Silver colloid preparation

Since the discovery of the SERS effect in 1974, the number of publication on this topic increased exponentially. Of major interest is the development of suitable SERS-active substrates. On the one hand, research focuses on the development of reproducible SERS substrates. On the other hand, SERS substrates are specifically designed for a particular application. Figure 4 presents different kinds of SERS-active substrates. Widely used SERS substrates are colloid solutions as shown in Fig. 4a, b. Figure 4a presents aggregated silver colloid prepared according to Lee and Meisel. In cluster arranged gold nanoparticles are shown in Fig. 4b. Colloids are easy to prepare and easy to... 

Rhodamine 6G or adenine) in methanol. Silver colloids prepared according to the Lee and Meisel method (17) and diluted with methanol tenfold. Two milliliters of the suspension were transferred to the syringe. The liquid was dispensed at a rate of 50 pL/min. The frequency of the sprayer was set to 1.6 Hz and the belt speed was set to Ift/min. 

Silver colloid is popular due to the relative ease of manufacture, low cost, and stability. One widely used method of silver colloid preparation is citrate reduction of silver nitrate (Figure 3). This results in an overall net negative charge on the colloid, which is high compared with many preparations (Figure 4). As a result, the colloid is stable for months and even years, and in some cases, with careful attention to detail, quantitative SERRS can be obtained from this colloid with relative standard deviations of less than 5%. There is, however, a change in enhancement with time, and so a standard needs to be used. 

FIG. 2 Ultraviolet absorbance of silver colloids prepared in the presence of various surfactants as stabilizers. 

TABLE 2 Properties of Silver Colloids Prepared in the Absence of a Surfactant or in the Presence of Various Surfactants... 

Actually, this sample was completely separated into water and Ag agglomerates after about 3 h. On the contrary, silver colloids prepared in the presence of surfactants showed relatively good stability compared with the sample prepared in a simple aqueous solution without a surfactant. But depending on the surfactant species, quite different stabilities were observed. Especially in the case of Tween 20 and SDS, the colloids remained basically stable for weeks. The silver nanoparticles in the colloid solution were adsorbed on the silica wall of glass vials. This effect was observed for Tween 20 just after 3 min from the start of the reduction in our experimental conditions, but in the case of NP-9 and SDS, this phenomenon was observed after 1 day. Such adsorption phenomenon was also reported by Liz-Marzan and Lado-Tourino [18] after their experiment on silver reduction through... 

UPD of Ag onto Au electrodes covered with SAM of alkanethiols has been described by Oyamatsu [319]. Hu et al. [320] have prepared nanoelectrode ensembles by assembling silver colloid and mercaptan on a gold electrode. 

Figure 19.2 Self-similarity analysis for nanotextured silver surfaces prepared in different ways. The root mean square roughness inferred from atomic force microscopy is plotted versus measurement area. The various surfaces are 100 nm thick evaporated silver films (solid squares, red line)-, 5.2 nm thick evaporated silver films (open circles, green line) nanoparticle films assembled from colloid attachment to self-assembled monolayers (solid circles, blue line) films from deliberate precipitation of silver colloid (solid up-triangles, black line) Tollens reaction films (open down-triangles, orange line). Lines with slopes H = 1.0 and H = l.S representing two-dimensional and 1.5 dimensional surfaces respectively are...

High levels of SERS activity can be expected if nanoparticle substrates were prepared by colloidal chemical methods because colloidal particles tend to aggregation, thus forming the narrow interparticle spacings needed for plasmon coupling. A traditional technique for the preparation of silver colloids is the sol formation according to Lee et al. [17]. 

Silver Nanoparticles Preparation. A colloidal suspension of citrate reduced silver nanoparticles was prepared using a modified Lee and Meisel [8] procedure. 

P. Mulvaney M. Giersig A. Henglein, Electrochemistry of multilayer colloids Preparation and absorption spectrum of gold-coated silver particles. J. Phys. Chem. 1993, 97, 7061-7064. 

Colloidal solutions of most all the metals can be obtained by forming an arc under water using an electrode of the metal of which the colloidal preparation is desired. For instance, if we desire to prepare a colloidal solution of silver we would draw an arc between two silver wires under water. It will be found difficult to maintain this subaqueous arc for any length of time. However, every time the wires are touched a small cloud of colloidal silver will be produced in the water. The water used should be as pure as possible as the colloidal particles are extremely sensitive to foreign matter. 

In this paper we demonstrate capabilities of double-pulse laser ablation (DPLA) in liquid environment for fabrication of metallic nanoparticles with a narrow size-distribution. We examined optical properties of the silver colloidal solutions prepared by DPLA in order to reveal the role of the second laser pulse in a size change of the particles produced in the ablation plume. 

Fig. 10. SERS spectra of poly-A and its building stones adenine, adenosine 5 -monophosphate and ribose 5-phosphate. Freshly prepared silver colloids, pH 4.5 4 x 10 M adenine, 5 -AMP or ribose 5-phosphate added poly-A concentration 1.6mg/ml Laser excitation line 514nm, laser power 200 mW. (The drawing of poly-A in d shows the adenine base and the sugar-phosphate backbone outside the molecule)...

Fig. 13. SERS-spectrum of a solution containing adenine, guanine, cytosine and thymine. Freshly prepared silver colloids, pH 4.5, 4x 10 M adenine, guanine, cytosine and thymine added laser excitation line 514 nm, laser power 100 mW...

Fig. 36. SERRS spectra of glucose oxidase in Ag sols (0.33 mM Ag) containing the indicated protein concentrations (half the flavin concentrations). Conditions laser power 20 mW, spectral slit width Scm, accumulation time 3 s/cm . The data were collected digitally and are unsmoothed. The silver colloids were prepared by the procedure of Creighton et 1. and the proteins were added subsequently (Copeland et al., Ref.

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