JP2012088222A - Surface-enhanced spectroscopy substrate - Google Patents
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- 239000000758 substrate Substances 0.000 title claims abstract description 121
- 238000004611 spectroscopical analysis Methods 0.000 title claims abstract description 21
- 239000010419 fine particle Substances 0.000 claims abstract description 174
- 229910052751 metal Inorganic materials 0.000 claims abstract description 76
- 239000002184 metal Substances 0.000 claims abstract description 76
- 230000000694 effects Effects 0.000 claims abstract description 14
- 239000002245 particle Substances 0.000 claims description 76
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 25
- 229910052709 silver Inorganic materials 0.000 claims description 24
- 239000004332 silver Substances 0.000 claims description 24
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 15
- 229910052737 gold Inorganic materials 0.000 claims description 15
- 239000010931 gold Substances 0.000 claims description 15
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 14
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 12
- 239000000203 mixture Substances 0.000 claims description 8
- 229910052697 platinum Inorganic materials 0.000 claims description 6
- 229910052782 aluminium Inorganic materials 0.000 claims description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 4
- 229920000642 polymer Polymers 0.000 claims description 3
- 239000000956 alloy Substances 0.000 claims description 2
- 229910045601 alloy Inorganic materials 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 239000010410 layer Substances 0.000 description 63
- 238000001069 Raman spectroscopy Methods 0.000 description 49
- 238000000034 method Methods 0.000 description 26
- 238000005259 measurement Methods 0.000 description 19
- 238000001179 sorption measurement Methods 0.000 description 16
- 238000001237 Raman spectrum Methods 0.000 description 12
- 239000000725 suspension Substances 0.000 description 12
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 10
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- VYXSBFYARXAAKO-WTKGSRSZSA-N chembl402140 Chemical compound Cl.C1=2C=C(C)C(NCC)=CC=2OC2=C\C(=N/CC)C(C)=CC2=C1C1=CC=CC=C1C(=O)OCC VYXSBFYARXAAKO-WTKGSRSZSA-N 0.000 description 6
- 239000002105 nanoparticle Substances 0.000 description 6
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- 238000004566 IR spectroscopy Methods 0.000 description 3
- 238000000137 annealing Methods 0.000 description 3
- 238000010894 electron beam technology Methods 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 239000002356 single layer Substances 0.000 description 3
- 238000004544 sputter deposition Methods 0.000 description 3
- 238000001771 vacuum deposition Methods 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 2
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- 238000002474 experimental method Methods 0.000 description 2
- 239000003574 free electron Substances 0.000 description 2
- 239000002086 nanomaterial Substances 0.000 description 2
- 238000004416 surface enhanced Raman spectroscopy Methods 0.000 description 2
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000000366 colloid method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
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- 238000000609 electron-beam lithography Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000010408 film Substances 0.000 description 1
- 238000001506 fluorescence spectroscopy Methods 0.000 description 1
- 239000007850 fluorescent dye Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000002082 metal nanoparticle Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
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- 239000004065 semiconductor Substances 0.000 description 1
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- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
- 238000002460 vibrational spectroscopy Methods 0.000 description 1
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- Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
- Powder Metallurgy (AREA)
Abstract
Description
本発明は、ラマン分光や赤外分光等の分光測定に有効な表面増強分光用基板に関する。 The present invention relates to a surface-enhanced spectroscopic substrate effective for spectroscopic measurements such as Raman spectroscopy and infrared spectroscopy.
振動分光の一種であるラマン分光法は、分子をレーザ光で照射した際に発生する散乱光の波長を分析することにより分子種の同定を可能にする分析方法である。有効な手法である反面、散乱断面積が非常に小さいため適用範囲が限定されている。 Raman spectroscopy, which is a type of vibrational spectroscopy, is an analysis method that enables identification of molecular species by analyzing the wavelength of scattered light generated when the molecules are irradiated with laser light. While it is an effective technique, its application range is limited because the scattering cross section is very small.
一方、表面増強効果を利用した光による分光測定が注目を集めている。金属あるいは半導体の微粒子の物理化学的特性は、微粒子の厚さ、サイズ、形状等に大きく依存する。例えば、サイズ１００ｎｍ以下の金、銀、プラチナ等のナノ粒子に光を照射すると、ナノ粒子近傍に近接場と呼ばれる局在した強力な光の場が発生する。測定対象である分子ないしは薄膜状のサンプルを貴金属ナノ粒子でコーティングされた基板に展開して光学的手法にて分析することより、信号が数十倍（蛍光法および赤外分光法）から１００万倍（ラマン分光法）増大されることが知られている。 On the other hand, spectroscopic measurement using light utilizing the surface enhancement effect has attracted attention. The physicochemical characteristics of metal or semiconductor fine particles depend greatly on the thickness, size, shape, etc. of the fine particles. For example, when a nanoparticle such as gold, silver, or platinum having a size of 100 nm or less is irradiated with light, a localized strong light field called a near field is generated in the vicinity of the nanoparticle. A molecule or thin film sample to be measured is developed on a substrate coated with noble metal nanoparticles and analyzed by an optical method, so that the signal is several tens of times (fluorescence and infrared spectroscopy) to 1 million. It is known to be doubled (Raman spectroscopy).
上記表面増強法を、例えばラマン分光に適用する場合は、金、銀等のナノ構造表面に測定対象を滴下し、レーザ光で励起して、ラマン散乱光を測定する。このようにすると、ラマン散乱光の強度が数桁から５、６桁程度まで増強される。 When the surface enhancement method is applied to, for example, Raman spectroscopy, a measurement object is dropped on the surface of a nanostructure such as gold or silver, and excited by laser light to measure Raman scattered light. In this way, the intensity of the Raman scattered light is increased from several digits to about 5 to 6 digits.
上記増強現象が発見された当初は、電気化学的に表面が荒らされた銀基板が用いられた。その後は、真空蒸着により自己組織的に形成された銀に対してアニーリング法を適用して作製されたグレインや、基板上に吸着された金及び銀コロイド（コロイド法）が用いられている（例えば、非特許文献１参照）。また、近年は、ナノリソグラフィー法と呼ばれる、基板上に形成された単分散のナノ粒子上に銀を蒸着して調製された帽子状の銀微粒子が用いられている（例えば、特許文献１参照）。さらに、電子ビームリソグラフィー法により基板上に形成されたナノサイズの銀構造体（電子ビーム法）等も用いられている。 At the beginning of the discovery of the enhancement phenomenon, an electrochemically roughened silver substrate was used. Thereafter, grains produced by applying an annealing method to silver formed in a self-organized manner by vacuum deposition, and gold and silver colloids adsorbed on a substrate (colloid method) are used (for example, Non-Patent Document 1). In recent years, hat-shaped silver fine particles prepared by vapor-depositing silver on monodisperse nanoparticles formed on a substrate, called a nanolithography method, have been used (for example, see Patent Document 1). . Further, a nano-sized silver structure (electron beam method) formed on a substrate by an electron beam lithography method is also used.
上記の方法は、原理的に表面増強ラマン分光測定に有効であることは実証されているが、実用化に際して様々な問題を抱えている。アニーリング法により作製した銀のグレインでは、増強率がさほど大きくなく再現性に乏しい。コロイド法により作製した金及び銀コロイドでは、アニーリング法同様、増強率がさほど大きくなく、高価なコロイド液が大量に必要であるといった問題がある。ナノリソグラフィー法により作製した帽子状の銀微粒子では、細密充填されたナノ粒子を大面積の基板上に形成することが困難である。電子ビーム法では、電子描画装置の価格が億単位と非常に高価であり、電子ビームの走査に時間を要することから製造スループットが非常に低いといった欠点がある。 The above method has been proved to be effective in principle for surface-enhanced Raman spectroscopy, but has various problems in practical use. Silver grains produced by the annealing method have a low enhancement rate and poor reproducibility. The gold and silver colloids produced by the colloidal method have a problem that the enhancement rate is not so large as in the annealing method, and a large amount of expensive colloidal liquid is required. With hat-shaped silver fine particles produced by nanolithography, it is difficult to form finely packed nanoparticles on a large-area substrate. The electron beam method has a drawback that the price of the electronic drawing apparatus is very high at 100 million units, and it takes time to scan the electron beam, so that the manufacturing throughput is very low.
表面増強ラマン法を実用化するには、性能の担保、再現性の保証、製造の容易さ、低価格化が不可欠である。これらの観点から、用いられている方法に、上記ナノリソグラフィー法がある。しかし、特許文献２に記載されたように、基板上に微粒子のみを相互に非接触状に配置する方法では、１０倍程度の増強率しか得られないことがわかっている。このため、ナノリソグラフィー法を用いる場合は、図１８に示すような細密充填構造に形成する。 In order to put the surface-enhanced Raman method into practical use, it is essential to guarantee performance, guarantee reproducibility, ease of manufacturing, and reduce the price. From these viewpoints, the above-mentioned nanolithography method is a method used. However, as described in Patent Document 2, it has been found that the method of arranging only fine particles on a substrate in a non-contact manner can obtain only an enhancement factor of about 10 times. For this reason, when a nanolithography method is used, a densely packed structure as shown in FIG. 18 is formed.
図１８は、基板上に形成された単分散のナノ粒子上に帽子状に銀を蒸着して得られた銀微粒子６０を上面から見た平面図を示す。このように、隙間なく細密に銀微粒子６０が配置される。また、細密充填構造を構成し、分光用基板の領域にかかわらず均一な性能を担保するためには、図１８のように、微粒子の粒径が揃っている（単分散性が非常に高い）ことが要求される。以上のように、ナノリソグラフィー法を用いても、性能を高めるためには、単分散性微粒子を細密充填配置しなければならないため、再現性、製造の容易さ、低価格化に問題があった。 FIG. 18 is a plan view of a silver fine particle 60 obtained by vapor-depositing silver in a cap shape on monodisperse nanoparticles formed on a substrate, as viewed from above. Thus, the silver fine particles 60 are arranged finely without gaps. Further, in order to configure a close packed structure and ensure uniform performance regardless of the region of the spectroscopic substrate, the particle diameters of the fine particles are uniform as shown in FIG. 18 (monodispersity is very high). Is required. As described above, even if the nanolithography method is used, in order to improve the performance, the monodisperse fine particles must be closely packed and arranged, which causes problems in reproducibility, ease of manufacture, and cost reduction. .
本発明は、上述した課題を解決するために創案されたものであり、増強効果及び再現性が高く、低価格で製造が容易な表面増強分光用基板を提供することを目的とする。 The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a surface-enhanced spectroscopic substrate that has a high enhancement effect and high reproducibility, and is easy to manufacture at a low price.
上記目的を達成するために、本発明の表面増強分光用基板は、金属が付着した金属付着微粒子が基板上に形成された表面増強効果を有する表面増強分光用基板であって、前記基板上には、複数の前記金属付着微粒子が集合して該金属付着微粒子の金属が相互に接触しているクラスターが間隔を置いて複数形成され、前記各クラスターは前記基板と電気的に分離されていることを主要な特徴とする。 In order to achieve the above object, the surface-enhanced spectroscopic substrate of the present invention is a surface-enhanced spectroscopic substrate having a surface-enhancing effect in which metal-adhered fine particles to which metal is attached are formed on the substrate, A plurality of the metal-attached fine particles are aggregated to form a plurality of clusters in which the metal of the metal-attached fine particles are in contact with each other, and each of the clusters is electrically separated from the substrate. Is the main feature.
本発明によれば、基板上のすべての領域について、細密充填構造を取る必要がないので、表面増強分光用基板の作製が容易になり、粒径が揃った金属付着微粒子を用いる必要もない。粒径が一様な金属付着微粒子を用いる必要がないので、低価格化が可能となる。また、作製が容易、低価格化が可能というだけではなく、基板上の金属付着微粒子をクラスター構造とすることにより、表面増強効果を向上させることができ、性能の再現性を高めることができる。 According to the present invention, since it is not necessary to have a close-packed structure for all regions on the substrate, it is easy to produce a surface-enhanced spectroscopic substrate, and it is not necessary to use metal-attached fine particles having a uniform particle size. Since it is not necessary to use metal-attached fine particles having a uniform particle size, the price can be reduced. Moreover, not only is the fabrication easy and the cost can be reduced, but the surface enhancement effect can be improved and the reproducibility of the performance can be improved by forming the metal-attached fine particles on the substrate into a cluster structure.
以下、図面を参照して本発明の一実施形態を説明する。構造に関する図面は模式的なものであり、現実のものとは異なる。また、図面相互間においても互いの寸法の関係や比率が異なる部分が含まれている。 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings relating to the structure are schematic and different from the actual ones. Moreover, the part from which the relationship and ratio of a mutual dimension differ also in between drawings is contained.
図１は、本発明の表面増強分光用基板の基本的な構成を示す。ガラス、プラスティックやシリコン等の基板１の上に、微小球形状の金属付着微粒子１０が形成されている。金属付着微粒子１０は、例えば、粒径３０ｎｍから１０μｍの微小球形状の微粒子２と微粒子２に付着した金属層３とで構成されている。基板１上に微粒子２が固相化されており、微粒子２の表面の上半分程度が金属層３で帽子状に被覆されている。微粒子２はポリマー又はシリカ粒子等で構成される。金属層３は、金、銀、プラチナ（白金）、アルミ等の金属で構成されている。また、金、銀、プラチナ、アルミによる合金又は混合体のいずれかで構成されていても良い。さらに、基板１上の領域によって、金属層３の組成を変えても良い。金属層３の厚さは、２ｎｍ〜５００ｎｍ程度に形成される。 FIG. 1 shows a basic structure of a substrate for surface enhanced spectroscopy according to the present invention. On a substrate 1 made of glass, plastic, silicon, or the like, microspherical metal-attached fine particles 10 are formed. The metal-attached fine particles 10 are composed of, for example, microsphere-shaped fine particles 2 having a particle diameter of 30 nm to 10 μm and a metal layer 3 attached to the fine particles 2. The fine particles 2 are solid-phased on the substrate 1, and the upper half of the surface of the fine particles 2 is covered with a metal layer 3 in a hat shape. The fine particles 2 are composed of polymer or silica particles. The metal layer 3 is made of a metal such as gold, silver, platinum (platinum), or aluminum. Moreover, you may be comprised with either the alloy by gold | metal | money, silver, platinum, aluminum, or a mixture. Furthermore, the composition of the metal layer 3 may be changed depending on the region on the substrate 1. The metal layer 3 is formed with a thickness of about 2 nm to 500 nm.
金属付着微粒子１０は、図１に示すように、細密充填構造を取らず、いくつかの金属付着微粒子１０が集合して、一つの集合体（クラスター）を形成する。クラスター内の金属付着微粒子１０の金属層３は隣接する金属層同士で一部が接触するように形成されている。また、クラスターは間隔を置いて複数形成され、大きさが異なるクラスターが形成されるとともに、各クラスターは基板１上に不規則に散在している。このように、様々な形状と大きさに構成されたクラスターによるクラスター群が形成されている。 As shown in FIG. 1, the metal-attached fine particles 10 do not have a finely packed structure, and several metal-attached fine particles 10 gather to form one aggregate (cluster). The metal layer 3 of the metal-attached fine particles 10 in the cluster is formed so that a part of the metal layers 3 are in contact with each other. Further, a plurality of clusters are formed at intervals, clusters having different sizes are formed, and each cluster is irregularly scattered on the substrate 1. In this way, a cluster group is formed by clusters having various shapes and sizes.
図２は、金属付着微粒子１０のクラスターが散在する様子を示す平面図である。図２は、同じ粒径の金属付着微粒子１０が複数集まってクラスターを形成する例を示す。金属付着微粒子１０の粒径とは、微粒子２の粒径とほぼ一致するものであるが、厳密には金属層３を含めた大きさが粒径となる。 FIG. 2 is a plan view showing a state where clusters of metal-attached fine particles 10 are scattered. FIG. 2 shows an example in which a plurality of metal-attached fine particles 10 having the same particle diameter gather to form a cluster. The particle size of the metal-attached fine particles 10 is substantially the same as the particle size of the fine particles 2, but strictly speaking, the size including the metal layer 3 is the particle size.
クラスターＡ１は、３個の金属付着微粒子１０が集合することにより形成されている。クラスターＡ２は、９個の金属付着微粒子１０が集合することにより形成されている。クラスターＡ３は、２個の金属付着微粒子１０が集合することにより形成されている。クラスターＡ４は、３個の金属付着微粒子１０が集合することにより形成されている。クラスターＡ５は、５個の金属付着微粒子１０が集合することにより形成されている。図２からわかるように、基板１上には、大きさが異なり、形状も異なるクラスターが不規則に散在している。 The cluster A1 is formed by gathering three metal-attached fine particles 10. The cluster A2 is formed by the assembly of nine metal-attached fine particles 10. Cluster A3 is formed by aggregation of two metal-attached fine particles 10. The cluster A4 is formed by gathering three metal-attached fine particles 10 together. Cluster A5 is formed by collecting five metal-attached fine particles 10. As can be seen from FIG. 2, clusters having different sizes and different shapes are irregularly scattered on the substrate 1.
図１、２からわかるように、各クラスター内における金属付着微粒子１０の金属層３は、隣接する金属層３と相互に接触しているので、１つのクラスター内における金属付着微粒子１０はすべて電気的に接続されている。一方、金属層３のいずれも、基板１と接触していないので、各クラスターは、基板１と電気的に分離されている。 As can be seen from FIGS. 1 and 2, since the metal layer 3 of the metal-attached fine particles 10 in each cluster is in contact with the adjacent metal layer 3, all the metal-attached fine particles 10 in one cluster are electrically connected. It is connected to the. On the other hand, since none of the metal layers 3 is in contact with the substrate 1, each cluster is electrically separated from the substrate 1.
図３は、実際に金属付着微粒子１０がクラスターを構成し、各クラスターが不規則に散在している様子を走査型電子顕微鏡で撮影した画像を示す。白っぽい粒子が金属付着微粒子１０に相当し、異なる形態のクラスターを形成していることがわかる。基板１上では、金属付着微粒子１０が、ランダムに吸着されており、数個から数十個のクラスターが形成されていることが望ましい。 FIG. 3 shows an image taken with a scanning electron microscope of how the metal-attached fine particles 10 actually constitute clusters and each cluster is scattered irregularly. It can be seen that the whitish particles correspond to the metal-attached fine particles 10 and form clusters of different forms. On the substrate 1, the metal-attached fine particles 10 are adsorbed at random, and it is desirable that several to several tens of clusters are formed.
本発明の表面増強分光用基板の製造方法を以下に示す。基板１上にポリマーもしくは、シリカ粒子による微粒子２の単層を形成する。微粒子２の単層の形成方法は色々あるが、一番簡便な方法としては、粒子懸濁液の塩濃度を増大させて粒子間の斥力を低減させ、粒子を高表面エネルギーの基板上に単層として物理吸着させることが、効果的かつ低コストである。 The manufacturing method of the substrate for surface enhanced spectroscopy of the present invention is shown below. A single layer of fine particles 2 made of polymer or silica particles is formed on a substrate 1. There are various methods for forming the single layer of the fine particles 2, but the simplest method is to increase the salt concentration of the particle suspension to reduce the repulsive force between the particles and to place the particles on a high surface energy substrate. It is effective and low-cost to physically adsorb as a layer.
適切に塩濃度を制御して若干の斥力を残すことにより、微粒子２が２層以上形成されることを防ぐことができる。次に微粒子２の上半分に金、銀、白金、アルミ等の金属層３を形成する。一番容易な形成方法としては、基板１に吸着した微粒子２を真空蒸着装置もしくはスパッタ装置内部に設置して、金属を飛散させる方法を挙げることができる。真空蒸着及びスパッタを用いた場合は、微粒子２の上方が金属で被覆されて金属層３が形成されるが、下方が金属で被覆されない。このため、金属付着微粒子１０が基板１から電気的に分離されるので表面増強効果にとって望ましい。 By appropriately controlling the salt concentration and leaving a slight repulsive force, it is possible to prevent two or more fine particles 2 from being formed. Next, a metal layer 3 such as gold, silver, platinum, or aluminum is formed on the upper half of the fine particles 2. As the easiest forming method, there can be mentioned a method in which the fine particles 2 adsorbed on the substrate 1 are placed inside a vacuum vapor deposition apparatus or a sputtering apparatus, and the metal is scattered. When vacuum deposition and sputtering are used, the upper part of the fine particles 2 is coated with metal to form the metal layer 3, but the lower part is not covered with metal. For this reason, since the metal-attached fine particles 10 are electrically separated from the substrate 1, it is desirable for the surface enhancement effect.
以上のように形成された表面増強分光用基板の金属付着微粒子１０の金属層３中には自由電子が存在し、近紫外から近赤外波長の光が照射されると、自由電子の共鳴的振動は粒子表面上に局在する強力な近接場の形成につながる。このプラズモン共鳴周波数は、金属層３のサイズ、形状、元素に依存するが、異なったプラズモン共鳴周波数を有する金属付着微粒子１０が共存することが表面増強効果の観点から望ましい。 Free electrons are present in the metal layer 3 of the metal-adhered fine particles 10 of the surface-enhanced spectroscopic substrate formed as described above, and when light having a wavelength of near-ultraviolet to near-infrared is irradiated, the free electrons are resonant. The vibration leads to the formation of a strong near field localized on the particle surface. The plasmon resonance frequency depends on the size, shape, and element of the metal layer 3, but it is desirable from the viewpoint of the surface enhancement effect that the metal-adhered fine particles 10 having different plasmon resonance frequencies coexist.
上記の手法によって得られる金属付着微粒子１０の金属層３による金属クラスターは、数個から数十個の帽子状半球から構成され、各金属層が相互に接触することにより金属クラスター内の領域は電気的に接続される。これらのクラスターが光を吸収すると、面積の大きい部分から先鋭な部位にプラズモンが伝播し、先鋭部分で極めて強力な近接場が形成されることとなる。 The metal cluster formed by the metal layer 3 of the metal-adhered fine particles 10 obtained by the above method is composed of several to several tens of hat-shaped hemispheres, and the regions in the metal cluster are electrically connected by the metal layers contacting each other. Connected. When these clusters absorb light, plasmons propagate from a large area to a sharp part, and an extremely strong near field is formed at the sharp part.
図２で示したクラスター群の各クラスターにおけるプラズモン伝播の様子を図４に示す。図中の矢印がプラズモン伝播方向を示す。クラスターＡ２では、中央部分が最も面積が大きいので、この領域から先鋭な部位、すなわちクラスターＡ２の角に相当する部位に向けてプラズモンが伝播する。他のクラスターでも同様に、面積が大きい領域から先鋭な部位に向かってプラズモンが伝播する。図５は、図４のようにプラズモンが伝播した場合に、発生する近接場を示す。近接場は、図の網掛線で表わされている領域である。このように、プラズモン伝播方向の先端部に近接場が生じる。 FIG. 4 shows the state of plasmon propagation in each cluster of the cluster group shown in FIG. The arrow in the figure indicates the direction of plasmon propagation. In the cluster A2, since the central portion has the largest area, the plasmon propagates from this region toward a sharp part, that is, a part corresponding to the corner of the cluster A2. Similarly, in other clusters, plasmons propagate from a large area to a sharp part. FIG. 5 shows a near field generated when plasmons propagate as shown in FIG. The near field is an area represented by a shaded line in the figure. Thus, a near field is generated at the tip in the plasmon propagation direction.
図６は、粒径の異なる微粒子２を用い、粒径の異なる金属付着微粒子１０によるクラスター形成の状態を示す図である。異なる粒径の微粒子２を基板１に不規則に吸着させた後、帽子状の金属層３をスパッタ又は真空蒸着により形成する。 FIG. 6 is a diagram showing a state of cluster formation using fine particles 2 having different particle diameters and metal-attached fine particles 10 having different particle diameters. After the fine particles 2 having different particle diameters are adsorbed irregularly on the substrate 1, a cap-shaped metal layer 3 is formed by sputtering or vacuum deposition.
図６のように、クラスターＢ１は、粒径が異なるものが含まれる３個の金属付着微粒子１０により形成される。クラスターＢ２は、粒径が異なるものが含まれる８個の金属付着微粒子１０により形成される。クラスターＢ３は、粒径が異なるものが含まれる３個の金属付着微粒子１０により形成される。クラスターＢ４は、粒径が同じの２個の金属付着微粒子１０により形成される。クラスターＢ５は、粒径が異なるものが含まれる３個の金属付着微粒子１０により形成される。クラスターＢ６は、粒径が異なるものが含まれる５個の金属付着微粒子１０により形成される。 As shown in FIG. 6, the cluster B <b> 1 is formed by three metal-attached fine particles 10 including particles having different particle sizes. The cluster B2 is formed by eight metal-attached fine particles 10 including particles having different particle diameters. The cluster B3 is formed by three metal-attached fine particles 10 including particles having different particle diameters. The cluster B4 is formed by two metal-attached fine particles 10 having the same particle size. Cluster B5 is formed by three metal-attached fine particles 10 including particles having different particle diameters. The cluster B6 is formed by five metal-attached fine particles 10 including particles having different particle diameters.
プラズモン共鳴周波数は、金属層３のサイズ、形状、元素に依存するが、図６は、金属層３の大きさ（サイズ）を変えた金属付着微粒子１０が共存する例を示している。図６のように、様々な粒径の金属付着微粒子１０が集合することにより、１つのクラスターに異なるプラズモン共鳴周波数が存在するようになるため、クラスターの共鳴周波数は一定の幅を持つことになる。 Although the plasmon resonance frequency depends on the size, shape, and element of the metal layer 3, FIG. 6 shows an example in which the metal-attached fine particles 10 having different sizes (sizes) of the metal layer 3 coexist. As shown in FIG. 6, when the metal-attached fine particles 10 having various particle diameters are gathered, different plasmon resonance frequencies exist in one cluster. Therefore, the resonance frequency of the cluster has a certain width. .
近接場強度をさらに増強するためには、サイズが異なる金属付着微粒子１０を２層目以上に形成することが望ましい。１層目の形成方法と同じ方法を用いて２層目を形成するが、２層目の形成には、１層目に用いた金属付着微粒子１０とは粒径が大きく異なる金属付着微粒子１０を用いることが望ましい。 In order to further enhance the near-field strength, it is desirable to form the metal-attached fine particles 10 having different sizes in the second layer or more. The second layer is formed using the same method as the first layer formation method. For the formation of the second layer, the metal adhesion fine particles 10 having a particle size significantly different from that of the metal adhesion fine particles 10 used for the first layer are used. It is desirable to use it.
図７は、１層目の金属付着微粒子１０の粒径を異なるようにし、さらに２層目でも金属付着微粒子１０の粒径を異なるように形成した例である。クラスターＣ１では、１層目は同じ粒径の微粒子２に金属層３が被覆されることにより、同じ粒径の金属付着微粒子が形成される。しかし、２層目では１層目とは異なる粒径の微粒子３２に金属層３３が被覆されることにより、金属付着微粒子が形成される。このように、１層目と２層目で金属付着微粒子の粒径が異なる。 FIG. 7 shows an example in which the first-layer metal-attached fine particles 10 have different particle sizes, and the second-layer metal-attached fine particles 10 have different particle sizes. In the cluster C1, the metal layer 3 is covered with the fine particles 2 having the same particle diameter in the first layer, thereby forming metal-attached fine particles having the same particle diameter. However, in the second layer, the metal layer 33 is coated with the fine particles 32 having a particle diameter different from that of the first layer, thereby forming metal-attached fine particles. Thus, the particle size of the metal-attached fine particles is different between the first layer and the second layer.
また、クラスターＣ２の１層目は、微粒子２上に金属層３が形成された金属付着微粒子、微粒子２２上に金属層２３が形成された金属付着微粒子、微粒子３２上に金属層３３が形成された金属付着微粒子により構成されている。微粒子２、２２、３２は、いずれも粒径が異なるため、粒径が異なる３種類の金属付着微粒子が形成される。一方、クラスターＣ２の２層目は、微粒子２２上に金属層２３が形成された金属付着微粒子、微粒子３２上に金属層３３が形成された金属付着微粒子等で構成されている。微粒子２２、３２は粒径が異なるため、粒径が異なる金属付着微粒子が形成される。 Further, the first layer of the cluster C 2 includes metal-attached fine particles in which the metal layer 3 is formed on the fine particles 2, metal-attached fine particles in which the metal layer 23 is formed on the fine particles 22, and a metal layer 33 on the fine particles 32. It consists of fine metal-attached fine particles. Since the fine particles 2, 22, and 32 all have different particle sizes, three types of metal-attached fine particles having different particle sizes are formed. On the other hand, the second layer of the cluster C2 is composed of metal-attached fine particles in which the metal layer 23 is formed on the fine particles 22, metal-attached fine particles in which the metal layer 33 is formed on the fine particles 32, and the like. Since the fine particles 22 and 32 have different particle diameters, metal-attached fine particles having different particle diameters are formed.
この場合に、プラズモンは、面積の大きな部分から先鋭な部位に伝播するので、図の矢印のように、粒径の大きな金属付着微粒子１０から粒径の小さな金属付着微粒子１０に伝播することになる。このように、１層目の領域内におけるプラズモン伝播及び２層目の領域内におけるプラズモン伝播に加えて、１層目から２層目あるいは２層目から１層目の方向にプラズモンの伝播が発生するので、近接場強度がさらに強くなる。 In this case, since plasmon propagates from a portion with a large area to a sharp portion, it propagates from the metal-attached fine particles 10 having a large particle size to the metal-attached fine particles 10 having a small particle size, as indicated by arrows in the figure. . Thus, in addition to plasmon propagation in the first layer region and plasmon propagation in the second layer region, plasmon propagation occurs in the direction from the first layer to the second layer or from the second layer to the first layer. As a result, the near-field strength is further increased.
図８は、単層ではなく、多層化された金属クラスターを走査型電子顕微鏡で撮影した画像を示す。図９は、異なる粒径の金属付着微粒子から構成される金属クラスターを走査型電子顕微鏡で撮影した画像データを示す。 FIG. 8 shows an image obtained by photographing a multi-layered metal cluster with a scanning electron microscope instead of a single layer. FIG. 9 shows image data obtained by photographing a metal cluster composed of metal-attached fine particles having different particle diameters with a scanning electron microscope.
次に、本発明の表面増強分光用基板の増強効果を図１０、図１１に示す。図１０（ａ）は、基板１上に金薄膜４を２０ｎｍの厚さに形成し、この金薄膜４上に微粒子２として粒径１００ｎｍのシリカ粒子を吸着させてクラスター化し、シリカ粒子上に帽子状の銀からなる厚さ８０ｎｍの金属層３を形成してラマン分光用基板を作製した。 Next, the enhancement effect of the substrate for surface enhanced spectroscopy of the present invention is shown in FIGS. FIG. 10A shows that a gold thin film 4 having a thickness of 20 nm is formed on a substrate 1, and silica particles having a particle diameter of 100 nm are adsorbed and clustered on the gold thin film 4 to form a cap on the silica particles. A substrate for Raman spectroscopy was prepared by forming a metal layer 3 made of silver and having a thickness of 80 nm.
図１０（ｂ）は、基板１上に金薄膜４を２０ｎｍの厚さに形成し、この金薄膜４上に微粒子２として粒径１００ｎｍのシリカ粒子を吸着させてクラスター化し、シリカ粒子上には金属層３を形成しなかった。このように、ラマン分光用基板を作製した。 FIG. 10B shows that a gold thin film 4 having a thickness of 20 nm is formed on a substrate 1 and silica particles having a particle diameter of 100 nm are adsorbed onto the gold thin film 4 as fine particles 2 to be clustered. The metal layer 3 was not formed. In this way, a Raman spectroscopic substrate was produced.
図１０（ｃ）は、基板１上に金薄膜を形成せずに、基板１上に粒径１００ｎｍのシリカ粒子の微粒子２を吸着させてクラスター化し、シリカ粒子上に帽子状の銀からなる厚さ８０ｎｍの金属層３を形成してラマン分光用基板を作製した。 FIG. 10 (c) shows a case in which fine particles 2 of silica particles having a particle diameter of 100 nm are adsorbed and clustered on the substrate 1 without forming a gold thin film on the substrate 1, and the thickness of the cap-shaped silver on the silica particles. A metal layer 3 having a thickness of 80 nm was formed to produce a substrate for Raman spectroscopy.
図１０（ｄ）は、基板１上に厚さ８０ｎｍの銀薄膜５のみを形成して表面増強分光用基板を作製した。図１０（ｅ）は、基板１上に厚さ２０ｎｍの金薄膜５のみを形成してラマン分光用基板を作製した。 In FIG. 10 (d), only the silver thin film 5 having a thickness of 80 nm is formed on the substrate 1 to produce a substrate for surface enhanced spectroscopy. In FIG. 10E, a Raman spectroscopic substrate was fabricated by forming only a 20 nm thick gold thin film 5 on the substrate 1.
上記図１０（ａ）〜１０（ｅ）までのラマン分光用基板を用いてラマン分光の測定を行った。図１０（ａ）〜１０（ｅ）までのラマン分光用基板上に、濃度１０ｍＭのローダミン６Ｇエタノール溶液を滴下し、乾燥させたものを試料として用いた。このローダミン６Ｇは、蛍光色素の１種である。ラマン散乱の励起光として発振波長５１４．５ｎｍのレーザを用い、光強度は４００μＷに設定した。ラマン散乱光は、レーザラマン分光装置により測定した。 The Raman spectroscopy was measured using the Raman spectroscopy substrates shown in FIGS. 10 (a) to 10 (e). A 10 mM concentration rhodamine 6G ethanol solution was dropped on the Raman spectroscopic substrates shown in FIGS. 10 (a) to 10 (e) and dried, and used as a sample. This rhodamine 6G is one type of fluorescent dye. A laser having an oscillation wavelength of 514.5 nm was used as excitation light for Raman scattering, and the light intensity was set to 400 μW. The Raman scattered light was measured with a laser Raman spectroscope.
上記測定結果を、図１１に示す。縦軸は信号強度を、横軸はラマンシフト（ｃｍ−１）を示す。図１１のグラフのうち、曲線Ａが１０（ａ）のラマン分光用基板による測定結果を、曲線Ｂが１０（ｂ）のラマン分光用基板による測定結果を、曲線Ｃが１０（ｃ）のラマン分光用基板による測定結果を、曲線Ｄが１０（ｄ）のラマン分光用基板による測定結果を、曲線Ｅが１０（ｅ）のラマン分光用基板による測定結果を示す。なお、曲線Ｄと曲線Ｅとは一致している。これらの曲線からわかるように、強い増強が見られたバンドが現われているのは、曲線Ａと曲線Ｃである。他の曲線については、増強を示すバンドは現われていない。図１１の測定結果から、１０（ａ）のラマン分光用基板と１０（ｃ）のラマン分光用基板においてのみ増強効果が見られることがわかる。 The measurement results are shown in FIG. The vertical axis represents signal intensity, and the horizontal axis represents Raman shift (cm −1 ). In the graph of FIG. 11, the measurement result using the Raman spectroscopy substrate with the curve A being 10 (a), the measurement result using the Raman spectroscopy substrate with the curve B being 10 (b), and the Raman having the curve C being 10 (c). The measurement results with the spectroscopic substrate, the measurement results with the Raman spectroscopic substrate with a curve D of 10 (d), and the measurement results with the Raman spectroscopic substrate with a curve E of 10 (e) are shown. Note that the curve D and the curve E coincide with each other. As can be seen from these curves, it is curve A and curve C that show bands with strong enhancement. For the other curves, no band showing enhancement appears. From the measurement results of FIG. 11, it can be seen that the enhancement effect can be seen only in the 10 (a) Raman spectroscopy substrate and the 10 (c) Raman spectroscopy substrate.
１０（ｃ）のラマン分光用基板は、図１の本発明の表面増強分光用基板と基本的に同一の構成であり、また、１０（ａ）のラマン分光用基板は、金薄膜４が存在することを除けば、図１の構成と基本的に同一であるので、これにより、本発明の表面増強分光用基板の増強効果が示された。 The substrate for Raman spectroscopy 10 (c) has basically the same structure as the substrate for surface enhanced spectroscopy of the present invention shown in FIG. 1, and the substrate for Raman spectroscopy 10 (a) has a gold thin film 4. Except for the above, since it is basically the same as the configuration of FIG. 1, the enhancement effect of the substrate for surface enhanced spectroscopy according to the present invention was shown.
次に、金属付着微粒子１０の基板１に対する吸着密度により、増強効果がどのように変わるのかを測定した。この測定には、図１、２のようにクラスター化された表面増強分光用基板を用いた。ここで、微粒子２には粒径１００ｎｍのシリカ粒子を用い、金属層３は膜厚１４０ｎｍの銀を蒸着することにより構成した。一方、基板１への微粒子２の吸着については、シリカ粒子懸濁液の塩濃度を適宜調整すること等により、吸着密度を５つのパターンに形成した。 Next, it was measured how the enhancement effect changes depending on the adsorption density of the metal-attached fine particles 10 to the substrate 1. For this measurement, a clustered surface-enhanced spectroscopic substrate as shown in FIGS. Here, silica particles having a particle diameter of 100 nm were used as the fine particles 2, and the metal layer 3 was formed by vapor-depositing silver having a film thickness of 140 nm. On the other hand, with respect to the adsorption of the fine particles 2 on the substrate 1, the adsorption density was formed in five patterns by appropriately adjusting the salt concentration of the silica particle suspension.
このように、微粒子２をクラスター化し、クラスターの分散度を変えることにより、金属付着微粒子１０の吸着密度が変えられた表面増強分光用基板上に、濃度１０ｍＭのローダミン６Ｇエタノール溶液を滴下し、乾燥させた。この試料によりラマン分光スペクトルをレーザラマン分光装置で測定した。励起光には、発振波長５１４．５ｎｍのレーザ光を用い、光強度は４００μＷとした。 In this way, a 10 mM rhodamine 6G ethanol solution is dropped onto a surface-enhanced spectroscopic substrate in which the adsorption density of the metal-attached fine particles 10 is changed by clustering the fine particles 2 and changing the dispersion degree of the clusters, and then drying. I let you. With this sample, the Raman spectrum was measured with a laser Raman spectrometer. As the excitation light, laser light having an oscillation wavelength of 514.5 nm was used, and the light intensity was 400 μW.
図１２に、金属付着微粒子１０の吸着密度が異なる５つのパターンを示す。図１２（ａ）〜図１２（ｅ）は、走査型電子顕微鏡による撮像画像を示す。白っぽく見えるのが、金属付着微粒子１０を示すが、図１２（ａ）が最も吸着密度が低く、図１２（ｂ）、図１２（ｃ）、図１２（ｄ）、図１２（ｅ）の順に吸着密度が高くなっている。 FIG. 12 shows five patterns with different adsorption densities of the metal-attached fine particles 10. FIG. 12A to FIG. 12E show images captured by a scanning electron microscope. The metal adhering fine particles 10 that appear whitish are shown in FIG. 12A. FIG. 12A shows the lowest adsorption density, and FIG. 12B, FIG. 12C, FIG. 12D, and FIG. The adsorption density is high.
次に、これらの吸着密度が異なる表面増強分光用基板を用いてラマン分光測定による結果を図１３に示す。縦軸は信号強度を、横軸はラマンシフト（ｃｍ−１）を示す。ラマンスペクトルのうち、曲線Ｘが図１２（ａ）の吸着密度の場合を、曲線Ｙが図１２（ｂ）の吸着密度の場合を、曲線Ｚが図１２（ｃ）の吸着密度の場合を、曲線Ｕが図１２（ｄ）の吸着密度の場合を、曲線Ｖが図１２（ｅ）の吸着密度の場合を示す。全体の信号強度を見ると、曲線Ｖが最も低く、曲線Ｕ、曲線Ｚ、曲線Ｙ、曲線Ｘの順に信号強度が高くなっている。したがって、粒子の吸着密度が低い方、すなわち金属付着微粒子がクラスター化されて分散している方が表面増強効果が高くなることがわかる。 Next, FIG. 13 shows the results of Raman spectroscopic measurement using these surface-enhanced spectroscopic substrates having different adsorption densities. The vertical axis represents signal intensity, and the horizontal axis represents Raman shift (cm −1 ). Of the Raman spectra, the curve X is the adsorption density of FIG. 12 (a), the curve Y is the adsorption density of FIG. 12 (b), and the curve Z is the adsorption density of FIG. 12 (c). The curve U shows the case of the adsorption density in FIG. 12D, and the curve V shows the case of the adsorption density in FIG. Looking at the overall signal strength, the curve V is the lowest, and the signal strength increases in the order of the curve U, the curve Z, the curve Y, and the curve X. Therefore, it can be seen that the surface enhancement effect is higher when the adsorption density of the particles is lower, that is, when the metal-attached fine particles are clustered and dispersed.
次に、図１の構成の表面増強分析基板を用いて金属付着微粒子の質が均一に形成されているかの確認を行った。ここで、微粒子２には粒径１５０ｎｍのシリカ粒子を用い、金属層３は膜厚２０ｎｍの銀を蒸着することにより構成した。表面増強分光用基板上に、濃度１０ｍＭのローダミン６Ｇエタノール溶液を滴下し、乾燥させた。この試料によりラマン分光スペクトルをレーザラマン分光装置で測定した。励起光には、発振波長５１４．５ｎｍのレーザ光を用い、光強度は４００μＷとした。そして、基板１上の異なる領域からのラマンスペクトルをレーザラマン分光装置で測定した。 Next, it was confirmed whether the quality of the metal-attached fine particles was uniformly formed using the surface-enhanced analysis substrate having the configuration shown in FIG. Here, silica particles having a particle diameter of 150 nm were used as the fine particles 2, and the metal layer 3 was formed by vapor-depositing silver having a thickness of 20 nm. A rhodamine 6G ethanol solution having a concentration of 10 mM was dropped on the surface-enhanced spectroscopic substrate and dried. With this sample, the Raman spectrum was measured with a laser Raman spectrometer. As the excitation light, laser light having an oscillation wavelength of 514.5 nm was used, and the light intensity was 400 μW. And the Raman spectrum from the different area | region on the board | substrate 1 was measured with the laser Raman spectrometer.
図１４には、基板１上の３つの領域からのラマンスペクトルが表示されている。縦軸は信号強度を、横軸はラマンシフト（ｃｍ−１）を示す。Ｄ１〜Ｄ３の曲線がそれぞれ基板１上の異なる領域からのラマン分光測定結果である。Ｄ１〜Ｄ３の曲線のピークの高さは、ほぼ同じであることがわかり、このことから金属付着微粒子の質は均一であると考えられる。 In FIG. 14, Raman spectra from three regions on the substrate 1 are displayed. The vertical axis represents signal intensity, and the horizontal axis represents Raman shift (cm −1 ). The curves D1 to D3 are the Raman spectroscopic measurement results from different regions on the substrate 1, respectively. It can be seen that the peak heights of the curves D1 to D3 are substantially the same, and it is considered that the quality of the metal-attached fine particles is uniform.
次に、粒径の異なる金属付着微粒子を混合して作製した表面増強分光用基板を用いてラマン分光測定を行った結果を図１６に示す。図１６の縦軸は信号強度を、横軸はラマンシフト（ｃｍ−１）を示す。このラマン分光測定には、図１５に示す２種類の粒径の金属付着微粒子を用いた。微粒子２Ａ上に帽子状の金属層３Ａが形成された金属付着微粒子１０Ａと、微粒子２Ｂ上に帽子状の金属層３Ｂが形成された金属付着微粒子１０Ｂである。微粒子２Ａ、２Ｂにはシリカ粒子を、金属層３Ａ、３Ｂには銀を用いた。図に示されるように、微粒子２Ａの粒径は１００ｎｍとし、微粒子２Ｂの粒径を５０ｎｍとした。これら２種類の粒径による金属付着微粒子が混合され、かつ、図６のようにクラスター化された表面増強分光用基板を上記ラマン分光測定に用いた。 Next, FIG. 16 shows the results of Raman spectroscopic measurement using a surface-enhanced spectroscopic substrate prepared by mixing metal-attached fine particles having different particle diameters. The vertical axis in FIG. 16 indicates the signal intensity, and the horizontal axis indicates the Raman shift (cm −1 ). In this Raman spectroscopic measurement, metal-attached fine particles having two types of particle diameters shown in FIG. A metal-attached fine particle 10A in which a hat-like metal layer 3A is formed on the fine particle 2A, and a metal-attached fine particle 10B in which a hat-like metal layer 3B is formed on the fine particle 2B. Silica particles were used for the fine particles 2A and 2B, and silver was used for the metal layers 3A and 3B. As shown in the figure, the particle diameter of the fine particles 2A was 100 nm, and the particle diameter of the fine particles 2B was 50 nm. A surface-enhanced spectroscopic substrate in which metal adhering fine particles having these two types of particle diameters were mixed and clustered as shown in FIG. 6 was used for the Raman spectroscopic measurement.
金属付着微粒子１０Ａ、１０Ｂが混合して形成された表面増強分光用基板は、上記の異なる粒径の微粒子２Ａと微粒子２Ｂを混合した微粒子混合懸濁液を作製し、この微粒子混合懸濁液を基板１に吸着させてクラスター化し、微粒子２Ａ上には金属層３Ａを、微粒子２Ｂ上には金属層３Ｂを形成して作製した。微粒子混合懸濁液は、微粒子２Ａと微粒子２Ｂの混合比率を変化させて４種類作製し、これらの微粒子混合懸濁液に基づき、それぞれ表面増強分光用基板を作製した。微粒子２Ａの懸濁液と微粒子２Ｂの懸濁液の混合比率が５０：５０の微粒子混合懸濁液による表面増強分光用基板をＥ１、混合比率が７０：３０の微粒子混合懸濁液による表面増強分光用基板をＥ２、混合比率が９０：１０の微粒子混合懸濁液による表面増強分光用基板をＥ３、混合比率が１００：０の微粒子混合懸濁液による表面増強分光用基板をＥ４として作製した。上記のように、粒径１００ｎｍの微粒子２Ａの混合割合を最初は５０％とし、次に順に混合割合を増加させ、最後は微粒子２Ａのみ、すなわち金属付着微粒子１０Ａのみとした。 The surface-enhanced spectroscopic substrate formed by mixing the metal-adhered fine particles 10A and 10B produces a fine particle mixed suspension in which the fine particles 2A and the fine particles 2B having different particle diameters are mixed. The metal layer 3A was formed on the fine particles 2A and the metal layer 3B was formed on the fine particles 2B. Four kinds of fine particle mixed suspensions were prepared by changing the mixing ratio of the fine particles 2A and the fine particles 2B, and based on these fine particle mixed suspensions, substrates for surface enhancement spectroscopy were prepared. Surface enhancement by a fine particle mixture suspension with a fine particle 2A suspension and a fine particle 2B suspension with a fine particle mixture suspension with a 50:50 fine particle mixture suspension with E1 and a mixing ratio of 70:30 The substrate for spectroscopic enhancement was E2, the substrate for surface-enhanced spectroscopy using a fine particle mixture suspension with a mixing ratio of 90:10 was made E3, and the substrate for surface-enhanced spectroscopy with a fine particle mixture suspension with a mixing ratio of 100: 0 was made E4. . As described above, the mixing ratio of the fine particles 2A having a particle diameter of 100 nm was initially set to 50%, then the mixing ratio was increased in order, and finally only the fine particles 2A, that is, only the metal-attached fine particles 10A were used.
Ｅ１〜Ｅ４の４種類の各表面増強分光用基板上に、濃度１０ｍＭのローダミン６Ｇエタノール溶液を滴下し、乾燥させた。この試料によりラマン分光スペクトルをレーザラマン分光装置で測定した。励起光には、発振波長５１４．５ｎｍのレーザ光を用い、光強度は５０μＷとした。図１６のラマンスペクトルＥ１〜Ｅ４は、上記各表面増強分光用基板Ｅ１〜Ｅ４に対応している。図１６を見ると、ピークの高さは、２種類の粒径の金属付着微粒子の混合比率が近くなる程、高くなっており、５０：５０の混合比率のときに最も高くなっていることがわかる。 A rhodamine 6G ethanol solution having a concentration of 10 mM was dropped on each of the four types of surface-enhanced spectroscopic substrates E1 to E4 and dried. With this sample, the Raman spectrum was measured with a laser Raman spectrometer. As the excitation light, laser light having an oscillation wavelength of 514.5 nm was used, and the light intensity was 50 μW. The Raman spectra E1 to E4 in FIG. 16 correspond to the respective surface enhanced spectroscopic substrates E1 to E4. When FIG. 16 is seen, the height of the peak becomes higher as the mixing ratio of the metal-attached fine particles having two kinds of particle diameters is closer, and is highest when the mixing ratio is 50:50. Recognize.
一方、金属付着微粒の粒径とラマン散乱光強度の関係を図１７に示す。まず、図１、２に示されるような、金属付着微粒子１０の粒径が同じものをクラスター化した表面増強分光用基板を作製した。金属付着微粒子１０の粒径を１００ｎｍにしてクラスター化した表面増強分光用基板をＦ１、金属付着微粒子１０の粒径を１５０ｎｍにしてクラスター化した表面増強分光用基板をＦ２、金属付着微粒子１０の粒径を５０ｎｍにしてクラスター化した表面増強分光用基板をＦ３として作製した。Ｆ１〜Ｆ３のすべてにおいて、微粒子２には、シリカ粒子を、金属層３には銀を用いた。 On the other hand, FIG. 17 shows the relationship between the particle size of the metal-attached fine particles and the Raman scattered light intensity. First, as shown in FIGS. 1 and 2, a surface-enhanced spectroscopic substrate in which the metal-attached fine particles 10 having the same particle diameter were clustered was prepared. The surface-enhanced spectroscopic substrate clustered with the particle size of the metal-attached fine particles 10 set to 100 nm is F1, the surface-enhanced spectroscopic substrate clustered with the particle size of the metal-attached fine particles 10 set to 150 nm is F2, and the metal-attached fine particle 10 particles A surface-enhanced spectroscopic substrate clustered with a diameter of 50 nm was prepared as F3. In all of F1 to F3, silica particles were used for the fine particles 2 and silver was used for the metal layer 3.
Ｆ１〜Ｆ３の３種類の各表面増強分光用基板上に、濃度１０ｍＭのローダミン６Ｇエタノール溶液を滴下し、乾燥させた。この試料によりラマン分光スペクトルをレーザラマン分光装置で測定した。励起光には、発振波長５１４．５ｎｍのレーザ光を用い、光強度は５００μＷとした。 A rhodamine 6G ethanol solution having a concentration of 10 mM was dropped on each of the three types of surface-enhanced spectroscopic substrates F1 to F3 and dried. With this sample, the Raman spectrum was measured with a laser Raman spectrometer. As excitation light, laser light having an oscillation wavelength of 514.5 nm was used, and the light intensity was 500 μW.
図１７のラマンスペクトルに示されるように、粒径１００ｎｍの金属付着微粒子を用いたＦ１と粒径１５０ｎｍの金属付着微粒子を用いたＦ２では信号強度は近くなっている。しかし、Ｆ１は、粒径５０ｎｍの金属付着微粒子を用いたＦ３より、全体に信号強度が高くなっている。このように、粒径の大きな金属付着微粒子を用いた表面増強分光用基板の方が信号強度が高くなる。他方、図１６からわかるように、粒径１００ｎｍのみの金属付着微粒子で表面増強分光用基板を作製するのではなく、他の異なる粒径の金属付着微粒子と混合して表面増強分光用基板を作製した方が、ラマン信号強度がさらに増強されることがわかる。 As shown in the Raman spectrum of FIG. 17, the signal intensity is close between F1 using metal-attached fine particles having a particle size of 100 nm and F2 using metal-attached fine particles having a particle size of 150 nm. However, the signal intensity of F1 as a whole is higher than that of F3 using metal-attached fine particles having a particle diameter of 50 nm. As described above, the signal intensity is higher in the surface-enhanced spectroscopic substrate using the metal-attached fine particles having a large particle diameter. On the other hand, as can be seen from FIG. 16, the surface-enhanced spectroscopic substrate is not mixed with metal-attached fine particles having a particle size of only 100 nm, but is mixed with other metal-attached fine particles with different particle sizes to produce a surface-enhanced spectroscopic substrate. This shows that the Raman signal intensity is further enhanced.
以上のように、本発明の表面増強分光用基板では、従来のナノリソグラフィー法による分光用基板と比較して、金属付着微粒子が細密充填されている必要がなく、また金属付着微粒子は単分散性である必要がない。また、細密充填構造でなく、金属付着微粒子がクラスター化されて分散されている方が増強効果が高いことがわかった。このため、金属付着微粒子をクラスター化し、各クラスターが不規則に散在するように構成している。本発明の表面増強分光用基板は、粒径に幅をもたせた金属付着微粒子をランダムに基板上に吸着させることで、簡単に上記の構造を実現できるものである。さらに、異なる粒径の金属付着微粒子層を複数積み上げることによっても、上記の構造を実現することができる。ランダムに金属付着微粒子を基板に吸着させるのは容易であり、大面積の基板を高い歩留まりで作製するのに有利である。 As described above, the surface-enhanced spectroscopic substrate of the present invention does not need to be finely packed with metal-attached fine particles, and the metal-attached fine particles are monodisperse as compared with a conventional nanolithographic spectroscopic substrate. There is no need to be. Further, it was found that the enhancement effect is higher when the metal-adhered fine particles are clustered and dispersed instead of the densely packed structure. For this reason, the metal-adhered fine particles are clustered so that each cluster is scattered irregularly. The surface-enhanced spectroscopic substrate of the present invention can easily realize the above structure by randomly adsorbing metal-adhered fine particles having a wide particle size on the substrate. Furthermore, the above structure can also be realized by stacking a plurality of metal-attached fine particle layers having different particle diameters. It is easy to randomly adsorb metal-adhered fine particles to a substrate, which is advantageous for producing a large-area substrate with a high yield.
本発明の表面増強分光用基板は、ラマン分光法、赤外分光法等の分光分析方法に幅広く適用することができ、例えば、臨床検査、環境モニタリング、品質管理等の分野に適用することができる。 The substrate for surface-enhanced spectroscopy of the present invention can be widely applied to spectroscopic analysis methods such as Raman spectroscopy and infrared spectroscopy, and can be applied to fields such as clinical examination, environmental monitoring, and quality control. .
１ 基板
２ 微粒子
３ 金属層
２２ 微粒子
２３ 金属層
３２ 微粒子
３３ 金属層
１０ 金属付着微粒子
DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Fine particle 3 Metal layer 22 Fine particle 23 Metal layer 32 Fine particle 33 Metal layer 10 Metal adhesion fine particle
Claims (6)
前記基板上には、複数の前記金属付着微粒子が集合して該金属付着微粒子の金属が相互に接触しているクラスターが間隔を置いて複数形成され、前記各クラスターは前記基板と電気的に分離されていることを特徴とする表面増強分光用基板。 A surface-enhanced spectroscopic substrate having a surface-enhancing effect in which metal-attached fine particles to which metal is attached are formed on the substrate,
On the substrate, a plurality of clusters in which a plurality of the metal-attached fine particles are aggregated and the metal of the metal-attached fine particles are in contact with each other are formed at intervals, and each of the clusters is electrically separated from the substrate. A surface-enhanced spectroscopic substrate, which is characterized in that:
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| GB2532356B (en) * | 2013-08-23 | 2020-04-15 | Ukon Craft Science Ltd | Substrate for surface-enhanced raman scattering spectroscopy, and device using same |
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