ZnS nanoparticle

A Facile One-Pot Synthesis of MSe (M = Cd or Zn) Nanoparticles Using Biopolymer as Passivating Agent... 

We have reported a simple, green, bench top, economical and environmentally benign room temperature synthesis of MSe (M=Cd or Zn) nanoparticles using starch, PVA and PVP as passivating agents. The whole process is a redox reaction with selenium acting as the oxidant and MSe as the reduction product. An entire "green" chemistry was explored in this synthetic procedure and it is reproducible. The optical spectroscopy showed that all the particles are blue shifted from the bulk band gap clearly due to quantum confinement. Starch capped CdSe nanoparticles showed the presence of monodispersed spherical... 

The time evolution of the mean size of CdS and ZnS nanoparticles in water/AOT/ -heptane microemulsions has been investigated by UV-vis spectrophotometry. It was shown that the initial rapid formation of fractal-hke nanoparticles is followed by a slow-growing process accompanied by superficial structural changes. The marked protective action of the surfactant monolayer adsorbed on the nanoparticle surface has been also emphasized [230,231],... 

Nanoparticles of Mn and Pr-doped ZnS and CdS-ZnS were synthesized by wrt chemical method and inverse micelle method. Physical and fluorescent properties wra cbaractmzed by X-ray diffraction (XRD) and photoluminescence (PL). ZnS nanopatlicles aniKaled optically in air shows higher PL intensity than in vacuum. PL intensity of Mn and Pr-doped ZnS nanoparticles was enhanced by the photo-oxidation and the diffusion of luminescent ion. The prepared CdS nanoparticles show cubic or hexagonal phase, depending on synthesis conditions. Core-shell nanoparticles rahanced PL intensity by passivation. The interfacial state between CdS core and shell material was unchan d by different surface treatment. 

PL spectra of Mn-doped ZnS nanoparticles optically annealai in air (a) and in vacuum (b) are shown in Fig. 2. For Mn-doped ZnS nanoparticles, the PL band is seen at around 585mn. When Mn-doped ZnS nanoparticles were annealed in air, PL intensity is increased more significantly with UV irradiation time compared with ones ann ed in vacuum. PL spectra of Pr-doped ZnS nanoparticles axe shown in Fig. 3. The broad emission at 430 nm corresponds to the emission of the undoped ZnS nanoparticles. The other peak is relaftrii to the Pr-related complexes. The effect of the optical aimealing in air is more notable than in vacuum on the enhancement of luminescent intensity. The incre e of PL intensity for Pr-doped ZnS nanoparticles in mr is more rapid than undoped or Mn-doped ZnS nanoparticles. 

Fig. 1. PL spectra of undoped ZnS nanoparticles optically annealed in air (a) and in vacuum (b)...

Fig. 4 shows PL spectra of Mn and Pr-codoped ZnS nanoparticles opdcaily aimealed in air and vacuum. Mn and Pr-codoped ZnS nanoparticles emit light of white color. The PL intoisity of the Pr-related peaks incirasrf more rapidly than that of Mn-related peak, for the codoped ZnS nanoparticles ann ed in air. The different rates may be assodated with the luminescent ions. Pr-related oimplaces are incaeased with the incrrasing UV irradiation time, but Mn ions are constant. In case of the arni ing in vacuum, Pr-related peaks are initially weaker in intensity than Mn-related peaks due to small Pr-related complexes. 

Undoped, Mn, and Pr-doped ZnS namopartides synthesized by wet chemiral mdhod were optically annealed in air or vacuum. PL emission inoeas with annulling time. This increase is attributed to the photo-oxidation, enhancanent in the crystal quality, and diffiision of the luminescent ions. PL intensity of nanoparticles annealed in air increased more significantly due to the photo-oxidation compared with the nanoparticles annealed in vacuum. Mn and Pr-codoped ZnS nanoparticles emitted white light due to the effects of dopants. The optical annealing enhanced the emission intensity. 

Efl s of Magnetic Processing on the Luminescence Properties of Monolayer Films with Mn -Doped ZnS Nanoparticles... 

Rana RK, Zhang L, Yu JC, Mastai Y, Gedanken A (2003) Mesoporous structures from supramolecular assembly of in situ generated ZnS nanoparticles. Langmuir 19(14) 5904—5911... 

Fig. 35 Clathrin vesicles help allatostatin-coated CdSe-ZnS nanoparticles penetrate cell membranes. (Adapted from [47])...

Kirchner C, Liedl T, Kudera S, Pellegrino T, Munoz Javier A, Gaub HE, Stolzle S, Fertig N, Parak WJ (2005) Cytotoxicity of colloidal CdSe and CdSe/ZnS nanoparticles. Nano Lett 5 331-338... 

Synthesis and Characterisation of Ce(III) Doped Polyvinylpyrollid-one Capped ZnS Nanoparticles... 

In situ formation and hydrolysis of Zn nanoparticles for H2 production by the 2-step ZnO/Zn water-splitting thermochemical cycle. Int J Hydrogen Energy 31 55-61... 

Qi LM, Ma JM, Cheng HM, Zhao ZG (1996) Synthesis and characterization of mixed CdS-ZnS nanoparticles in reverse micelles. CoUoids Snrf A 111 195-202... 

Calandra P, Goffredi M, Liveri VT (1999) Study of the growth of ZnS nanoparticles in water/AOT/n-heptane microemulsions by UV-absorption spectroscopy. Colloids Surf A 160 9-13... 

Cao LX, Zhang JH, Ren SL, Huang SH (2002) Luminescence enhancement of coreshell ZnS Mn/ZnS nanoparticles. Appl Phys Lett 80 4300-4302... 

Fig. 9.4.24 Time course of the ESR spectra of Zn nanoparticles suspended in acetone. The diameter of particles was 1.5 nm (a) immediately, (b) 30 min, (c) 80 min, and (d) 24 h after the sedimentation process started. (From Ref. 25.)...

In the preceding section, we treated the surface reaction of Zn nanoparticles with oxygen. Here we mention the surface reaction of metallic particles with liquid molecules. We have found that alkali and alkaline earth metals are unstable in many polar organic solvents. 

In the temperature interval of —70 to 0°C and in the low-frequency range, an unexpected dielectric relaxation process for polymers is detected. This process is observed clearly in the sample PPX with metal Cu nanoparticles. In sample PPX + Zn only traces of this process can be observed, and in the PPX + PbS as well as in pure PPX matrix the process completely vanishes. The amplitude of this process essentially decreases, when the frequency increases, and the maximum of dielectric losses have almost no temperature dependence [104]. This is a typical dielectric response for percolation behavior [105]. This process may relate to electron transfer between the metal nanoparticles through the polymer matrix. Data on electrical conductivity of metal containing PPX films (see above) show that at metal concentrations higher than 5 vol.% there is an essential probability for electron transfer from one particle to another and thus such particles become involved in the percolation process. The minor appearance of this peak in PPX + Zn can be explained by oxidation of Zn nanoparticles. 

Figure 6 Schematic of an integrated microreactor for the continuous synthesis of CdSe/ZnS and CdS/ZnS nanoparticles (Sl-syringe pump with Se precursor, S2-syringe pump with S precursor, S3-syringe pump with Cd-OA-OLA, S4-syringe pump with Cd-OA-OLA-TOPO, Y—Y conjunction, M-micromixer, V-stop valve, C-channel images reproduced, with permission, from Yang et al., 2009).

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