KR101515898B1 - Silver particle complex and method for preparing the same - Google Patents

Abstract

Silver particle composites and methods for their preparation are disclosed. The silver particle composite of the present invention comprises a core comprising silver and having a hierarchical surface morphology; And chitosan bonded to the surface of the core. Thus, a silver particle composite which can be used as a substrate for SERS probing can be produced by a one-pot simple process at room temperature, and is environmentally friendly. Further, by controlling the chitosan concentration and the amount of silver nitrate used, Can be easily controlled. Since the silver particle composite thus prepared has a hierarchical surface morphology, the SERS signal of the probe molecule can be dramatically enhanced.

Description

TECHNICAL FIELD [0001] The present invention relates to a silver particle composite,

The present invention relates to a silver particle composite and a method for producing the same, and more particularly, to a method for producing a silver halide emulsion by preparing a flower-shaped dendritic silver / silver nanoparticle composite using chitosan and then subjecting it to a probe for surface enhanced Raman scattering And is used as a substrate.

Surface enhanced Raman scattering (SERS) has been intensively studied in recent years as a promising technology for ultra-sensitive detection of bioassays by providing fingerprint information at low concentrations.

The local electromagnetic effect (EM) is known to dominate the enormous enhancement of Raman scattering. This occurs from the collective oscillation of conductive electrons excited by light irradiation on the surface of the noble metal. Another contributory contribution of the overall SERS signal is chemical enhancement using a charge transfer (CT) mechanism. While EM can occur at a certain distance from the surface, CT can only occur when the molecule is chemically adsorbed on the metal surface. Because of the relatively low chemical build-up, most sensor designs can control the development of complex topography of metal nanostructures and / or the inter-particle distance between neighboring particles, which can provide many hot-spots By concentrating on EM enhancement. These hot-spots are known to be associated with greatly enhancing local electromagnetic fields and are known to amplify the Raman scattering of probe molecules located in the region.

Recent studies have shown that many of the complex structures used as highly sensitive SERS substrates, such as dendrite, nanorods, prisms, triangles, wires ), Pods (multipodes), stars, and flowers. Among them, hierarchical assemblies for designing blocks on a nanoscale in a complex architecture, for example, from one-dimensional nano-rods / nanowires to branched nanostructures or from ordered triangular nanoplates scattered in orderly assemblies with anisotropic orientations Hierarchical assembly is very important.

Because hierarchical nanostructures exhibit new, collective physico - chemical properties, which are not found at the level of individual nanoparticles. However, the synthesis of anisotropic nanostructures still requires multiple processes and long process times. Various techniques for producing dendritic metal nanoparticles have been reported. For example, electrochemical (or electroless) metal deposition, galvanic substitution reaction, hydrothermal reaction, ultraviolet irradiation reduction, and ultrasound assisted reaction. However, these reactions are very difficult to control size and particle morphology simply by controlling the consumption of time, unclear particle surface, low reaction yield and reaction parameters.

Recent studies have been based on wet-chemical synthesis. So-called colloidal chemistry is the most convenient, cost-saving, shape-controllable and exhibits high yields for producing dendritic metal particles using a template of polymerization as a surfactant or growth control or stabilizer. The synthesis of dendritic metal nanostructures generally takes a long time in the aging process and is only possible with some special types of polymers and reducing agents.

For example, there is a PVP having a pyrrolidone group that has proved to be an effective capping agent in the synthesis of silver dendrites when hydroxylamine is used as a reducing agent. This is also observed in the formation of other types of polymers such as cetyltrimethylammonium chloride (CTAC), sodium dodecyl benzenesulfonate (SDBS), and tetrabutylamonium bromide (TBAB) in the formation of anisotropic nanostructures. Although surfactants have been successfully used to produce composite nanostructures, non-biodegradable agents must be removed from the particles for SERS applications in the biomedical field. However, it is difficult to develop a simple synthesis method of nanostructures for dendritic resins which are biocompatible and use only nontoxic components.

It is an object of the present invention to provide a method for easily synthesizing a flower-type silver particle complex using a chitosan biopolymer at a room temperature in a one-pot process, (SERS) as a probe substrate for high-sensitivity surface-enhanced scattering (SERS) analysis of molecules.

According to an aspect of the present invention, there is provided a silver halide lamp, comprising: a core including silver and having a hierarchical surface morphology; And chitosan bonded to the surface of the core.

The silver particle composite may be dendritic.

The silver particle composite may be in the form of a face centered cubic (fcc).

The hierarchical surface of the core may include a plurality of crevices and a plurality of edges.

The shape of the silver particle composite may be a flower or a multiple-branch type.

The hierarchical surface of the core includes a plurality of sheets, and the sheets may be grown separately from each other about the center of the core.

The core may be one having an anisotropic optical crystal structure.

The chitosan may be capped at the core or embedded in the core.

The thickness of the edge may range from 50 to 300 nm.

The diameter of the silver particle composite may range from 500 to 3000 nm.

The silver particle composite can be used as a substrate for probe of surface enhanced Raman scattering (SERS).

The surface enhanced Raman scattering (SERS) using the above substrate can be applied as a probe molecule to at least one selected from the group consisting of CTP (2-chlorothiophenol), ATP (aminothiophenol) and Rhodamine 6G.

According to another aspect of the present invention, there is provided a method for producing a chitosan solution, comprising the steps of: (a) preparing a chitosan solution; Adding silver ions (Ag ⁺ ) to the chitosan solution to prepare a mixed solution (step b); And a step of adding a reducing agent to the mixed solution (step c).

After step c, the step of centrifuging and ultrasonicating the result of step c may be further performed.

After step d, a step of diluting with water (step e) may be additionally performed.

The chitosan solution may be prepared by chitosan having a deacetylation degree of 65% or more.

The concentration of the chitosan solution may be 0.05 to 0.5 wt%

In step (a), the chitosan solution may be prepared by dissolving chitosan in an acetic acid solution.

The steps may be performed at room temperature.

The silver ion (Ag ⁺ ) may be added as a silver nitrate (AgNO ₃ ) solution.

The silver ion (Ag ⁺ ) may be added in a silver ion solution of 0.1 to 1.0 M.

The reducing agent may be at least one selected from the group consisting of ascorbic acid, hydroxylamine and sodium borohydride.

The preparation of the silver particle composite of the present invention can be easily performed by one-pot at room temperature. It is environmentally friendly using chitosan, and its shape and size can be easily controlled by adjusting the amount of chitosan and the amount of silver nitrate used . Since the silver particle composite thus prepared has a hierarchical surface morphology, the surface enhancement scattering signal of the probe molecule can be dramatically enhanced.

Figure 1 schematically illustrates a proposed mechanism for producing silver particle composites.
2 shows SEM images of silver particle composites prepared according to Example 1 at different resolutions.
3 shows the XPS and EDX analysis results of the silver particle composite prepared according to Example 1. Fig.
4 is a TEM image showing the morphological evolution of the crystal structure with respect to the reaction time during synthesis of the silver particle composite.
5 is a SEAD pattern of a silver particle composite prepared according to Example 1. Fig.
6 shows the XRD spectrum of the silver particle composite prepared according to Example 1. Fig.
7 is an SEM image of a silver particle complex according to chitosan concentration.
8 is an SEM image of a silver particle composite according to the amount of silver nitrate used.
9 shows an SEM image of a silver particle composite according to a temperature condition.
10 shows the UV-Vis spectrum according to the chitosan concentration (A) and (B) silver nitrate usage of the silver particle composite of the present invention.
Figure 11 shows an SEM image of two types of silver particle composites of different shapes.
FIG. 12 is a graph showing the SERS test result of CTP using two types of silver particle composites compared to the case of not using the silver particle composite. FIG.
13 is an SEM image of a silver particle composite spread on a silica slice.
Figure 14 shows the SERS spectrum for the CTP molecule of a silver particle complex spread on a silica slice.
15 is an SEM image of a silver particle composite prepared according to Examples 14 and 15 of the present invention.
16 is a graph showing the results of ATPdml SERS test using silver particle composites prepared according to Examples 14 and 15 of the present invention.

Hereinafter, the structure and manufacturing method of the silver particle composite of the present invention will be described in order.

The silver particle composite of the present invention has a structure in which the silver particle composite prepared according to the method described above has a hierarchical surface shape including silver; And chitosan bonded to the core.

The core may be in the form of a dendritic or a face-centered cubic (fcc) form.

The hierarchical surface includes a plurality of crevices and a plurality of edges and the plurality of gaps and edges serve to enhance the signal of surface enhancement Raman analysis (SERS) by hot-spot can do.

The shape of the silver particle composite may be a flower or a multiple-branch type. In this case, the multi-branch type is a type in which silver particles grow concentrically and some basic branches are formed. In the flower type, silver atoms are deposited on the surface of the multi-branch type, Of the sheets are formed.

As such, the hierarchical surface of the core includes a plurality of discrete sheets, which are grown concentrically around the center of the core and may have an optically anisotropic structure.

The chitosan may be capped at the end of chitosan or may be embedded in the core.

The thickness of the edge may range from 50 to 100 nm, and the silver particle composite may have a spherical boundary as a whole, and the size may have a diameter of 500 to 3000 nm.

The silver particle composite of the present invention can be used as a substrate for probe of surface enhanced Raman scattering (SERS), and can be used as a probe for CSP (2-chlorothiophenol), ATP (4-aminothiophenol), and Rhodamine It can be applied as a molecule.

However, the scope of the present invention is not limited thereto, and molecules including at least one of an amine group (-NH ₂ ) and a sulfide group (-SH) can be applied.

Hereinafter, a method for producing the silver particle composite of the present invention will be described.

First, a chitosan solution is prepared (step a).

The chitosan solution is prepared by dissolving chitosan in an acid solution. The chitosan preferably has a deacetylation degree of 70% or more, more preferably 85% or more. Further, it is preferable to apply an acetic acid solution to the acid solution, and other weak acids having biocompatibility may be applied.

The concentration of the finally prepared chitosan solution is preferably 0.05 to 0.5 wt%. And more preferably 0.1 to 0.2 wt%.

Next, a solution containing silver ions (Ag ⁺ ) is added to the chitosan solution to prepare a mixed solution (step b).

When the mixed solution is prepared, it is preferable to stir vigorously.

The silver ion (Ag ⁺ ) -containing solution is preferably a silver nitrate (AgNO ₃ ) solution.

Thereafter, a reducing agent is added to the mixed solution prepared in step b) (step c).

As the reducing agent, ascorbic acid, hydroxylamine, sodium borohydride (NaBH ₄ ) or the like may be used, but it is more preferable to use ascorbic acid.

After the reducing agent is added, the mixture is sufficiently stirred to obtain a silver particle composite.

Next, the obtained silver particle complex is subjected to centrifugal separation and ultrasonic treatment in order to purify (step d).

Preferably, the centrifugal separation and the ultrasonic treatment are repeatedly performed a plurality of times. After purification, it can be diluted again with water.

It is preferable to use ultrapure water which can be used as water for HPLC.

Next, the mechanism of the silver particle composite production of the present invention will be described.

Figure 1 schematically illustrates a proposed mechanism for producing silver particle composites.

According to FIG. 1, firstly, the silver atom is slowly released by a mild redox reaction between the ascorbic acid reducing agent and the Ag + ion trapped in the chitosan matrix. Although scrolling of the chitosan chains and actuation of the surface tension of the Ag atoms are reduced, these Ag atoms are quickly aggregated in the nucleation process to form an initial seed. These newly formed seeds are stabilized by extra-repulsive forces between the positive chitosan chains adsorbed on the other Ag seeds and dispersed in the chitosan solution.

However, the presence of chitosan in the Ag / solvent combination did not participate in diffusion-limited silver atom deposition on the surface of the initial seed particles. It is because of the attraction between the positive amine of the chitosan and the negative nature of the silver. Thus, these seeds acted as centers for capturing free silver atoms from solution. Thus, a dendritic silver particle composite was formed. The Ag atoms will then continue to diffuse towards the aggregate and are deposited further on the empty surface of the branches, the branches become thicker and rough surfaces of dendritic silver particles can be obtained.

[Example]

Hereinafter, preferred embodiments of the present invention will be described. However, this is for illustrative purposes only, and thus the scope of the present invention is not limited thereto.

Reagent preparation

Acetic acid (99.0%) was purchased from Duksan Pure Chem Co., Ltd. (Sigma Aldrich), and deacetyl was purchased from Sigma Aldrich with 85% chitosan (molecular weight = 50000), AgNO ₃ (99.0%) and 2-clorothiophenol . Ltd., South Korea. All reagents were used without further purification.

Example  One

Glass Experiments are newly prepared in aqua regia _{(HCl: HNO 3 = 3:} 1) fully rinsed by, was again washed with distilled water prior to use. In addition, the synthesis of the silver nanostructure of the present invention was carried out at room temperature.

1.0 wt% chitosan was dissolved in 1.0 v / v% acetic acid solution by ultrasonication until it became clear, and then it was diluted with HPLC (high performance liquid chromatography) water. Then, 60 쨉 l of 1.0 M AgNO ₃ was added to 3 ml of the chitosan solution with vigorous stirring for 5 minutes.

Next, dendritic Ag nanoparticles (or silver mesophytes) were obtained by adding 60 μl of ascorbic acid (1.0 M) to the mixed solution and stirring for another 10 minutes. The silver particles were purified by three successive centrifugation-ultrasound steps and again diluted in HPLC water.

Example  2

A silver particle composite was synthesized in the same manner as in Example 1, except that the concentration of the chitosan solution was changed to 0.05 wt%.

Example  3

A silver particle composite was synthesized in the same manner as in Example 1, except that the concentration of the chitosan solution was changed to 0.1 wt%.

Example  4

A silver particle composite was synthesized in the same manner as in Example 1, except that the concentration of the chitosan solution was changed to 0.2 wt%.

Example  5

A silver particle composite was synthesized in the same manner as in Example 1, except that the concentration of the chitosan solution was changed to 0.3 wt%.

Example  6

A silver particle composite was synthesized in the same manner as in Example 1, except that the concentration of the chitosan solution was changed to 0.4 wt%.

Example  7

A silver particle composite was synthesized in the same manner as in Example 1, except that the amount of the silver nitrate solution was changed to 10 μl.

Example  8

A silver particle composite was synthesized in the same manner as in Example 1, except that the amount of the silver nitrate solution was changed to 30 μl.

Example  9

A silver particle composite was synthesized in the same manner as in Example 1, except that the amount of silver nitrate solution used was changed to 45 μl.

Example  10

A silver particle composite was synthesized in the same manner as in Example 1, except that the amount of silver nitrate solution used was changed to 60 μl.

Example  11

A silver particle composite was synthesized in the same manner as in Example 1, except that the amount of the silver nitrate solution was changed to 90 μl.

Example  12

A silver particle composite was synthesized in the same manner as in Example 1, except that the temperature of the experiment was maintained at 60 캜.

Example  13

A silver particle composite was synthesized in the same manner as in Example 1, except that the experimental temperature was maintained at 0 ° C.

Example  14

A silver particle composite was synthesized in the same manner as in Example 1, except that the experimental temperature was maintained at 25 占 폚 and the chitosan concentration was changed to 0.2 wt.

Example  15

A silver particle composite was synthesized in the same manner as in Example 14 except that the experimental temperature was maintained at 60 캜.

[Test Example]

The size and shape of the silver particle composite is represented by a scanning electron microscope (SEM, S-4700 Hitachi) and a transmission electron microscope (TEM, HITACHI, H7600) at 300 KV in an excitation electron beam of 15 KV. X-Ray diffraction (XRD; Rigaku Corp.) with Cu Ka radiation was used to analyze the crystal structure of the solid samples. UV-Vis spectrometer (CARY) and Raman spectroscopy (LabRam HR) were used to characterize the optical properties of the prepared materials. The Raman spectrograph used an 1800 g / mm grating and the He-Ne laser excitation at 632.8 nm was used with 60 accumulations.

Test Example  1: Confirmation of synthesis of silver particle complex and analysis of surface characteristics

FIG. 2 is a SEM image of a layered silver particle composite prepared according to Example 1 at different resolutions, and FIG. 3 is a result of XPS and EDX analysis of a silver particle composite prepared according to Example 1. FIG.

According to Fig. 2, the silver particle composite showed a homogeneous distribution of particle size (ca. 1400 nm). The hierarchical morphology of the silver particle complexes was evident by the high magnification SEM. The dendritic particle composite had a spherical grain boundary, approximately 50-100 nm thick, but did not appear uniformly in length. The results of XPS and EDX analysis according to FIG. 3 show that the O, C, and N atoms derived from chitosan are present in the silver particle composite prepared according to Example 1.

Test Example  2: Crystal structure analysis of silver particle composites

4 to 6 show the results of crystal structure analysis of the silver particle composite prepared according to Example 1. Fig. 4 is a TEM image showing the morphological evolution of the crystal structure according to the reaction times (20, 60 and 150 seconds, respectively) during synthesis of the silver particle composite, FIG. 5 shows the SEAD pattern, FIG. 6 shows the XRD spectrum Lt; / RTI >

To find out the growth mechanism of the dendritic grains, the dendrites were recorded by TEM images of samples (20, 60 and 150 s) obtained at different growth times in time-dependent morphology evolution of the particle complexes. The reaction mixture was then centrifuged at 10,000 rpm for 1 minute to remove residual reactants. Significant changes in shape over reaction time were evident from irregular particles to dendritic multiple-branched particles and silver particles such as a layered submicron flower shape. The particles grew homocentrically, assuming that some of the basic branches were first formed and acted as the framework for the deposition of a second Ag atom to form multiple layers of thin sheets on the surface . The SAED analysis identifies a single crystalline structure of the silver particle composite.

The XRD pattern shows five steep diffraction peaks associated with {111}, {200}, {220}, {311} and {222} facets. This indicates that the synthesized resin phase is (fcc) particles in which the particle composite crystal is well formed. The remarkable intensity of the {111} diffraction peak is much higher than other peaks. Silver particle complexes first exhibit {111} facet and crystal growth preferentially parallel to the {111} direction. A kinetically-controlled synthetic process can be established by slowing down the reduction process and can be seen as primarily related to the formation of dendritic nanostructures.

It is considered that the low redox ratio of AgNO ₃ for Ag formation is controlled by the mild reducing power of steric hindrance and ascorbic acid in the chitosan chain as a capping agent. Selective adsorption processes are known to affect crystal habits. Thus, it can be seen that the formation of a single crystal with a floral morphology complex can be obtained, first of all leading to a separate crystal surface growth inhibition, and when the multiple steps are included in such processes. Conversely, chitosan is believed to help crystal growth in such orientation because it is selectively attached to a preferential plane and affinity to metal atoms.

Test Example  3: Analysis of formation of silver particle composites by chitosan concentration and silver nitrate usage

FIG. 7 is an SEM image of the silver particle composite according to the chitosan concentration, and FIG. 8 is an SEM image of the silver particle composite according to the amount of silver nitrate used.

According to Figures 7 and 8, a series of experiments were conducted to investigate the effect of chitosan on the formation of the synthesized silver particle complex, where other experimental parameters were fixed and the chitosan concentration was varied. The size and shape of the silver particle complexes were found to be strongly influenced by the concentration of chitosan in the reaction solution as shown in the SEM image of FIG.

Immediately after the addition of ascorbic acid to the stirred mixture of silver nitrate and chitosan, rapid color change from clear to gray, dark gray and turbid color was observed for several minutes. The SEM images of Examples 5 and 6 at high chitosan concentration (0.3-0.4 wt%) show a distinct hierarchical structure of silver particle composites with a number of well-separated sheet assemblies. The sheets appear to be formed concentrically from the body center, and the deposited Ag Numerous projections appear due to the atom.

The morphology and size of the synthesized dendritic silver particle complexes apparently changed as the chitosan concentration decreased from 0.1 to 0.05 wt%. The resulting silver particles appeared to have a spherical grain boundary consisting of many coarse nanoscale edges and nanodots on the surface instead of the sheet.

From this fact, chitosan can be absorbed at the surface of the silver particle complex and the Ag And to protect the silver particle complexes from compacting. Therefore, it is judged that the crystallographic growth of the dendritic particle composite is well controlled. In other words, chitosan not only served as a capping agent but also played a crucial role in controlling the shape and size of the resulting particles.

The structural evolution of these dendritic grains contributes to the anisotropic growth of silver nanocrystals under different Ag ⁺ ion concentrations. It means that AgNO ₃ administration affects the nucleation and growth processes. As a result, the characteristic shape of the formed particles can be controlled.

The volume (10 to 90 μl) of AgNO ₃ (1.0 M) was varied to investigate the effect of Ag ⁺ ion administration on the characteristic morphology of the silver particle complex. When AgNO ₃ was added at low volume (10 to 30 μl), the morphology of the silver particle complex was very similar to that obtained at high chitosan concentration and consisted of numerous thin single sheets. AgNO ₃ Increasing the used volume to 60-90 μL resulted in an apparent change in shape to the rough surface constituting the edge and nanodot. This seems to be due to the gradual deposition of silver atoms on thin sheets or cracks to form thick sheets until they are rough edges.

 As mentioned earlier, kinetic-controlled (or nonequilibrium) synthesis is deeply involved in the formation of transparent nanostructures by reducing the rate of reaction. It has been found that the use of high chitosan concentration and / or low silver nitrate slows down the redox rate and is consequently an important factor controlling the properties of the final formed particles.

Test Example  4: Characteristic Analysis of Silver Particle Composite Structure by Temperature Condition

9 shows an SEM image of the silver particle composite according to the tempering condition.

Since a kinetic-controlled reaction takes place in a non-equilibrium state, a small change in the reaction temperature can amplify the change in the growth rate of individual crystal phases, resulting in a change in the shape and size of the crystal structure It affects.

Therefore, the following three different reaction temperatures were selected. Hot temperature (60 占 폚) (Example 12), room temperature (Example 1), and cold temperature (0 占 폚) (Example 13). Unlike the SEM image shown in Figure 9, considerable size increase and form complexity were observed in the synthesized particles at lower reaction temperatures. At higher temperatures, the synthesized silver particles appeared to have a polyhedral structure rather than a dendritic structure with an unambiguous shape and size.

Coexistence of 2-D hexagonal plates was also observed. Higher temperatures increase the reaction rate and the diffusion rate of the components, resulting in the rapid formation of irregular nanostructures. Moreover, high temperatures reduce the viscosity of the chitosan solution, which can be an important factor controlling the anisotropic growth of silver particles. In particular, the lower temperature effects of fabricating nanostructured composites are based on slower reaction and diffusion rates.

The silver particle composites prepared at cold temperatures exhibited a complex shape with larger size and a larger number of thin, short edges compared to samples prepared at room temperature. At cold temperatures, a low diffusivity caused more supersaturation of the reactants and thus prolonged nucleation and crystallographic growth time. In other words, the reaction temperature significantly affects the final morphology and the size of nanocrystals produced by changing the diffusion rate as well as the reaction rate.

Experimental Example  5: Optical properties of silver particle composites

The size and shape of the silver particle composite has a significant effect on the optical properties such as the width and position of the plasmon absorption band of the final particles. Agglomerated nano-particles with spherical geometry generally exhibit only one size-dependent absorption band, although this optical property varies depending on the shape of the silver nanoparticles. For example, non-spherical Ag particles (e.g., prism and triangle) exhibit three to four SPR absorption bands. The dendritic silver nanostructures exhibit two SPR absorption bands in the UV-Vis zone and the flower-shaped silver nanostructures with a rough surface can be seen red-shifted to the near infrared region (NIR).

10 shows the UV-Vis spectrum according to the chitosan concentration (A) and the silver nitrate (1.0 M) used in the silver particle composite of the present invention.

According to FIG. 10, all spectra exhibit a similar broad absorption band regardless of the shape and size of the dendritic particle complex from 420 nm to the NIR zone. At high chitosan concentrations, two unclear peaks appearing at 380 nm and approximately 550 nm appear to contribute to dipole resonance outside the plane and within the plane, respectively. The two peaks gradually disappeared when the chitosan concentration was reduced to 0.2 wt%. Probably because of the thick deposition of silver atoms.

It seems to be due to the anisotropic morphology of the silver particles formed in these conditions. The same trend was observed in the UV-Vis spectra of the silver particle composites even with increasing amounts of AgNO ₃ (1.0 M) due to the similarity of the structure of the silver particle composites.

Test Example  6: CTP (2- chlorothiophenol ) For detection SERS ( Surface enhanced Raman scattering )

For SERS analysis, a predetermined amount of 2-chlorothiophenol (CTP) was added to the same volume of the silver particle complex prepared according to Example 1. The mixture was shaken for several minutes to obtain a complete equilibrium state of the CTP absorbed on the surface of the silver particle complex and allowed to stand at room temperature for 4 hours. The unbound CTP was then removed by centrifugation and again diluted in HPLC water. Finally, the CTP bound to the silver particle composite was dropped onto a silicon slide. And allowed to dry at room temperature prior to SERS measurement.

Figure 11 shows SEM images of two different types of type (type 1 and type 2) particle composites, and Figure 12 shows SERS results of CTP using the two types of silver particle composites as a silver particle composite And is compared with the case where it is not used. Where the concentration of CTP was 10 ^-4 M and all spectra were recorded in a 632.8 nm excitation laser with 20,000 counts per section.

According to Figures 11 and 12, two types of silver particle composites were chosen because of their different surface structure for comparison of SERS enhancement. type 1 is a spherical structure with some corroded cracks and type 2 has a much more hierarchical structure with numerous coarse nano-edges and small cavities in the random direction. The SERS sensitivity of these particles was evaluated by using CTP as a probe molecule. It is known that CTP chemisorbs to the silver particle surface by thiol group interaction.

As shown in FIG. 12, no noticeable signal was observed in the SERS spectrum when the silver particle composite was not used. The Raman signal, which is derived from the fact that the silver particles are easily affected by oxidation at ambient conditions, appeared. It can be seen that the SERS efficiency of CTP detection is not compromised. Because the location and intensity of all Raman peaks differs from that of CTP peaks.

In the case of the SERS spectra of the two particle composites, the typical SERS peak is clearly enhanced. This indicates that an effective encoding process of CTP has been achieved in the two types of silver particle composites. However, more dramatic enhancement was observed in the SERS spectrum than in type 2 to type 1. Specifically, the difference in relative enhancement was calculated to be 50 times as high as the peak enhancement ratio at 1042, 1110, and 1573 cm ^-1 , respectively.

The distinctive form of the type 2 silver particle complex with numerous small cavities and coarse nano-edges increases the surface area exponentially and can serve as a hot spot for SERS detection. Therefore, the local electromagnetic field and plasmon can be expected to enhance the Raman intensity of the particle composite. In particular, the appearance of chitosan on the surface of silver particle composites did not provide any noticeable noisy peaks in SERS detection of CTP. Likewise, it did not interfere with the silver particle surface from the encoded process.

Test Example  7: of the silver particle composite SERS   Sensitivity analysis

To study the SERS sensitivities of the floral form of the present invention in CTP detection, the silver particle complex is incubated with CTP (10 ^-6 M) for 4 hours so that the CTP is completely absorbed onto the surface of the silver particle complex Respectively. Thereafter, it was centrifuged to remove unbound CTP and diluted again with HPLC water. Subsequently, the concentration of the silver particle complex in the colloidal solution was adjusted by 10 ^-4 M (AgNO ₃ ) to prevent excessive aggregation of the particles. The silver particle composite droplets prepared as described above were spread on the silicon surface and dried in an untouched state at room temperature for a sufficient time.

Figure 13 is a SEM image of a dendritic silver particle composite spread on a silica slice and Figure 14 is a SERS spectrum of CTP molecules of a dendritic silver particle complex spread on a silica slide. At this time, the concentration of CTP was 10 ^-6 M, and all the spectra were recorded in 632.8 nm excitation laser light. In FIG. 13A, the accumulation time was 60 seconds, 200 counts per section, and 5000 counts in (B).

According to Figs. 13 and 14, as shown in the SEM image, it was observed that the isolated particles and the close-packed silver particle cluster coexist. Adsorption and film formation of chitosan on the silicon slice after solvent evaporation can prevent the mass accumulation of silver particle complexes. The SERS spectra of CTP molecules adsorbed on three separate silver particle complexes at positions 1, 2 and 3 of the SEM photograph are clearly shown. This indicates that these enhancing elements show average enhancement on all surfaces of each particle. It was also found that local enhancement occurred in the inside of cracks or at the end of protruded part of each particle table. SERS enhancement was observed in the cluster of silver particle assembled at 4 and 5 positions. By comparison with the peak intensity, it was confirmed that the silver particle composite clusters showed a SERS signal enhancement almost 100 times higher than the peak intensity of the separated silver particle complex. This result is believed to be due to the large number of plasmon gaps created between adjacent particles, so-called hot-spots, and additional field enhancement can be given to the intrinsic field of the individual particles.

Test Example  8: ATP (4- aminothiophenol ) For detection SERS ( Surface enhanced Raman scattering )

SEM images of the silver particle composites prepared according to Examples 14 and 15 are shown in FIG. 15, and SERS (surface enhanced Raman scattering) tests using the silver particle composites according to Examples 14 and 15 were performed, The spectrogram is shown in Fig.

Test Example 8 was carried out in the same manner as in Test Example 6 except that 10 ^-4 M of ATP (4-aminothiophenol) was used instead of CTP as a probe molecule of the SERS test.

As shown in FIG. 16, it was confirmed that the SERS signal intensity of the silver particle composite prepared according to Example 14 increased to twice or more as compared with the silver particle composite prepared according to Example 15. FIG. This result shows that the silver particle composite of Example 14 prepared at a relatively low temperature was well formed into a complex form in which the crystal was larger and had a larger number of thinner and shorter edges so that SERS It can be judged that the signal is strongly displayed.

As described above, the present invention is applicable to a silver-particle composite having a sub-micron hierarchical flower shape at room temperature, which is a one-pot process and can be easily produced by an environmentally friendly synthesis method . In the synthesis process, the chitosan biopolymer acts as a stabilizer and structure-directing agent, and anisotropy helps to grow the particle complex. It can be seen that the morphology of silver nanocomposite structures with a lot of rough nanoedges and cracks is highly dependent on chitosan concentration and silver nitrate usage and is preferably performed at a low reaction temperature. As individual particles or dense clusters, it can be seen that the silver particle composites are very sensitive to SERS measurements for CTP detection.

Claims (22)

A core comprising silver and having a hierarchical surface morphology; And
And chitosan bonded to the surface of the core,
Wherein the hierarchical surface configuration comprises a plurality of discrete sheets, the sheets being in the form of a flower growing concentrically with the center of the core,
And a diameter of 500 to 3000 nm. delete The method according to claim 1,
Wherein the silver particle composite is in the form of a face centered cubic (fcc). delete delete delete The method according to claim 1,
Wherein the core has an anisotropic optical crystal structure. The method according to claim 1,
Wherein the chitosan is capped at the core or embedded in the core. delete delete The method according to claim 1,
Wherein said silver particle complex is used as a substrate for probe of surface enhanced Raman scattering (SERS). 12. The method of claim 11,
The surface enhanced Raman scattering (SERS) using the probe base is characterized in that at least one selected from the group consisting of CTP (2-chlorothiophenol), ATP (aminothiophenol) and Rhodamine 6G is applied as a probe molecule Silver particle complexes. delete delete delete delete delete delete delete delete delete delete

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