JP2016222805A - Spherical zinc oxide particle, manufacturing method therefor and plasmon sensor chip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spherical zinc oxide particle high in plasmon resonance strength and a manufacturing method therefor, and a plasmon sensor chip high in sensitivity using the same.SOLUTION: The spherical zinc oxide particle has a dopant which is selected from a group consisting of gallium, europium, cerium, praseodymium, samarium, gadolinium, terbium, niobium, ytterbium and indium, where average percentage content of the dopant of a surface part from outermost surface of the spherical zinc oxide particle to depth of 10 nm is higher than average percentage content from the outermost surface to inner more than 10 nm and average percentage content of the dopant of the surface part is in a range of 0.5 to 15 mol%.SELECTED DRAWING: Figure 1

Description

  The present invention relates to spherical zinc oxide particles having high plasmon resonance intensity, a method for producing the same, and a plasmon sensor chip having high sensitivity using the same.

  Optical measurement technology using evanescent light that totally reflects light on a metal thin film and oozes out to the reflecting surface has been widely studied and applied. In particular, a sensor using an optical system that uses a thin film of gold, silver or the like on the reflecting surface and causes surface plasmon resonance (SPR) by light is called an SPR sensor.

  In actual measurement, light having a continuous wavelength is incident from the opposite surface of the sample at a critical angle or more, and a valley having a low reflectance at a wavelength at which the evanescent wave and the surface plasmon resonate is observed.

  Since the nature of the object to be measured can be known from the wavelength at which this SPR phenomenon occurs, the SPR sensor is applied to immunosensors using the antigen-antibody reaction, detection of DNA, and detection of interactions between receptors and proteins. It's getting on.

  The metal thin film used for the sensor chip of the SPR sensor is generally a gold or silver thin film. In this case, light in the ultraviolet to visible light range is used for SPR.

  Recently, plasmon research has been conducted on oxide semiconductors instead of metals. Since the oxide semiconductor has a wide band gap and the number of carriers can be arbitrarily controlled by the introduced dopant concentration, it can be used from the visible to the near infrared region, and can be used as an SPR sensor using infrared rays, which has been difficult in the past. In particular, it is expected to be applied to the bio field, such as a non-invasive blood sugar level sensor.

  Among oxide semiconductors, metal-doped zinc oxide (ZnO) is attracting attention from the viewpoint of practical use because it has high carrier mobility and carrier density, can easily control the measurement wavelength region, and can be expected to have high sensitivity. .

  On the other hand, a plasmon sensor using plasmon resonance on the surface of a particle using a particle having a small particle size instead of an SPR sensor using a metal thin film as a sensor chip can be considered. In such a plasmon sensor, unlike an SPR sensor using a metal thin film, the incident angle dependency is small, and stable measurement can be expected. Moreover, there exists a merit which can be manufactured cheaply.

  In order to efficiently resonate plasmons using particles, spherical monodisperse particles having a small particle size are preferable. Patent Document 1 discloses spherical zinc oxide particles having a high sphericity. However, since the particle diameter is large and the monodispersity is low, the plasmon resonance intensity is low and not suitable for use in a plasmon sensor. Patent Document 2 discloses spherical zinc oxide particles having a small particle size and high sphericity. However, the monodispersity is low, and the plasmon resonance intensity is low and not suitable for use in a plasmon sensor.

  As another method for increasing the plasmon resonance intensity, it is conceivable to increase the carrier density in the particles by containing a large amount of dopant such as Ga in the particles. However, as the amount of dopant in the particles increases, the crystallinity is destroyed, so that the plasmon resonance intensity cannot be increased simply by increasing the amount of dopant.

  Therefore, spherical zinc oxide particles that can efficiently perform plasmon resonance have been desired.

Japanese Patent No. 5617410 JP 2013-60375 A

  The present invention has been made in view of the above problems and circumstances, and a problem to be solved is to provide spherical zinc oxide particles having high plasmon resonance intensity and a method for producing the same. Another object of the present invention is to provide a plasmon sensor chip having high sensitivity using the same.

  In order to solve the above-mentioned problems, the inventor of the present invention contains a larger amount of dopant on the surface of spherical zinc oxide particles that greatly contribute to the intensity of plasmon resonance in the process of examining the cause of the above-mentioned problems than the inside of the particles. The present inventors have found that the intensity of plasmon resonance can be increased and have reached the present invention.

That is, the said subject which concerns on this invention is solved by the following means.
1. A spherical zinc oxide particle containing a dopant, wherein the dopant is a dopant selected from the group consisting of gallium, europium, cerium, praseodymium, samarium, gadolinium, terbium, niobium, ytterbium and indium, and the spherical zinc oxide particles The average content of the dopant in the surface portion from the outermost surface to a depth of 10 nm is higher than the average content of the dopant inside from 10 nm from the outermost surface, and the average content of the dopant in the surface portion is Spherical zinc oxide particles characterized by being in the range of 0.5 to 15 mol%.

  2. The spherical zinc oxide particles have a core-shell structure including a core layer and a shell layer, and the average content of the dopant in the shell layer is higher than the average content in the core layer. Spherical zinc oxide particles.

  3. 3. The spherical zinc oxide according to claim 1 or 2, wherein the spherical zinc oxide particles have a layer having a concentration gradient in which the concentration of the dopant increases from the center of the spherical zinc oxide particles toward the surface. particle.

  4). The average content of the dopant in the surface portion from the outermost surface of the spherical zinc oxide particles to a depth of 10 nm is in the range of 11 to 13 mol%, and any one of items 1 to 3 The spherical zinc oxide particles according to claim 1.

  5. The spherical zinc oxide particles according to any one of Items 2 to 4, wherein an average content of the dopant in the core layer is in a range of 0 to 5 mol%.

  6). 6. The spherical zinc oxide particles according to any one of items 1 to 5, wherein an average particle diameter is in a range of 50 to 5000 nm.

  7). It is a manufacturing method of the spherical zinc oxide particle which manufactures the spherical zinc oxide particle as described in any one of Claim 1-6, Comprising: The aqueous solution of the said dopant, zinc aqueous solution, and urea aqueous solution are mixed. Zinc of spherical zinc oxide particles having an average content of the dopant in the surface portion from the outermost surface of the spherical zinc oxide particles to a depth of 10 nm higher than the average content of the dopant inside from 10 nm from the outermost surface. A method for producing spherical zinc oxide particles, comprising the steps of forming system compound precursor particles and firing the zinc-based compound precursor particles to obtain spherical zinc oxide particles.

  8). In the step of forming the zinc-based compound precursor particles, an aqueous solution of the dopant is continuously added to a solution obtained by mixing an aqueous urea solution and at least one of an aqueous zinc solution or an aqueous solution of the dopant, from the center of the spherical zinc oxide particles to the surface. 8. The method for producing spherical zinc oxide particles according to item 7, wherein a layer having a concentration gradient that becomes higher is formed.

  9. A plasmon sensor chip comprising a detection unit and a substrate containing the spherical zinc oxide particles according to any one of items 1 to 6.

  By the above means of the present invention, spherical zinc oxide particles having a high plasmon resonance intensity and a method for producing the same can be provided. In addition, it is possible to provide a plasmon sensor chip with high sensitivity using the same.

  The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows. By distributing a large amount of dopant on the particle surface, which has a high contribution to plasmon resonance intensity, it is not necessary to increase the amount of dopant in the entire particle, and there is less crystal distortion than spherical zinc oxide particles in which the dopant is uniformly distributed. In addition, it is considered that spherical zinc oxide particles having high plasmon resonance intensity can be realized.

Schematic diagram of the structure of spherical zinc oxide particles according to an embodiment of the present invention The graph which shows typically the density | concentration of the dopant in the spherical zinc oxide particle which concerns on embodiment of this invention Schematic diagram showing an example of a plasmon sensor using a plasmon sensor chip

  The spherical zinc oxide particles of the present invention are spherical zinc oxide particles containing a dopant, wherein the dopant is selected from the group consisting of gallium, europium, cerium, praseodymium, samarium, gadolinium, terbium, niobium, ytterbium and indium. The average content of the dopant in the surface portion from the outermost surface of the spherical zinc oxide particles to a depth of 10 nm is higher than the average content of the dopan inside 10 nm from the outermost surface, and the surface The average content of the dopant in part is in the range of 0.5 to 15 mol%. This feature is a technical feature common to the inventions according to claims 1 to 8.

  The present embodiment is not limited to the embodiments described below, but from the viewpoint of expressing the effect of solving the problem, the spherical zinc oxide particles have a core-shell structure including a core layer and a shell layer. The average content of the dopant in the shell layer is preferably higher than the average content in the core layer.

  In addition, it is preferable to have a layer having a concentration gradient in which the concentration of the dopant in the spherical zinc oxide particles increases from the center to the surface of the spherical zinc oxide particles in order to reduce local crystal distortion.

  Further, the average content of the dopant in the surface portion from the outermost surface of the spherical zinc oxide particles to a depth of 10 nm is in the range of 11 to 13 mol%, thereby obtaining an effect of increasing the intensity of plasmon resonance. This is preferable.

  Furthermore, in the embodiment, the average content of the dopant in the core layer is in the range of 0 to 5 mol%, the viewpoint of reducing crystal distortion due to the dopant in the spherical zinc oxide particles, and the dopant Is preferable from the viewpoint of reducing the amount of use since it is expensive.

  As a production method for producing the spherical zinc oxide particles of this embodiment, an aqueous solution of the dopant, a zinc aqueous solution and a urea aqueous solution are mixed, and the surface portion of the spherical zinc oxide particles from the outermost surface to a depth of 10 nm is mixed. It is preferable to have a step of forming zinc-based compound precursor particles of spherical zinc oxide particles whose average content of the dopant is higher than the average content of the dopant inside from 10 nm from the outermost surface. Further, in the step of forming the zinc-based compound precursor particles, an aqueous solution of the dopant is continuously added to a mixture of an aqueous urea solution and at least one of an aqueous zinc solution or an aqueous solution of the dopant, and the surface is formed from the center of the spherical zinc oxide particles. It is preferable that it is a manufacturing method of the aspect which forms the layer which has a concentration gradient which becomes high toward.

  Furthermore, a plasmon sensor chip having a detection part and a substrate containing spherical zinc oxide particles is preferable.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

《Spherical zinc oxide particles》
Spherical zinc oxide particles according to an embodiment of the present invention are spherical zinc oxide particles containing a dopant, wherein the dopant is a group consisting of gallium, europium, cerium, praseodymium, samarium, gadolinium, terbium, niobium, ytterbium and indium. An average content of the dopant in the surface portion from the outermost surface of the spherical zinc oxide particles to a depth of 10 nm is higher than an average content of the dopan inside 10 nm from the outermost surface. And the average content rate of the said dopant of the said surface part exists in the range of 0.5-15 mol%, It is characterized by the above-mentioned. The spherical zinc oxide particles have high plasmon resonance intensity and are useful for realizing a highly sensitive plasmon sensor chip.

<Structure of spherical zinc oxide particles>
As shown in FIG. 1 (a), the spherical zinc oxide particles according to the embodiment of the present invention have an average content of the dopant in the surface portion 2 from the outermost surface to a depth of 10 nm from the innermost surface of 10 nm from the outermost surface. Is higher than the average content of the dopant, and the average content of the dopant in the surface portion 2 is in the range of 0.5 to 15 mol%.

  As the spherical zinc oxide particles, core-shell structure spherical zinc oxide particles 1 having a core layer 4 and a shell layer 3 covering the core layer 4 can be used as shown in FIG. The surface portion 2 from the outermost surface to a depth of 10 nm can be the shell layer 5 or a part of the shell layer 5 (surface layer portion). Further, as will be described later, a layer having a concentration gradient may be present inside the spherical zinc oxide particles. In FIG. 1B, the form in which a layer having a concentration gradient is present adjacent to the core layer 4 is illustrated by a broken line.

  The spherical zinc oxide particles are doped with a dopant selected from the group consisting of gallium, europium, cerium, praseodymium, samarium, gadolinium, terbium, niobium, ytterbium and indium, and the surface from the outermost surface of the dopant to a depth of 10 nm. The average content of the dopant in the part 2 is higher than the average content of the dopant in the interior 3 from 10 nm from the outermost surface.

  Further, the spherical zinc oxide particles have a core / shell structure, and the average content of the dopant in the shell layer 5 of the dopant can be made higher than the average content in the core layer 4.

  The average content of the dopant in the shell layer 5 is preferably 0.5 to 15 mol%.

  The average content of the dopant in the inner part 3 and the core layer 4 from 10 nm from the outermost surface is not particularly limited as long as it is lower than the surface part 2 and the shell layer 5 from the outermost surface to a depth of 10 nm, but the dopant in the spherical zinc oxide particles From the viewpoint of reducing the distortion of the crystal due to the above and from the viewpoint of reducing the amount of use because the dopant is expensive, it is preferably in the range of 0 to 5 mol%. From the viewpoint of enhancing the compositional affinity between the surface portion 2 and the interior 3 or between the shell layer 5 and the core layer 4, a dopant may be present in the interior 3 and the core layer 4, 5 may be provided with a layer 6 having a concentration gradient. The difference in the average content of the dopants in the core layer 4 and the shell layer 5 or in the inner portion 3 and the surface portion 2 can be in the range of 0.5 to 15 mol%.

  Moreover, the average content rate of the said dopant of the surface part 2 from the outermost surface of spherical zinc oxide particle which may be a part of the shell layer 5 to the depth of 10 nm exists in the range of 0.5-15 mol%. . It is preferable that it is in the range of 11 to 13 mol% since the effect of increasing the intensity of plasmon resonance is obtained.

  With such a configuration, spherical zinc oxide particles having high plasmon resonance intensity can be obtained.

(Profile of dopant concentration in spherical zinc oxide particles)
FIG. 2 is a graph schematically showing the concentration of the dopant in the spherical zinc oxide particles according to the embodiment of the present invention. The horizontal axis indicates the distance from the particle center to the outermost surface in the spherical zinc oxide particles, and the vertical axis indicates the dopant concentration.

  The dopant concentration (content ratio) in the spherical zinc oxide particles has, for example, a core / shell structure as shown in FIGS. 2 (a) to 2 (f), and the dopant concentration of the shell layer 5 is higher than that of the core layer 4. can do.

  As shown in FIGS. 2 (a) and 2 (b), spherical zinc oxide particles having a core / shell having a dopant concentration changed stepwise may be used, but as shown in FIGS. 2 (c) to 2 (f). Furthermore, it is preferable to have a layer having a concentration gradient 6 that increases from the center of the spherical zinc oxide particles toward the surface. The layer having the concentration gradient 6 may be a shell layer as shown in FIGS. 2 (e) and 2 (f), and may be a part of the shell layer as shown in FIGS. 2 (c) and 2 (d). There may be.

  Further, as shown in FIGS. 2 (g) and 2 (h), the shape may be such that the dopant concentration is continuously increased from the particle center to the particle outermost surface. Even if the concentration gradient is convex upward or downward, it is sufficient that the dopant concentration is continuously increased toward the particle surface.

  By having such a concentration gradient 6, it is possible to suppress crystal distortion caused by doping with a dopant during crystal growth.

  The ratio of the core to the shell is preferably such that the core is in the range of 15 to 98% by volume of the whole particle.

  In this specification, the core layer refers to a region where the dopant concentration is low until the concentration of the dopant suddenly increases in the direction from the center of the particle toward the surface. For example, FIGS. A portion where the dopant content is constant from the center of the particle. In the core layer, the concentration of the dopant may gradually increase. The shell layer refers to a layer on the particle surface side where the dopant content is higher than that of the core layer.

<Dopant>
Spherical zinc oxide particles include gallium (Ga), europium (Eu), cerium (Ce), praseodymium (Pr), samarium (Sm), gadolinium (Gd), terbium (Tb), niobium (Nb), ytterbium (Yb). And spherical zinc oxide particles containing a dopant selected from the group consisting of indium (In). Unlike SPR sensors using metals, the number of carriers can be controlled by doping zinc oxide, which is a semiconductor having a large band gap, with the above-described dopant, and the plasmon resonance wavelength over the visible to infrared region. Can be controlled. Such control can be performed by the kind of metal element to be doped and the content thereof.

  Among the above dopants, Ga and Eu are preferable, and Ga is more preferable. Moreover, you may include several types of said dopant suitably according to the objective. Further, other metal atoms may be included as a dopant as long as the expression of plasmon resonance is not impaired.

  It is preferable that the content rate of the said dopant of the whole spherical zinc oxide particle exists in the range of 0.001-10.00 mol%. More preferably, it exists in the range of 0.01-7.00 mol%.

  Here, regarding the composition distribution of the spherical zinc oxide particles, the composition of the core-shell structure can be obtained by performing elemental analysis of the cross section of the spherical zinc oxide particles. For example, the spherical zinc oxide particles are subjected to cross-section processing using a focused ion beam (FB-2000A) manufactured by Hitachi High-Technologies, and a surface passing through the vicinity of the particle center is cut out. And elemental analysis can be performed from the cut surface using STEM-EDX (HD-2000) manufactured by Hitachi High-Technologies to determine the composition distribution of each dopant of the spherical zinc oxide particles.

  In addition, content of the whole dopant contained in spherical zinc oxide particle can be calculated | required by elemental analysis. For example, 1 g of spherical zinc oxide particles is dissolved in a mixed solution of 10 mL of nitric acid aqueous solution and 1.0 mL of hydrogen peroxide solution, and elemental analysis is performed using an ICP emission spectral plasma apparatus (ICP-AES) manufactured by SII Nano Technology. Do. It can obtain | require as composition ratio (mol%) from content of each dopant of spherical zinc oxide particle.

About the average content rate of the dopant of the surface part from the outermost surface to the depth of 10 nm, it can measure using an X-ray photoelectron spectrometer (ESCALAB-200R by VG Scientific). Specifically, Mg can be used for the X-ray anode and measurement can be performed at an output of 600 W (acceleration voltage: 15 kV, emission current: 40 mA). The energy resolution was set to be 1.5 to 1.7 eV when defined by the half width of a clean Ag ₃ d _5/2 peak. As a measurement, first, the range of the binding energy of 0 to 1100 eV is measured at a data acquisition interval of 1.0 eV to determine what elements are detected, and then, for all the detected elements, data acquisition is performed. A narrow scan is performed on the photoelectron peak giving the maximum intensity at an interval of 0.2 eV, and the spectrum of each element is measured. The obtained spectrum is COMMON DATA PROCESSING SYSTEM manufactured by VAMAS-SCA-JAPAN (preferably Ver. 2.3 or later) so as not to cause a difference in the content calculation result due to a difference in measuring apparatus or computer. After the above transfer, the process is performed with the same software, and the value of the average content of each analysis target element can be obtained as the atomic concentration (at%).

  Before performing the quantitative process, the calibration of the count scale is performed for each element, and a 5-point smoothing process is performed. In the quantitative processing, the peak area intensity (cps * eV) from which the background is removed is used. For background processing, a method by Shirley is used. For the Shirley method, see D.C. A. Shirley, Phys. Rev. , B5, 4709 (1972).

<Shape of spherical zinc oxide particles>
The spherical zinc oxide particles of the present embodiment preferably have an average particle size in the range of 50 to 5000 nm and a variation coefficient of particle size distribution in the range of 1.0 to 10%. By setting it as such a range, the absorption intensity in a plasmon resonance frequency can be raised.

  The spherical shape is defined based on a scanning micrograph (SEM image) of spherical zinc oxide particles. Specifically, a scanning micrograph is taken for the spherical zinc oxide particles, and 100 spherical zinc oxide particles are randomly selected. When the major axis of each selected particle is a and the minor axis is b, an average value of a / b values is obtained as an aspect ratio. In addition, when drawing a circumscribing rectangle for each particle (referred to as “the circumscribing rectangle”), the shortest short side of the circumscribed rectangle is the shortest length, and the longest long side is the length. Is the major axis.

  When the aspect ratio is in the range of 1.00 to 1.15, more preferably in the range of 1.00 to 1.05, it is classified as spherical. If it is outside the range of 1.00 to 1.15, it is classified as an indeterminate form. The closer the aspect ratio is to 1, the higher the sphericity.

  The average particle diameter of the spherical zinc oxide particles is preferably in the range of 50 to 5000 nm. In the case of 50 or more, the particles are preferred since no aggregation occurs during the synthesis. The thickness of 5000 nm or less is preferable because the efficiency of plasmon resonance is good. Preferably it exists in the range of 50-3000 nm, More preferably, it exists in the range of 80-2500 nm.

  The average particle diameter can be determined as an area circle equivalent particle diameter based on the area of a photographic image of 100 randomly selected spherical zinc oxide particles, which can be used as the average particle diameter.

  Moreover, it is preferable that the variation coefficient of the particle size distribution of the spherical zinc oxide particles is in the range of 1.0 to 10%. The variation coefficient of the particle size distribution is preferably 10% or less because plasmon resonance can be efficiently performed. 1-8% is preferable, More preferably, it exists in the range of 1-7%.

  The variation coefficient of the particle size distribution can be defined by the variation coefficient of the particle size distribution that can be obtained from a scanning micrograph (SEM image) of a predetermined number of spherical zinc oxide particles.

  For example, the coefficient of variation (also referred to as “monodispersity”) of the particle size distribution can be obtained from an SEM image of 100 spherical zinc oxide particles, and the monodispersity can be evaluated. The variation coefficient of the particle size distribution is obtained by the following formula.

Coefficient of variation (%) = (standard deviation of particle size distribution / average particle size) × 100
In addition, the measurement of the said particle diameter, distribution, etc. can be performed using an image processing measuring device (for example, Luzex AP; Nireco Corporation make).

<< Production Method of Spherical Zinc Oxide Particles >>
The method for producing spherical zinc oxide particles of the present embodiment includes a step of mixing a zinc aqueous solution, an aqueous solution of the dopant and an aqueous urea solution to form zinc-based compound precursor particles, and firing the zinc-based compound precursor particles. And a step (also referred to as a firing step), desirably, as described below, “raw material liquid preparation step”, “step of forming zinc-based compound precursor particles”, “solid-liquid separation” It consists of four steps, “step” and “step of firing the zinc-based compound precursor particles”. It is preferable that the “step of firing the zinc-based compound precursor particles” further includes a “core layer forming step” and a “shell layer forming step”.

1. Raw Material Solution Preparation Step The raw material solution preparation step is a step of preparing an aqueous zinc solution, an aqueous dopant solution, and an aqueous urea solution.

<Urea aqueous solution preparation process>
The urea aqueous solution preparation step is a step of preparing a urea aqueous solution having a predetermined concentration.

  As ureas, in addition to urea, urea salts (for example, nitrates, hydrochlorides, etc.), N, N′-dimethylacetylurea, N, N′-dibenzoylurea, benzenesulfonylurea, p-toluenesulfonylurea, Examples thereof include trimethylurea, tetraethylurea, tetramethylurea, triphenylurea, tetraphenylurea, N-benzoylurea, methylisourea, ethylisourea, ammonium carbonate, and ammonium bicarbonate.

  Ureas act as a precipitating agent, and are considered to generate zinc-based compound precursor particles as basic carbonates when an aqueous zinc oxide solution and an aqueous dopant solution are mixed with water and heated. Among the ureas described above, urea is preferable in that it gradually hydrolyzes to form a precipitate slowly and a uniform precipitate is obtained.

  The urea aqueous solution is an aqueous solution containing ureas. What is necessary is just to mix and prepare the said ureas and water. If necessary, an additive such as a pH adjusting agent may be added.

  Although there is no restriction | limiting in particular in the density | concentration of urea aqueous solution, It is desirable to exist in the range of 0.01-10.00 mol / L. Preferably, it is in the range of 0.10 to 5.00 mol / L.

<Dopant aqueous solution preparation process>
The aqueous solution preparation process of the dopant includes gallium (Ga), europium (Eu), cerium (Ce), praseodymium (Pr), samarium (Sm), gadolinium (Gd), terbium (Tb), niobium (Nb), ytterbium (Yb ) And indium (In), and a step of preparing an aqueous solution of the dopant, which is an aqueous solution containing a dopant selected from the group consisting of indium (In).

  As salts of these elements that can be used to prepare an aqueous solution of these dopants, nitrates, hydrochlorides, sulfates and the like can be used, but it is preferable to use nitrates. Thereby, spherical zinc oxide particles with few impurities can be manufactured.

  The ion concentration of the aqueous solution of the dopant in the aqueous solution is not particularly limited, but is preferably in the range of 0.00001 to 5.00 mol / L. More preferably, it is in the range of 0.0001 to 3.00 mol / L.

  The aqueous solution of the dopant may contain one or more of the above dopants.

<Zinc aqueous solution preparation process>
The zinc aqueous solution preparation step is a step of preparing an aqueous solution containing zinc element. As a zinc salt that can be used to prepare an aqueous solution containing elemental zinc, nitrates, hydrochlorides, sulfates, and the like can be used, but it is preferable to use nitrates. Thereby, spherical zinc oxide particles with few impurities can be manufactured.

  The ion concentration of the aqueous zinc solution is not particularly limited, but is preferably in the range of 0.0001 to 10.00 mol / L. More preferably, it is in the range of 0.001 to 5.00 mol / L.

2. Step of forming zinc-based compound precursor particles In the step of forming zinc-based compound precursor particles, the aqueous solution of the dopant, the aqueous zinc solution, and the aqueous urea solution are mixed to obtain a depth from the outermost surface of the spherical zinc oxide particles. Zinc-based compound precursor particles of spherical zinc oxide particles in which the average content of the dopant in the surface portion up to 10 nm is higher than the average content of the dopant inside from 10 nm from the outermost surface are formed. The method for producing spherical zinc oxide particles of the present embodiment preferably includes (i) a core layer forming step and (ii) a shell layer forming step.

(I) Core layer forming step In the core layer forming step, first, at least one selected from the group consisting of an aqueous zinc solution and optionally gallium, europium, cerium, praseodymium, samarium, gadolinium, terbium, niobium, ytterbium and indium. An aqueous urea solution is added to an aqueous solution of various dopants to prepare a dispersion solution in which a basic carbonate is dispersed.

  In the following, a case where a basic carbonate is formed using urea will be described, but this is an example and the present invention is not limited to this. The spherical zinc oxide particles are produced through basic carbonates, but the basic carbonates may remain in the particles.

  The ion concentration in the aqueous solution of the above elements is preferably in the range of 0.001 to 0.1 mol / L, and the urea concentration is preferably in the range of 5 to 50 times the above-described ion concentration. This is because, as a result, spherical spherical zinc oxide particles exhibiting monodispersity can be synthesized as long as the ion concentration and urea concentration in the aqueous solution of the above elements are within the above ranges.

  The mixed reaction liquid is heated and stirred at 80 ° C. or higher to grow a basic carbonate dispersed in the reaction solution, thereby forming a core layer. The reaction liquid refers to a liquid in which an aqueous urea solution and at least one of an aqueous zinc solution and an aqueous dopant solution are mixed.

  In the case of heating and stirring, the stirrer is not particularly limited as long as sufficient stirring efficiency can be obtained. However, in order to obtain higher stirring efficiency, it is preferable to use a rotor / stator type stirrer.

(Ii) Shell layer forming step In forming the shell layer, after forming the core layer in the liquid phase, in the shell layer forming step, the shell layer has an average content of the dopant higher than that of the core layer using the aqueous solution of the dopant. Is preferably formed. At this time, after forming the core layer, the basic carbonate particles once formed through the solid-liquid separation step described later are added to the reaction solution to which the aqueous urea solution, the aqueous zinc solution and the aqueous dopant solution are added, as shown in FIG. Spherical zinc oxide particles having a dopant concentration changed stepwise as shown in a) and FIG. 2B can be formed.

  In this case, the shell layer can be formed by the same method as the formation of the core layer, but the concentration of the dopant in the reaction solution needs to be higher than that in the case of forming the core layer. The concentration can be appropriately adjusted according to the average content of the dopant of the desired core / shell particles.

  Preferably, after the core layer is formed, in the continuous shell layer forming step, an aqueous solution of the dopant is continuously added to a solution obtained by mixing an aqueous urea solution and at least one of an aqueous zinc solution or an aqueous solution of the dopant to form spherical zinc oxide particles. This is a mode of forming a layer having a concentration gradient that increases from the center to the surface.

  Specifically, after forming the core layer, the shell layer is continuously formed in the liquid phase, and the shell layer is formed by setting the dopant concentration in the reaction solution higher than that of the core layer.

  In addition, when the core layer and the shell layer are continuously formed, an aqueous solution of a dopant having a higher concentration is added before the aqueous zinc solution is sufficiently changed to a basic carbonate during the formation of the core layer. The spherical zinc oxide particles having a core-shell structure having a shell having a gentle concentration gradient such as e) and 2 (f) can be obtained.

  Moreover, you may form the layer which has a concentration gradient by adding to the reaction liquid using the aqueous solution of the dopant prepared so that a density | concentration might become high continuously.

  Further, from the start of the production of spherical zinc oxide particles without forming a core layer, an aqueous solution of a dopant is continuously added to a mixture of an aqueous urea solution and at least one of an aqueous zinc solution or an aqueous solution of a dopant to form spherical zinc oxide particles. By forming a layer having a concentration gradient that increases from the center to the surface, spherical zinc oxide particles with continuously increasing dopant concentration as shown in FIG. 2 (g) and FIG. 2 (h) are formed. You can also.

  The aqueous solution containing the salt of the dopant is preferably added at a rate of addition within the range of 0.003 to 3.0 mmol / min per liter while heating and stirring at 80 ° C. or higher. This is because if the addition rate is out of the range, it becomes difficult for the spherical zinc oxide particles to be formed into spherical particles exhibiting monodispersity. As for the heating temperature, when heated and stirred at 80 ° C. or lower, decomposition of urea added in the core layer forming step does not proceed and particle formation is inhibited.

3. Solid-liquid separation step After heating and stirring, solid-liquid separation is performed to separate the produced precipitate (precursor of spherical zinc oxide particle fine particles) from the solution. The solid-liquid separation method may be a general method. For example, a precursor of spherical zinc oxide particles can be obtained by filtration using a filter or the like.

4). The step of firing The step of firing (also referred to as the firing step) involves firing the precursor of spherical zinc oxide particles obtained by the solid-liquid separation step at 200 ° C. or higher in air or in an oxidizing atmosphere. The precursor of the calcined spherical zinc oxide particles becomes an oxide and becomes spherical zinc oxide particles containing a dopant. Preferably, the firing temperature is in the range of 300-600 ° C.

  In addition, you may bake, after washing | cleaning and drying with water or alcohol before baking as needed.

  After cooling through the firing step, the spherical zinc oxide particles can be recovered and then recovered.

  By producing spherical zinc oxide particles using such a production method, spherical zinc oxide particles having a high degree of sphericity and containing almost no anisotropically grown spherical zinc oxide particles can be obtained.

<Plasmon sensor chip>
The plasmon sensor chip of this embodiment has a detection unit and a substrate containing the spherical zinc oxide particles described above. Spherical zinc oxide particles are used as a chip that generates plasmon resonance in a plasmon sensor.

  FIG. 3 shows an example of a plasmon sensor using a plasmon sensor chip. The plasmon sensor 11 includes a plasmon sensor chip 14 including a substrate 12 and a detection unit 13 containing spherical zinc oxide particles thereon, and a surface of the substrate 12 opposite to the detection unit 13 containing spherical zinc oxide particles. The optical prism 15 is closely attached. A test object 19 is fixed by a mounting part 18 on the detection part 13 containing spherical zinc oxide particles.

Near infrared light emitted from the light source 16 is polarized through the polarizing plate 17 and applied to the transparent substrate 12 through the optical prism 15. Incident light is incident at an incident angle θ ₁ under the condition of total reflection. Localized plasmon resonance appears at a certain wavelength by the evanescent wave that oozes out to the surface side of the spherical zinc oxide particles of incident light. This is performed with infrared light having different wavelengths. When surface plasmon resonance occurs, the evanescent wave is absorbed by the surface plasmon, so that the reflection intensity is significantly reduced. The functional group in the molecule of the test object can be quantified from this resonance frequency. The amount of reflected light reflected at the reflection angle θ ₂ is measured by the light receiving unit 20.

  In the plasmon sensor of the present embodiment, it is considered that surface plasmon resonance with high sensitivity can be caused by using a layer containing spherical zinc oxide particles having a high sphericity having a core / shell structure as a detection unit. .

<Base material>
The substrate used for the plasmon sensor chip is preferably transparent from the visible light to the infrared region and has a high refractive index. The refractive index of the substrate is preferably in the range of 1.3 to 4.0. More preferably, it is 1.4-3.0. For example, glass and resin are preferably used.

  Various conventionally known resin films can be used as the resin base material. For example, cellulose ester film, polyester film, polycarbonate film, polyarylate film, polysulfone (including polyethersulfone) film, polyethylene terephthalate, polyethylene naphthalate polyester film, polyethylene film, polypropylene film, cellophane, Cellulose diacetate film, cellulose triacetate film, cellulose acetate propionate film, cellulose acetate butyrate film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene vinyl alcohol film, syndiotactic polystyrene film, polycarbonate film, norbornene resin film , Polymethylpentenef Can Lum, polyether ketone film, polyether ketone imide film, a polyamide film, a fluororesin film, a nylon film, polymethyl methacrylate film, and acrylic films. Among these, polycarbonate films, polyester films such as polyethylene terephthalate, norbornene resin films, cellulose ester films, and acrylic films are preferable. It is particularly preferable to use a polyester film such as polyethylene terephthalate or an acrylic film. The resin film may be a film manufactured by melt casting film formation or a film manufactured by solution casting film formation.

  The thickness of the substrate is preferably in the range of 0.001 to 10 mm, for example.

<Formation of detection part containing spherical zinc oxide particles>
A layer containing spherical zinc oxide particles can be formed on the substrate as a detection part. Various methods can be used for forming the layer containing spherical zinc oxide particles. For example, spray coating, inkjet coating, dispenser coating, slit coating, roll coating, spin coating, dip coating, and the like can be used.

  The layer thickness of the layer containing spherical zinc oxide particles is preferably in the range of 50 nm to 50 μm for the purpose of increasing the efficiency of plasmon resonance. More preferably, it exists in the range of 50 nm-10 micrometers.

  Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "mass part" or "mass%" is represented.

[Example 1]
<< Preparation of spherical zinc oxide particles 1 >>
(1) 1.0 L of a 2.52 mol / L urea aqueous solution was prepared.
(2) Pure water was added to 500 mL of a 1.00 mol / L zinc nitrate aqueous solution to make 9 L.
(3) The urea prepared in (1) above was added to the aqueous zinc nitrate solution prepared in (2) above, and the mixture was heated and stirred at 90 ° C. for 60 minutes.
(4) Particles precipitated in the mixed solution heated and stirred in the above (3) were separated by a membrane filter.
(5) 1.0 L of a 2.52 mol / L urea aqueous solution was prepared.
(6) A 500 mL 1.14 mol / L zinc nitrate aqueous solution was prepared.
(7) The above (6) and pure water were added to 500 mL of 0.006 mol / L gallium nitrate aqueous solution to make 9 L.
(8) The urea prepared in (5) above and the particles obtained in (4) above were added to the gallium nitrate aqueous solution prepared in (7) above, and the mixture was heated and stirred at 90 ° C. for 60 minutes.
(9) The precursor of the particles deposited in the mixed liquid heated and stirred in the above (8) was separated by a membrane filter.
(10) The particle precursors separated in (9) above were calcined at 400 ° C. to obtain spherical zinc oxide particles 1 having a profile of the type shown in FIG.

<< Preparation of spherical zinc oxide particles 2 >>
(1) 1.0 L of a 2.52 mol / L urea aqueous solution was prepared.
(2) Pure water was added to 500 mL of a 1.00 mol / L zinc nitrate aqueous solution to make 9 L.
(3) The urea prepared in (1) above was added to the aqueous zinc nitrate solution prepared in (2) above, and the mixture was heated and stirred at 90 ° C. for 60 minutes.
(4) Particles precipitated in the mixed solution heated and stirred in the above (3) were separated by a membrane filter.
(5) 1.0 L of a 2.52 mol / L urea aqueous solution was prepared.
(6) A 500 mL 1.13 mol / L zinc nitrate aqueous solution was prepared.
(7) The above (6) and pure water were added to 500 mL of a 0.14 mol / L gallium nitrate aqueous solution to make 9 L.
(8) The urea prepared in (5) above and the particles obtained in (4) above were added to the gallium nitrate aqueous solution prepared in (7) above, and the mixture was heated and stirred at 90 ° C. for 60 minutes.
(9) The precursor of the particles deposited in the mixed liquid heated and stirred in the above (8) was separated by a membrane filter.
(10) The precursor of the particles separated in (9) above was fired at 400 ° C. to obtain spherical zinc oxide particles 2 having a profile of the type shown in FIG.

<< Preparation of spherical zinc oxide particles 3 >>
(1) 1.0 L of a 2.52 mol / L urea aqueous solution was prepared.
(2) Pure water was added to 500 mL of a 1.00 mol / L zinc nitrate aqueous solution to make 9 L.
(3) The urea prepared in (1) above was added to the aqueous zinc nitrate solution prepared in (2) above, and the mixture was heated and stirred at 90 ° C. for 60 minutes.
(4) Particles precipitated in the mixed solution heated and stirred in the above (3) were separated by a membrane filter.
(5) 1.0 L of a 2.52 mol / L urea aqueous solution was prepared.
(6) A 500 mL 1.14 mol / L zinc nitrate aqueous solution was prepared.
(7) The above (6) and pure water were added to 500 mL of a 0.17 mol / L gallium nitrate aqueous solution to make 9 L.
(8) The urea prepared in (5) above and the particles obtained in (4) above were added to the gallium nitrate aqueous solution prepared in (7) above, and the mixture was heated and stirred at 90 ° C. for 60 minutes.
(9) The precursor of the particles deposited in the mixed liquid heated and stirred in the above (8) was separated by a membrane filter.
(10) The precursor of the particles separated in (9) above was fired at 400 ° C. to obtain spherical zinc oxide particles 3 having a profile of the type shown in FIG.

<< Preparation of spherical zinc oxide particles 4 >>
(1) 1.0 L of a 2.52 mol / L urea aqueous solution was prepared.
(2) Pure water was added to 500 mL of a 1.00 mol / L zinc nitrate aqueous solution to make 9 L.
(3) The urea prepared in (1) above was added to the aqueous zinc nitrate solution prepared in (2) above, and the mixture was heated and stirred at 90 ° C. for 60 minutes.
(4) Particles precipitated in the mixed solution heated and stirred in the above (3) were separated by a membrane filter.
(5) 1.0 L of a 2.52 mol / L urea aqueous solution was prepared.
(6) A 500 mL 1.14 mol / L zinc nitrate aqueous solution was prepared.
(7) The above (6) and pure water were added to 500 mL of a 0.20 mol / L gallium nitrate aqueous solution to make 9 L.
(8) To the gallium nitrate aqueous solution prepared in (7) above, the urea prepared in (5) and the particles obtained in (4) above were added, and the mixture was heated and stirred at 90 ° C. for 60 minutes.
(9) The precursor of the particles deposited in the mixed liquid heated and stirred in the above (8) was separated by a membrane filter.
(10) The precursor of the particles separated in (9) above was fired at 400 ° C. to obtain spherical zinc oxide particles 4 having a profile of the type shown in FIG.

<< Preparation of spherical zinc oxide particles 5 >>
(1) 1.0 L of a 2.52 mol / L urea aqueous solution was prepared.
(2) Pure water was added to 500 mL of a 1.00 mol / L zinc nitrate aqueous solution to make 9 L.
(3) The above (2) and pure water were added to 500 mL of 0.05 mol / L gallium nitrate aqueous solution to make 9 L.
(4) The urea prepared in (1) above was added to the gallium nitrate aqueous solution prepared in (3) above, and heated and stirred at 90 ° C. for 60 minutes.
(5) The particles precipitated in the mixed solution heated and stirred in the above (3) were separated by a membrane filter.
(6) 1.0 L of a 2.52 mol / L urea aqueous solution was prepared.
(7) 1.14 mol / L zinc nitrate aqueous solution 500mL was prepared.
(8) The above (7) and pure water were added to 500 mL of a 0.17 mol / L gallium nitrate aqueous solution to make 9 L.
(9) To the gallium nitrate aqueous solution prepared in (8) above, the urea prepared in (6) above and the particles obtained in (4) above were added and heated and stirred at 90 ° C. for 60 minutes.
(10) The precursor of the particles precipitated in the mixed solution heated and stirred in the above (9) was separated by a membrane filter.
(11) The precursor of the particles separated in (10) above was fired at 400 ° C. to obtain spherical zinc oxide particles 5 having a profile of the type shown in FIG.

<< Preparation of spherical zinc oxide particles 6 >>
(1) 1.00 L of a 2.52 mol / L urea aqueous solution was prepared.
(2) 500 mL of 0.012 mol / L gallium nitrate aqueous solution was prepared.
(3) The above (2) and pure water were added to 500 mL of a 1.14 mol / L zinc nitrate aqueous solution to make 9 L.
(4) The urea prepared in (1) above was added to the zinc nitrate aqueous solution prepared in (3) above, and the mixture was heated and stirred at 90 ° C. for 60 minutes.
(5) The particles deposited in the mixed solution heated and stirred in the above (4) were separated by a membrane filter.
(6) 1.0 L of a 2.52 mol / L urea aqueous solution was prepared.
(7) 1.14 mol / L zinc nitrate aqueous solution 500mL was prepared.
(8) The above (7) and pure water were added to 500 mL of a 0.17 mol / L gallium nitrate aqueous solution to make 9 L.
(9) The urea prepared in (6) above and the particles obtained in (5) above were added to the gallium nitrate aqueous solution prepared in (8) above, and the mixture was heated and stirred at 90 ° C. for 60 minutes.
(10) The precursor of the particles precipitated in the mixed solution heated and stirred in the above (9) was separated by a membrane filter.
(11) The particle precursors separated in (10) above were fired at 400 ° C. to obtain spherical zinc oxide particles 6 having a profile of the type shown in FIG.

<< Preparation of spherical zinc oxide particles 7 >>
(1) 1.0 L of a 2.52 mol / L urea aqueous solution was prepared.
(2) Pure water was added to 500 mL of a 1.14 mol / L zinc nitrate aqueous solution to make 8 L.
(3) The urea prepared in (1) above was added to the aqueous zinc nitrate solution prepared in (2) above and heated to 90 ° C.
(4) A 0.32 mol / L zinc nitrate aqueous solution and a 0.25 mol / L urea aqueous solution were added to the dispersion solution of (3) at 90 ° C. with heating and stirring at an addition rate of 10 mL / min.
(5) After adding for 60 minutes, 0.05 mol / L gallium nitrate aqueous solution and 0.25 mol / L urea aqueous solution were added at a rate of 10 mL / min for 60 minutes respectively while heating and stirring at 90 ° C.
(6) The precursor of the particles deposited in the mixed liquid heated and stirred in the above (5) was separated by a membrane filter.
(7) The precursor of the particles separated in (6) above was fired at 400 ° C. to obtain spherical zinc oxide particles 7 having a profile of the type shown in FIG.

<< Preparation of Spherical Zinc Oxide Particles 8-16 >>
In preparation of the spherical zinc oxide particles 2, Ga was changed to the dopants shown in Table 1, and each was prepared using a nitric acid aqueous solution of the same concentration of the dopant.

<< Preparation of spherical zinc oxide particles 17 >>
(1) 1.0 L of a 2.52 mol / L urea aqueous solution was prepared.
(2) Pure water was added to 500 mL of a 1.14 mol / L zinc nitrate aqueous solution to make 8 L.
(3) The urea prepared in (1) above was added to the aqueous zinc nitrate solution prepared in (2) above and heated to 90 ° C.
(4) Add 0.15 mol / L gallium nitrate aqueous solution and 0.25 mol / L urea aqueous solution to the dispersion solution of (3) above at a rate of 10 mL / min for 120 minutes while heating and stirring at 90 ° C. did.
(5) The precursor of the particle which precipitated in the liquid mixture heated and stirred by said (4) was isolate | separated with the membrane filter.
(6) The precursor of the particles separated in (5) above was fired at 400 ° C. to obtain spherical zinc oxide particles 17 having a profile of the type shown in FIG.

<< Preparation of spherical zinc oxide particles 18 >>
(1) 1.00 L of 2.10 mol / L urea aqueous solution was prepared.
(2) 500 mL of 0.15 mol / L gallium nitrate aqueous solution was prepared.
(3) Pure water was added to 500 mL of a 1.0 mol / L zinc nitrate aqueous solution to make 8.5 L.
(4) The zinc nitrate aqueous solution prepared in (3) above was heated to 90 ° C.
(5) The aqueous urea solution prepared in (1) and the aqueous gallium nitrate solution prepared in (2) were added to the aqueous zinc nitrate solution heated in (4) above, and the mixture was heated and stirred for 1 hour.
(6) The precursor of the particles deposited in the mixed liquid heated and stirred in the above (5) was separated by a membrane filter.
(7) The precursor of the particles separated in (6) above was fired at 400 ° C. to obtain spherical zinc oxide particles 18.

<< Preparation of spherical zinc oxide particles 19 >>
(1) 1.00 L of 2.10 mol / L urea aqueous solution was prepared.
(2) 500 mL of 0.0045 mol / L gallium nitrate aqueous solution was prepared.
(3) Pure water was added to 500 mL of a 0.90 mol / L zinc nitrate aqueous solution to make 8.5 L.
(4) The zinc nitrate aqueous solution prepared in (3) above was heated to 90 ° C.
(5) To the aqueous zinc nitrate solution heated in (4) above, the aqueous urea solution prepared in (1) above and (2)
The gallium nitrate aqueous solution prepared in step 1 was added, and the mixture was heated and stirred for 1 hour.
(6) The precursor of the particles deposited in the mixed liquid heated and stirred in the above (5) was separated by a membrane filter.
(7) The precursor of the particles separated in (6) above was fired at 400 ° C. to obtain spherical zinc oxide particles 19.

<< Production of Spherical Zinc Oxide Particles 20 >>
(1) 1.0 L of a 2.52 mol / L urea aqueous solution was prepared.
(2) Pure water was added to 500 mL of a 1.00 mol / L zinc nitrate aqueous solution to make 9 L.
(3) The urea prepared in (1) above was added to the aqueous zinc nitrate solution prepared in (2) above, and the mixture was heated and stirred at 90 ° C. for 60 minutes.
(4) Particles precipitated in the mixed solution heated and stirred in the above (3) were separated by a membrane filter.
(5) 1.0 L of a 2.52 mol / L urea aqueous solution was prepared.
(6) 500 mL of 1.12 mol / L zinc nitrate aqueous solution was prepared.
(7) The above (6) and pure water were added to 500 mL of 0.23 mol / L gallium nitrate aqueous solution to make 9 L.
(8) The urea prepared in (5) above and the particles obtained in (4) above were added to the gallium nitrate aqueous solution prepared in (7) above, and the mixture was heated and stirred at 90 ° C. for 60 minutes.
(9) The precursor of the particles deposited in the mixed liquid heated and stirred in the above (8) was separated by a membrane filter.
(10) The precursor of the particles separated in (9) above was fired at 400 ° C. to obtain spherical zinc oxide particles 20.

<< Evaluation of spherical zinc oxide particles >>
As the evaluation of the spherical zinc oxide particles, the average content of dopant, the average particle size, the particle size variation coefficient (CV value) aspect ratio and the plasmon strength were evaluated.

<Average particle size, particle size variation coefficient (CV value)>
The average particle size and the coefficient of variation of the particle size distribution were determined from a scanning micrograph (SEM image) of 100 particles. For 100 particles, the diameter of a circle having the same area as the photographed particle image was measured, and the average particle diameter of the particles was determined. The particle size distribution variation coefficient was determined by the following formula.

Coefficient of variation (%) = (standard deviation of particle size distribution / average particle size) × 100
<Plasmon strength evaluation>
For the plasmon intensity evaluation, an infrared sensor was prepared, and the incident light angle dependency of the plasmon intensity and the plasmon intensity was evaluated.

  5 g of the produced spherical zinc oxide particles were dispersed in 100 mL of water, dropped onto a glass substrate, and a layer containing the spherical zinc oxide particles was produced as a detector so that the thickness after drying was 1 μm. This was used as a plasmon sensor chip.

<Average dopant content of spherical zinc oxide particles>
Five spherical zinc oxide particles were randomly collected and subjected to cross-section processing using a focused ion beam (FB-2000A) manufactured by Hitachi High-Technologies, and a surface passing through the vicinity of the particle center was cut out. From the cut surface, elemental analysis was performed using STEM-EDX (HD-2000) manufactured by Hitachi High-Technologies, and the dopant content of the core and shell of spherical zinc oxide particles having a core / shell structure from the average value of 5 It was measured.

  Regarding the dopant content of the entire spherical zinc oxide particles, 1 g of spherical zinc oxide particles was solubilized with nitric acid for each spherical zinc oxide particle, and then zinc and gallium were measured with an inductively coupled plasma emission spectrometer (ICP-OES). Quantification was performed.

  The measurement was performed by a matrix-matched calibration curve method, and Y (yttrium) was used as an internal standard.

  About the average content rate of the dopant of the surface part from the outermost surface of spherical zinc oxide particle to the depth of 10 nm, about each of the five spherical zinc oxide particles collected at random, XPS surface analyzer (ESCALAB made by VG Scientific) -200R), the content values of zinc, oxygen, and gallium were determined as atomic concentration (at%), respectively, and the average value was defined as the average content of dopant in the surface portion.

  About the average content rate of the dopant inside from 10 nm from the outermost surface of the spherical zinc oxide particle, the dopant content rate of the entire spherical zinc oxide particle and the average content of the dopant in the surface portion from the outermost surface of the spherical zinc oxide particle to a depth of 10 nm It was calculated from the rate.

<aspect ratio>
For each spherical zinc oxide particle, a scanning micrograph was taken, and 100 spherical zinc oxide particles were randomly selected. When the major axis of each selected particle is a and the minor axis is b, a / b The average value was obtained as the aspect ratio. In addition, when drawing a circumscribing rectangle for each particle (referred to as “the circumscribing rectangle”), the shortest short side of the circumscribed rectangle is the shortest length, and the longest long side is the length. Was the major axis.

<Evaluation of plasmon resonance intensity>
The plasmon resonance spectrum of water was measured using an FT-IR apparatus (FTIR-6000 manufactured by JASCO Corporation), and an absorption value at a wavelength of 1500 nm, which is absorption of OH groups of water molecules, was obtained. As for the numerical value of the table, 1.00 is the maximum, and a large value indicates that the plasmon resonance intensity is high.

  The results are shown in Table 1. The surface portion from the outermost surface to a depth of 10 nm is abbreviated as “surface portion”, and the inner portion from 10 nm from the outermost surface is abbreviated as “inner”.

  From Table 1, it can be seen that the spherical zinc oxide particles 1 to 17 have high plasmon resonance intensity when used for the plasmon sensor chip with respect to the spherical zinc oxide particles 18 to 20. In addition, when spherical zinc oxide particles Nos. 7 and 17 having a layer having a concentration gradient in which the dopant concentration increases from the center of the spherical zinc oxide particle toward the surface, the plasmon resonance intensity is high. Recognize.

DESCRIPTION OF SYMBOLS 1 Spherical zinc oxide particle 2 Surface part from outermost surface to depth 10nm 3 Inner than 10nm from outermost surface 4 Core layer 5 Shell layer 6 Layer with concentration gradient 11 Plasmon sensor 12 Substrate 13 Detection part containing spherical zinc oxide particle 14 Plasmon sensor chip 15 Optical prism 16 Light source 17 Polarizing plate 18 Mounting portion 19 Test object 20 Light receiving portion θ ₁ Incident angle θ ₂ Reflection angle

Claims (9)

  Spherical zinc oxide particles containing a dopant, wherein the dopant is a dopant selected from the group consisting of gallium, europium, cerium, praseodymium, samarium, gadolinium, terbium, niobium, ytterbium and indium, The average content of the dopant in the surface portion from the outermost surface to a depth of 10 nm is higher than the average content of the dopant inside from 10 nm from the outermost surface, and the average content of the dopant in the surface portion is Spherical zinc oxide particles characterized by being in the range of 0.5 to 15 mol%.   The spherical zinc oxide particles have a core / shell structure including a core layer and a shell layer, and the average content of the dopant in the shell layer is higher than the average content in the core layer. Spherical zinc oxide particles.   3. The spherical zinc oxide according to claim 1, comprising a layer having a concentration gradient in which the concentration of the dopant in the spherical zinc oxide particles increases from the center to the surface of the spherical zinc oxide particles. particle.   The average content of the dopant in the surface portion from the outermost surface of the spherical zinc oxide particle to a depth of 10 nm is in the range of 11 to 13 mol%, wherein any one of claims 1 to 3 The spherical zinc oxide particles according to claim 1.   The spherical zinc oxide particles according to any one of claims 2 to 4, wherein an average content of the dopant in the core layer is in a range of 0 to 5 mol%.   6. The spherical zinc oxide particles according to any one of claims 1 to 5, wherein an average particle diameter is in a range of 50 to 5000 nm. A method for producing spherical zinc oxide particles for producing the spherical zinc oxide particles according to any one of claims 1 to 6,
By mixing an aqueous solution of the dopant, an aqueous zinc solution, and an aqueous urea solution, the average content of the dopant in the surface portion from the outermost surface of the spherical zinc oxide particles to a depth of 10 nm is less than 10 nm from the outermost surface. A step of forming zinc-based compound precursor particles of spherical zinc oxide particles higher than the average content of the dopant, and a step of firing the zinc-based compound precursor particles to obtain spherical zinc oxide particles. A method for producing spherical zinc oxide particles.   In the step of forming the zinc-based compound precursor particles, an aqueous solution of the dopant is continuously added to a solution obtained by mixing an aqueous urea solution and at least one of an aqueous zinc solution or an aqueous solution of the dopant, from the center of the spherical zinc oxide particles to the surface. The method for producing spherical zinc oxide particles according to claim 7, wherein a layer having a concentration gradient that becomes higher is formed.   A plasmon sensor chip comprising a detection part and a substrate containing the spherical zinc oxide particles according to any one of claims 1 to 6.

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