JP6423137B2 - Manufacturing method of substrate for surface enhanced spectroscopy - Google Patents

Description

  The present invention relates to a method for producing a substrate for surface-enhanced spectroscopy that is effective for spectroscopic measurements such as Raman spectroscopy and infrared spectroscopy.

    In optical analysis methods such as Raman spectroscopy and infrared spectroscopy, surface enhancement methods using noble metal nanostructures are widely studied. A surface-enhanced spectroscopic substrate for using the surface-enhancement method forms a noble metal nanostructure solid-phased on the substrate.

    A typical example of a conventional method for producing a substrate for surface-enhanced spectroscopy is a method of chemically etching the surface of silver which is a noble metal. In addition, for example, FIG. 9A is a method of forming a noble metal nanostructure 51b by forming a noble metal thin film 51a from noble metal particles 52 on the surface of a substrate 50 by vacuum deposition and annealing by heating. FIG. 9B shows a method in which the noble metal colloid 53 is adsorbed on the surface of the substrate 50.

  FIG. 9C shows a method of patterning noble metals 54 and 55 having various nano-sized shapes on the substrate 50 by making full use of a fine processing technique including an electron beam drawing system. FIG. 9D shows a method performed in recent years, in which the noble metal particles 56 are deposited on the single-layered nanoparticles 57 formed on the surface of the substrate 50 by vacuum evaporation to form the noble metal 58. It is a method to do.

JP-A-11-1703

Ralph A. Tripp et al., Nanotoday JUN-AUG 2008 VOLUME3 NUMBER3-4 “Novel nanostructures for SERS biosensing”

    By the way, the important points in the production of the substrate for surface-enhanced spectroscopy are that it has a desirable structure and can exhibit the enhancement rate, that the enhancement rate is uniform, that the change over time is small, and that a general-purpose manufacturing apparatus is inexpensive. It can be prepared.

  However, the chemical etching method, which is a typical example of the conventional manufacturing method, is simple but has poor controllability and cannot be expected to have a high enhancement rate. The annealing method of FIG. 9A has a controllability problem, the form of the produced noble metal nanostructure easily changes, and the change with time is remarkable. Furthermore, since most of the precious metals consumed in vacuum deposition adhere to the inside of the deposition apparatus, there is a problem that waste is very large and the cost is high. The colloidal adsorption method of FIG. 9B also has a high enhancement rate, requires a large amount of expensive colloidal liquid, and is expensive.

  In the electronic drawing system of FIG. 9 (c), the degree of freedom of the shape capable of producing the noble metal nanostructure is very large, but the manufacturing apparatus is expensive and the throughput is extremely low. The nanoparticle deposition method of FIG. 9 (d) is excellent in performance and uniformity, and the manufacturing process is simple, but most of the precious metals consumed in vacuum deposition adhere to the inside of the deposition apparatus, which is very wasteful. There is a problem that it is large and expensive.

  The present invention was devised to solve the above-described problems, and is excellent in performance and uniformity of the enhancement rate, and can be manufactured by a simple process, so that the entire cost can be obtained without wasting precious metals. It is an object of the present invention to provide a method for manufacturing a substrate for surface enhanced spectroscopy that can suppress the above.

  In order to achieve the above object, a method for producing a substrate for surface enhanced spectroscopy according to the present invention comprises a step of forming a base metal nanostructure on a substrate and a step of adding a silver nitrate solution to the base metal nanostructure. This is the main feature.

  According to the present invention, a substrate for surface enhanced spectroscopy can be produced by a simple process with excellent performance and uniformity of enhancement rate, and cost can be suppressed without wasting precious metals.

    First, since the base metal nanostructure is formed in the first step, even if a large amount of base metal is used in this step, the cost is low. In addition, since the ionization tendency of the base metal is larger than that of silver, silver is replaced with the base metal by a chemical reaction between the base metal nanostructure and the silver nitrate solution in the next step. In this way, by using a base metal as a seed, silver can be used in a necessary amount, so that the cost can also be suppressed from this point.

    Further, by using different types of base metals, various forms of silver nanostructures can be produced, so that silver nanostructures optimized for a specific application can be selected.

It is a figure which shows the manufacturing method of the board | substrate for surface enhancement spectroscopy of this invention. It is a figure which shows the noble metal nanostructure of various shapes, and the fluorescent dye adsorb | sucked to the surface. It is a SEM photograph which shows the nanostructure at the time of not forming the silver nanostructure manufactured using the base metal of copper and aluminum as a seed, and a base metal. It is a SEM photograph which shows a silver nanostructure at the time of making a base metal into copper and changing the vapor deposition thickness of copper. It is a SEM photograph which shows the silver nanostructure at the time of changing reaction time with a silver nitrate solution with respect to the same base metal. It is a SEM photograph which shows the form of the substrate surface when not using a nanoparticle. It is a figure which shows that the silver nanostructure in this invention is excellent in the performance of the enhancement rate irrespective of the kind of base metal, and the particle size of a nanoparticle. It is a figure which shows the influence which the kind of base metal, vapor deposition thickness, and the particle size of a nanoparticle have on fluorescence intensity. It is a figure which shows the preparation methods of the conventional noble metal nanostructure.

  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.

    In the method for producing a substrate for surface-enhanced spectroscopy of the present invention, first, as shown in FIG. 1A, base metal particles 4 are deposited on the nanoparticles 2 adsorbed on the substrate 1 and solidified by vacuum deposition or sputtering. To form a hat-shaped base metal layer 3.

  Next, as shown in FIG. 1B, a silver nitrate solution 5 is added to the structure of FIG. When the silver nitrate solution 5 is added, the ionization tendency of the base metal 3 is higher than the ionization tendency of silver, so that the base metal dissolves into the solution as + ions, and at the same time, silver is deposited on the surfaces of the nanoparticles 2. In this manner, not only the hat-shaped silver layer 6a but also the filament-shaped silver layer 6b is formed on the nanoparticle 2.

  Here, the substrate 1 is made of a material such as glass, plastic, quartz, or silicon. The nanoparticles 2 are made of a dielectric material such as silica, polystyrene, titanium oxide, or the like.

  Silver has various crystal structures depending on the type of base metal used. In FIG. 1A, when another base metal layer is formed on the nanoparticles 2 by changing the type of base metal, when the silver nitrate solution 5 is added, for example, as shown in FIG. In addition, a hat-shaped silver layer 7 a and a plate-shaped silver layer 7 b are formed on the nanoparticles 2.

  Thus, in the conventional nanoparticle deposition method shown in FIG. 9D, only a hat-shaped silver layer was obtained on the nanoparticles, whereas in the method of FIG. In addition to the silver layer, a silver layer having a filament shape, a plate shape, or the like can be formed, and various shapes of silver nanostructures suitable for surface-enhanced spectroscopy can be produced.

    As will be described later, various silver nanostructures can be produced by changing the base metal deposition thickness, particle size, etc., in addition to the base metal type.

  In addition, when compared with the conventional FIGS. 9A and 9D, in the present invention, silver is not directly formed on the nanoparticles or the substrate by a method such as vapor deposition or sputtering, but first becomes a seed or a dummy. After the base metal layer is formed, silver is deposited on the nanoparticles. Thus, unlike the conventional method, the waste of silver, which is a noble metal, is remarkably suppressed, so that the cost can be reduced. Compared with the colloidal adsorption method of FIG. 9B, the amount of silver used is suppressed, so that the cost can be reduced.

  In the description of FIG. 1, the base metal nanostructure formed on the substrate has a structure in which the base metal layer 3 is formed on the nanoparticles 2 produced by vacuum deposition or sputtering. For example, FIG. First, a base metal nanostructure may be formed on a substrate using the methods a) to (c). After this step, a silver nitrate solution may be added to the base metal nanostructure to produce a silver nanostructure.

  As one of the above production examples, a method in which a copper colloid that is a base metal is adsorbed on a substrate and a silver nanostructure is produced by treatment with silver nitrate is also conceivable. However, the number of parameters that can be controlled in silver nanoparticle production is extremely limited as compared with the case where a base metal nanostructure is formed by vacuum deposition or sputtering and finally a silver nanostructure is produced. Silver nanoparticles are also formed by treating the glass surface with a silver mirror reaction, but in this case as well, the degree of freedom in production is extremely limited.

  Here, desirable noble metal nanostructures in the surface enhancement method are irregularities, colloidal particles, and protrusions of about several nm to several hundred nm, and it is preferable that a plurality of adjacent structures are arranged at intervals of less than 10 nm. FIG. 2 (a) shows a plan view and shows noble metal nanostructures 12, 13, 14, 15, 16 that may be desirable for surface enhancement effects.

    It is considered that the fluorescence signal and the Raman scattered light from the phosphor 20 adsorbed on the surfaces of the noble metal nanostructures 12 to 16 are enhanced. FIG. 2B shows a structure in which a plurality of the noble metal nanostructures 12 to 16 in FIG. 2A are gathered. When the phosphor 20 is present between the noble metal nanostructures, the enhancement rate is further improved. Is expected to do.

(Example)
A slide glass is used as the substrate 1, and silica nanoparticles are used as the nanoparticles 2. In order to adsorb the silica nanoparticles on the slide glass, the surface of the slide glass is chemically modified. Prepare an aqueous solution of a silane coupling reagent such as 3-aminopropyltrimethoxysilane or 3-aminopropyltriethoxysilane in a weight ratio of 0.1 to 10%, and place the slide glass in the aqueous solution for 10 seconds to 1 minute. Soak between. Next, the slide glass is washed with purified water and dried.

  A suspension of silica nanoparticles having a particle size of 20 to 1000 nm (20 nm or more and 1000 nm or less) having a weight ratio of 0.1 to 5% is transferred to purified water, and excess silica nanoparticles are washed away from the surface of the slide glass. When the slide glass is sufficiently dried at room temperature, the substrate is placed in a vacuum deposition apparatus.

  Base metals have a greater tendency to ionize than the noble metal silver. For this reason, copper (Cu), aluminum (Al), iron (Fe), nickel (Ni), chromium (Cr), titanium (Ti), zinc (Zn), manganese (Mn), lead (Pb) which are base metals And the like are deposited in a thickness of 5 nm to 1000 nm (5 nm or more and 1000 nm or less). Next, the nanoparticles on which the cap-shaped base metal layer is formed by vapor deposition are immersed in a silver nitrate solution. The concentration is suitably from 0.01 to 0.1 mol, and the reaction time is preferably from 30 seconds to 1 hour. Finally, the reaction is terminated by immersing in pure water.

    FIG. 3A is an SEM photograph showing a silver nanostructure formed when the base metal formed on the nanoparticles is copper. Similarly, FIG. 3B is an SEM photograph showing a silver nanostructure when the base metal formed on the nanoparticles is aluminum.

  3 (a) and 3 (b), silica nanoparticles are used as the nanoparticles 2, the silica nanoparticles have a particle size of 100 nm, a silver nitrate concentration of 0.1 mol, and a reaction time of 30 minutes. In the case of FIG. 3A, the base metal is copper, and the vapor deposition thickness is 30 nm. In the case of FIG.3 (b), a base metal is aluminum and the vapor deposition thickness is 20 nm. FIG.3 (c) is a case where silver nitrate is made to react with the nanoparticle in which a base metal is not formed, the silver nanostructure is not formed, but only the shape of the silica nanoparticle is image | photographed. .

  The SEM photograph of FIG. 4 shows silver nanostructures produced by changing the thickness of the base metal copper. The particle diameter of the silica nanoparticles is 100 nm, the concentration of silver nitrate is 0.1 mol, and the reaction time is 5 minutes. Moreover, the vapor deposition thickness of copper is 10 nm in the case of FIG. 4A, 30 nm in the case of FIG. 4B, and 100 nm in the case of FIG. 4C. As can be seen from FIGS. 4A to 4C, the obtained silver nanostructures vary greatly depending on the thickness of the base metal.

FIG. 5 shows a silver nanostructure produced by changing the reaction time between the base metal and the silver nitrate solution in FIGS. 1 (b) and 1 (c). The particle diameter of the silica nanoparticles is 100 nm, the concentration of silver nitrate is 0.1 mol, and the deposition thickness of copper is 30 nm. Further, the reaction time is 5 minutes in the case of FIG. 5 (a), 10 minutes in the case of FIG. 5 (b), and 60 minutes in the case of FIG. 5 (c). As can be seen from FIGS. 5A to 5C , the reaction time does not significantly affect the silver nanostructure.

  FIG. 6 is an SEM photograph showing a comparison between the case where silica nanoparticles are used (FIG. 6A) and the case where silica nanoparticles are not used (FIG. 6B). In FIG. 6 (a), aluminum was deposited as a base metal on silica nanoparticles having a particle size of 100 nm, and then reacted with a silver nitrate solution. In FIG. 6B, aluminum having a thickness of 20 nm was directly deposited on a glass substrate and then reacted with a silver nitrate solution. The hexagonal nanostructure seen in FIG. 6 (a) cannot be observed in FIG. 6 (b). Thus, it can be seen that silica nanoparticles covered with a base metal are effective for producing silver nanostructures.

    Next, these silver nanostructures were immersed in an ethanol solution of 1 mmol of fluorescein for 10 minutes, and the fluorescence intensity was measured with a fluorescent device FLE-1000 (blue excitation) manufactured by Nippon Sheet Glass Co., Ltd. FIG. .

  The “metal particles” shown in FIGS. 7A and 7B are surface-enhanced spectroscopy substrates made of silver nanostructures produced according to the present invention. "Glass" is a glass-only substrate with nothing formed on it, "particles" is a substrate using silica nanoparticles that are not coated with metal, and "thin film" is a silver nitrate reaction by depositing base metal directly on a slide glass The board | substrate which performed is shown.

  7A and 7B, the fluorescence intensity was measured by changing the particle diameter of the silica nanoparticles to 100 nm and 200 nm, respectively. A white bar graph in FIG. 7 indicates a particle size of 100 nm, and a diagonal line rising to the right indicates a particle size of 200 nm. In FIG. 7A, copper is used as the base metal and 20 nm thick copper is vapor-deposited. In FIG. 7B, aluminum is used as the base metal and aluminum 20 nm thick is vapor-deposited to measure fluorescence intensity. It was. In both FIGS. 7A and 7B, the vertical axis indicates the fluorescence intensity (arbitrary unit).

  7A and 7B show that the fluorescence signal intensity from the “metal particle” having the silver nanostructure in which the silver layer is formed on the silica nanoparticle is strongest. That is, it can be seen that the enhancement factor of the surface-enhanced spectroscopic substrate produced by the method for producing a surface-enhanced spectroscopic substrate of the present invention is the best.

  FIG. 8 shows the results of fluorescence intensity measurement when the type of base metal deposited on silica nanoparticles is changed to copper, aluminum, and iron, the deposition thickness of each type of base metal is changed, and the particle size of silica nanoparticles is also changed. Indicates. The vertical axis | shaft of Fig.8 (a)-(c) shows a fluorescence intensity.

    8 (a), (b), and (c), the open bar graph indicates the case where the base metal is copper, the slanted bar graph that rises to the right indicates that the base metal is aluminum, and the slanted bar graph that increases the left shoulder indicates the base metal. Shows the case where is iron. Moreover, the particle diameter of the silica nanoparticle is changed and measured, and the particle diameter of 100 nm and the particle diameter of 200 nm indicate the particle diameter of the silica nanoparticle.

  Further, FIG. 8A shows the case where the deposition thickness of each base metal of copper, aluminum and iron is 10 nm, and FIG. 8B shows the case where the deposition thickness of each base metal is 20 nm. ) Shows the case where the deposition thickness of each base metal is 40 nm.

  As can be seen from FIG. 8, aluminum is the most effective base metal when the deposition thickness is 20 nm or less, but copper is as effective as aluminum when the deposition thickness is 40 nm. On the other hand, when iron is used as the base metal, the fluorescence intensity is low regardless of the deposition thickness or the particle size of the silica nanoparticles, and it is understood that the effect is inferior compared to copper or aluminum.

  The surface-enhanced spectroscopic substrate according to the method for producing a surface-enhanced spectroscopic substrate of the present invention can be widely applied to spectroscopic analysis methods such as Raman spectroscopy and infrared spectroscopy, for example, clinical examination, environmental monitoring, quality It can be applied to fields such as management.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Nanoparticle 3 Base metal layer 4 Base metal particle 5 Silver nitrate solution 6a Silver layer 6b Silver layer 7a Silver layer 7b Silver layer 10 Silver nanostructure 11 Silver nanostructure

Claims (5)

A base metal nanostructure comprising a nanoparticle having a uniform particle diameter made of a dielectric material and solidified on a substrate and in contact with the substrate, and a base metal layer formed on the nanoparticle , Forming on top;
A silver nitrate solution is added to the base metal nanostructure so that the base metal having a higher ionization tendency than silver is dissolved in the silver nitrate solution and silver is deposited on the surface of the nanoparticles to completely replace the base metal with silver. Forming a silver nanostructure in which the dielectric is in contact with the substrate;
A method for producing a surface-enhanced spectroscopic substrate, comprising: The method for producing a substrate for surface enhanced spectroscopy according to claim 1, wherein the shape of the silver nanostructure is different from the shape of the base metal nanostructure . The method for manufacturing a substrate for surface-enhanced spectroscopy according to claim 1 or 2 , wherein the base metal layer is formed on the nanoparticles by vacuum deposition or sputtering. The method for producing a substrate for surface enhanced spectroscopy according to claim 3 , wherein the nanoparticles are silica nanoparticles, polystyrene nanoparticles, or titanium oxide nanoparticles. 5. The surface according to claim 1 , wherein a particle diameter of the nanoparticles is configured in a range of 20 nm to 1 μm, and a thickness of the base metal layer is formed in a range of 5 nm to 1 μm. A method of manufacturing a substrate for enhanced spectroscopy.