CN102849722B - Carbon nano-dot, and preparation method and application thereof - Google Patents

Abstract

The invention discloses a carbon nano-dot, and a preparation method and an application thereof, and solves a problem that the application of present nano-dots is restricted because of high preparation cost and easy fluorescent quenching appearance of an aggregate state. According to the invention, the carbon nano-dot having a high fluorescence quantum efficiency is prepared through adopting a polycarboxyl or polyhydroxy contained organic compound, or an amino acid as a raw material, and urea as a surface passivation modification agent, and through a microwave process, and a carbon nano-dot fluorescent ink is prepared through using the carbon nano-dot. The preparation method disclosed in the invention has the advantages of simplicity, low cost and convenient large-scale production; the fluorescent quenching of the prepared carbon nano-dot on the surface of a biological product does not appear, and the highest fluorescence quantum efficiency is 42%; and the prepared carbon nano-dot fluorescent ink is nontoxic, does not generate a precipitate after long-time dispose, and can be applied to the biological imaging field, the biological product identification field, the information storage field, the information encryption field, the false proof field, the illumination display field, the photovoltaic device field and the like.

Description

A kind of carbon nano dot and its preparation method and application

technical field

The invention relates to a carbon nano-dot and its preparation method and application, belonging to the field of nano-material science.

Background technique

Carbon nanodots, a new type of nanomaterial, have attracted increasing attention due to their many unique advantages (such as chemical stability, no light flickering, resistance to photobleaching, non-toxicity, and excellent biocompatibility) ( Luminescent Carbon Nanodots: Emergent Nanolights, Sheila N. Baker, Gary A. Baker, Angew. Chem. Int. Ed., 2010, 49, 6726). Carbon nanodots with fluorescent properties have potential applications in biological imaging, lasers, optoelectronic devices and other fields.

Carbon nanodots can be prepared by various methods, such as laser ablation, electrochemical method, arc discharge method, pyrolysis method, ultrasonic generation and microwave method. Among these methods, the microwave method is favored due to its low cost and relative environmental friendliness. The microwave method can rapidly increase the temperature of the reactant, accelerate the reaction speed and pyrolysis speed, realize the effect of the pyrolysis method and greatly shorten the preparation time. Carbon nanodots prepared by pyrolysis and microwave methods usually use organic compounds containing polycarboxylates or polyhydroxyl groups as raw materials, for example, literature (Microwave synthesis of fluorescentcarbon nanoparticles with electrochemiluminescence properties, Hui Zhu, Xiaolei Wang, Yali Li, Zhongjun Wang, Fan Yang, Xiurong Yang, Chem. Commun., 2009, 51), using sugar derivatives such as glucose and fructose as raw materials, prepared carbon nano-dots by microwave method; literature (Microwave assisted one-step green synthesis of cell-permeable multicolor photoluminescent carbon dots without surface passivation reagents, Xiaohui Wang, Konggang Qu, Bailu Xu, Jinsong Ren, Xiaogang Qu, J. Mater. Chem., 2011, 21, 244), using glycerol as raw material, prepared carbon nanodots by microwave method; literature (Tuning of photoluminescence on different surface functionalized carbon quantum dots, Sourov Chandra, Shaheen H.Pathan, Shouvik Mitra, Binita H. Modha, Arunava Goswami, Panchanan Pramanik, RSC Adv., 2012, 2, 3602), with chitosan, Alginic acid and starch were used as raw materials, and carbon nanodots were prepared by microwave method.

In order to obtain carbon nanodots with fluorescent properties, it is usually necessary to introduce surface passivation modifiers containing polymer chains. For example, literature (Microwave synthesis of fluorescent carbon nanoparticles with electrochemiluminescence properties, Hui Zhu, Xiaolei Wang, Yali Li, Zhongjun Wang, Fan Yang, Xiurong Yang, Chem. Commun., 2009, 51), derived from glucose and fructose In the absence of a surface passivation modifier, the carbon nanodots prepared by the microwave method exhibited very weak fluorescence. When polyethylene glycol (average molecular weight 200) was added as a surface passivation modifier, the The carbon nanodots prepared by the microwave method show enhanced fluorescence, and the fluorescence quantum efficiency is 3%-6%. However, the cost of the surface passivation modifier containing polymer chains is relatively high, and the residual surface passivation modifier containing polymer chains is not easy to remove. Carbon nanodots can have good dispersion properties in a dilute solution state, and dilute solutions of surface-passivated carbon nanodots can exhibit strong fluorescence properties. In the aggregated state, the nano-size effect of the material disappears, which will show a strong fluorescence quenching phenomenon, which greatly limits the application of this type of material in solid-state light-emitting systems. In the prior art, there is no carbon nanodot that has low preparation cost, simple preparation method, environmental protection, high fluorescence quantum yield in solid state system, and can be applied to daily life.

Contents of the invention

The purpose of the present invention is to reduce the preparation cost of fluorescent carbon nano-dots, broaden the application fields of carbon nano-dots, and provide a carbon nano-dot and its preparation method and application.

The invention provides a carbon nano-dot, which is prepared from an organic compound containing polycarboxylates or polyhydroxyl groups, or amino acid as a raw material, and urea as a surface passivating agent. The steps are as follows:

① Urea and organic compounds containing polycarboxylates or polyhydroxyl groups, or amino acids are formulated into an aqueous solution at a mass ratio of 0.1:1-4:1;

② The aqueous solution prepared in ① is reacted by microwave heating to obtain a brown-black solid;

③ Heating the brown-black solid under vacuum to remove residual small molecule compounds, and obtain carbon nanodots.

Preferably, the polycarboxy or polyhydroxy organic compound is citric acid, ethylenediaminetetraacetic acid, glycerol, glucose, fructose, sucrose, chitosan or starch; more preferably, citric acid, glycerol, glucose or sucrose; most preferred is citric acid.

Preferably, the amino acid is glycine or glutamic acid; more preferably, glycine.

Preferably, in step ①, the urea is prepared into a saturated aqueous solution with an organic compound containing polycarboxylate or polyhydroxyl groups, or an amino acid at a mass ratio of 0.1:1-4:1.

Preferably, in step ②, the aqueous solution is heated by a microwave with a power of 500-900W for 3-10 minutes, more preferably heated with a microwave with a power of 700W for 4 minutes.

Preferably, in step ③, the vacuum degree of the vacuum heating is 0.001-0.1 Pa, the heating temperature is 50-70 degrees Celsius, and the heating time is 1-2 hours; more preferably, the vacuum heating of the vacuum The temperature is 0.01 Pa, the heating temperature is 60 degrees Celsius, and the heating time is 1 hour.

The invention provides a method for preparing carbon nano-dots, comprising the following steps:

① Prepare an aqueous solution of urea and organic compounds containing polycarboxylates or polyhydroxyl groups, or amino acids at a mass ratio of 0.1:1-4:1;

② The aqueous solution prepared in ① is reacted by microwave heating to obtain a brown-black solid;

③ Heating the brown-black solid under vacuum to remove residual small molecular compounds to obtain carbon nanodots.

The present invention also provides an application of carbon nano-dots in the preparation of fluorescent ink. The carbon nano-dots are dissolved in water, centrifuged to obtain a supernatant; the obtained supernatant is diluted with water or an organic solvent to obtain carbon nano-dots. Dot fluorescent ink.

Preferably, the organic solvent is ethanol.

Preferably, the centrifugal speed is 2000-4000 rpm, and the time is 15-30 minutes; more preferably, the centrifugal speed is 3000 rpm, and the time is 20 minutes.

Beneficial effects of the present invention:

(1) The present invention uses organic compounds containing polycarboxylates or polyhydroxyl groups, or amino acids as raw materials, uses urea as a surface passivation modifier, and prepares carbon nano-dots with high fluorescent quantum efficiency by the microwave method, which overcomes the prior art to polymerize As a surface passivation modifier, the preparation cost of the compound chain is high, and the aggregation state is prone to fluorescence quenching. The preparation method of the present invention is simple, low in cost, and convenient for large-scale production;

(2) The maximum fluorescence quantum efficiency of the carbon nano-dots prepared by the present invention can be as high as 42%;

(3) The surface of carbon nanodots prepared by the present invention contains abundant amide groups and carboxyl groups, has excellent biocompatibility, and can be effectively dispersed and attached to the surface of solid biological products such as paper, plant fiber, fur, etc., avoiding carbon nanodots The dots are agglomerated to retain the strong fluorescence emission characteristics of carbon nanodots, and the fluorescence emission peak depends on the wavelength of the excitation light; the prepared carbon nanodots are attached to the surface of inorganic materials, plastics, and chemical fibers, and the carbon nanodots are agglomerated, and their fluorescence emission is greatly quenched According to this characteristic, the carbon nano-dots of the present invention can be used as the identification basis of biological products;

(4) The carbon nano-dot fluorescent ink prepared by the present invention is non-toxic, will not produce precipitation after long-term storage, has strong fluorescent characteristics, can safely mark fluorescent patterns on the skin, and can be applied to biological imaging, biological product identification, information Storage, information encryption, anti-counterfeiting, lighting display, photovoltaic devices and other fields.

Description of drawings

Fig. 1 is the transmission electron microscope picture of the carbon nano dot of embodiment 1 of the present invention;

Fig. 2 is the atomic force scanning picture of the carbon nano-dot of embodiment 1 of the present invention and the height curve of A to B position in the atomic force scanning picture;

Fig. 3 is the infrared spectrogram of the carbon nano-dot of embodiment 1 of the present invention;

Fig. 4 is the ultraviolet absorption spectrum of the aqueous solution of the carbon nano-dot of embodiment 12 of the present invention and the fluorescence emission spectrum figure under different excitation wavelengths;

Fig. 5 is the fluorescent emission spectrum curves at different excitation wavelengths after the carbon nanodot fluorescent ink of Example 12 of the present invention is dropped on filter paper and dried in the air;

Fig. 6 is the photo of the bean sprouts with fluorescent characteristics grown by the carbon nano-dot fluorescent ink of Example 12 of the present invention under different wave bands of light;

Fig. 7 is the fluorescence spectrogram of the urine of rats drinking the carbon nano dot fluorescent ink of Example 12 of the present invention at different excitation wavelengths for one month;

Fig. 8 is the fluorescence spectrogram of the urine under different excitation wavelengths when rats drink the carbon nano-dot fluorescent ink of Example 12 of the present invention for one month, stop drinking the carbon nano-dot fluorescent ink, and drink normal drinking water for 1 month ;

Fig. 9 is the fluorescence spectrogram of the urine of rats drinking normal drinking water under different excitation wavelengths;

Fig. 10 is the fluorescent photo of carbon nano dot fluorescent ink and commercially available green highlighter forming encrypted numbers on paper according to Example 12 of the present invention;

Fig. 11 is the photo of the cotton thread and the nylon fiber of the carbon nano-dot fluorescent ink of the embodiment 12 of the present invention contaminated and uncontaminated at different excitation wavelengths;

Fig. 12 is the photo of the fingerprint imprint left on paper using the carbon nano-dot fluorescent ink of embodiment 12 of the present invention under different excitation wavelengths;

Fig. 13 is a fluorescent photo of the fluorescent ink of the carbon nano-dot fluorescent ink in Example 12 of the present invention leaving a fluorescent pattern on the skin;

Fig. 14 is the fluorescence emission spectrum of the ethanol solution of the carbon nano-dots in Example 13 of the present invention under different excitation wavelengths;

15 is a fluorescence emission spectrum diagram of an aqueous solution of carbon nanodots in Example 14 of the present invention at different excitation wavelengths;

Fig. 16 is the fluorescence emission spectrum curves at different excitation wavelengths after the carbon nanodot fluorescent ink of Example 14 of the present invention is dropped on filter paper and air-dried;

Fig. 17 is the fluorescence emission spectrum of the ethanol solution of carbon nano-dots in Example 15 of the present invention under different excitation wavelengths;

18 is a fluorescence emission spectrum diagram of an aqueous solution of carbon nanodots in Example 16 of the present invention at different excitation wavelengths;

19 is a fluorescence emission spectrum diagram of an aqueous solution of carbon nanodots in Example 17 of the present invention at different excitation wavelengths;

Fig. 20 is the fluorescence emission spectrum curves at different excitation wavelengths after the carbon nanodot fluorescent ink of Example 17 of the present invention is dropped on filter paper and dried in the air;

Fig. 21 is the fluorescence emission spectrum of the ethanol solution of carbon nanodots in Example 18 of the present invention under different excitation wavelengths;

22 is a fluorescence emission spectrum diagram of an aqueous solution of carbon nanodots in Example 19 of the present invention at different excitation wavelengths;

23 is a fluorescence emission spectrum diagram of an aqueous solution of carbon nanodots in Example 20 of the present invention at different excitation wavelengths;

24 is a fluorescence emission spectrum diagram of an aqueous solution of carbon nanodots in Example 21 of the present invention at different excitation wavelengths;

FIG. 25 is a graph of fluorescence emission spectra of an aqueous solution of carbon nanodots in Example 22 of the present invention at different excitation wavelengths.

Detailed ways

The invention provides a carbon nano-dot, which is prepared from an organic compound containing polycarboxylates or polyhydroxyl groups, or amino acid as a raw material, and urea as a surface passivating agent. The steps are as follows:

① Prepare an aqueous solution of urea and organic compounds containing polycarboxylates or polyhydroxyl groups, or amino acids at a mass ratio of 0.1:1-4:1;

② The aqueous solution prepared in ① is reacted by microwave heating to obtain a brown-black solid;

③ The prepared brown-black solid is heated in vacuum to remove residual small molecule compounds to obtain carbon nanodots.

The performance of the carbon nano-dot prepared by the present invention depends on the mass ratio relationship between the raw material for preparing the carbon nano-dot and the selected raw material and urea; when urea and organic compounds containing many carboxyl groups or polyhydroxyl groups, or amino acids by mass ratio 0.1: 1-4:1 is formulated into a saturated aqueous solution, and the performance of the prepared carbon nano-dots is better; as long as organic compounds containing polycarboxylates or polyhydroxyl groups, or amino acids can be used as raw materials of the present invention to prepare carbon nano-dots; urea is not limited, commercial Just buy it.

Preferably, the organic compound containing polycarboxylate or polyhydroxyl is citric acid, ethylenediaminetetraacetic acid, glycerol, glucose, fructose, sucrose, chitosan or starch; more preferably, citric acid, glycerin, Glucose or sucrose; most preferred is citric acid.

Preferably, the amino acid is glycine or glutamic acid; more preferably, glycine.

Microwave heating in step ② of the present invention is a technology well known in the art. It is preferred that the aqueous solution in ① is put into a microwave oven and heated for 3-10 minutes by microwave power of 500-900W; more preferably, it is heated by microwave power of 700W 4 minutes.

Preferably, in step ③, the vacuum degree of the vacuum heating is 0.001-0.1 Pa, the heating temperature is 50-70 degrees Celsius, and the heating time is 1-2 hours; more preferably, the vacuum heating of the vacuum The temperature is 0.01 Pa, the heating temperature is 60 degrees Celsius, and the heating time is 1 hour.

The small molecule compound that step 3. of the present invention removes is mainly residual urea.

The invention provides a method for preparing carbon nano-dots, comprising the following steps:

① Urea and organic compounds containing polycarboxylates or polyhydroxyl groups, or amino acids are formulated into an aqueous solution at a mass ratio of 0.1:1-4:1;

② The aqueous solution prepared in ① is reacted by microwave heating to obtain a brown-black solid;

③ Prepare a brownish-black solid and heat it under vacuum to remove residual small molecule compounds to obtain carbon nanodots.

The present invention also provides an application of carbon nano-dots in the preparation of fluorescent ink, which is to dissolve the carbon nano-dots in water or an organic solvent, and centrifuge to obtain a supernatant; dilute the obtained supernatant with water or an organic solvent , to obtain carbon nanodot fluorescent ink.

Preferably, the organic solvent is ethanol.

Preferably, the centrifugal speed is 2000-4000 rpm, and the time is 15-30 minutes; more preferably, the centrifugal speed is 3000 rpm, and the time is 20 minutes.

The present invention will be further described below in conjunction with the examples, and the materials used in the examples can be obtained commercially.

Examples 1-11 are preparation examples of carbon nanodots of the present invention.

Example 1

Embodiment 1 is illustrated in conjunction with Fig. 1-3

Preparation of carbon nano-dots of the present invention:

① Dissolve 3 grams of urea and 3 grams of citric acid in 10 ml of water;

② Put the aqueous solution of urea and citric acid prepared in ① into a microwave oven, and heat it in a microwave with a power of 700W for 4 minutes to obtain a brown-black solid;

③The prepared brown-black solid was placed in a vacuum oven with a vacuum degree of 0.01 Pa and a temperature of 60 degrees Celsius, and heated for 1 hour to remove residual small molecular compounds and obtain carbon nanodots.

FIG. 1 is a transmission electron microscope image of carbon nanodots in Example 1 of the present invention.

Fig. 2 is the atomic force scanning picture a of the carbon nano-dots in Example 1 of the present invention and the height curve b of positions A to B in the atomic force scanning picture.

Fig. 3 is the infrared transmission spectrogram of the carbon nano-dot of the embodiment 1 of the present invention; The absorption band at 3100-3500 cm ^-1 is the absorption vibration band of ν(OH) and ν(NH), 1600-1770cm ^-1 is the absorption vibration band of ν(C=O), indicating that the surface of the prepared carbon nanodots contains abundant amide groups and carboxyl groups.

Example 2

Preparation of carbon nano-dots of the present invention:

① Dissolve 3 grams of urea and 3 grams of citric acid in 10 ml of water;

② Put the aqueous solution of urea and citric acid prepared in ① into a microwave oven, and heat it in a microwave with a power of 500W for 10 minutes to obtain a brown-black solid;

③The prepared brown-black solid was placed in a vacuum oven with a vacuum degree of 0.01 Pa and a temperature of 60 degrees Celsius, and heated for 1 hour to remove residual small molecular compounds and obtain carbon nanodots.

Example 3

Preparation of carbon nano-dots of the present invention:

①Dissolve 0.3g of urea and 3g of citric acid in 10ml of water;

② Put the aqueous solution of urea and citric acid prepared in ① into a microwave oven, and heat it in a microwave with a power of 700W for 4 minutes to obtain a brown-black solid;

③The prepared brown-black solid was placed in a vacuum oven with a vacuum degree of 0.01 Pa and a temperature of 50 degrees Celsius, and heated for 2 hours to remove residual small molecular compounds and obtain carbon nanodots.

Example 4

Preparation of carbon nano-dots of the present invention:

①Dissolve 0.3g of urea and 3g of citric acid in 10ml of water;

② Put the aqueous solution of urea and citric acid prepared in ① into a microwave oven, and heat it in a microwave with a power of 700W for 4 minutes to obtain a brown-black solid;

③The prepared brown-black solid was placed in a vacuum oven with a vacuum degree of 0.001 Pa and a temperature of 60 degrees Celsius, and heated for 1 hour to remove residual small molecular compounds and obtain carbon nanodots.

Example 5

Preparation of carbon nano-dots of the present invention:

① Dissolve 6 grams of urea and 3 grams of citric acid in 10 ml of water;

② Put the aqueous solution of urea and citric acid prepared in ① into a microwave oven, and heat it in a microwave with a power of 900W for 3 minutes to obtain a brown-black solid;

③The prepared brown-black solid was placed in a vacuum oven with a vacuum degree of 0.01 Pa and a temperature of 55 degrees Celsius, and heated for 2 hours to remove residual small molecular compounds to obtain carbon nanodots.

Example 6

Preparation of carbon nano-dots of the present invention:

① Dissolve 12 grams of urea and 3 grams of citric acid in 15 ml of water;

② Put the aqueous solution of urea and citric acid prepared in ① into a microwave oven, and heat it in a microwave with a power of 700W for 5 minutes to obtain a brown-black solid;

③The prepared brown-black solid was placed in a vacuum oven with a vacuum degree of 0.01 Pa and a temperature of 70 degrees Celsius, and heated for 1 hour to remove residual small molecular compounds and obtain carbon nanodots.

Example 7

Preparation of carbon nano-dots of the present invention:

① Dissolve 12 grams of urea and 3 grams of citric acid in 10 ml of water;

② Put the aqueous solution of urea and citric acid prepared in ① into a microwave oven, and heat it in a microwave with a power of 500W for 9 minutes to obtain a brown-black solid;

③The prepared brown-black solid was placed in a vacuum oven with a vacuum degree of 0.1 Pa and a temperature of 60 degrees Celsius, and heated for 1 hour to remove residual small molecular compounds and obtain carbon nanodots.

Example 8

Preparation of carbon nano-dots of the present invention:

① Dissolve 3 grams of urea and 3 grams of glycerin in 12 ml of water;

② Put the aqueous solution of urea and glycerin prepared in ① into a microwave oven, and heat it in a microwave with a power of 600W for 8 minutes to obtain a brown-black solid;

③The prepared brown-black solid was placed in a vacuum oven with a vacuum degree of 0.05 Pa and a temperature of 55 degrees Celsius, and heated for 2 hours to remove residual small molecular compounds and obtain carbon nanodots.

Example 9

Preparation of carbon nano-dots of the present invention:

① Dissolve 3 grams of urea and 3 grams of glucose in 12 ml of water;

② Put the aqueous solution of urea and glucose prepared in ① into a microwave oven, and heat it in a microwave with a power of 600W for 8 minutes to obtain a brown-black solid;

③The prepared brown-black solid was placed in a vacuum oven with a vacuum degree of 0.01 Pa and a temperature of 60 degrees Celsius, and heated for 1 hour to remove residual small molecular compounds and obtain carbon nanodots.

Example 10

Preparation of carbon nano-dots of the present invention:

① Dissolve 3 grams of urea and 3 grams of sucrose in 15 ml of water;

② Put the aqueous solution of urea and sucrose prepared in ① into a microwave oven, and heat it in a microwave with a power of 700W for 6 minutes to obtain a brown-black solid;

③The prepared brown-black solid was placed in a vacuum oven with a vacuum degree of 0.01 Pa and a temperature of 70 degrees Celsius, and heated for 1 hour to remove residual small molecular compounds and obtain carbon nanodots.

Example 11

Preparation of carbon nano-dots of the present invention:

① Dissolve 3 grams of urea and 3 grams of glycine in 10 ml of water;

② Put the aqueous solution of urea and glycine prepared in ① into a microwave oven, and heat it in a microwave with a power of 700W for 7 minutes to obtain a brown-black solid;

③The prepared brown-black solid was placed in a vacuum oven with a vacuum degree of 0.01 Pa and a temperature of 60 degrees Celsius, and heated for 2 hours to remove residual small molecular compounds and obtain carbon nanodots.

Examples 12-22 are application examples of the carbon nanodots of the present invention in the preparation of fluorescent inks.

Example 12

This embodiment is described in conjunction with Fig. 4-13

Application of the carbon nano-dots of the present invention in the preparation of fluorescent inks:

Dissolve the carbon nanodots obtained in Example 1 in 100 ml of water, and centrifuge at a speed of 3000 rpm for 20 minutes to obtain a supernatant; the obtained supernatant is diluted with water to obtain a concentration of 1 mg The aqueous solution of carbon nano-dots per milliliter, that is, carbon nano-dot fluorescent ink.

The prepared carbon nano-dot fluorescent ink will not produce precipitation for a long time.

Fig. 4 is the ultraviolet absorption spectrum of the aqueous solution of the carbon nano-dot of embodiment 12 of the present invention and the fluorescence emission spectrum figure under different excitation wavelengths: Curve 1 is the ultraviolet absorption spectrum figure, and curve 2 is the fluorescence emission spectrum figure under 340nm excitation, Curve 3 is the fluorescence emission spectrum figure excited under 380nm, and curve 4 is the fluorescence emission spectrum figure excited under 420nm, and curve 5 is the fluorescence emission spectrum figure excited under 460nm, and curve 6 is the fluorescence emission spectrum figure excited under 500nm; From Fig. 1 It can be seen that the strongest fluorescence emission peak is 540nm when the excitation wavelength is 420nm, and the maximum fluorescence quantum efficiency is 14%.

Fig. 5 is that the carbon nano-dot fluorescent ink of embodiment 12 of the present invention is dripped on the filter paper, after drying in the air, the fluorescence emission spectrum curves under different excitation wavelengths: curve 1 is the fluorescence emission spectrum figure under 340nm excitation, and curve 2 is Fluorescence emission spectrum diagram under 380nm excitation, curve 3 is the fluorescence emission spectrum diagram under 420nm excitation, curve 4 is the fluorescence emission spectrum diagram under 460nm excitation, and curve 5 is the fluorescence emission spectrum diagram under 500nm excitation; Can see from Fig. 2 The strongest fluorescence emission peak is 515nm when the excitation wavelength is 420nm, and the maximum fluorescence quantum efficiency is 40%.

Fig. 6 is that the carbon nano-dot fluorescent ink of embodiment 12 of the present invention makes mung bean grow into the photo of the bean sprouts with fluorescence characteristics under different waveband illumination: (a) photo under natural light, (b) excitation wavelength 340 nm, receiving wavelength Fluorescence photo of light greater than 395 nm, bean sprouts are blue, (c) fluorescence photo of excitation wavelength 420 nm, acceptance wavelength greater than 450 nm, bean sprouts are green, (d) fluorescence photo of excitation wavelength 500 nm, acceptance wavelength greater than 550 nm , the bean sprouts are orange; it shows that the carbon nano-dot fluorescent ink of the present invention is non-toxic to plants and can be used to dye plants in vivo.

Fig. 7 is the fluorescence spectrogram of the urine of rats drinking the carbon nano-dot fluorescent ink of Example 12 of the present invention for one month at different excitation wavelengths: curve 1 is the fluorescence emission spectrum under the excitation of 340nm, and curve 2 is the excitation of 360nm The fluorescence emission spectrum diagram below, the curve 3 is the fluorescence emission spectrum diagram under the excitation of 380nm, the curve 4 is the fluorescence emission spectrum diagram under the excitation of 400nm, the curve 5 is the fluorescence emission spectrum diagram under the excitation of 420nm, and the curve 6 is the fluorescence emission spectrum diagram under the excitation of 460nm Fluorescence emission spectrum figure, curve 7 is the fluorescence emission spectrum figure under the excitation of 480nm, and curve 8 is the fluorescence emission spectrum figure under the excitation of 500nm, and the fluorescence band that occurs at 500-600 nm shows that urine contains carbon prepared by the present invention nano dots.

Fig. 8 is the urine of rats drinking the carbon nano-dot fluorescent ink of Example 12 of the present invention for one month, then stopping drinking the carbon nano-dot fluorescent ink of the present invention, and drinking normal drinking water for one month at different excitation wavelengths The fluorescence spectrum diagram: curve 1 is the fluorescence emission spectrum diagram under 340nm excitation, curve 2 is the fluorescence emission spectrum diagram under 360nm excitation, curve 3 is the fluorescence emission spectrum diagram under 380nm excitation, and curve 4 is the fluorescence emission spectrum diagram under 400nm excitation Spectrogram, curve 5 is the fluorescence emission spectrum diagram under 420nm excitation, curve 6 is the fluorescence emission spectrum diagram under 460nm excitation, and the fluorescence band that appears at 500-600 nm disappears.

Fig. 9 is the fluorescence spectrogram of the urine of rats drinking normal drinking water (not drinking the carbon nano-dot fluorescent ink of the present invention) at different excitation wavelengths: curve 1 is the fluorescence emission spectrum under 340nm excitation, and curve 2 is The fluorescence emission spectrum diagram under 360nm excitation, curve 3 is the fluorescence emission spectrum diagram under 380nm excitation, curve 4 is the fluorescence emission spectrum diagram under 400nm excitation, curve 5 is the fluorescence emission spectrum diagram under 420nm excitation, and curve 6 is the fluorescence emission spectrum diagram under 460nm excitation The fluorescence emission spectrum below.

Figures 7-9 show that long-term drinking of the carbon nano-dot fluorescent ink prepared by the present invention with citric acid and urea will not cause death or produce abnormal phenomena, and the carbon nano-dot fluorescent ink of the present invention can be excreted through urine , non-toxic to animals.

Fig. 10 is the fluorescent photo of the carbon nano-dot fluorescent ink of Example 12 of the present invention and a commercial green highlighter (commercially available) forming encrypted numbers on paper: write "395" on the paper with carbon nano-dot fluorescent ink, and then Use a commercially purchased green highlighter to smear the unused carbon nano-dot fluorescent ink, and replace "395" with the number "888"; Figure a, the excitation wavelength is 450-480 nm, the light receiving wavelength is greater than 515 nm, and the exposure time is 50 milliseconds ; Figure b, excitation wavelength 510-550 nm, receiving light with a wavelength greater than 590 nm, exposure time 150 milliseconds; it can be seen that what figure a shows is green 888, and what figure b shows is red 395, indicating that carbon nano dots of the present invention Fluorescent inks can be displayed under different excitation wavelengths and can be used to encrypt numbers.

Fig. 11 is the photo of cotton thread and nylon fiber stained and not stained with the carbon nano-dot fluorescent ink of Example 12 of the present invention at different excitation wavelengths: the cotton thread and nylon fiber not stained with the carbon nano-dot fluorescent ink of Example 12 of the present invention, (a) Optical photo, (b) Fluorescence photo of excitation wavelength 450-480 nm, acceptance wavelength greater than 515 nm, exposure time 50 milliseconds, (c) fluorescence photo of excitation wavelength 510-550 nm, acceptance wavelength greater than 590 nm , Exposure time 150 milliseconds; Contaminate the carbon nano-dot fluorescent ink of the embodiment of the present invention 12, and the (d) optical photo of cotton thread and nylon fiber after drying in air, (e) excitation wavelength 450-480 nm, receiving wavelength is greater than 515 nm fluorescence photo, exposure time 50 milliseconds, it can be seen that the cotton fiber is green, (f) the excitation wavelength is 510-550 nm, the fluorescence photo of receiving wavelength greater than 590 nm, the exposure time is 150 milliseconds, it can be seen that the cotton fiber is green Red; As can be seen from Figure 11, the cotton fiber that is stained with the carbon nano-dot fluorescent ink of the embodiment of the present invention 12 shows the fluorescence phenomenon that strong excitation wavelength depends on, and is stained with the carbon nano-dot fluorescent ink of the embodiment of the present invention 12 The nylon fiber has no fluorescence phenomenon, indicating that the carbon nano-dot fluorescent ink of the present invention can effectively identify biological products and chemical products.

Fig. 12 is the photograph that uses the carbon nano-dot fluorescent ink of embodiment 12 of the present invention to leave fingerprint imprint on paper under different excitation wavelengths, (a) optical photograph, (b) excitation wavelength 340 nm, receiving wavelength is greater than 395 nm light It can be seen that (b) shows blue fingerprints, (c) the fluorescence photos with excitation wavelength of 420 nm and receiving wavelength greater than 450 nm, it can be seen that (c) shows green fingerprints; the obtained Fingerprints can be stored for a long time.

Fig. 13 is a fluorescent photo of the fluorescent pattern left on the skin by the carbon nanodot fluorescent ink of Example 12 of the present invention.

Example 13

Embodiment 13 is illustrated in conjunction with FIG. 14

Application of the carbon nano-dots of the present invention in the preparation of fluorescent inks:

The carbon nano dots obtained in Example 2 were dissolved in 200 ml of ethanol, and after centrifugation, the centrifugation speed was 3000 rpm, and the centrifugation time was 20 minutes, and the supernatant was obtained; the obtained supernatant was diluted with ethanol to obtain a concentration of 1 mg/ml ethanol solution of carbon nano-dots, that is, carbon nano-dot fluorescent ink.

Fig. 14 is the fluorescence emission spectrum diagram of the ethanol solution of carbon nanodots in Example 13 of the present invention under different excitation wavelengths: Curve 1 is the fluorescence emission spectrum diagram under 340nm excitation, curve 2 is the fluorescence emission spectrum diagram under 380nm excitation, Curve 3 is the fluorescence emission spectrum diagram under the excitation of 420nm, curve 4 is the fluorescence emission spectrum diagram under the excitation of 460nm, and curve 5 is the fluorescence emission spectrum diagram under the excitation of 500nm; the strongest fluorescence emission peak is 520nm (excitation wavelength 420nm), the maximum fluorescence The quantum efficiency is 38%.

Example 14

Embodiment 14 is illustrated in conjunction with FIGS. 15 and 16

Application of the carbon nano-dots of the present invention in the preparation of fluorescent inks:

The carbon nanodots obtained in Example 3 were dissolved in 100 ml of water, and after centrifugation, the centrifugation speed was 2000 rpm, and the centrifugation time was 30 minutes, and the supernatant was obtained; the obtained supernatant was diluted with water to obtain a concentration of 1 mg The aqueous solution of carbon nano-dots per milliliter, that is, carbon nano-dot fluorescent ink.

Fig. 15 is the fluorescence emission spectrum diagram of the aqueous solution of carbon nano-dots in Example 14 of the present invention under different excitation wavelengths: Curve 1 is the fluorescence emission spectrum diagram under 320nm excitation, curve 2 is the fluorescence emission spectrum diagram under 360nm excitation, curve 3 is the fluorescence emission spectrum diagram under 380nm excitation, curve 4 is the fluorescence emission spectrum diagram under 390nm excitation, curve 5 is the fluorescence emission spectrum diagram under 400nm excitation, and curve 6 is the fluorescence emission spectrum diagram under 460nm excitation; the strongest fluorescence The emission peak at 445nm (excitation wavelength at 360nm) has a maximum fluorescence quantum efficiency of 18%.

Fig. 16 is that the carbon nano-dot fluorescent ink of embodiment 14 of the present invention is dripped on the filter paper, and after drying in air, the fluorescence emission spectrum figure under different excitation wavelengths: curve 1 is the fluorescence emission spectrum figure under 320nm excitation, curve 2 is the fluorescence emission spectrum under 360nm excitation, curve 3 is the fluorescence emission spectrum under 380nm excitation, curve 4 is the fluorescence emission spectrum under 400nm excitation, curve 5 is the fluorescence emission spectrum under 420nm excitation, and curve 6 is Fluorescence emission spectrum under 480nm excitation; the strongest fluorescence emission peak is 443nm (excitation wavelength 360nm), and the maximum fluorescence quantum efficiency is 18%.

Example 15

Embodiment 15 is illustrated in conjunction with FIG. 17

Application of the carbon nano-dots of the present invention in the preparation of fluorescent inks:

The carbon nano dots obtained in Example 4 were dissolved in 100 ml of ethanol, and after centrifugation, the centrifugation speed was 3000 rpm, and the centrifugation time was 25 minutes, and the supernatant was obtained; the obtained supernatant was diluted with ethanol to obtain a concentration of 1 mg/ml ethanol solution of carbon nano-dots, that is, carbon nano-dot fluorescent ink.

Fig. 17 is the fluorescence emission spectrum diagram of the ethanol solution of carbon nanodots in Example 15 of the present invention under different excitation wavelengths: Curve 1 is the fluorescence emission spectrum diagram under 320nm excitation, curve 2 is the fluorescence emission spectrum diagram under 360nm excitation, Curve 3 is the fluorescence emission spectrum diagram under the excitation of 380nm, curve 4 is the fluorescence emission spectrum diagram under the excitation of 420nm, curve 5 is the fluorescence emission spectrum diagram under the excitation of 460nm, and curve 6 is the fluorescence emission spectrum diagram under the excitation of 500nm; the strongest The fluorescence emission peak is 467nm (excitation wavelength 380nm), and the maximum fluorescence quantum efficiency is 18%.

Example 16

Embodiment 16 is illustrated in conjunction with FIG. 18

Application of the carbon nano-dots of the present invention in the preparation of fluorescent inks:

Dissolve the carbon nanodots obtained in Example 5 in 100 ml of water, centrifuge at a speed of 4000 rpm, and centrifuge for 16 minutes to obtain a supernatant; the obtained supernatant is diluted with water to obtain a concentration of 1 mg The aqueous solution of carbon nano-dots per milliliter, that is, carbon nano-dot fluorescent ink.

Fig. 18 is the fluorescence emission spectrum diagram of the aqueous solution of carbon nano-dots in Example 16 of the present invention under different excitation wavelengths: Curve 1 is the fluorescence emission spectrum diagram under 320nm excitation, curve 2 is the fluorescence emission spectrum diagram under 360nm excitation, curve 3 is the fluorescence emission spectrum diagram under 380nm excitation, curve 4 is the fluorescence emission spectrum diagram under 390nm excitation, curve 5 is the fluorescence emission spectrum diagram under 400nm excitation, and curve 6 is the fluorescence emission spectrum diagram under 460nm excitation; the strongest fluorescence The emission peak is 535nm (excitation wavelength 420nm), and the maximum fluorescence quantum efficiency is 18%.

Example 17

Embodiment 17 is illustrated in conjunction with FIGS. 19 and 20

Application of the carbon nano-dots of the present invention in the preparation of fluorescent inks:

Dissolve the carbon nanodots obtained in Example 6 in 100 ml of water, centrifuge at a speed of 3000 rpm, and centrifuge for 20 minutes to obtain a supernatant; the obtained supernatant is diluted with water to obtain a concentration of 1 mg The aqueous solution of carbon nano-dots per milliliter, that is, carbon nano-dot fluorescent ink.

Fig. 19 is the fluorescence emission spectrum diagram of the aqueous solution of carbon nano-dots in Example 17 of the present invention under different excitation wavelengths: Curve 1 is the fluorescence emission spectrum diagram under 350nm excitation, curve 2 is the fluorescence emission spectrum diagram under 360nm excitation, curve 3 is the fluorescence emission spectrum diagram under 380nm excitation, curve 4 is the fluorescence emission spectrum diagram under 420nm excitation, curve 5 is the fluorescence emission spectrum diagram under 460nm excitation, curve 6 is the fluorescence emission spectrum diagram under 480nm excitation, and curve 7 is Fluorescence emission spectrum under 500nm excitation; the strongest fluorescence emission peak is 535nm (excitation wavelength 420nm) and the maximum fluorescence quantum efficiency is 18%.

Fig. 20 is the fluorescence emission spectrum diagram under different excitation wavelengths after the carbon nano-dot fluorescent ink of embodiment 17 of the present invention is dripped on the filter paper and dried in the air: curve 1 is the fluorescence emission spectrum diagram under 320nm excitation, curve 2 is the fluorescence emission spectrum under 360nm excitation, curve 3 is the fluorescence emission spectrum under 380nm excitation, curve 4 is the fluorescence emission spectrum under 420nm excitation, curve 5 is the fluorescence emission spectrum under 460nm excitation, and curve 6 is Fluorescence emission spectrum under 480nm excitation; the strongest fluorescence emission peak is 520nm (excitation wavelength 420nm), and the maximum fluorescence quantum efficiency is 42%.

Example 18

Embodiment 18 is illustrated in conjunction with FIG. 21

Application of the carbon nano-dots of the present invention in the preparation of fluorescent inks:

The carbon nano-dots obtained in Example 7 were dissolved in 100 ml of ethanol, and after centrifugation, the centrifugation speed was 3000 rpm, and the centrifugation time was 22 minutes, and the supernatant was obtained; the obtained supernatant was diluted with ethanol to obtain a concentration of 1 mg/ml ethanol solution of carbon nano-dots, that is, carbon nano-dot fluorescent ink.

Figure 21 is the fluorescence emission spectrum diagram of the ethanol solution of carbon nanodots in Example 18 of the present invention under different excitation wavelengths: Curve 1 is the fluorescence emission spectrum diagram under 340nm excitation, curve 2 is the fluorescence emission spectrum diagram under 380nm excitation, Curve 3 is the fluorescence emission spectrum diagram under the excitation of 420nm, curve 4 is the fluorescence emission spectrum diagram under the excitation of 460nm, and curve 5 is the fluorescence emission spectrum diagram under the excitation of 500nm; the strongest fluorescence emission peak is 527nm (excitation wavelength 420nm), the maximum fluorescence The quantum efficiency is 40%.

Example 19

Embodiment 19 is illustrated in conjunction with FIG. 22

Application of the carbon nano-dots of the present invention in the preparation of fluorescent inks:

Dissolve the carbon nanodots obtained in Example 8 in 100 ml of water, centrifuge at a speed of 3000 rpm, and centrifuge for 25 minutes to obtain a supernatant; the obtained supernatant is diluted with water to obtain a concentration of 1 mg The aqueous solution of carbon nano-dots per milliliter, that is, carbon nano-dot fluorescent ink.

Fig. 22 is the fluorescence emission spectrum diagram of the aqueous solution of carbon nanodots in Example 19 of the present invention under different excitation wavelengths: Curve 1 is the fluorescence emission spectrum diagram under 300nm excitation, curve 2 is the fluorescence emission spectrum diagram under 340nm excitation, curve 3 is the fluorescence emission spectrum diagram under 380nm excitation, curve 4 is the fluorescence emission spectrum diagram under 420nm excitation, curve 5 is the fluorescence emission spectrum diagram under 450nm excitation, and curve 6 is the fluorescence emission spectrum diagram under 480nm excitation; the strongest fluorescence The emission peak is 428nm (excitation wavelength is 340nm), and the maximum fluorescence quantum efficiency is 10%.

Example 20

Embodiment 20 is illustrated in conjunction with FIG. 23

Application of the carbon nano-dots of the present invention in the preparation of fluorescent inks:

Dissolve the carbon nanodots obtained in Example 9 in 100 ml of water, centrifuge at a speed of 4000 rpm, and centrifuge for 20 minutes to obtain a supernatant; the obtained supernatant is diluted with water to obtain a concentration of 1 mg The aqueous solution of carbon nano-dots per milliliter, that is, carbon nano-dot fluorescent ink.

Fig. 23 is the fluorescence emission spectrum diagram of the aqueous solution of carbon nano-dots in Example 20 of the present invention under different excitation wavelengths: Curve 1 is the fluorescence emission spectrum diagram under 300nm excitation, curve 2 is the fluorescence emission spectrum diagram under 340nm excitation, curve 3 is the fluorescence emission spectrum diagram under 380nm excitation, curve 4 is the fluorescence emission spectrum diagram under 420nm excitation, curve 5 is the fluorescence emission spectrum diagram under 450nm excitation, and curve 6 is the fluorescence emission spectrum diagram under 480nm excitation; the strongest fluorescence The emission peak is 420nm (excitation wavelength 340nm), and the maximum fluorescence quantum efficiency is 8%.

Example 21

Embodiment 21 is illustrated in conjunction with FIG. 24

Application of the carbon nano-dots of the present invention in the preparation of fluorescent inks:

Dissolve the carbon nanodots obtained in Example 10 in 100 ml of water, centrifuge at a speed of 3000 rpm, and centrifuge for 20 minutes to obtain a supernatant; the obtained supernatant is diluted with water to obtain a concentration of 1 mg The aqueous solution of carbon nano-dots per milliliter, that is, carbon nano-dot fluorescent ink.

Fig. 24 is the fluorescence emission spectrum diagram of the aqueous solution of carbon nano-dots in Example 21 of the present invention under different excitation wavelengths: Curve 1 is the fluorescence emission spectrum diagram under 320nm excitation, curve 2 is the fluorescence emission spectrum diagram under 360nm excitation, curve 3 is the fluorescence emission spectrum diagram under 400nm excitation, curve 4 is the fluorescence emission spectrum diagram under 440nm excitation, and curve 5 is the fluorescence emission spectrum diagram under 480nm excitation; the strongest fluorescence emission peak is 425nm (excitation wavelength 400nm), the largest fluorescence quantum The efficiency is 6%.

Example 22

Embodiment 22 is illustrated in conjunction with FIG. 25

Application of the carbon nano-dots of the present invention in the preparation of fluorescent inks:

Dissolve the carbon nanodots obtained in Example 11 in 100 ml of water, centrifuge at a speed of 3000 rpm, and centrifuge for 20 minutes to obtain a supernatant; the obtained supernatant is diluted with water to obtain a concentration of 1 mg The aqueous solution of carbon nano-dots per milliliter, that is, carbon nano-dot fluorescent ink.

Fig. 25 is the fluorescence emission spectrum diagram of the aqueous solution of carbon nano-dots in Example 22 of the present invention under different excitation wavelengths: Curve 1 is the fluorescence emission spectrum diagram under 300nm excitation, curve 2 is the fluorescence emission spectrum diagram under 320nm excitation, curve 3 is the fluorescence emission spectrum diagram under 340nm excitation, curve 4 is the fluorescence emission spectrum diagram under 360nm excitation, curve 5 is the fluorescence emission spectrum diagram under 380nm excitation, curve 6 is the fluorescence emission spectrum diagram under 420nm excitation, and curve 7 is Fluorescence emission spectrum under 460nm excitation; the strongest fluorescence emission peak is 390nm (excitation wavelength 340nm), and the maximum fluorescence quantum efficiency is 12%.

Claims (10)

1. a carbon nano dot, is characterized in that, this carbon nano dot is to contain many carboxyls or polyhydric organic compound as raw material, or taking amino acid as raw material, is prepared from taking urea as surface passivation agent, and step is as follows:

1. urea with containing many carboxyls or polyhydric organic compound, or amino acid in mass ratio 0.1:1-4:1 be mixed with the aqueous solution;

2. the 1. prepared aqueous solution is reacted and obtained brownish black solid by microwave heating;

3. the brownish black solid obtaining, through heating under vacuum, is removed residual micromolecular compound, obtains carbon nano dot;

Described carbon nano dot surface has amide group and carboxylic group.

2. a kind of carbon nano dot according to claim 1, is characterized in that, described many carboxyls or polyhydric organic compound are citric acid, ethylenediamine tetraacetic acid (EDTA), glycerine, glucose, fructose, sucrose, chitosan or starch.

3. a kind of carbon nano dot according to claim 1, is characterized in that, described amino acid is glycine or L-glutamic acid.

4. a kind of carbon nano dot according to claim 1, is characterized in that, step 1. in, described urea with containing many carboxyls or polyhydric organic compound, or amino acid in mass ratio 0.1:1-4:1 be mixed with saturated aqueous solution.

5. a kind of carbon nano dot according to claim 1, is characterized in that, step 2. in, the described aqueous solution is through 500-900W power microwave heating 3-10 minute.

6. a kind of carbon nano dot according to claim 1, is characterized in that, step 3. in, the vacuum tightness of described heating under vacuum is 0.001-0.1 handkerchief, Heating temperature is 50-70 degree Celsius, heat-up time 1-2 hour.

7. a preparation method for carbon nano dot, is characterized in that, comprises the following steps:

1. urea with containing many carboxyls or polyhydric organic compound, or amino acid in mass ratio 0.1:1-4:1 be mixed with the aqueous solution;

2. the 1. prepared aqueous solution is reacted and obtained brownish black solid by microwave heating;

3. by brownish black solid through heating under vacuum, remove residual micromolecular compound, obtain carbon nano dot.

8. a kind of carbon nano dot of claim 1-6 described in any one is in the application of preparing in fluorescent ink.

9. a kind of carbon nano dot according to claim 8, in the application of preparing in fluorescent ink, is characterized in that, by soluble in water carbon nano dot, through centrifugal, obtains supernatant liquor; The supernatant liquor obtaining, through water or organic solvent diluting, is obtained to carbon nano dot fluorescent ink.

10. a kind of carbon nano dot according to claim 9, in the application of preparing in fluorescent ink, is characterized in that, centrifugal rotational speed is 2000-4000 rev/min, and the time is 15-30 minute.