Particles lead sulfide

Lead sulfide, PbS, nanoparticulate thin films having pancake-like geometry and exhibiting ID quantum confinement, as controlled by the lowest dimension of the particles, have been synthesized by cathodic electrodeposition on TTO/glass and titanium electrodes from a pH 0.62 solution containing Pb(N03)2 and Na2S203 [162]. 

It is found that the dissolution of zinc sulfides occurs more rapidly when they are in contact with copper sulfide or iron sulfide than when the sulfides of these types are absent. This enhancement is brought about by the formation of a galvanic cell. When two sulfide minerals are in contact, the condition for dissolution in acidic medium of one of the sulfides is that it should be anodic to the other sulfide in contact. This is illustrated schematically in Figure 5.3 (A). Thus, pyrite behaves cathodically towards several other sulfide minerals such as zinc sulfide, lead sulfide and copper sulfide. Consequently, pyrite enhances the dissolution of the other sulfide minerals while these minerals themselves understandably retard the dissolution of pyrite. This explains generally the different leaching behavior of an ore from different locations. The ore may have different mineralogical composition. A particle of sphalerite (ZnS) in contact with a pyrite particle in an aerated acid solution is the right system combination for the sphalerite to dissolve anodically. The situation is presented below ... 

Ogawa S, Fu K, Fan FRF, Bard AJ (1997) Photoelectrochemistiy of films of quantum sized lead sulfide particles incorporated in self-assembled monolayer of gold. J Phys Chem 101 5707-5711... 

Chiu prepared monodisperse crystalline particles of metal sulfides, such as lead sulfide (PbS cubes 100 A) (I), cupric sulfide (CuS hexagonal bipyramids 200 A) (2), and zinc sulfide (ZnS multifaceted spheres 0.1-0.4 p,m) (3) by introducing hydrogen sulfide gas into dilute acidic solutions of the ethylenediamine tetraacetic acid (EDTA) complexes of the corresponding metal ions (10 4-10-1 mol dm-3) for several minutes at room temperature. 

All of these metal sulfide particles except lead sulfide are polycrystalline spherical particles consisting of much smaller randomly oriented subcrystals, while lead... 

FIG. 1.13 Spherical and cubic model particles with crystalline or amorphous microstructure (a) spherical zinc sulfide particles (transmission electron microscopy, TEM, see Section 1.6a.2a) x-ray diffraction studies show that the microstructure of these particles is crystalline (b) cubic lead sulfide particles (scanning electron microscopy, SEM, see Section 1.6a.2a) (c) amorphous spherical particles of manganese (II) phosphate (TEM) and (d) crystalline cubic cadmium carbonate particles (SEM). (Reprinted with permission of Matijevic 1993.)... 

Zinc and lead usually occur together in nature as sulfides. Earlier separation processes involved the fine grinding of the combined sulfides and then treating the particles with chemical reagents to cause one sulfide to be preferentially wetted and rhns the two sulfides separated by the froth flotation process. In a first stage, the lead sulfide is floated while the zinc sulfide sinks to the bottom of the tank. In the second stage, the process is reversed and the zinc sulfide is floated. Gangue and other nonmetals collect at the bottom of the tank. The separated sulfides are dewatered to a 6-7% moisture content and are referred to as the zinc concentrate and the lead concentrate. 

This relation was developed by Dean and Koster (1935) to determine whether galena (lead-sulfide ore) followed Ohm s law at low current densities. Experiments were made using particles of various sizes... 

Zhu, R. Min, G. Wei, Y. Schmitt, H. J. Scanning Tunneling Microscopy and UV-Visible Spectroscopy Studies of Lead Sulfide Ultrafine Particles Synthesized in Langmuir-Blodgett Films. J. Phys. Chem. 1992, 96, 8210-8211. 

A sedimentation process is to be used to separate pulverized coal from slate. A suspension of finely divided particles of galena (lead sulfide, SG - 7.44) in water is prepared. The overall specific gravity of the suspension is 1.48. 

Lead sulfide (PbS) is a narrow band gap semiconductor used for many optical applications, like IR detectors [1], It is well known that semiconducting properties of PbS can be tailored by reducing the size of particles down to the nanometer scale. Semiconducting properties are greatly affected by the atomic structure. However, the atomic structure of nanoparticles may not be the same as the structure of the same substance in bulk. This paper focuses on study of the atomic structure of PbS nanoparticles. 

Photochemistry of Titanium Dioxide Colloids. Another semiconductor colloid used in our studies is titanium dioxide which has a band gap of 3.2 eV. As in the case of cadmium sulfide, excitation of aqueous suspensions of this particle leads to electron-hole pair separation which can be intercepted with suitable redox reagents. In the absence of externally added solutes, the photogenerated electron-hole pair recombines to give the starting material and the light energy is dissipated to the medium as heat. Two types of TiOj samples are used in this study. TiOj prepared at high temperature (80°C) which behaves very similarly to commercial samples, and TlOj prepared at low temperature (35°C) which has a particle size of 300 100 A radius and shows different properties. 

Ward, A.J.I., O Sullivan, E.C., Rang, J.C., Nedeljkovic, J. and Patel, R.C. (1993) The synthesis of quantum size lead sulfide particles in surfactant based complex fluid media.. Colloid Interface Sci., 161, 316-320. 

Nanocrystalline metal (silver and copper) and metal sulfide (silver sulfide, cadmium sulfide, and lead sulfide) particles were prepared via RESOLV (Rapid Expansion of a Supercritical Solution into a Liquid SOLVent) with water-in-carbon dioxide microemulsion as solvent for the rapid expansion. The nanoparticles were characterized using UV/vis absorption. X-ray powder diffraction, and transmission electron microscopy methods. The results of the different nanoparticles are compared and discussed in reference to those of the same nanoparticles produced via RESOLV with the use of conventional supercritical solvents. 

Preparation of Lead Sulfide-Coated Polystyrene Core-Shell Particles... 

Herein is described a novel method for preparing core-shell (c-s) particles of polystyrene coated with lead sulfide nanocrystals. The reaction is performed at room ten erature, in an aqueous bath, firom lead acetate and thioacetamide in the presence of ethylenediamine. 

A correlation has been established between the sulfide concentration and nanoparticle size by various X-ray scattering methods. With an increase in the concentration of lead sulfide, the mean sulfide particle size increases from 3.3 to 6.8 nm and the distance between them extends from 3.7 to 7.3 nm. 

In Fig. IV.4 we show the change in charge of lead sulfide particles (the normal type and also those with metallic or nonmetallic properties) in relation to the substrate potential. 

Since the electron work function for lead sulfide is greater than that for copper or cadmium, the particles acquire a negative charge if there is no external potential (intersection of curve 1 with the vertical axis) the work function for cadmium is less than that for copper, and therefore the difference in work functions of the lead sulfide-cadmium pair is greater than for the lead sulfide-copper pair (curves a and b). 

Fig. IV.4. Charge of lead sulfide particles on copper (a) or cadmium (b) substrate as a function of potential impressed on substrate (1) natural powder (2) powder with metallic properties after vacuum treatment (3) powder with non-metallic properties after treatment in sulfur vapor.

For example, zinc sulfide, copper sulfide, cadmium sulfide, and lead sulfide Qdots were attached to four different secondary antibodies to detect four different proteins [56]. The four different Qdots were dissolved to yield four different metal ions, each associated with a different protein. These were measured by stripping voltammetry after dissolution of the particles following the binding steps. Multiple metal striped rods, spheres or alloy rods were also used for multiplexing. The rods were capped with a gold end for attachment to Ab2. Upon dissolution, these materials give a series of metal stripping peaks whose peak potentials and relative intensities are associated with individual analyte proteins [38]. Such bar code labels have the potential to determine many proteins in patient samples, but this has yet to be reported. 

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