CN1762622A

CN1762622A - A kind of method for preparing silver-colored nano-hollow ball by displacement reaction

Info

Publication number: CN1762622A
Application number: CN 200510029557
Authority: CN
Inventors: 高濂; 陈名海
Original assignee: Shanghai Institute of Ceramics of CAS
Current assignee: Shanghai Institute of Ceramics of CAS
Priority date: 2005-09-09
Filing date: 2005-09-09
Publication date: 2006-04-26

Abstract

The invention provides a kind of method for preparing silver-colored nano-hollow ball by displacement reaction.Principal character is that the elemental metals cobalt nano-particle with liquid-phase reduction preparation serves as to sacrifice template, according to Co ²⁺/ Co (0.277V) and Ag ⁺/ Ag (+0.799V) bigger electrical potential difference, Co and Ag ⁺Displacement reaction takes place, and simple substance Ag generates also at the Co surface in situ and progressively consumes Co, finally forms hollow ball.Be stabilizing agent with the citric acid in the preparation process, NaBH ₄Be reducing agent, cobalt nitrate is the cobalt source, and silver nitrate provides silver ion, prepared silver-colored nano-hollow ball external diameter 40-60nm, and internal diameter 15-30nm, particle size distribution is narrow, good dispersion.This method adopts the sacrifice template to synthesize the silver-colored nano-hollow ball of simple substance, save the secondary operations that other Form board tapes of use come the removal template of complexity, and possible template self is to pollution and the interference of target material Ag.This method has productive rate height, evident characteristic such as simple, easy to operate, with low cost and environmental friendliness fast.

Description

Method for preparing silver hollow nanospheres through displacement reaction

Technical Field

The invention relates to amethod for preparing a simple substance silver hollow nanosphere, in particular to a method for preparing a silver hollow nanosphere through a displacement reaction. Belongs to the field of nanometer material.

Background

Silver is an important noble metal material, the nano structure of the silver is attracted by people, and the silver is widely applied to the fields of catalysis, imaging, optics, electronics, photoelectricity, information storage, biology, chemical sensing, surface enhanced Raman scattering and the like. Particularly, the surface plasma resonance spectrum characteristics of silver are influenced by the shape, size and structure, and in recent years, a great deal of research is focused on preparing simple substance silver nanocrystals with different shapes and structures, such as nanowires, nanorods, nanotubes, trigonal crystals, platelets, monodisperse nanoparticles and the like. Although a great deal of reports are provided on the research of Au and Pt hollow nanospheres which are both noble metals, the research on Ag hollow nanospheres is relatively less, and the main reason is that the preparation method is lack. While it is convenient to prepare various hollow structures of Au and Pt by displacement reaction using Ag as a template, as proposed by Xia et al, it is impossible to realize the hollow structure of Ag, and it is necessary to use a metal more active than Ag as a sacrificial template (Yugang Sun, Younan Xia, j.am.chem.soc., 2004, 126, 3892). The existing preparation method is mainly based on a template method, and commonly used templates such as Polystyrene (PS) (Weili Shi, y.saho, Mark t.swihart, p.n.prasad, Langmuir, 2005, 21, 1610) and silica microspheres (Lehui Lu, Hongjie Zhang, Cuoying Sun, Shiquan Xi, Haishui Wang, Langmuir, 2003, 19, 9490) are prepared by performing appropriate chemical modification on the outersurface of the template to adsorb metal particles to the surface of the microspheres, and then performing in-situ reduction. Sonochemical methods have also been very successful in recent years in the encapsulation of PS and silica microspheres, as are the commonly used seed growth methods, layer-by-layer (LBL) methods, etc. (JianhuiZhang, junbin Liu, Sizhen Wang, Peng Zhang, Zhenlin Wang, Naiben Ming, adv.funct.mater, 2004, 14, 1089; v.g.pol, h.grisaru, a.gedanken, Langmuir, 2005, 21, 3635). These have been successfully used in photonic crystal assembly. But due to the existence of the template, the electronic and spectroscopic behaviors of the silver nanostructure are often affected in some adverse ways. In order to obtain a real hollow structure, subsequent treatment for removing the template is also needed, for example, PS and silicon oxide are corroded by benzene and hydrofluoric acid, but the hollow sphere prepared by the method is large, so that the hollow structure is easily damaged by the subsequent treatment.

Recently, reports of core/shell synthesis using relatively active metal nanoparticles as templates have also been developed, commonly used core materials such asMetals Pb, Ni and Co, etc. But mostly only in the core/shell structure, e.g. Ni_coreAg_shell(Tanushree Bala，S.D.Bhame，P.A.Joy，B.L.V.Prasad，Murali Sastry，J.Mater.Chem.，2004，14，2941)、Co_coreAg_shell(Tanushree Bala，Sujatha K.Arumugam，Renu Pasricha，B.L.V.Prasad，Murali Sastry，J.Mater.Chem.，2004，14，1057；Nelli S.Sobal，Michael Hilgendorff，Helmuth Mohwald，Michael Giersig，Marina Spasova，Tamara Radetic，Michael Farle，Nano Lett.，2002，2，621)、Pb_coreAg_shell(Yuliang Wang, Lu Cai, Younan Xia, adv.mater., 2005, 17, 473), a hollow structure could not be really formed, and the case of using Ni and Co was more that the magnetic particles were prepared, failing to be concentrated on the silver hollow structure. Recently Liang reported the use of Co as a template to produce nano-scale Au and Pt nano-hollow structures (Hanpu Liang, Huimin Zhang, Jinsong Hu, Yuguo Guo, Lijun Wan, Chunli Bai, Angew. chem. int. Ed., 2004, 43, 1540; Hanpu Liang, Lijun Wan, Chunli Bai, Li Liang, J.Phys. chem. B., 2005, 109, 7795). However, reports on the synthesis of the silver hollow sphere still exist, and the research and invention in the aspect is developed, so that the method has important theoretical and practical significance for expanding the potential application of silver (such as the fields of surface plasma resonance spectroscopy and photothermal conversion).

Disclosure of Invention

The invention aims to provide a method for preparing a silver hollow nanosphere through a displacement reaction. The invention provides a method for preparing silver hollow nanospheres by a displacement reaction, which is characterized by comprising the following steps: firstly, citric acid is used as a stabilizing agent, and NaBH is used₄Reducing cobalt nitrate to prepare simple substance metal cobalt nanoparticles as sacrificial templates, then performing a displacement reaction with silver nitrate to generate simple substance silver nanoparticles on the surface of the metal cobalt, and gradually consuming the metal cobalt to finally form the hollow nanospheres. The whole process is carried out at room temperature, no protective atmosphere is needed, the process is simple, no complex experimental equipment is needed, and the reaction is rapidA method for preparing high-quality silver hollow nanospheres efficiently, quickly and environmentally friendly.

The invention is implemented as follows: the used raw materials are cobalt nitrate, silver nitrate and NaBH₄Citric acid, in which NaBH is used₄Preparing nano cobalt particlesfor a reducing agent; citric acid is used as a stabilizer to prevent the particles from agglomerating and settling, and cobalt nitrate and silver nitrate are used as respective metal sources. FIG. 1 is a flow chart of preparation of Ag hollow nanospheres.

(1) Firstly, preparing a solution A: adding 1.6-8mmol NaBH₄And 0.16-0.8mmol citric acid in 200mL deionized water, and rapidly injecting 0.8-4mL Co (NO) with concentration of 0.1M₃)₂And (3) solution. With vigorous reaction, the solution immediately appeared brown and transparent. Due to excess NaBH₄The reaction with water continued, and a large amount of bubbles emerged. Preparing stable suspension of metallic simple substance cobalt.

(2) At the same time, solution B was prepared: 0.8-8mL of 0.1M AgNO₃Dilute to 50 mL.

(3) After solution a reacted for 4 minutes, solution B was mixed with solution a, and the mixed solution immediately became dark green.

(4) Magnetically stirring for 1 hr, collecting at 6000r/min, washing with deionized water for 3 times, and dispersing in anhydrous ethanol.

Characterised by the NaBH₄The molar ratio of the citric acid to the cobalt nitrate is 20: 2: 1.

Characterized in that the AgNO prepared in the step (b) is added after the stable suspension of the metallic simple substance cobalt prepared in the step (a) has no obvious bubbles₃。

Characterized by a centrifugation collection time of 25 minutes.

Is characterized in that the outer diameter of the prepared silver hollow nanosphere is 40-60nm, and the inner diameter is 15-30 nm.

The invention provides a method for preparing a silver hollow nanosphere by a displacement reaction, which is characterized by comprising the following steps of:

(1) with an excess of NaBH₄The reaction is rapid and excessive NaBH is used as a reducing agent to prepare the metallic cobalt nano-particles₄Can pass through with waterThe reaction is quickly decomposed, so that the subsequent reaction of silver nitrate and simple substance cobalt is not influenced.

(2) Citric acid is taken as a stabilizing agent, and fine nano metal cobalt particles are prevented from agglomerating and settling through a mechanism of mutual repulsion of same charges. And the silver hollow nanospheres prepared subsequently can be stabilized simultaneously, and can be stabilized without settling for more than one week.

(3) Because the prepared nano cobalt particles have small sizes, the prepared nano cobalt particles can be used as templates to prepare hollow spheres with the outer diameter of less than 100nm, so that the true hollow nanospheres are realized, and the prepared nano cobalt particles have higher flexibility than polystyrene and silicon oxide microsphere templates used in the prior art. The metal Co template is important for controlling the size of the Ag nano hollow sphere, and can improve NaBH by adopting lower cobalt nitrate concentration₄Citric acid concentration to reduce the size of the Co nanoparticles produced, reports on this have made the control of Co nanoparticle size practical (i.lisiecki, m.p.pileni, Langmuir; 2003, 19, 9486).

(4) Due to Co²⁺Co (-0.277V) and Ag⁺There is a large potential difference between Ag (+0.799V) and Co⁺And carrying out replacement reaction to generate a simple substance silver film on the surface of the cobalt particles in situ. Associated with Co²⁺And Ag⁺The cobalt in the core part is gradually consumed through mutual diffusion of film gaps, so that a hollow structure is finally formed. FIG. 2 shows a schematic diagram of the formation mechanism, and the specific reaction equation is as follows:

(5) the experimental process route is simple and the operation is convenient. The whole process is carried out at room temperature, no protective atmosphere is needed, the process is simple, no complex experimental equipment is needed, the reaction is rapid, and the method is an efficient, rapid and environment-friendly method for preparing the high-quality silver hollow nanospheres.

(6) The prepared silver hollow nanospheres have the outer diameter of 40-60nm and the inner diameter of 15-30nm, are good in dispersity, have no obvious agglomeration and can be kept not to settle for more than one week.

Drawings

FIG. 1 is a flow chart of Ag hollow nanospheres

Fig. 2 shows a mechanism for forming the Ag hollow nanospheres, wherein (a) Co nuclei are formed, (b) Ag nanoparticles are gathered around the Co nuclei, (c) elemental silver films are generated on the surfaces of the cobalt particles in situ, and thus the Ag hollow nanospheres are formed.

FIG. 3 TEM (a) and SEM (d) photographs of Ag nanospheres prepared in example 1, (b) are polycrystalline electron diffraction rings, and (c) are high-magnification TEM photographs

FIG. 4 HRTEM photographs (a), (b) and Fourier transform map (c) of the silver nanospheres prepared in example 1 at different magnifications

FIG. 5 EDS spectra of hollow nanospheres prepared in example 1

FIG. 6 TEM photograph ofsample prepared in example 2

Detailed Description

The essential features and the remarkable advantages of the present invention will be further elucidated by the following non-limiting examples, in conjunction with the accompanying drawings:

example 1

As shown in fig. 1, first, a solution a: 0.16mmol of citric acid and 1.6mmol of NaBH₄Dissolved in 200mL of deionized water and rapidly injected with 0.8mL of 0.1M Co (NO)₃)₂And (3) solution. With vigorous reaction, the solution immediately appeared brown and transparent. Due to excess NaBH₄The reaction with water continued, and a large amount of bubbles emerged. At the same time, solution B was prepared: 1.6mL of 0.1M AgNO₃Dilute to 50 mL. After the solution A reacts for 4 minutes, the solution B is mixed with the solution A, the mixed solution is immediately green, is magnetically stirred for 1 hour, is centrifuged on a centrifugal machine at the rotating speed of 6000r/min for 25 minutes and then is collected, is washed three times by deionized water and finally is dispersed in absolute ethyl alcohol. FIG. 2 is a schematic diagram of the formation of hollow Ag nanospheres, which is prepared by preparing elemental cobalt nanoparticles as sacrificial templates (cobalt cores), and reducing the nanoparticles with silver nitrate to form Ag⁺Aggregated around the cobalt core, Ag⁺The replacement reaction is carried out on the surface of the metal cobalt, and the silver film grows on the surface of the cobalt particles in situAnd finally forming the Ag nano hollow sphere. Fig. 3 is a photograph of the elementary Ag hollow nanospheres prepared in this example and their corresponding electron diffraction patterns. From the contrast between the edge and the center of the particles in the TEM photograph of FIG. 3(a), it can be seen that the elemental Ag prepared in this exampleThe nano-spheres are hollow nano-spheres, and have the advantages of uniform particle distribution, 40-50nm particle size, good dispersion and no obvious agglomeration. FIG. 3(b) shows the corresponding polycrystalline electron diffraction rings, and the diffraction rings from the inside to the outside correspond to the (111), (200), (220), and (311) crystallographic planes of fcc Ag in this order. The high magnification TEM image of FIG. 3(c) further shows the hollow features, with a center inner diameter of 20nm and an outer diameter of 50 nm. FIG. 3(d) is a SEM image of morphology with a large number of particles stacked but without significant hard agglomeration and a narrow particle size distribution. FIG. 4 is a single particle high resolution Electron micrograph (HRTEM) and its corresponding Fourier transform map. By measuring the lattice fringe spacing 0.236nm corresponds to the {111} crystal plane of face-centered cubic silver and 0.2nm corresponds to the {200} crystal plane. The Fourier transformed spot of FIG. 4(c) is well matched to face centered cubic silver along the ribbon axis [011]]And (4) direction. FIG. 5 is an EDS (EDS) energy spectrum diagram of the prepared hollow sphere, and the EDS energy spectrum diagram shows that simple substance silver with good purity is formed, no energy spectrum peak of cobalt is seen, and the cobalt serving as a template is completely consumed.

Example 2

Firstly, preparing a solution A: 0.16mmol of citric acid and 1.6mmol of NaBH₄Dissolved in 200mL of deionized water and rapidly injected with 0.8mL of 0.1M Co (NO)₃)₂And (3) solution. With vigorous reaction, the solution immediately appeared brown and transparent. Due to excess NaBH₄The reaction with water continued, and a large amount of bubbles emerged. At the same time, solution B was prepared: 1.6mL of 0.1M AgNO₃Dilute to 50 mL. By mixing B with A, unequal NaBH₄Sufficiently decomposed in water to allow silver ions to be partially absorbed by NaBH₄Reducing, wherein the mixed solution is immediately green, magnetically stirring for 1 hour, centrifuging for 25 minutes at the rotating speed of 6000r/min on a centrifugal machine, collecting, washing with deionized water for three times, and finally dispersing in absolute ethyl alcohol. FIG. 6 is a TEM photograph of the sample prepared in this example, showing that many nanoparticles are present in addition to the hollow structure, and thus it can be seen that the time for strictly controlling the mixing of A and B is required for preparing a high yieldThe silver nano hollow sphere of the rate is important.

Example 3

Firstly, preparing a solution A: 0.8mmol of citric acid and 8mmol of NaBH₄Dissolved in 200mL of deionized water and rapidly injected with 4mL of 0.1M Co (NO)₃)₂And (3) solution. With vigorous reaction, the solution immediately appeared brown and transparent. Due to excess NaBH₄Continuously reacting with water and largely emittingAir bubbles. At the same time, solution B was prepared: 8mL of 0.1M AgNO₃Dilute to 50 mL. After the solution A reacts for 4 minutes, the solution B is mixed with the solution A, the mixture is magnetically stirred for 1 hour, centrifuged for 25 minutes on a centrifugal machine at the rotating speed of 6000r/min and then collected, washed three times by deionized water and finally dispersed in absolute ethyl alcohol. The diameter of the prepared hollow nanosphere is increased to 60nm, and the thickness of the shell layer is thicker. The rest is the same as the example 1.

Example 4

Firstly, preparing a solution A: 0.16mmol of citric acid and 1.6mmol of NaBH₄Dissolved in 200mL of deionized water and rapidly injected with 0.8mL of 0.1M Co (NO)₃)₂And (3) solution. With vigorous reaction, the solution immediately appeared brown and transparent. Due to excess NaBH₄The reaction with water continued, and a large amount of bubbles emerged. At the same time, solution B was prepared: 0.8mL of 0.1M AgNO₃Dilute to 50 mL. After the solution A reacts for 4 minutes, the solution B is mixed with the solution A, the mixture is magnetically stirred for 1 hour, centrifuged for 25 minutes on a centrifugal machine at the rotating speed of 6000r/min and then collected, washed three times by deionized water and finally dispersed in absolute ethyl alcohol. The prepared sample has an outer diameter of 40-50nm and a shell thickness of only about 10 nm. The rest is the same as the example 1.

Claims

1.A method for preparing silver hollow nanospheres by a displacement reaction comprises the processes of mixing and washing, and is characterized in that: firstly, citric acid is taken as a stabilizing agent, and NaBH is used₄Reducing cobalt nitrate to prepare simple substance metal cobalt nano particles as sacrificial templates, then carrying out displacement reaction with silver nitrate to generate simple substance silver nano particles on the surface of the metal cobalt, and gradually consuming the metalCobalt, finally forming the hollow nanospheres.

2. The method for preparing the silver hollow nanospheres by the displacement reaction according to claim 1, which is characterized by comprising the following specific process flows:

(a) firstly, preparing a solution A: adding 1.6-8mmol NaBH₄And 0.16-0.8mmol citric acid in 200mL deionized water, and rapidly injecting 0.8-4mL Co (NO) with concentration of0.1M₃)₂A solution; preparing a stable suspension of metallic simple substance cobalt;

(b) preparing a solution B: 0.8-8mL of 0.1M AgNO₃Diluting to 50 mL; (c) after the solution A reacts for a plurality of minutes, the solution B is mixed with the solution A, and the mixed solution immediately turns dark green;

(d) magnetically stirring for 1 hr, collecting at 6000r/min, washing with deionized water, and dispersing in anhydrous ethanol.

3. The method for preparing hollow silver nanospheres by displacement according to claim 1 or 2, wherein NaBH is used as the catalyst₄The molar ratio of the citric acid to the cobalt nitrate is 20: 2: 1.

4. The method for preparing hollow silver nanospheres by displacement reaction as claimed in claim 2, wherein the stable suspension of elemental cobalt prepared in step (a) is substantially bubble-free and then AgNO prepared in step (b) is added₃。

5. The method for preparing silver nanospheres by displacement according to claim 2 wherein the centrifugation collection time is 25 minutes.

6. The method for preparing hollow silver nanospheres by displacement reaction as claimed in claim 2, wherein the washing with deionized water is repeated 3 times.

7. The method for preparing a hollow silver nanosphere by displacement reaction according to any of claims 1, 2, 4, 5 or 6, wherein the hollow silver nanosphere is prepared to have an outer diameter of 40 to 60nm and an inner diameter of 15 to 30 nm.

8. The method for preparing hollow silver nanospheres by displacement reaction according to claim 3, wherein the hollow silver nanospheres have an outer diameter of 40 to 60nm and an inner diameter of 15 to 30 nm.