Zinc nanoparticles, preparation

As expected, the formation of ZnS-(GSH) nanoclusters is analogous to CdS. Beginning with the Zn(II)(GSH)2 precursor complex, nanocluster formation is initiated by the addition of the sulfide. Mehra et al. has shown that the precursor Zn(II)GSH complex does indeed closely follow the synthetic route of CdS-(GSH) nanoparticles. Considering the similarities between the thiol chemistry of zinc and cadmium, studies to optimize ZnS nanocluster formation primarily focused on the ratio of zinc to sulfide ions in solution. Varying equivalents of sulfide (0.1-2.0) were studied for the formation of nanoclusters. An optimal ratio of Zn + S was obtained at 1 1. The average size of nanoparticles prepared at this ratio was shown to be about 3.45 0.5nm. Elution profiles from SEC highlighted the dispersity of nanoparticle populations synthesized in aqueous solutions. By size dependent absorption, the reaction mixtures revealed two cluster populations with an approximate diameter of 22.6 A and 19.54 A, respectively. Any excess of sulfide added greater than 1 equivalent was volatilized and not incorporated into the nanoclusters. ... 

The UV-vis spectra of zinc sulfide colloidal dispersions are characterized by narrow maximum at 280 nm. Changing the precursor concentration from 0.01 M to 0.05 M results in the little (about 5 nm) red shift and the evidence of the size increase. The similar phenomenon was observed in the case of CdS nanoparticles prepared via the reverse micelle method [9]. For ZnS nanoparticles, the band gap (280 nm) shifts towards the blue region with respect to ZnS bulk semiconductor (350 nm) which is ascribed to the quantum... 

Recently, hierarchical nanostructured ZnO has been fabricated through electrospinning technique to enhance the photocatalytic performance. For example, Kanjwal and co-workers prepared ZnO nanobranches by electrospinning of the colloidal solution containing zinc nanoparticles, zinc acetate dehydrate, and PVA, followed by the calcination process and the hydrothermal treatment [29]. The photocatalytic activity of the hierarchical structure of ZnO is much higher than that of traditional electrospun ZnO nanofibers for the degradation of MB under UV light irradiation. 

Dhas NA, Zaban A, Gedanken A (1999) Surface synthesis of zinc sulfide nanoparticles on silica microspheres sonochemical preparation, characterization, and optical properties. Chem Mater 11(3) 806-813... 

Immobilizing DENs within a sol-gel matrix is another potential method for preparing new supported catalysts. PAMAM and PPI dendrimers can be added to sol-gel preparations of silicas " and zinc arsenates to template mesopores. In one early report, the dendrimer bound Cu + ions were added to sol-gel silica and calcined to yield supported copper oxide nanoparticles. Sol-gel chemistry can also be used to prepare titania supported Pd, Au, and Pd-Au nanoparticle catalysts. Aqueous solutions of Pd and Au DENs were added to titanium isopropoxide to coprecipitate the DENs with Ti02. Activation at 500°C resulted in particles approximately 4 nm in diameter. In this preparation, the PAMAM dendrimers served two roles, templating both nanoparticles and the pores of the titania support. 

Crystalline nanorings, literally closed circular nanoparticles with a hollow centre, were first prepared from zinc oxide in 2004 by a spontaneous self-coiling process from polar nanobelts.44 Semiconductor nanorings and indeed interestingly shaped nanoobjects in general, promise much in the way of applications as tools to probe fundamental physical phenomena and as nanoscale sensors, transducers, and resonators. 

Metal nanoparticles have extraordinary size-dependent optical properties, not present in the bulk metal and have, consequently, been the subject of intense research during the past decade or so.27 Attention has recently focused on functionalising colloidal nanoparticles with molecular recognition components for potential sensing applications.28,29,30 We have prepared a new amido-disulfide functionalised zinc metalloporphyrin (8) which was self-assembled on to gold nanoparticles to produce a novel anion-selective optical sensing system (9) (Scheme 3).4... 

ZnO nanoparticles were prepared by the sol-gel technique starting with zinc acetate as the precursor as described earlier [16]. ZnO nanorods were synthesized by stirring a fine powder of Zn(CH3C00)2-2H20 (Qualigens, 98.5% pure) in 100 ml of methanol at 60°C for I h, followed by dropwise addition of 0.03 M KOH (Ranbaxy) to the solution [13], The resulting solution was refluxed for 24 h to obtain the product, which was washed with ethanol and dried at 60 °C in air. 

Virion templates of TMV were also used in combination with different synthetic routes for CdS, PbS, and Fe oxide nanoparticles. Nanoparticle-virion tubules were prepared by reacting a buffered solution of TMV in CdCl2 (pH 7) or TMV in Pb(N03)2 (pH 5) with H2S gas. The formation of metal sulfide nanoparticles occurred over 6 hours as observed by a uniform coating of CdS and PbS nanocrystals on the TMV surface from TEM analysis. Selected area electron diffraction of the mineralized products indicated a zinc blende crystal stracture for CdS particles and a rock salt structure for single domain PbS nanocrystals. The iron oxide nanoparticles were mineralized by the TMV templates by the oxidative hydrolysis of an Fe VFe acidic solution with NaOH. Consequently, a mineral coating of irregular ferrihydrite particles grew on the surface to a thickness of 2 nm. 

Figure 2. The mechanism for preparation of Nano ZnO-CHIT electrode and immobilization of ChOx onto NanoZnO-CHIT Nanocomposite, Reprinted from Analytica Chimica Acta, 616, R. Khan, A. Kaushik, P. R. Solanki, A.A. Ansari, M.K. Pandy, B.D. Malhotra, Zinc oxide nanoparticles -chitosan composite film for cholesterol biosensor, 209,Copyright( 2008) with permission fom Elsevier.

One extensively studied material system among the nanocrystal-polymer blends is zinc oxide (ZnO) in combination with MDMO-PPV or P3HT [273-282]. Beek et al. presented the first polymer solar cells containing ZnO nanoparticles, reaching power conversion efficiencies of 1.6% [273]. In this case the nanoparticles were prepared separately and then intermixed with MDMO-PPV in solution. Shortly after this study the Janssen group presented another route to ZnO-polymer hybrid solar cells by forming the nanocrystals in situ inside the film by applying a precursor [274]. Here, diethylzinc served as the precursor and was spin cast in blends with MDMO-PPV. Process-... 

In addition to the above, preparation in w/o microemulsions of nanoparticles of various other types of compounds, viz. silica-coated iron oxide, Fe203-Ag nanocomposite, oxides of ytrium, erbium, neodymium, vanadium and cobalt, titanates of barium and lead, ferrites of barium, strontium, manganese, cobalt and zinc, oxide superconductors, aluminates, zirconium silicate, barium tungstate, phosphates of calcium, aluminium and zinc, carbonates of calcium and barium, sulphides of molybdenum and sodium, selenides of cadmium and silver etc. have been reported. Preparative sources and related elaboration can be found in [24]. 

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