CN108971512B

CN108971512B - Green preparation method and application of porous spongy Ag square particles

Info

Publication number: CN108971512B
Application number: CN201811071545.6A
Authority: CN
Inventors: 门丹丹; 张洪华; 向军淮
Original assignee: Jiangxi Science and Technology Normal University
Current assignee: Jiangxi Science and Technology Normal University
Priority date: 2018-09-14
Filing date: 2018-09-14
Publication date: 2021-04-02
Anticipated expiration: 2038-09-14
Also published as: CN108971512A

Abstract

The invention relates to the field of nano materials, in particular to green preparation of porous spongy Ag square particles and application of the porous spongy Ag square particles in near-infrared SERS (surface enhanced Raman scattering), and provides sodium borohydride (NaBH)₄) Reduction of silver phosphate (Ag)₃PO₄) The sponge-like microstructure Ag square particles prepared by the invention have strong absorption in near infrared, and can realize near infrared SERS detection. The method solves the problems that in the process of Raman test, if visible light is used as excitation wavelength, Raman signals of target molecules are annihilated due to strong light scattering and fluorescence background, and therefore large detection errors and low detection sensitivity are caused, and substantial progress is achieved.

Description

Green preparation method and application of porous spongy Ag square particles

Technical Field

The invention relates to the field of nano materials, in particular to green preparation and application of porous spongy Ag square particles.

Background

The porous noble metal (such as Au and Ag) nanoparticles have good application prospects in various fields such as electro-catalysis, drug slow release, biological imaging, Surface Enhanced Raman Scattering (SERS) and the like due to the large specific Surface area, high loading capacity, Surface Plasmon Resonance (SPR) existence in near infrared and the like.

At present, the methods for synthesizing porous or spongy metal micro/nano materials are mainly a template method and a dealloying corrosion method. For example, Walsh et al have synthesized spongy silver, gold, copper, silver-copper oxide, and silver-titanium dioxide composites using dextran as the soft template. The method is simple, low in cost and environment-friendly, but requires a high calcination temperature (600 ℃ -900 ℃). In addition, the specific surface area of the spongy metal nanoparticles produced by the templating method is generally small (< 2m²/g) which limits its practical application. The dealloying corrosion method is to synthesize noble metal alloy nanoparticles (e.g., Au-Ag)And then porous metal nanoparticles are prepared by means of a dealloying process (chemical or electrochemical method). In this method, noble metal alloy nanoparticles are generally prepared by a wet chemical process. In the wet chemical method preparation process, a surfactant is inevitably used, which not only influences the adsorption of the target molecules, but also may interfere the raman signal of the target molecules. Recently, Li project group proposed to synthesize spongy metal nanoparticles by using a single-layer two-dimensional colloidal crystal as a template through metal layer deposition, high-temperature annealing, and dealloying processes. The method solves the problem that the nano-particles prepared by a wet chemical method have a surfactant. Based on the method, the subject group successfully prepares a spongy Au-Ag, Au-Cu and Au-Ag-Cu alloy nanoparticle array. However, this method has a low yield (only one layer of the spongy nanoparticles can be prepared at a time) and requires a high temperature (600-. Recently, the Yin and Wang groups have achieved great success in the synthesis of metallic nanomaterials in sponge form, solving the problem of low yield of surfactants and colloidal templates in wet chemistry methods, but the methods used are relatively complex (multi-layer coating and multi-step reaction are required) and the reaction conditions are harsh (high temperature annealing).

To solve the above problems, the present application proposes sodium borohydride (NaBH)₄) Reduction of silver phosphate (Ag)₃PO₄) Square nanoparticles, a method for preparing porous sponge-like Ag square particles. The method is simple, rapid, environment-friendly and economical, and does not need to use a surfactant and high-temperature treatment in the whole process.

Disclosure of Invention

Aiming at the defects of complex process, surfactant, small specific surface area and the like of the traditional method for preparing the spongy porous noble metal nanoparticles, the invention provides a green, simple and economic method for preparing the porous spongy Ag square particles and researches the application of the porous spongy Ag square particles in near-infrared SERS.

The green preparation method of the porous spongy Ag square particles comprises the following specific steps:

(1) preparing [ Ag (NH)₃)₂]⁺Solution: 0.45M aqueous ammonia solution was added dropwise to 2mL of 0 while stirring.45M AgNO₃In solution until the solution becomes clear, [ Ag (NH) ] is obtained₃)₂]⁺And (3) solution.

(2) The [ Ag (NH) prepared in the step (1)₃)₂]⁺The solution was dropped into 100mL of deionized water, after which 1mL of 0.15M Na was added₂HPO₄Dropping the above [ Ag (NH) into the aqueous solution₃)₂]⁺Stirring for 10min, and centrifuging to obtain square Ag₃PO₄Nanoparticles, which are a chalky appearance.

(3) Mixing Ag with water₃PO₄The square nanoparticles were redispersed in 10mL of water and 50. mu.L of 0.5M NaBH added dropwise₄And (3) uniformly reacting the aqueous solution for about 2-5min by stirring to obtain porous sponge Ag square particles.

The Ag square particles prepared by the invention are applied to: the Ag square particles with the spongy microstructure are used as a substrate for SERS detection of biochemical substances.

The porous spongy Ag square particles prepared by the method have large specific surface area and high porosity, so that the number of target molecules to be detected in the action range of a local enhanced electric field can be remarkably increased, high-density hot points can be generated among the nano holes, absorption exists in an infrared band, and the porous spongy Ag square particles are a good near-infrared SERS substrate.

The invention has the advantages of

(1) Compared with the synthesis method in the prior art, the method for preparing the Ag square particles with the spongy microstructures provided by the embodiment of the invention has the advantages of mild reaction conditions (normal temperature), environmental protection (reaction is carried out in aqueous solution), convenience and high efficiency in operation, clean particle surfaces and great benefit for adsorption and subsequent functionalization of target molecules.

(2) The sponge-like microstructure Ag square particles prepared by the method have strong absorption in near infrared, and can realize near infrared SERS detection. The method solves the problems that in the process of Raman test, if visible light is used as excitation wavelength, Raman signals of target molecules are annihilated due to strong light scattering and fluorescence background, and therefore large detection errors and low detection sensitivity are caused, and substantial progress is achieved.

(3) The invention is realized by adding proper NaBH₄The addition amount of (a) is such that the prepared cubic structure with sponge-like Ag square particles face-centered is obtained.

Drawings

FIG. 1 is a diagram of a process for preparing porous Ag square particles with a spongy microstructure;

FIG. 2 is a scanning electron micrograph of the porous sponge-like Ag square particles produced;

FIG. 3 is an X-ray energy spectrum of a sponge-like square Ag particle;

FIG. 4 is an X-ray diffraction (XRD) pattern of sponge-like Ag square particles;

FIG. 5 shows different NaBH₄The porous sponge-like Ag square particles prepared by the above amount are observed by a scanning electron microscope and then taken as SEM pictures;

FIG. 6 is a sponge-like Ag square particle absorption spectrum characterization;

FIG. 7 shows the measured concentration of 4-ATP (10) based on the sponge-like Ag square nanoparticles^-6M-10^-11M) SERS spectrum.

In order to more clearly show the technical scheme and the technical effects provided by the present invention, the following detailed description of the porous spongy Ag square particle material and the near-infrared SERS detection provided by the embodiments of the present invention is provided by specific examples.

Example 1

The process flow diagram shown in the attached figure 1 of the specification is that the porous sponge-shaped microstructure Ag square particles are prepared by the following steps:

step a, firstly preparing [ Ag (NH)₃)₂]⁺Solution: 0.45M ammonia water is dropwise added into 0.45M AgNO under the condition of stirring₃In solution until the solution becomes clear, [ Ag (NH) ] is obtained₃)₂]⁺A solution; then [ Ag (NH) to be prepared₃)₂]⁺The solution is dropped into 100mL deionized water and stirred evenly. 1mL of 0.15M Na₂HPO₄Dropping the above [ Ag (NH) into the aqueous solution₃)₂]⁺Continuously stirring for 10-20min, and centrifuging to obtain square Ag₃PO₄Nanoparticles, which are a chalky appearance.

Step b, mixing Ag₃PO₄The square nano particles are re-dispersed in 10mL of deionized water, and 50 mu L of 0.5M NaBH is added₄Reacting the aqueous solution for 2-5min at normal temperature, and centrifuging to obtain porous sponge-like Ag square particles.

Further, scanning electron microscope photographs, absorption spectra and raman spectra were respectively performed on the porous sponge-like microstructure Ag square particles prepared according to the above procedure of example 1 of the present invention, and the specific detection results were as follows:

(1) observing the porous spongy Ag square particles prepared in step b in example 1 of the invention with a Sirion 200 field emission scanning electron microscope, and taking a scanning electron microscope photograph (SEM image) as shown in figure 2 of the specification; among them, fig. 2a is a low porous sponge-like Ag square particle, from which it can be seen that a square particle with uniform dispersion is prepared. The particles are in a porous sponge-like structure, intersecting like a plurality of nanorods (see fig. 2b and 2 c). Further from its high power plot (fig. 2d) it can be seen that the nanorods constituting the framework of the Ag microstructure are composed of a plurality of small particles. Due to NaBH₄Reduction of Ag₃PO₄In the process, small nano particles are generated firstly, and then the small nano particles are fused to form nano rods.

(2) An X-ray energy spectrum (EDS) obtained by an Inca.Oxford type X-ray energy spectrometer is used for the prepared sponge-shaped microstructure Ag square particles, and the attached figure 3 of the specification is shown. From EDS, it is known that the constituent element of the porous sponge-like Ag square particles is Ag element (Si element is derived from Si substrate).

(3) The prepared porous sponge-like square Ag particles were uniformly dispersed on a glass slide, and then tested by a German Bruker D8-Advance X-ray diffractometer to obtain an X-ray diffraction (XRD) pattern, which is shown in the attached figure 4 of the specification. Wherein, the ordinate of the spectrum is relative diffraction intensity, and the abscissa is diffraction angle. XRD data showed by NaBH₄After reduction, Ag₃PO₄The structural characteristic peak of (A) disappears, and an obvious Ag face-centered cubic structural characteristic peak appears, thus proving that the obtained particles are Ag particles and EDThe S results are consistent.

(4) FIG. 5 is a graph of different NaBH₄The prepared porous sponge-like Ag square particles were observed with a Sirion 200 field emission scanning electron microscope and then photographed in SEM photographs. As can be seen from the graph, when NaBH4 was added in amounts of 5. mu.L (FIG. 5a) and 15. mu.L (FIG. 5b), respectively, the generated Ag nanoparticles were randomly distributed in the Ag₃PO₄On the surface of the particles, porous sponge-like Ag square nanoparticles were not obtained. Further increase of NaBH₄At an addition amount of 25. mu.L (FIG. 5c), the produced Ag nanoparticles increased, but Ag₃PO₄Still present. When the amount of NaBH4 added was further increased to 100. mu.L (FIG. 5d), porous sponge-like Ag square particles were obtained, in which NaBH was added₄The morphology did not change significantly compared to the porous sponge-like Ag square particles obtained with an addition of 50 μ L (see fig. 2). The above results illustrate NaBH₄The amount of addition is critical to the preparation of the sponge-like Ag square particles. NaBH₄When the amount of (A) is small, only Ag is added₃PO₄Ag nanoparticles are produced; and with NaBH₄The addition amount of (b) is increased, and the produced Ag nanoparticles are gradually increased. This is because NaBH₄Addition of Ag₃PO₄Is reduced to produce Ag nuclei. The Ag nuclei are generated to become nucleation centers and thus grow into Ag nanoparticles. Therefore, the amount of Ag nuclei produced is equal to that of NaBH₄Is in direct proportion with the addition of NaBH₄The addition amount of (b) is increased, and the produced Ag nanoparticles are gradually increased. In addition, when NaBH concentration is high₄When the content is low, the formed Ag nano particles cannot be fused in time, so that sponge-shaped Ag square particles cannot be constructed; when NaBH₄When the addition amount of the Ag nanoparticles reaches a certain concentration, the formed Ag nanoparticles can be fused in time, so that porous sponge-shaped Ag square particles are constructed.

(5) The sponge-like microstructure Ag square particles are subjected to absorption spectrum characterization by using Cary 500, and see the attached figure 6 of the specification, wherein the abscissa of the spectrum is wavelength (unit is nm), and the ordinate is intensity. The absorption spectrum of the sponge square Ag nano-particles shows that besides the intrinsic SPR absorption peak of Ag at 400nm, the absorption spectrum has a wide absorption band in the visible light and near infrared regions. The reason is that the sponge-like Ag square particle structure is formed by intersecting Ag nanorods, so that the whole sponge-like particle network structure has a length scale, and the sponge-like particle network structure shows an SPR phenomenon in the whole visible light region and near infrared region.

(6) FIG. 7 shows 4-ATP (10) with different concentrations measured by using a confocal micro-Raman spectrometer (Nexus, Nicolet), 4-aminothiophenol (4-ATP) as a probe molecule, an excitation wavelength of 785nm and sponge-like Ag square nanoparticles as a substrate^-6 M-10^-11M) SERS spectrum. Wherein the horizontal axis of the graph is wavenumber (unit is cm)^-1) And the ordinate is intensity. As can be seen, the sponge-like Ag square nanoparticle substrate has a concentration as low as 10^-10M4-ATP still has high SERS sensitivity, which indicates that the structure has high SERS activity.

Claims

1. A green preparation method of porous spongy Ag square particles is characterized by comprising the following steps:

(1) preparing [ Ag (NH)₃)₂]⁺Solution: 0.45M ammonia water was dropwise added into 0.45M AgNO3 solution under stirring until the solution became clear to obtain [ Ag (NH)₃)₂]⁺A solution;

(2) to prepare [ Ag (NH) ]₃)₂]⁺The solution is dropped into 100mL deionized water and stirred evenly, 2mL of 0.15M Na₂HPO₄Dropping the above [ Ag (NH) into the aqueous solution₃)₂]⁺Stirring for 20min, and centrifuging to obtain square Ag₃PO₄Nanoparticles, the appearance of which is a tan color;

(3) mixing Ag with water₃PO₄The square nanoparticles were redispersed in 10mL of water and 50. mu.L of 0.5M NaBH added dropwise₄Reacting the aqueous solution for 2-5min at normal temperature, and centrifuging to obtain sponge-like Ag square particles.

2. Use of porous sponge-like Ag square particles prepared by the method of claim 1, wherein: the sponge-shaped Ag square particles are used as a substrate for SERS detection of biochemical substances.