Researchers Submit Patent Application, "Composite Substrate, Lspr Sensor Including the Same, Method of Using Lspr Sensor, and Detection Method Using Lspr Sensor", for Approval
The patent's assignee is
News editors obtained the following quote from the background information supplied by the inventors: "This invention relates to a composite substrate that may utilize the local surface plasmon resonance (LSPR), an LSPR sensor including the substrate, a method of using the LSPR sensor, and a detection method using the LSPR sensor.
"Nano-size particle has a geometrically high specific surface area and a quantum mechanical size effect, and exhibits altered optical properties, a lower melting point, higher catalytic effects, and better magnetic properties, etc. Therefore, the nano-size particle is expected to have new functions that cannot be obtained with bulk materials, such as improved chemical and physical conversion properties including catalytic effect, light-emitting property, etc., and has become a very important material in various fields such as electronic materials, catalytic materials, phosphor materials, light-emitter materials, and medical materials, etc. Particularly, in a metal fine-particle with a size of several to 100 nanometers, the electrons interact and resonate with light of a specific wavelength. This phenomenon is known as local surface plasmon resonance (LSPR). Recently, LSPR was actively studied for application in various devices. Because the LSPR is sensitive to the change of the dielectric constant .di-elect cons..sub.m(.lamda.) [.varies.(n.sub.m(.lamda.)).sup.2, wherein n.sub.m is the refractive index] of the medium around the metal fine-particles, it has a characteristic that the resonance wavelength changes in response to a change in the dielectric constant (or refractive index) of the medium around the metal fine-particles. Due to the characteristic, the application of LSPR in the fields of sensing such as frost sensors, humidity sensors, bio-sensors, and chemical sensors, etc., have been investigated actively.
"A conventional technique utilizing a detection of scattered light from LSPR, which uses a microscope to detect scattered light from LSPR of a single metal nano-particle among the metal nano-particles immobilized on the substrate in a 2D manner, has been proposed (e.g., in Non-Patent Documents 1, 2 and 3). For the prior art utilizes LSPR of a single metal nano-particle, there are problems such as low intensity of the scattered light and requirements of a complicated apparatus and a high-end measuring method. Moreover, detecting scattered light from LSPR in a liquid cell using a gold colloidal solution has also been proposed (e.g., in Patent Documents 3 and 4). However, because such technique utilizes gold colloidal, it is limited to be used in liquids, and the upper limit of the content of the metal fine-particles in the liquid cell is limited so that an increase of the intensity of the scattered light is limited.
"[Non-Patent Document 1]
As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "Accordingly, this invention provides a composite substrate that utilizes scattered light from LSPR and can be suitably used in various devices, an LSPR sensor including the composite substrate, a method of using the LSPR sensor, and a detection method using the LSPR sensor.
"After active studies with respect to the foregoing, the Inventors discovered that the above problems can be solved by using a composite material that is dispersed with metal fine-particles immobilized in a matrix having a 3D network structure.
"The composite material of this invention includes a metal fine-particle dispersed layer and a light transmission layer laminated with the same. The metal fine-particle dispersed layer has the following features a) to f). Feature a) is that the metal fine-particle dispersed layer includes a matrix having a solid framework and voids formed by the solid framework, and metal fine-particles immobilized in the solid framework. Feature b) is that the solid framework contains aluminum oxyhydroxide or an alumina hydrate to form a three-dimensional network structure. Feature c) is that the metal fine-particles have a mean particle diameter in a range of 20 to 100 nm, with a proportion of 50% or more thereof having particle diameters in the range of 20 to 100 nm. Feature d) is that the metal fine-particles are separated from each other with a distance that is greater than or equal to a particle diameter of a larger one of neighboring fine-particles. Feature e) is that the metal fine-particles have portions exposed in the voids of the matrix and are three-dimensionally dispersed in the matrix. Feature f) is that the metal fine-particle dispersed layer has a thickness in a range of 0.5 to 5 .mu.m and a metal fine-particle content with a range of 22 to 900 .mu.g/cm.sup.2.
"In an embodiment, the void proportion of the metal fine-particle dispersed layer is within the range of 15 to 95%.
"In an embodiment, the volume fraction of the metal fine-particles in the metal fine-particle dispersed layer in within the range of 1 to 9% relative to the metal fine-particle dispersed layer.
"In an embodiment, the metal fine-particles include gold (Au) or silver (Ag).
"In an embodiment, the metal fine-particles are able to interact with light having a wavelength of 380 nm or longer to induce a local surface plasmon resonance (LSPR).
"The LSPR sensor of this invention includes the composite substrate of claim 1, a light source irradiating the composite substrate with light, a light receptor receiving a scattered light from LSPR of the metal fine-particles in the composite substrate; and a spectrometer measuring the scatter spectrum of the scattered light, or a photo-detector measuring the intensity of the scattered light.
"In an embodiment, the LSPR sensor further includes a means for concentrating the scattered light.
"In an embodiment, the LSPR sensor further includes a means for concentrating the irradiation light.
"In an embodiment, the irradiation light from the light source is inclined with respect to a lamination direction of the composite substrate.
"In an embodiment, the light irradiation and the measurement of the scatter spectrum are accomplished through the light transmission layer.
"The method of using the LSPR sensor of this invention includes exposing, in the atmosphere or a gas, or in a liquid, the metal fine-particle dispersed layer in the LSPR sensor.
"The detection method of this invention is for detecting an inorganic or organic substance, including: providing the above LSPR sensor, and measuring the change of the scatter spectrum of the scattered light from the LSPR, the change of the intensity of the scatter spectrum of the scattered light from the LSPR, or the change of the intensity of the scattered light from the LSPR.
"The composite substrate of this invention can increase the intensity of the scatter spectrum of LSPR, for the metal fine-particle dispersed composite has a matrix with a 3D network structure having a solid framework and voids formed thereby, in which the metal fine-particles are 3D-dispersed. Moreover, by controlling the particle diameter of the metal fine-particles in the matrix within the predetermined range, the particles can be dispersed evenly to maintain the inter-particle distance, so the scatter spectrum of LSPR is sharp. Furthermore, because the metal fine-particles have portions exposed in the voids in the matrix network, the characteristic that the resonance wavelength changes in response to change in the dielectric constant (or refractive index) of the medium around the metal fine-particles can be taken advantage to the maximal extent, so the composite substrate of this invention are suitably applied to the devices taking advantage of the characteristic.
"In order to make the aforementioned and other objects, features and advantages of this invention comprehensible, a preferred embodiment accompanied with figures is described in detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
"FIG. 1 illustrates a cross-sectional view of a composite substrate according to an embodiment of this invention.
"FIG. 2 schematically illustrates the dispersion state of the metal fine-particles in a cross section of the nano-composite in the thickness direction.
"FIG. 3 schematically illustrates the dispersion state of the metal fine-particles in a cross section of the nano-composite of FIG. 2 parallel with the surface of the same.
"FIG. 4 illustrates the structure and the arrangement of the metal fine-particles.
"FIG. 5 illustrates a locally magnified view of a nano-composite having a binding species (ligand) according to an alternative embodiment of this invention.
"FIG. 6 illustrates a specific binding based on the binding species.
"FIG. 7 schematically illustrates the constitution of an LSPR sensor according to an embodiment of this invention.
"FIGS. 8A and 8B respectively show the absorption spectrum of LSPR and the scatter spectrum of LSPR observed in Example 1.
"FIGS. 9A and 9B respectively show the absorption spectrum of LSPR and the scatter spectrum of LSPR observed in Example 7.
"FIGS. 10A and 10B respectively show the absorption spectrum of LSPR and the scatter spectrum of LSPR observed in Comparative Example 1."
For additional information on this patent application, see:
Keywords for this news article include: Analytical Chemistry,
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