the carbon (solid) is brought into contact with the hydrogen peroxide, the decomposition reaction proceeds according to the stoichiometric formulas of the following formulas (1) and (2), the carbon is decomposed, and finally the CO , Released as CO 2 .
しかし、実際の反応状態では、前記過酸化水素の自己分解反応が進むとともに、高い温度条件では、前記過酸化水素が蒸発し、このような化学量論で前記炭素と前記過酸化水素を混合しても前記炭素を完全に分解しないことが考えられる。なお、前記過酸化水素又は前記過酸化水素を水に溶解させた過酸化水素水の沸点は、次の通りである。即ち、２７ｗｔ％過酸化水素水の沸点は、１０５℃であり、３５ｗｔ％過酸化水素水の沸点は、１０８℃であり、５０ｗｔ％過酸化水素水の沸点は、１１４℃であり、７０ｗｔ％過酸化水素水の沸点は、１２６℃であり、９０ｗｔ％過酸化水素水の沸点は、１４１℃であり、１００ｗｔ％過酸化水素の沸点は、１５０．２℃である。
前記分解反応は、前記過酸化水素と接触する前記炭素のエッジ部から進行し、炭素粒子を徐々に小さく削っていく過程である。したがって、前記炭素粒子が前記過酸化水素により完全に分解されて気中に放出される前に、前記分解反応を停止させることとすれば、極めて小粒径の前記炭素粒子が得られる。
また、この過程で、前記炭素粒子のエッジにカルボキシル基、ヒドロキシル基などの親水性基が生成し、粒子全体が親水性基で覆われるようになる。
したがって、前記炭素粒子のサイズが十分小さく、表面を覆う親水性基の量が十分多くなれば、前記炭素粒子が液中に均一分散した安定コロイド系が得られる。
なお、本明細書において、炭素量子ドットとは、光（例えば、波長３６５ｎｍの紫外光）を照射したときに、自己発光可能な炭素粒子のことを指す。
However, in the actual reaction state, the hydrogen peroxide self-decomposition reaction proceeds, and under high temperature conditions, the hydrogen peroxide evaporates, and the carbon and the hydrogen peroxide are mixed with such stoichiometry. However, it is conceivable that the carbon is not completely decomposed. In addition, the boiling points of the hydrogen peroxide or hydrogen peroxide water obtained by dissolving the hydrogen peroxide in water are as follows. That is, the boiling point of 27 wt% hydrogen peroxide solution is 105 ° C., the boiling point of 35 wt% hydrogen peroxide solution is 108 ° C., the boiling point of 50 wt% hydrogen peroxide solution is 114 ° C., and 70 wt% excess. The boiling point of hydrogen oxide water is 126 ° C., the boiling point of 90 wt% hydrogen peroxide water is 141 ° C., and the boiling point of 100 wt% hydrogen peroxide is 150.2 ° C.
The decomposition reaction is a process of proceeding from the edge portion of the carbon that comes into contact with the hydrogen peroxide and gradually scraping the carbon particles. Therefore, if the decomposition reaction is stopped before the carbon particles are completely decomposed by the hydrogen peroxide and released into the air, the carbon particles having a very small particle size can be obtained.
In this process, a hydrophilic group such as a carboxyl group or a hydroxyl group is generated at the edge of the carbon particle, and the entire particle is covered with the hydrophilic group.
Therefore, when the size of the carbon particles is sufficiently small and the amount of hydrophilic groups covering the surface is sufficiently large, a stable colloidal system in which the carbon particles are uniformly dispersed in the liquid can be obtained.
In the present specification, the carbon quantum dots refer to carbon particles that can self-emit when irradiated with light (for example, ultraviolet light having a wavelength of 365 nm).
＜炭素量子ドット生成液調製工程＞
前記炭素量子ドット生成液調製工程は、炭素材と前記過酸化水素とを混合し、前記過酸化水素により前記炭素材中の炭素を分解反応させ、前記炭素材由来の前記炭素量子ドットを生成させた炭素量子ドット生成液を調製する工程である。
<Carbon quantum dot production liquid preparation process>
In the carbon quantum dot production liquid preparation step, a carbon material and the hydrogen peroxide are mixed, the carbon in the carbon material is decomposed by the hydrogen peroxide, and the carbon quantum dots derived from the carbon material are generated. This is a step of preparing a carbon quantum dot production solution.
＜炭素材＞
前記炭素材としては、特に制限はなく、公知の炭素材を用いることができるが、グラファイト構造又はグラフェン構造を有する粉末状の炭素材が好ましい。
前記グラファイト構造又はグラフェン構造を有する粉末状の炭素材としては、特に制限はなく、例えば、カーボンナノチューブ、フラーレン、炭素繊維の粉状体、活性炭、カーボンブラックなどが挙げられ、特にポア（細孔）構造を有するものが好ましい。
中でも、安価に入手でき、均質な粒子構造を有する活性炭が好ましい。前記活性炭では、ポア壁中にマイクログラファイトセグメントが存在し、その間がダングリボンドで結合されることが知られており、前記炭素粒子のエッジ部だけでなく、マイクログラファイトセグメント間の結合部においても前記分解反応の反応性が高い。前記活性炭のポア内に過酸化水素が吸着されると、反応性の高い部位に前記過酸化水素が接触し、速やかに前記活性炭中の前記炭素粒子を微粉化し、水中に安定分散可能な量子サイズの炭素量子ドットを生成せることができる。
<Carbon material>
There is no restriction | limiting in particular as said carbon material, Although a well-known carbon material can be used, The powdery carbon material which has a graphite structure or a graphene structure is preferable.
The powdery carbon material having the graphite structure or the graphene structure is not particularly limited, and examples thereof include carbon nanotubes, fullerenes, carbon fiber powders, activated carbon, and carbon black, and particularly pores (pores). Those having a structure are preferred.
Among these, activated carbon having a homogeneous particle structure that can be obtained at low cost is preferable. In the activated carbon, it is known that there are micrographite segments in the pore wall, and the gaps are bonded by dangling bonds, and the decomposition is not only at the edges of the carbon particles but also at the bonds between the micrographite segments. The reactivity of the reaction is high. When hydrogen peroxide is adsorbed in the pores of the activated carbon, the hydrogen peroxide comes into contact with a highly reactive site, quickly pulverizes the carbon particles in the activated carbon, and can be stably dispersed in water. Carbon quantum dots can be generated.
本発明では、前記炭素の分解反応に用いる酸として、前記過酸化水素を用いる。弱酸性（ｐＨ４〜６）の前記過酸化水素を前記分解反応に用いることで、大量のアルカリ中和処理が不要となり、簡便かつ効率的に前記炭素量子ドットを製造することができる。
また、前記過酸化水素を用いて得られる前記炭素量子ドットは、水溶性であることから、様々な技術分野に応用することができる。
前記過酸化水素としては、特に制限はなく、前記過酸化水素そのものを用いてもよく、前記過酸化水素水を用いてもよい。
前記過酸化水素水の濃度としては、特に制限はなく、用いる前記炭素材の量等に応じて適宜選択することができるが、例えば、入手し易い３０ｗｔ％過酸化水素水を好適に用いることができる。
In the present invention, the hydrogen peroxide is used as the acid used for the carbon decomposition reaction. By using the weakly acidic (pH 4 to 6) hydrogen peroxide for the decomposition reaction, a large amount of alkali neutralization treatment becomes unnecessary, and the carbon quantum dots can be produced simply and efficiently.
The carbon quantum dots obtained using the hydrogen peroxide are water-soluble and can be applied to various technical fields.
The hydrogen peroxide is not particularly limited, and the hydrogen peroxide itself may be used, or the hydrogen peroxide solution may be used.
There is no restriction | limiting in particular as the density | concentration of the said hydrogen peroxide solution, Although it can select suitably according to the quantity etc. of the said carbon material to be used, For example, it is preferable to use easily available 30 wt% hydrogen peroxide solution. it can.
前記炭素量子ドット生成液調製工程としては、特に制限はなく、室温条件下で実施してもよいが、前記混合液に対し、加熱処理を実施する工程であることが好ましい。
前記加熱処理を行うと、アレニウスの式に基づき、昇温温度に応じて前記分解反応が速く進み、異なるサイズの前記炭素量子ドットを効率的に製造することが可能となる。
前記加熱処理における加熱温度としては、特に制限はなく、前記炭素材に対する前記過酸化水素の配合量、前記過酸化水素の濃度、処理時間等に基づき、適宜決定することができる。ただし、前記過酸化水素の沸点を大幅に超える温度とすると、前記分解反応と前記過酸化水素の気化が競争的となることから、却って前記炭素量子ドットの生成効率が低下することがある。
なお、前記炭素量子ドット生成液の調製においては、生成工程中、追加の前記過酸化水素や水を適宜添加して前記炭素量子ドットの生成をコントロールしてもよい。
また、前記炭素量子ドット生成液調製工程における処理時間としては、特に制限はなく、前記炭素材と前記過酸化水素の配合量、処理温度等の条件に応じて、適宜選択することができる。
There is no restriction | limiting in particular as said carbon quantum dot production | generation liquid preparation process, Although you may implement under room temperature conditions, It is preferable that it is a process of heat-processing with respect to the said liquid mixture.
When the heat treatment is performed, based on the Arrhenius equation, the decomposition reaction proceeds rapidly according to the temperature rise temperature, and the carbon quantum dots having different sizes can be efficiently manufactured.
There is no restriction | limiting in particular as heating temperature in the said heat processing, It can determine suitably based on the compounding quantity of the said hydrogen peroxide with respect to the said carbon material, the density | concentration of the said hydrogen peroxide, processing time, etc. However, if the temperature is much higher than the boiling point of the hydrogen peroxide, the decomposition reaction and the vaporization of the hydrogen peroxide become competitive, and the production efficiency of the carbon quantum dots may be lowered.
In the preparation of the carbon quantum dot production liquid, the production of the carbon quantum dots may be controlled by appropriately adding additional hydrogen peroxide or water during the production process.
Moreover, there is no restriction | limiting in particular as processing time in the said carbon quantum dot production | generation liquid preparation process, According to conditions, such as the compounding quantity of the said carbon material and the said hydrogen peroxide, and processing temperature, it can select suitably.
＜炭素量子ドット取得工程＞
前記炭素量子ドット取得工程は、前記炭素量子ドット生成液中の前記炭素量子ドットと前記過酸化水素を分離して前記分解反応を停止させ、前記炭素量子ドットを取得する工程である。
<Carbon quantum dot acquisition process>
The carbon quantum dot acquisition step is a step of acquiring the carbon quantum dots by separating the carbon quantum dots and the hydrogen peroxide in the carbon quantum dot production liquid to stop the decomposition reaction.
前記分解反応を停止させる停止方法としては、特に制限はなく、例えば、前記炭素量子ドット生成液を前記過酸化水素（前記過酸化水素水を含む）の沸点以上の温度で加熱処理し、前記過酸化水素を気化させる方法、前記炭素量子ドット生成液を減圧乾燥させて、前記過酸化水素を除去する方法などが挙げられる。
なお、前記停止方法には、前記加熱処理を沸点未満の温度で実施するか、室温環境下で徐々に前記過酸化水素を気化させる方法や、限外濾過、逆浸透法等により、前記炭素量子ドット生成液から前記炭素量子ドットを分離する方法など、前記炭素量子ドット生成液中の前記炭素量子ドットと前記過酸化水素を分離する種々の方法が含まれる。
The stopping method for stopping the decomposition reaction is not particularly limited. For example, the carbon quantum dot production liquid is heated at a temperature equal to or higher than the boiling point of the hydrogen peroxide (including the hydrogen peroxide solution), and the excess Examples thereof include a method of vaporizing hydrogen oxide and a method of removing the hydrogen peroxide by drying the carbon quantum dot production liquid under reduced pressure.
As the stopping method, the heat treatment is performed at a temperature below the boiling point, or the hydrogen peroxide is gradually vaporized in a room temperature environment, the ultrafiltration, the reverse osmosis method, or the like. Various methods for separating the carbon quantum dots and the hydrogen peroxide in the carbon quantum dot production liquid, such as a method for separating the carbon quantum dots from a dot production liquid, are included.
前記過酸化水素の沸点以上の温度で加熱処理し、前記過酸化水素を気化させる場合、前記炭素量子ドット生成液調製工程及び前記炭素量子ドット取得工程を一連の工程として、前記炭素材と前記過酸化水素との混合液に対して、前記過酸化水素の沸点以上の温度で加熱処理を実施し、前記炭素量子ドットを生成させるとともに前記炭素量子ドット生成液中の過酸化水素を気化させて分解反応を停止させる工程として実施することが好ましい。このように実施すれば、簡便かつ効率的に前記炭素量子ドットを製造することができる。 When the hydrogen peroxide is vaporized by heat treatment at a temperature equal to or higher than the boiling point of the hydrogen peroxide, the carbon material and the carbon quantum dot production liquid preparation step and the carbon quantum dot acquisition step are a series of steps. The mixed liquid with hydrogen oxide is subjected to heat treatment at a temperature equal to or higher than the boiling point of the hydrogen peroxide to generate the carbon quantum dots and to decompose by vaporizing the hydrogen peroxide in the carbon quantum dot generating liquid. It is preferable to carry out the step of stopping the reaction. If implemented in this manner, the carbon quantum dots can be produced simply and efficiently.
また、この場合、前記炭素材中の炭素１モルに対して、２モル以上の前記過酸化水素を混合させることが好ましい。即ち、前記過酸化水素の沸点以上の温度で加熱する場合には、前記分解反応と前記過酸化水素の気化が競争的となって、前記分解反応の進行が低下することがあり、前記炭素に対してより多くの前記過酸化水素を配合して、前記分解反応の進行を促進させることが好ましい。なお、前記過酸化水素の配合量が、炭素１モルに対して、３，０００モルを超える場合には、前記炭素の分解反応が速く進み過ぎ、前記分解反応の停止をコントロールすることが難しくなることから、前記配合量の上限としては、３，０００モル以下であることが好ましい。 In this case, it is preferable that 2 moles or more of the hydrogen peroxide is mixed with 1 mole of carbon in the carbon material. That is, when heating at a temperature equal to or higher than the boiling point of the hydrogen peroxide, the decomposition reaction and vaporization of the hydrogen peroxide become competitive, and the progress of the decomposition reaction may be reduced. On the other hand, it is preferable to blend more hydrogen peroxide to promote the progress of the decomposition reaction. When the blending amount of the hydrogen peroxide exceeds 3,000 mol with respect to 1 mol of carbon, the decomposition reaction of the carbon proceeds too quickly and it becomes difficult to control the termination of the decomposition reaction. Therefore, the upper limit of the amount is preferably 3,000 mol or less.
前記減圧乾燥させて、過酸化水素を除去する方法としては、特に制限はなく、例えば、真空乾燥法、冷凍乾燥法等が挙げられる。 The method for removing hydrogen peroxide by drying under reduced pressure is not particularly limited, and examples thereof include a vacuum drying method and a freeze drying method.
前記炭素量子ドット生成液調製工程及び前記炭素量子ドット取得工程としては、特に制限はなく、各工程を１度ずつ実施してもよいが、これら工程を一連の工程として、複数回繰り返して実施してもよい。この場合、前記炭素量子ドット取得工程後の前記炭素粒子を前記炭素材として、再度、前記炭素量子ドット生成液調製工程を実施する。このような逐次処理方法によれば、前記分解反応をコントロールし易く、また、処理回数によって異なる発光特性を有する前記炭素量子ドットを得ることができる。 There is no restriction | limiting in particular as said carbon quantum dot production | generation liquid preparation process and said carbon quantum dot acquisition process, Each process may be implemented once, but these processes are repeatedly implemented as a series of processes. May be. In this case, the said carbon particle after the said carbon quantum dot acquisition process is implemented as the said carbon material, and the said carbon quantum dot production liquid preparation process is implemented again. According to such a sequential processing method, it is easy to control the decomposition reaction, and it is possible to obtain the carbon quantum dots that have different emission characteristics depending on the number of processing times.
＜その他の工程＞
前記その他の工程としては、特に制限はなく、目的に応じて適宜選択することができ、例えば、前記炭素量子ドット取得工程に後続して実施される遠心分離工程、濾過工程が挙げられる。
前記遠心分離工程は、前記炭素量子ドットを含む水分散液から、上澄み液を得る工程であり、このような工程を実施することで、前記水中に分散せず、沈殿した状態のサイズが大きい不要な炭素粒子を除去することができる。
また、前記濾過工程は、前記炭素量子ドットを含む水分散液から、目の細かいフィルタ（例えば、孔径０．１μｍ以下）で分散液を濾別する工程であり、このような工程を実施することで、前記フィルタに濾し取られるサイズの大きい不要な炭素粒子を除去することができる。なお、前記サイズの大きい炭素粒子を原料として、再度、前記各工程を実施し、前記炭素量子ドットを得ることとしてもよい。
<Other processes>
There is no restriction | limiting in particular as said other process, According to the objective, it can select suitably, For example, the centrifugation process and filtration process implemented following the said carbon quantum dot acquisition process are mentioned.
The centrifugal separation step is a step of obtaining a supernatant from the aqueous dispersion containing the carbon quantum dots. By carrying out such a step, it is unnecessary to disperse in the water and the size of the precipitated state is large. Carbon particles can be removed.
Moreover, the said filtration process is a process of separating a dispersion liquid from the aqueous dispersion liquid containing the said carbon quantum dot with a fine filter (for example, pore diameter of 0.1 micrometer or less), and implements such a process. Thus, it is possible to remove unnecessary large carbon particles filtered by the filter. In addition, it is good also as implementing the said process again using the carbon particle with the said large size as a raw material, and obtaining the said carbon quantum dot.
（炭素量子ドット）
本発明の炭素量子ドットは、前記炭素量子ドットの製造方法により製造される炭素量子ドットに係り、その特徴としては、前記炭素量子ドットの製造方法において説明した事項が該当する。
(Carbon quantum dots)
The carbon quantum dot of the present invention relates to a carbon quantum dot produced by the carbon quantum dot production method, and the features described in the carbon quantum dot production method are applicable.
以下では、本発明の実施例を詳細に説明するが、本発明の技術的思想は、これらの例に限定されるものではない。 Examples of the present invention will be described in detail below, but the technical idea of the present invention is not limited to these examples.
（実施例１：処理時間の影響の検討）
２ｍｇの活性炭（関西熱化学社製、ＭＳＣ３０）を測り取り、１ｍＬの３０ｗｔ％過酸化水素水に添加した。これを磁気撹拌しながら８０℃にて加熱処理し、経時変化を観察した。活性炭が徐々に溶け出し、３時間経過後、殆どの活性炭が処理液中に分散した。
このような方法で、それぞれ３時間（実施例１−１）、４時間（実施例１−２）、６時間（実施例１−３）、８時間（実施例１−４）、１０時間（実施例１−５）、１２時間（実施例１−６）、１４時間（実施例１−７）、１８時間（実施例１−８）で加熱処理し、活性炭を分散させた各分散液サンプルを調製した。
(Example 1: Examination of influence of processing time)
2 mg of activated carbon (manufactured by Kansai Thermal Chemical Co., Ltd., MSC30) was measured and added to 1 mL of 30 wt% hydrogen peroxide solution. This was heat-treated at 80 ° C. with magnetic stirring, and the change with time was observed. Activated carbon gradually melted out, and after 3 hours, most of the activated carbon was dispersed in the treatment liquid.
In such a method, 3 hours (Example 1-1), 4 hours (Example 1-2), 6 hours (Example 1-3), 8 hours (Example 1-4), 10 hours ( Examples 1-5), 12 hours (Example 1-6), 14 hours (Example 1-7), 18 hours (Example 1-8), each dispersion sample in which activated carbon was dispersed by heat treatment Was prepared.
図１（ａ）に、励起波長３６０ｎｍの光で励起させた実施例１−１〜１−８に係る各分散液サンプルの蛍光スペクトルを示す。なお、蛍光スペクトルは、分光蛍光光度計（島津製作所社製、ＲＦ−５３００ＰＣ）にて測定した。また、図１（ｂ）に実施例１−６に係る分散液サンプルに対するブラックライト（波長３６５ｎｍ）照射前後の写真を示す。該図１（ｂ）中、左側が照射前の状態を示し、右側が照射後の状態を示す。この分散液サンプルは、太陽光（通常環境光）下では、透明であるが、ブラックライト照射後では、青色に発光している。 FIG. 1A shows the fluorescence spectrum of each dispersion sample according to Examples 1-1 to 1-8 excited with light having an excitation wavelength of 360 nm. The fluorescence spectrum was measured with a spectrofluorometer (manufactured by Shimadzu Corporation, RF-5300PC). Moreover, the photograph before and behind black light (wavelength 365nm) irradiation with respect to the dispersion liquid sample which concerns on Example 1-6 at FIG.1 (b) is shown. In FIG. 1 (b), the left side shows a state before irradiation, and the right side shows a state after irradiation. This dispersion sample is transparent under sunlight (normal environmental light), but emits blue light after irradiation with black light.
図１（ａ）に示すように、各分散液サンプルでは、波長４５０ｎｍ付近を中心とした青色発光のスペクトルが確認され、特に、実施例１−４（８時間）及び実施例１−５（１０時間）に係る分散液サンプルでは、波長４５０ｎｍ付近に急峻なピークを有することが確認された。
一方、実施例１−１〜１−３に係る分散液サンプルでは、発光強度が低く、ブロードのピークが確認され、活性炭の炭素分解反応が十分に進んでいないことが推察される。また、実施例１−６〜１−８に係る分散液サンプルでは、加熱処理時間が長くなるにつれて、発光強度が低くなるとともに、ピークがブロード化することが確認され、活性炭の炭素分解反応が持続的に進むと、液中の炭素が徐々に分解されて、ＣＯ又はＣＯ２として気中に放出され、最終的に存在しなくなることが推察される。特に、本実施例１−１〜１−８の条件では、過酸化水素と炭素のモル比（Ｈ２Ｏ２／Ｃ）が約６０で、過酸化水素の配合量を大過剰としているため、最終的に液中から炭素が存在しなくなる。
したがって、所望の発光を示す炭素量子ドットを得るためには、炭素分解反応を行う処理時間を適宜コントロールし、処理時間経過後は、分散液から過酸化水素を除去する必要がある。
ここでは、各処理時間経過後、分散液サンプルを真空乾燥機に入れ、過酸化水素を気化させることで、実施例１−１〜１−８に係る炭素量子ドットを製造することとしている。なお、以降の実施例においても、同様の方法で過酸化水素を気化させて炭素量子ドットを製造することができる。
As shown to Fig.1 (a), in each dispersion liquid sample, the spectrum of the blue light emission centering on wavelength 450nm center was confirmed, and especially Example 1-4 (8 hours) and Example 1-5 (10 It was confirmed that the dispersion sample according to (time) has a sharp peak in the vicinity of a wavelength of 450 nm.
On the other hand, in the dispersion liquid samples according to Examples 1-1 to 1-3, the emission intensity is low, a broad peak is confirmed, and it is surmised that the carbon decomposition reaction of activated carbon does not proceed sufficiently. In addition, in the dispersion liquid samples according to Examples 1-6 to 1-8, it was confirmed that the emission intensity decreased and the peak broadened as the heat treatment time increased, and the carbon decomposition reaction of activated carbon continued. It is inferred that the carbon in the liquid is gradually decomposed and released into the air as CO or CO 2 and finally disappears. In particular, under the conditions of Examples 1-1 to 1-8, the molar ratio of hydrogen peroxide to carbon (H 2 O 2 / C) is about 60, and the amount of hydrogen peroxide is excessively large. Eventually no carbon will be present in the liquid.
Therefore, in order to obtain carbon quantum dots exhibiting desired light emission, it is necessary to appropriately control the treatment time for performing the carbon decomposition reaction and to remove hydrogen peroxide from the dispersion after the treatment time has elapsed.
Here, the carbon quantum dots according to Examples 1-1 to 1-8 are manufactured by putting the dispersion liquid sample in a vacuum dryer and evaporating hydrogen peroxide after each treatment time has elapsed. In the following examples, carbon quantum dots can be produced by vaporizing hydrogen peroxide in the same manner.
（実施例２：低温処理の検討）
２．３ｍｇの活性炭（関西熱化学社製、ＭＳＣ３０）を測り取り、１ｍＬの３０ｗｔ％過酸化水素水に添加した。これを磁気撹拌しながら室温（２１℃〜２５℃）にて３９日間撹拌処理した。この処理液に８ｍＬの蒸留水を加え、実施例２−１に係る分散液サンプルを調製した。なお、この分散液サンプルは、太陽光（通常環境光）下で薄い褐色を呈していた。
また、実施例２−１に係る分散液サンプルを６６日間室温で静置し、実施例２−２に係る分散液サンプルを調製した。
(Example 2: Examination of low temperature treatment)
2.3 mg of activated carbon (manufactured by Kansai Thermal Chemical Co., Ltd., MSC30) was measured and added to 1 mL of 30 wt% hydrogen peroxide solution. This was stirred for 39 days at room temperature (21 ° C. to 25 ° C.) with magnetic stirring. 8 mL of distilled water was added to this treatment liquid to prepare a dispersion sample according to Example 2-1. The dispersion sample had a light brown color under sunlight (normal ambient light).
Moreover, the dispersion liquid sample which concerns on Example 2-1 was left still at room temperature for 66 days, and the dispersion liquid sample which concerns on Example 2-2 was prepared.
撹拌処理を５０℃の加熱条件下で３日間行ったこと、蒸留水の添加量を８．１６ｍＬに変えたこと以外は、実施例２−１と同様にして、実施例２−３に係る分散液サンプルを調製した。なお、この分散液サンプルは、太陽光（通常環境光）下で薄い褐色を呈していた。
また、実施例２−３に係る分散液サンプルを１０１日間室温で静置し、実施例２−４に係る分散液サンプルを調製した。
Dispersion according to Example 2-3 in the same manner as in Example 2-1, except that the stirring treatment was performed for 3 days under a heating condition of 50 ° C., and the addition amount of distilled water was changed to 8.16 mL. A liquid sample was prepared. The dispersion sample had a light brown color under sunlight (normal ambient light).
Moreover, the dispersion liquid sample which concerns on Example 2-3 was left still at room temperature for 101 days, and the dispersion liquid sample which concerns on Example 2-4 was prepared.
図２に、励起波長３３０ｎｍの光で励起させた実施例２−１〜２−４に係る各分散液サンプルの蛍光スペクトルを示す。なお、蛍光スペクトルは、分光蛍光光度計（島津製作所社製、ＲＦ−５３００ＰＣ）にて測定した。
該図２に示すように、実施例２−１に係る分散液サンプルの蛍光スペクトルは、波長約４５０ｎｍ（青色）を中心にした、やや複雑な形状であった。
これに対し、実施例２−１に係る分散液サンプルを６６日経過させた実施例２−２に係る分散液サンプルの蛍光スペクトルは、綺麗な青色を発光する単純スペクトルとなり、炭素の分解反応が徐々に進行していることを示している。
また、実施例２−３に係る分散液サンプルの蛍光スペクトルは、青色（４００ｎｍ）から黄緑色（６００ｎｍ）までの波長範囲にまたがるブロードな形状であった。
これに対し、実施例２−３に係る分散液サンプルを１０１日経過させた実施例２−４に係る分散液サンプルの蛍光スペクトルは、青色の発光強度が大きく強められたより単純なものであり、炭素の分解反応が徐々に進行し、大きい粒子が小さくなり、より大量の小さいサイズの炭素量子ドットが生成されていることが推察される。
以上のように、室温、５０℃の温度条件で攪拌処理する炭素の分解反応条件においても、炭素量子ドットを製造することができる。ただし、これら低温の温度条件では、炭素量子ドットの製造に長時間を要することから、適宜、加熱処理の好適な温度条件を検討する必要がある。
FIG. 2 shows fluorescence spectra of the respective dispersion liquid samples according to Examples 2-1 to 2-4 excited with light having an excitation wavelength of 330 nm. The fluorescence spectrum was measured with a spectrofluorometer (manufactured by Shimadzu Corporation, RF-5300PC).
As shown in FIG. 2, the fluorescence spectrum of the dispersion sample according to Example 2-1 had a slightly complicated shape centered on a wavelength of about 450 nm (blue).
On the other hand, the fluorescence spectrum of the dispersion sample according to Example 2-2 in which the dispersion sample according to Example 2-1 has been passed for 66 days becomes a simple spectrum that emits a beautiful blue color, and the decomposition reaction of carbon occurs. It shows that it is progressing gradually.
Moreover, the fluorescence spectrum of the dispersion liquid sample according to Example 2-3 had a broad shape extending over a wavelength range from blue (400 nm) to yellow green (600 nm).
On the other hand, the fluorescence spectrum of the dispersion sample according to Example 2-4 in which the dispersion sample according to Example 2-3 was allowed to pass for 101 days is simpler than the blue emission intensity greatly increased, It is inferred that the carbon decomposition reaction proceeds gradually, the large particles become smaller, and a larger amount of small-sized carbon quantum dots are generated.
As described above, carbon quantum dots can also be produced under carbon decomposition reaction conditions in which stirring treatment is performed at room temperature and 50 ° C. However, since these low temperature conditions require a long time for the production of carbon quantum dots, it is necessary to appropriately examine suitable temperature conditions for the heat treatment.
（実施例３：加熱処理の温度の検討）
７．５ｍｇの活性炭（関西熱化学社製、ＭＳＣ３０）を測り取り、１ｍＬの３０ｗｔ％過酸化水素水に添加した。磁気撹拌しながら８０℃、１００℃、１１０℃、１２０℃にて加熱処理を行った。ここでは、加熱処理の温度条件を８０℃とした例を実施例３−１、１００℃とした例を実施例３−２、１１０℃とした例を実施例３−３、１２０℃とした例を実施例３−４とする。
実施例３−１（８０℃）では、約２３時間の加熱処理で、処理液中に活性炭が溶け出し、ほぼ活性炭が処理液中に分散した状態となった。この状態の処理溶液中に８ｍＬの蒸留水を加えて撹拌し、太陽光（通常環境光）下で褐色を呈する分散液サンプルを得た。
実施例３−２（１００℃）では、約７時間の加熱処理で分散状態となり、この状態の処理液中に８ｍＬの蒸留水を加えて撹拌し、太陽光（通常環境光）下で極めて薄い褐色を呈する分散液サンプルを得た。
実施例３−３（１１０℃）、実施例３−４（１２０℃）では、より短時間の加熱処理で活性炭が分散状態となると同時に、過酸化水素の蒸発もより速くなり、それぞれ約３．５時間後、約２時間後に活性炭の粉末を処理容器内に残して、処理液が完全に蒸発した。それぞれの処理容器を加熱槽から取り出し、それぞれ約８ｍＬの蒸留水を加え、再度それぞれの温度で蒸留水が完全に蒸発するまで加熱処理した。加熱処理後の溶液にそれぞれ８ｍＬ、４ｍＬの蒸留水を再度加えて撹拌し、太陽光（通常環境光）下で薄い褐色を呈する分散液サンプルをそれぞれ得た。
(Example 3: Examination of temperature of heat treatment)
7.5 mg of activated carbon (manufactured by Kansai Thermal Chemical Co., Ltd., MSC30) was measured and added to 1 mL of 30 wt% hydrogen peroxide solution. Heat treatment was performed at 80 ° C., 100 ° C., 110 ° C., and 120 ° C. with magnetic stirring. Here, an example in which the temperature condition of the heat treatment is set to 80 ° C. is Example 3-1, an example in which 100 ° C. is set to Example 3-2, an example in which 110 ° C. is set to Example 3-3, an example in which 120 ° C. is set To Example 3-4.
In Example 3-1 (80 ° C.), the activated carbon was dissolved in the treatment liquid by the heat treatment for about 23 hours, and the activated carbon was almost dispersed in the treatment liquid. 8 mL of distilled water was added to the treatment solution in this state and stirred to obtain a dispersion liquid sample having a brown color under sunlight (normal ambient light).
In Example 3-2 (100 ° C.), the dispersion is brought about by heat treatment for about 7 hours, and 8 mL of distilled water is added to the treatment liquid in this state and stirred, and is extremely thin under sunlight (normal ambient light). A dispersion sample exhibiting a brown color was obtained.
In Example 3-3 (110 ° C.) and Example 3-4 (120 ° C.), the activated carbon becomes dispersed in a shorter heat treatment, and at the same time, the evaporation of hydrogen peroxide becomes faster. After about 5 hours, after about 2 hours, the activated carbon powder was left in the processing vessel, and the processing solution was completely evaporated. Each processing container was taken out from the heating tank, and about 8 mL of distilled water was added to each of the processing containers. The heating treatment was performed again at each temperature until the distilled water completely evaporated. 8 mL and 4 mL of distilled water were added again to the solution after the heat treatment, followed by stirring to obtain a dispersion sample exhibiting a light brown color under sunlight (normal ambient light).
図３（ａ）に、励起波長３６５ｎｍの光で励起させた実施例３−１〜３−４に係る各分散液サンプルの蛍光スペクトルを示す。なお、蛍光スペクトルは、分光蛍光光度計（島津製作所社製、ＲＦ−５３００ＰＣ）にて測定した。また、図３（ｂ）に実施例３−１〜３−４に係る各分散液サンプルに対して、ブラックライト（波長３６５ｎｍ）を照射した時の写真を示す。該図３（ｂ）中、左側から実施例３−１、実施例３−２、実施例３−３、実施例３−４に係る分散液サンプルの写真であり、それぞれ、明るい水色（実施例３−１）、緑色を帯びた青色（実施例３−２）、明るい黄緑色（実施例３−３）、水色（実施例３−４）が確認される。 FIG. 3A shows the fluorescence spectra of the respective dispersion liquid samples according to Examples 3-1 to 3-4 excited with light having an excitation wavelength of 365 nm. The fluorescence spectrum was measured with a spectrofluorometer (manufactured by Shimadzu Corporation, RF-5300PC). FIG. 3B shows a photograph when each dispersion liquid sample according to Examples 3-1 to 3-4 is irradiated with black light (wavelength 365 nm). FIG. 3B is a photograph of the dispersion sample according to Example 3-1, Example 3-2, Example 3-3, and Example 3-4 from the left side. 3-1), greenish blue (Example 3-2), bright yellow-green (Example 3-3), and light blue (Example 3-4) are confirmed.
活性炭の添加量を７．５ｍｇとする実施例３−１〜３−４に係る分散液サンプルの系では、加熱処理の温度条件を高温側に設定することで、より速く活性炭が分散状態となることが確認され、また、実施例３−３、実施例３−４では、過酸化水素水の完全気化により、炭素分解反応を停止させることができている。 In the dispersion sample system according to Examples 3-1 to 3-4 in which the amount of activated carbon added is 7.5 mg, the activated carbon is dispersed more quickly by setting the temperature condition of the heat treatment to the high temperature side. In Example 3-3 and Example 3-4, the carbon decomposition reaction can be stopped by complete vaporization of the hydrogen peroxide solution.
次に、活性炭の添加量を１０ｍｇに変更して、同様の実験を行った。即ち、１０ｍｇの活性炭（関西熱化学社製、ＭＳＣ３０）を測り取り、１ｍＬの３０ｗｔ％過酸化水素水に添加後、磁気撹拌しながら１００℃、１１０℃、１２０℃にて加熱処理を行った。１０ｍｇの活性炭を用い、加熱処理の温度条件を１００℃とした例を実施例３−５、１１０℃とした例を実施例３−６、１２０℃とした例を実施例３−７とする。
実施例３−５では、加熱処理開始後、活性炭が徐々に分散状態となり、６時間〜７時間の加熱処理で、活性炭の粉末を処理容器内に残して、処理液が完全に蒸発した。次いで、８ｍＬの蒸留水を加え、一旦蒸留水を完全に蒸発させた後、再度、８ｍＬの蒸留水を加えて撹拌し、深い褐色を呈する分散液サンプルを得た。
実施例３−６では、加熱処理開始後、活性炭が徐々に分散状態となり、約３．５時間の加熱処理で、活性炭の粉末を処理容器内に残して、処理液が完全に蒸発した。次いで、８ｍＬの蒸留水を加え、一旦蒸留水を完全に蒸発させた後、再度、８ｍＬの蒸留水を加えて撹拌し、深い褐色を呈する分散液サンプルを得た。
実施例３−７では、加熱処理開始後、活性炭が徐々に分散状態となり、約１時間の加熱処理で、活性炭の粉末を処理容器内に残して、処理液が完全に蒸発した。次いで、８ｍＬの蒸留水を加えて撹拌し、深い褐色を呈する分散液サンプルを得た。
Next, the same experiment was performed by changing the amount of activated carbon added to 10 mg. That is, 10 mg of activated carbon (manufactured by Kansai Thermal Chemical Co., Ltd., MSC30) was measured, added to 1 mL of 30 wt% hydrogen peroxide solution, and then subjected to heat treatment at 100 ° C., 110 ° C., and 120 ° C. with magnetic stirring. An example in which 10 mg of activated carbon was used and the temperature condition of the heat treatment was set to 100 ° C was set to Example 3-5, 110 ° C was set to Example 3-6, and 120 ° C was set to Example 3-7.
In Example 3-5, after the heat treatment was started, the activated carbon gradually became dispersed, and the heat treatment for 6 to 7 hours left the activated carbon powder in the treatment container, whereby the treatment liquid was completely evaporated. Next, 8 mL of distilled water was added and once distilled water was completely evaporated, 8 mL of distilled water was added again and stirred to obtain a dispersion liquid sample having a deep brown color.
In Example 3-6, after the heat treatment was started, the activated carbon gradually became dispersed, and the heat treatment for about 3.5 hours left the activated carbon powder in the treatment container, and the treatment liquid completely evaporated. Next, 8 mL of distilled water was added and once distilled water was completely evaporated, 8 mL of distilled water was added again and stirred to obtain a dispersion liquid sample having a deep brown color.
In Example 3-7, after the heat treatment was started, the activated carbon gradually became dispersed, and the heat treatment for about 1 hour left the activated carbon powder in the treatment container, and the treatment liquid completely evaporated. Next, 8 mL of distilled water was added and stirred to obtain a dispersion sample exhibiting a deep brown color.
図４（ａ）に、励起波長３６５ｎｍの光で励起させた実施例３−５〜３−７に係る各分散液サンプルの蛍光スペクトルを示す。なお、蛍光スペクトルは、分光蛍光光度計（島津製作所社製、ＲＦ−５３００ＰＣ）にて測定した。また、図４（ｂ）に実施例３−５〜３−７に係る各分散液サンプルに対して、ブラックライト（波長３６５ｎｍ）を照射した時の写真を示す。該図４（ｂ）中、左側から実施例３−５、実施例３−６、実施例３−７に係る分散液サンプルの写真であり、それぞれ、濃い褐色（実施例３−５）、明るい黄緑色（実施例３−６）、黄緑色（実施例３−７）が確認される。 FIG. 4A shows the fluorescence spectrum of each dispersion sample according to Examples 3-5 to 3-7 excited with light having an excitation wavelength of 365 nm. The fluorescence spectrum was measured with a spectrofluorometer (manufactured by Shimadzu Corporation, RF-5300PC). FIG. 4B shows a photograph when each dispersion liquid sample according to Examples 3-5 to 3-7 is irradiated with black light (wavelength 365 nm). FIG. 4B is a photograph of the dispersion sample according to Example 3-5, Example 3-6, and Example 3-7 from the left side, dark brown (Example 3-5) and bright, respectively. Yellow-green (Example 3-6) and yellow-green (Example 3-7) are confirmed.
活性炭の添加量を１０ｍｇとする実施例３−５〜３−７に係る分散液サンプルの系では、加熱処理の温度条件を高温側に設定することで、より速く活性炭が分散状態となることが確認され、また、実施例３−５〜３−７では、過酸化水素水の完全気化により、炭素分解反応を停止させることができている。また、図４（ａ）に示すように、最高温度で加熱した実施例３−７（１２０℃）よりも低い温度で加熱した実施例３−６（１１０℃）の方が、高い発光強度を得ることができている。所望の発光特性を得る観点から、こうした実験例を通じて、適宜、加熱処理の温度の最適条件を見出すことができる。 In the dispersion sample system according to Examples 3-5 to 3-7 in which the addition amount of activated carbon is 10 mg, the activated carbon may be dispersed more quickly by setting the temperature condition of the heat treatment to the high temperature side. In addition, in Examples 3-5 to 3-7, it was possible to stop the carbon decomposition reaction by complete vaporization of the hydrogen peroxide solution. In addition, as shown in FIG. 4A, Example 3-6 (110 ° C.) heated at a lower temperature than Example 3-7 (120 ° C.) heated at the highest temperature has higher emission intensity. Have been able to get. From the viewpoint of obtaining desired light emission characteristics, the optimum conditions for the temperature of the heat treatment can be appropriately found through such experimental examples.
（実施例４：逐次加熱処理法により得られる炭素量子ドットの発光特性の検討）
＜１回目＞
１５ｍｇの活性炭（関西熱化学社製、ＭＳＣ３０）を測り取り、１ｍＬの３０ｗｔ％過酸化水素水に添加した。磁気撹拌しながら５０℃、８０℃、１００℃、１１０℃、１２０℃にて加熱処理を行った。ここでは、加熱処理の温度条件を５０℃とした例を実施例４−１−１、８０℃とした例を実施例４−２−１、１００℃とした例を実施例４−３−１、１１０℃とした例を実施例４−４−１、１２０℃とした例を実施例４−５−１とする。
実施例４−１−１（５０℃）では、加熱処理開始後、活性炭が徐々に分散状態となり、約５０時間の加熱処理で、活性炭の粉末を処理容器内に残して、処理液が完全に蒸発した。次いで、８ｍＬの蒸留水を加え、一旦蒸留水を完全に蒸発させた後、再度、８ｍＬの蒸留水を加えて撹拌した。この分散液に対し、３，５００ｒｐｍで５分間遠心分離をかけ、固液分離させ、活性炭を含む上澄み液を取り出し、１回目の分散液サンプルを得た。
実施例４−２−１（８０℃）では、約２１時間の加熱処理で処理液が完全に蒸発した。得られた活性炭の粉末に対して、実施例４−１−１と同様の処理を行って、１回目の分散液サンプルを得た。
実施例４−３−１（１００℃）では、約５時間の加熱処理で処理液が完全に蒸発した。得られた活性炭の粉末に対して、実施例４−１−１と同様の処理を行って、１回目の分散液サンプルを得た。
実施例４−４−１（１１０℃）では、約２時間の加熱処理で処理液が完全に蒸発した。得られた活性炭の粉末に対して、実施例４−１−１と同様の処理を行って、１回目の分散液サンプルを得た。
実施例４−５−１（１２０℃）では、約１時間の加熱処理で処理液が完全に蒸発した。得られた活性炭の粉末に対して、実施例４−１−１と同様の処理を行って、１回目の分散液サンプルを得た。
(Example 4: Examination of light emission characteristics of carbon quantum dots obtained by sequential heating method)
<First time>
15 mg of activated carbon (manufactured by Kansai Thermal Chemical Co., Ltd., MSC30) was measured and added to 1 mL of 30 wt% hydrogen peroxide solution. Heat treatment was performed at 50 ° C., 80 ° C., 100 ° C., 110 ° C., and 120 ° C. with magnetic stirring. Here, an example in which the temperature condition of the heat treatment is set to 50 ° C. is Example 4-1-1, an example in which 80 ° C. is set in Example 4-2-1, and an example in which 100 ° C. is set in Example 4-3-1 An example in which the temperature is 110 ° C. is referred to as Example 4-4-1, and an example in which the temperature is 120 ° C. is referred to as Example 4-5-1.
In Example 4-1-1 (50 ° C.), after the heat treatment was started, the activated carbon gradually became dispersed, and the heat treatment for about 50 hours left the activated carbon powder in the treatment container, so that the treatment liquid was completely Evaporated. Next, 8 mL of distilled water was added and once distilled water was completely evaporated, 8 mL of distilled water was added again and stirred. The dispersion was centrifuged at 3,500 rpm for 5 minutes to cause solid-liquid separation, and the supernatant liquid containing activated carbon was taken out to obtain a first dispersion liquid sample.
In Example 4-2-1 (80 ° C.), the treatment liquid was completely evaporated by the heat treatment for about 21 hours. The obtained activated carbon powder was treated in the same manner as in Example 4-1-1 to obtain a first dispersion sample.
In Example 4-3-1 (100 ° C.), the treatment liquid was completely evaporated by the heat treatment for about 5 hours. The obtained activated carbon powder was treated in the same manner as in Example 4-1-1 to obtain a first dispersion sample.
In Example 4-4-1 (110 ° C.), the treatment liquid was completely evaporated by the heat treatment for about 2 hours. The obtained activated carbon powder was treated in the same manner as in Example 4-1-1 to obtain a first dispersion sample.
In Example 4-5-1 (120 ° C.), the treatment liquid was completely evaporated by the heat treatment for about 1 hour. The obtained activated carbon powder was treated in the same manner as in Example 4-1-1 to obtain a first dispersion sample.
図５（ａ）に、励起波長３６５ｎｍの光で励起させた実施例４−１−１〜４−５−１に係る各分散液サンプル（１回目）の蛍光スペクトルを示す。なお、蛍光スペクトルは、分光蛍光光度計（島津製作所社製、ＲＦ−５３００ＰＣ）にて測定した。
また、図５（ｂ）に実施例４−１−１〜４−５−１に係る各分散液サンプル（１回目）に対して、ブラックライト（波長３６５ｎｍ）照射前後の写真を示す。該図５（ｂ）中、上段がブラックライト照射前の写真であり、下段がブラックライト照射後の写真である。また、左側から実施例４−１−１、実施例４−２−１、実施例４−３−１、実施例４−４−１、実施例４−５−１に係る分散液サンプルの写真であり、上段、下段のそれぞれで、薄い褐色と薄い青色（実施例４−１−１）、無色透明と薄い青色（実施例４−２−１）、薄い褐色と明るい水色（実施例４−３−１）、無色透明とやや明るい水色（実施例４−４−１）、無色透明と青色（実施例４−５−１）が確認される。
FIG. 5A shows the fluorescence spectrum of each dispersion liquid sample (first time) according to Examples 4-1-1 to 4-5-1 excited with light having an excitation wavelength of 365 nm. The fluorescence spectrum was measured with a spectrofluorometer (manufactured by Shimadzu Corporation, RF-5300PC).
Moreover, the photograph before and behind black light (wavelength 365nm) irradiation with respect to each dispersion liquid sample (1st time) which concerns on Example 4-1-1 to 4-5-1 is shown in FIG.5 (b). In FIG. 5B, the upper part is a photograph before the black light irradiation, and the lower part is a photograph after the black light irradiation. Moreover, the photograph of the dispersion liquid sample which concerns on Example 4-1-1, Example 4-2-1, Example 4-3-1, Example 4-4-1, and Example 4-5-1 from the left side. In each of the upper stage and the lower stage, light brown and light blue (Example 4-1-1), colorless and transparent and light blue (Example 4-2-1), light brown and light blue (Example 4- 3-1) Colorless and transparent and slightly light blue (Example 4-4-1), colorless and transparent and blue (Example 4-5-1) are confirmed.
図５（ａ）に示すように、実施例４−１−１、実施例４−２−１では、発光強度が実施例４−３−１よりも低いことが確認される。発光強度は、活性炭由来の発光可能な炭素粒子の濃度を反映しているものと推察される。こうした観点から、低温側の実施例４−１−１（５０℃）、実施例４−２−１（８０℃）では、１回目の処理の段階で発光可能な炭素粒子が一部にしか生じていないものと推察される。
また、実施例４−４−１、実施例４−５−１も、実施例４−３−１より低い発光強度であることが確認される。３０％過酸化水素水の沸点は、約１０６℃であり、高温側の実施例４−４−１（１１０℃）、実施例４−５−１（１２０℃）の加熱処理では、過酸化水素の蒸発が激しくなった。高温での加熱処理は、炭素の分解反応を促進させるが、過酸化水素の蒸発と炭素の分解反応が競争過程となり、結果的に実施例４−３−１（１００℃）で加熱処理する場合と比べ、活性炭由来の発光可能な炭素粒子の量が少なかったものと推察される。
As shown to Fig.5 (a), in Example 4-1-1 and Example 4-2-1, it is confirmed that emitted light intensity is lower than Example 4-3-1. It is presumed that the emission intensity reflects the concentration of luminescent carbon particles derived from activated carbon. From this viewpoint, in Example 4-1-1 (50 ° C.) and Example 4-2-1 (80 ° C.) on the low temperature side, only a part of carbon particles capable of emitting light is generated in the first treatment stage. It is assumed that it is not.
Moreover, it is confirmed that Example 4-4-1 and Example 4-5-1 also have lower emission intensity than Example 4-3-1. The boiling point of 30% hydrogen peroxide water is about 106 ° C., and in the heat treatment of Example 4-4-1 (110 ° C.) and Example 4-5-1 (120 ° C.) on the high temperature side, hydrogen peroxide The evaporation of became intense. Heat treatment at a high temperature promotes carbon decomposition reaction, but the evaporation of hydrogen peroxide and carbon decomposition reaction become a competitive process, resulting in heat treatment in Example 4-3-1 (100 ° C.). The amount of carbon particles capable of light emission derived from activated carbon is estimated to be small compared to.
また、図５（ａ）に示すように、実施例４−１−１、４−２−１に係る各分散液サンプルは、４００ｎｍ〜６５０ｎｍの波長領域でブロードなピークとなり、各波長における発光強度差も比較的均一なため、液中に異なるサイズ或いは構造の発光炭素粒子が生成されているものと推測される。
また、実施例４−５−１（１２０℃）の分散液サンプルのピーク波長が、実施例４−４−１（１１０℃）の分散液サンプルのピーク波長よりも長波長側にシフトしているのは、炭素の分解反応がより十分には進行し、比較的小さい炭素粒子がより多く含まれているためであると推測される。
Moreover, as shown to Fig.5 (a), each dispersion liquid sample which concerns on Example 4-1-1, 4-2-1 becomes a broad peak in the wavelength range of 400 nm-650 nm, and the luminescence intensity in each wavelength. Since the difference is also relatively uniform, it is estimated that luminescent carbon particles having different sizes or structures are generated in the liquid.
Moreover, the peak wavelength of the dispersion liquid sample of Example 4-5-1 (120 degreeC) has shifted to the long wavelength side rather than the peak wavelength of the dispersion liquid sample of Example 4-4-1 (110 degreeC). This is presumably because the carbon decomposition reaction proceeds more sufficiently and contains a larger number of relatively small carbon particles.
＜２回目＞
１回目の加熱処理における遠心分離により、固体として分離された活性炭由来の炭素粉末に対し、過酸化水素水を添加し、同じ加熱温度で２回目の加熱処理を行った。
実施例４−１−１（５０℃）、実施例４−２−１（８０℃）の加熱処理において残留した炭素粉末が入った処理容器内に１ｍＬの３０ｗｔ％過酸化水素水を加え、それぞれ、５０℃、８０℃での加熱処理を行った。ここでは、５０℃で２回目の加熱処理を行った例を実施例４−１−２、８０℃で２回目の加熱処理を行った例を実施例４−２−２とする。
また、実施例４−３−１（１００℃）、実施例４−４−１（１１０℃）、実施例４−５−１（１２０℃）の加熱処理において残留した炭素粉末が入った処理容器内に０．２ｍＬの３０ｗｔ％過酸化水素水と０．８ｍＬの蒸留水を加え、それぞれ、１００℃、１１０℃、１２０℃での加熱処理を行った。ここでは、１００℃で２回目の加熱処理を行った例を実施例４−３−２、１１０℃で２回目の加熱処理を行った例を実施例４−４−２、１２０℃で２回目の加熱処理を行った例を実施例４−５−２とする。
<Second time>
Hydrogen peroxide water was added to the carbon powder derived from activated carbon separated as a solid by centrifugation in the first heat treatment, and the second heat treatment was performed at the same heating temperature.
1 mL of 30 wt% hydrogen peroxide solution was added to the processing vessel containing the carbon powder remaining in the heat treatment of Example 4-1-1 (50 ° C.) and Example 4-2-1 (80 ° C.), respectively. , Heat treatment at 50 ° C. and 80 ° C. was performed. Here, an example in which the second heat treatment is performed at 50 ° C. is an example 4-1-2, and an example in which the second heat treatment is performed at 80 ° C. is an example 4-2-2.
Moreover, the processing container containing the carbon powder which remained in the heat processing of Example 4-3-1 (100 degreeC), Example 4-4-1 (110 degreeC), and Example 4-5-1 (120 degreeC). 0.2 mL of 30 wt% hydrogen peroxide solution and 0.8 mL of distilled water were added therein, and heat treatment was performed at 100 ° C., 110 ° C., and 120 ° C., respectively. Here, the example of performing the second heat treatment at 100 ° C. is Example 4-3-2, the example of performing the second heat treatment at 110 ° C. is the second example of Example 4-4-2, 120 ° C. An example of performing the heat treatment is referred to as Example 4-5-2.
実施例４−１−２（５０℃）では、加熱処理開始後、炭素粉末が徐々に分散状態となり、処理液中に溶解するとともに、約４９時間の加熱処理で炭素粉末を残して処理液が完全に蒸発した。次いで、８ｍＬの蒸留水を加え、一旦蒸留水を完全に蒸発させた後、再度、８ｍＬの蒸留水を加えて撹拌した。この分散液に対して、孔径０．１μｍのセルロースアセテートタイプのメンブレンフィルタを用いて吸引濾過し、フィルタを通過した濾液として２回目の分散液サンプルを得た。
実施例４−２−２（８０℃）では、熱処理開始後、炭素粉末が徐々に分散状態となり、処理液中に溶解するとともに、約２４時間の加熱処理で炭素粉末を残して処理液が完全に蒸発した。得られた炭素粉末に対して、実施例４−１−２と同様の処理を行って、２回目の分散液サンプルを得た。
実施例４−３−２（１００℃）では、熱処理開始後、炭素粉末が徐々に分散状態となり、処理液中に溶解するとともに、約５時間の加熱処理で炭素粉末を残して処理液が完全に蒸発した。得られた炭素粉末に対して、実施例４−１−２と同様の処理を行って、２回目の分散液サンプルを得た。
実施例４−４−２（１１０℃）では、熱処理開始後、炭素粉末が徐々に分散状態となったが、過酸化水素の蒸発が激しくなり、処理液中に完全に溶解することなく、一部が処理液中に沈殿し、約２時間の加熱処理で炭素粉末を残して処理液が完全に蒸発した。次いで、８ｍＬの蒸留水を加え、一旦蒸留水を完全に蒸発させた後、再度、８ｍＬの蒸留水を加えて撹拌した。この分散液に対し、３，５００ｒｐｍで５分間遠心分離をかけ、固液分離させ、溶解した炭素粉末を含む上澄み液を取り出した。この上澄み液に対して、孔径０．１μｍのセルロースアセテートタイプのメンブレンフィルタを用いて吸引濾過し、フィルタを通過した濾液として２回目の分散液サンプルを得た。
実施例４−５−２（１２０℃）でも、熱処理開始後、炭素粉末が徐々に分散状態となったが、過酸化水素の蒸発が激しくなり、処理液中に完全に溶解することなく、一部が処理液中に沈殿し、約１時間の加熱処理で炭素粉末を残して処理液が完全に蒸発した。得られた炭素粉末に対して、実施例４−４−２と同様の処理を行って、２回目の分散液サンプルを得た。
In Example 4-1-2 (50 ° C.), after the heat treatment was started, the carbon powder gradually dispersed and dissolved in the treatment liquid, and the treatment liquid was left in the heat treatment for about 49 hours to leave the carbon powder. Completely evaporated. Next, 8 mL of distilled water was added and once distilled water was completely evaporated, 8 mL of distilled water was added again and stirred. The dispersion was subjected to suction filtration using a cellulose acetate type membrane filter having a pore size of 0.1 μm, and a second dispersion sample was obtained as the filtrate that passed through the filter.
In Example 4-2-2 (80 ° C.), after the start of heat treatment, the carbon powder gradually disperses and dissolves in the treatment liquid, and the treatment liquid is completely left in the heat treatment for about 24 hours, leaving the carbon powder. Evaporated to. The obtained carbon powder was treated in the same manner as in Example 4-1-2 to obtain a second dispersion sample.
In Example 4-3-2 (100 ° C.), after the start of heat treatment, the carbon powder gradually becomes dispersed and dissolves in the treatment liquid, and the treatment liquid is completely left in the heat treatment for about 5 hours, leaving the carbon powder. Evaporated to. The obtained carbon powder was treated in the same manner as in Example 4-1-2 to obtain a second dispersion sample.
In Example 4-4-2 (110 ° C.), the carbon powder gradually became dispersed after the start of the heat treatment, but the evaporation of hydrogen peroxide became violent, and the carbon powder was not completely dissolved in the treatment liquid. Part of the solution was precipitated in the treatment solution, and the treatment solution was completely evaporated leaving a carbon powder by heat treatment for about 2 hours. Next, 8 mL of distilled water was added and once distilled water was completely evaporated, 8 mL of distilled water was added again and stirred. The dispersion was centrifuged at 3,500 rpm for 5 minutes to cause solid-liquid separation, and a supernatant containing dissolved carbon powder was taken out. The supernatant liquid was subjected to suction filtration using a cellulose acetate type membrane filter having a pore diameter of 0.1 μm, and a second dispersion sample was obtained as the filtrate that passed through the filter.
Even in Example 4-5-2 (120 ° C.), the carbon powder gradually became dispersed after the start of the heat treatment, but the evaporation of hydrogen peroxide became violent, and the carbon powder was not completely dissolved in the treatment liquid. Part of the solution was precipitated in the treatment solution, and the treatment solution was completely evaporated leaving a carbon powder by heat treatment for about 1 hour. The resulting carbon powder was treated in the same manner as in Example 4-4-2 to obtain a second dispersion sample.
また、実施例４−１−２、実施例４−２−２、実施例４−３−２における処理において、フィルタ上に留まった炭素粉末残渣を蒸留水で洗い集め、各分散液サンプルを調製した。これら分散液サンプルをそれぞれ、実施例４−１−２ｆ、実施例４−２−２ｆ、実施例４−３−２ｆとする。 Further, in the treatments in Example 4-1-2, Example 4-2-2, and Example 4-3-2, the carbon powder residue remaining on the filter was washed and collected with distilled water to prepare each dispersion liquid sample. did. These dispersion liquid samples are referred to as Example 4-1-2f, Example 4-2-2f, and Example 4-3-2f, respectively.
図６（ａ）に、励起波長３６５ｎｍの光で励起させた実施例４−１−２〜４−５−２に係る各分散液サンプル（２回目）の蛍光スペクトルを示す。なお、蛍光スペクトルは、分光蛍光光度計（島津製作所社製、ＲＦ−５３００ＰＣ）にて測定した。
また、図６（ｂ）に実施例４−１−２〜４−５−２に係る各分散液サンプル（２回目）に対して、ブラックライト（波長３６５ｎｍ）照射前後の写真を示す。該図６（ｂ）中、上段がブラックライト照射前の写真であり、下段がブラックライト照射後の写真である。また、左側から実施例４−１−２、実施例４−２−２、実施例４−３−２、実施例４−４−２、実施例４−５−２に係る分散液サンプルの写真であり、上段、下段のそれぞれで、暗めの薄い褐色と暗めの緑色（実施例４−１−２）、暗めの薄い褐色と明るい緑色（実施例４−２−２）、暗めの濃い褐色とやや青色味を帯びた緑色（実施例４−３−２）、褐色とやや緑色味を帯びた黄色（実施例４−４−１）、薄い黄色と明るい黄緑色（実施例４−５−２）が確認される。
図６（ａ）に示すように、２回の加熱処理を行った各分散液サンプルでは、１回目の加熱処理を行って得られた各分散液サンプルと異なる発光特性が得られることが確認される。
FIG. 6A shows the fluorescence spectrum of each dispersion liquid sample (second time) according to Examples 4-1 to 4-5-2 excited with light having an excitation wavelength of 365 nm. The fluorescence spectrum was measured with a spectrofluorometer (manufactured by Shimadzu Corporation, RF-5300PC).
Moreover, the photograph before and behind black light (wavelength 365nm) irradiation is shown to FIG.6 (b) with respect to each dispersion liquid sample (2nd time) which concerns on Examples 4-1-2 to 4-5-2. In FIG. 6B, the upper part is a photograph before the black light irradiation, and the lower part is a photograph after the black light irradiation. Also, from the left side, photographs of dispersion samples according to Example 4-1-2, Example 4-2-2, Example 4-3-2, Example 4-4-2, and Example 4-5-2 In each of the upper stage and the lower stage, dark light brown and dark green (Example 4-1-2), dark light brown and light green (Example 4-2-2), dark dark brown and Slightly blueish green (Example 4-3-2), brown and slightly greenish yellow (Example 4-4-1), light yellow and light yellowish green (Example 4-5-2) ) Is confirmed.
As shown in FIG. 6 (a), it was confirmed that each dispersion liquid sample subjected to the two heat treatments can obtain different light emission characteristics from each dispersion liquid sample obtained by performing the first heat treatment. The
＜３回目＞
１１０℃、１２０℃の温度条件で行った１回目、２回目の加熱処理において、処理液中に溶解せず、なお残留した活性炭由来の炭素粉末に対し、過酸化水素水を添加し、同じ加熱温度で３回目の加熱処理を行った。
実施例４−４−２（１１０℃）、実施例４−５−２（１２０℃）の加熱処理において残留した炭素粉末が入った処理容器内に０．２ｍＬの３０ｗｔ％過酸化水素水と０．８ｍＬの蒸留水を加え、それぞれ、１１０℃、１２０℃での加熱処理を行った。ここでは、１１０℃で３回目の加熱処理を行った例を実施例４−４−３、１２０℃で３回目の加熱処理を行った例を実施例４−５−３とする。
実施例４−４−３（１１０℃）では、加熱処理開始後、炭素粉末が徐々に分散状態となり、処理液中に溶解するとともに、約２時間の加熱処理で炭素粉末を残して処理液が完全に蒸発した。次いで、８ｍＬの蒸留水を加え、一旦蒸留水を完全に蒸発させた後、再度、８ｍＬの蒸留水を加えて撹拌した。この分散液に対して、孔径０．１μｍのセルロースアセテートタイプのメンブレンフィルタを用いて吸引濾過し、フィルタを通過した濾液として３回目の分散液サンプルを得た。
実施例４−５−３（１２０℃）では、加熱処理開始後、炭素粉末が徐々に分散状態となり、処理液中に溶解するとともに、約１時間の加熱処理で炭素粉末を残して処理液が完全に蒸発した。得られた炭素粉末に対して、実施例４−４−３と同様の処理を行って、３回目の分散液サンプルを得た。
<3rd time>
In the first and second heat treatments performed at 110 ° C. and 120 ° C., hydrogen peroxide water was added to the remaining carbon powder derived from activated carbon that did not dissolve in the treatment liquid, and the same heating. A third heat treatment was performed at the temperature.
0.2 mL of 30 wt% hydrogen peroxide water and 0 in the processing vessel containing the carbon powder remaining in the heat treatment of Example 4-4-2 (110 ° C.) and Example 4-5-2 (120 ° C.) .8 mL of distilled water was added, and heat treatment was performed at 110 ° C. and 120 ° C., respectively. Here, an example in which the third heat treatment is performed at 110 ° C. is an example 4-4-3, and an example in which the third heat treatment is performed at 120 ° C. is referred to as an example 4-5-3.
In Example 4-4-3 (110 ° C.), after the heat treatment was started, the carbon powder gradually dispersed and dissolved in the treatment liquid, and the treatment liquid was left in the heat treatment for about 2 hours to leave the carbon powder. Completely evaporated. Next, 8 mL of distilled water was added and once distilled water was completely evaporated, 8 mL of distilled water was added again and stirred. The dispersion was subjected to suction filtration using a cellulose acetate type membrane filter having a pore size of 0.1 μm, and a third dispersion sample was obtained as the filtrate that passed through the filter.
In Example 4-5-3 (120 ° C.), after the heat treatment was started, the carbon powder gradually dispersed and dissolved in the treatment liquid, and the treatment liquid was left in the heat treatment for about 1 hour to leave the carbon powder. Completely evaporated. The resulting carbon powder was treated in the same manner as in Example 4-4-3 to obtain a third dispersion sample.
また、実施例４−４−３、実施例４−５−３における処理において、フィルタ上に留まった炭素粉末残渣を蒸留水で洗い集め、各分散液サンプルを調製した。これら分散液サンプルをそれぞれ、実施例４−４−３ｆ、実施例４−５−３ｆとする。 Moreover, in the processing in Example 4-4-3 and Example 4-5-3, the carbon powder residue remaining on the filter was washed and collected with distilled water to prepare each dispersion liquid sample. These dispersion liquid samples are referred to as Example 4-4-3f and Example 4-5-3f, respectively.
図７（ａ）に、励起波長３６５ｎｍの光で励起させた実施例４−４−３、実施例４−５−３に係る各分散液サンプル（３回目）の蛍光スペクトルを示す。なお、蛍光スペクトルは、分光蛍光光度計（島津製作所社製、ＲＦ−５３００ＰＣ）にて測定した。
また、図７（ｂ）に実施例４−４−３、実施例４−５−３に係る各分散液サンプル（３回目）に対して、ブラックライト（波長３６５ｎｍ）照射前後の写真を示す。該図７（ｂ）中、上段がブラックライト照射前の写真であり、下段がブラックライト照射後の写真である。また、左側から実施例４−４−３、実施例４−５−３に係る分散液サンプルの写真であり、上段、下段のそれぞれで、薄い褐色と黄緑色（実施例４−４−３）、褐色とやや褐色味を帯びた緑色（実施例４−５−３）が確認される。
図７（ａ）に示すように、３回の加熱処理を行った各分散液サンプルでは、１回目、２回目の加熱処理を行って得られた各分散液サンプルと異なる発光特性が得られることが確認される。
FIG. 7A shows the fluorescence spectrum of each dispersion liquid sample (third time) according to Example 4-4-3 and Example 4-5-3 excited with light having an excitation wavelength of 365 nm. The fluorescence spectrum was measured with a spectrofluorometer (manufactured by Shimadzu Corporation, RF-5300PC).
Moreover, the photograph before and behind black light (wavelength 365nm) irradiation is shown to FIG.7 (b) with respect to each dispersion liquid sample (3rd time) based on Example 4-4-3 and Example 4-5-3. In FIG. 7B, the upper part is a photograph before the black light irradiation, and the lower part is a photograph after the black light irradiation. Moreover, it is a photograph of the dispersion liquid sample which concerns on Example 4-4-3 and Example 4-5-3 from the left side, and is light brown and yellowish green in each of the upper stage and the lower stage (Example 4-4-3). A brownish and slightly brownish green (Example 4-5-3) is confirmed.
As shown in FIG. 7 (a), each dispersion sample that has been subjected to the heat treatment three times can obtain light emission characteristics different from those of the respective dispersion samples obtained by performing the first and second heat treatments. Is confirmed.
図８（ａ）に、励起波長３６５ｎｍの光で励起させた実施例４−１−２ｆ〜４−３−２ｆ及び実施例４−４−３ｆ、４−５−３ｆに係る各分散液サンプル（２回目フィルタ後及び３回目フィルタ後）の蛍光スペクトルを示す。なお、蛍光スペクトルは、分光蛍光光度計（島津製作所社製、ＲＦ−５３００ＰＣ）にて測定した。
また、図８（ｂ）に実施例４−１−２ｆ〜４−３−２ｆ及び実施例４−４−３ｆ、４−５−３ｆに係る各分散液サンプル（２回目フィルタ後及び３回目フィルタ後）に対して、ブラックライト（波長３６５ｎｍ）照射前後の写真を示す。該図８（ｂ）中、上段がブラックライト照射前の写真であり、下段がブラックライト照射後の写真である。また、左側から実施例４−１−２ｆ、実施例４−２−２ｆ、実施例４−３−２ｆ、実施例４−４−３ｆ、実施例４−５−３ｆに係る分散液サンプルの写真であり、上段、下段のそれぞれで、黒褐色と緑色（実施例４−１−２ｆ）、薄い黒褐色とやや黄色味を帯びた緑色（実施例４−２−２ｆ）、黒褐色とやや赤色味を帯びた褐色（実施例４−３−２ｆ）、濃い褐色と黄緑色（実施例４−４−３ｆ）、濃い褐色とより濃い褐色を帯びた緑褐色（実施例４−５−３ｆ）が確認される。
これら図８（ａ）、（ｂ）に示すようにフィルタを通過しない０．１μｍを超えるサイズの炭素粒子中にも、より長い波長の光を発光するサイズの大きい粒子が含まれているか、より長い波長の光を発光する粒子構造が含まれていることが分かる。
FIG. 8A shows the respective dispersion liquid samples according to Examples 4-1-2f to 4-3-2f and Examples 4-4-3f and 4-5-3f excited with light having an excitation wavelength of 365 nm ( The fluorescence spectra after the second filter and after the third filter are shown. The fluorescence spectrum was measured with a spectrofluorometer (manufactured by Shimadzu Corporation, RF-5300PC).
Further, FIG. 8B shows each of the dispersion samples according to Examples 4-1-2f to 4-3-2f and Examples 4-4-3f and 4-5-3f (after the second filter and the third filter). For (after), photographs before and after irradiation with black light (wavelength 365 nm) are shown. In FIG. 8B, the upper part is a photograph before the black light irradiation, and the lower part is a photograph after the black light irradiation. Moreover, the photograph of the dispersion liquid sample which concerns on Example 4-1-2f, Example 4-2-2f, Example 4-3-2f, Example 4-4-3f, and Example 4-5-3f from the left side In each of the upper and lower stages, black brown and green (Example 4-1-2f), light black brown and slightly yellowish green (Example 4-2-2f), black brown and slightly reddish Dark brown (Example 4-3-2f), dark brown and yellowish green (Example 4-4-3f), dark brown and dark brownish-brown (Example 4-5-3f) The
As shown in FIGS. 8A and 8B, the carbon particles having a size exceeding 0.1 μm that do not pass through the filter also contain large-sized particles that emit light having a longer wavelength. It can be seen that a particle structure that emits light of a long wavelength is included.
以上に示した逐次処理法によれば、炭素原料量、過酸化水素濃度、処理温度、処理回数の組み合わせを変えていけば、水に不溶な炭素粉末から、効率よくバラエティに富んだ発光特性を示す溶解性の炭素ナノ粒子（炭素量子ドット）に製造することができる。 According to the sequential processing method shown above, by changing the combination of the amount of carbon raw material, the concentration of hydrogen peroxide, the processing temperature, and the number of times of processing, it is possible to efficiently produce a wide variety of light emission characteristics from carbon powder insoluble in water. The soluble carbon nanoparticles (carbon quantum dots) shown can be manufactured.
本発明の前記炭素量子ドットは、水溶性であり、毒性がないことから、汚染物診断・計測・除去分野、バイオ（分子及び細胞）イメージング・センシング・ラべリング・遺伝子発現研究試薬、ＤＤＳ（Ｄｒｕｇ Ｄｅｌｉｖｅｒｙ Ｓｙｓｔｅｍ）分野、太陽光エネルギー変換用等の量子ドット太陽電池分野など、電気、化学、バイオの種々の分野で広く利用できる。 Since the carbon quantum dots of the present invention are water-soluble and non-toxic, the field of contaminant diagnosis / measurement / removal, bio (molecular and cell) imaging, sensing, labeling, gene expression research reagents, DDS ( It can be widely used in various fields of electricity, chemistry, and biotechnology, such as the field of Drug Delivery System) and the field of quantum dot solar cells for solar energy conversion.
Claims (7)
前記炭素量子ドット生成液中の前記炭素量子ドットと前記過酸化水素を分離して前記分解反応を停止させ、前記炭素量子ドットを取得する炭素量子ドット取得工程と、
を含むことを特徴とする炭素量子ドットの製造方法。 A carbon material and a hydrogen peroxide solution having a concentration of 50 wt% or less are mixed, a mixed solution of the carbon material and the hydrogen peroxide solution is heated at a temperature of 80 ° C. or more, and hydrogen peroxide in the carbon material Carbon quantum dot production liquid preparation step of preparing a carbon quantum dot production liquid by causing carbon to decompose and producing carbon quantum dots derived from the carbon material,
Separating the carbon quantum dots and the hydrogen peroxide in the carbon quantum dot production liquid to stop the decomposition reaction and obtaining the carbon quantum dots; and
The manufacturing method of the carbon quantum dot characterized by including.
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