Cadmium sulfide sensitized

A number of workers have described methods for the determination of mercury in which the mercury is first reduced to the element or collected as the sulfide on a cadmium sulfide pad. It is then volatilized into a chamber for measurement. These techniques are extremely sensitive. Thillez108) recently described a procedure for urinary mercury in which the mercury is collected on platinum and then volatilized into an air stream. Rathje109) treated 2 ml of urine with 5 ml of nitric acid for 3 min, diluted to 50 ml, and added stannuous chloride to reduce the mercury to the element. A drop of Antifoam 60 was added and nitrogen was blown through the solution to carry the mercury vapor into a quartz end cell where it is measured. Six nanograms of mercury can be detected. Willis 93) employed more conventional methods to determine 0.04 ppm of mercury in urine by extracting it with APDC into methyl-n-amyl ketone. Berman n°) extracted mercury with APDC into MIBK to determine 0.01 ppm. 

Since the photophoretic force depends on the electromagnetic absorption efficiency Q y , which is sensitive to wavelength, photophoretic force measurements can be used as a tool to study absorption spectroscopy. This was first recognized by Pope et al. (1979), who showed that the spectrum of the photophoretic force on a 10 foa diameter perylene crystallite agrees with the optical spectrum. This was accomplished by suspending a perylene particle in a Millikan chamber with electro-optic feedback control and measuring the photophoretic force as a function of the wavelength of the laser illumination. Improvements on the technique and additional data were obtained by Arnold and Amani (1980), and Arnold et al. (1980) provided further details of their photophoretic spectrometer. A photophoretic spectrum of a crystallite of cadmium sulfide reported by Arnold and Amani is presented in Fig. 11. 

It is known that cadmium sulfide (CdS) and ion oxide Te203) are visible light-sensitive materials, in particular, one-step photocata ysis of wate - is possible for CdS.25) Recently, Kudc et at. reported that bismuth vanadate (BiV04) snowed photocatalytic activity for 02 evolution from an aqueous silver nitrate solution under visible light.26 271 BiVCX is a very attractive photocatalyst although it is impossible to decompose water by a one-step process. Thus this material is a candidate for an 02 evolution photocatalyst to construct a two-phoion process 26) In other words, this material is expected to be an 02 evolution photocatalyst to... 

The actions of photoexcited semiconductor particles on organic compounds under oxygen is of significant importance from both practical and basic aspects. Semiconductors like titanium dioxide and cadmium sulfide were shown to induce oxidation of olefins and aromatic hydrocarbons under oxygen, and also to sensitize isomerization of unsaturated systems. The mechanisms of these reactions are discussed. 

Watanabe et al. have reported similar action spectrum analysis of photoin-duced degradation of Rhodamine B with a cadmium sulfide suspension and pointed out a similar dye-sensitization mechanism Watanabe, T. Takizawa, T. Honda, K. J. Phys. Chem. 1977, 81, 1845. Photocatalytic reaction of MB in aerated titania suspensions was reported in 1937 by a Japanese photochemist Horio, M. Nihon Gakujutsu Kyokai Hokoku 1937, 12, 204 (in Japanese). As far as the author knows, this is the first report on titania photocatalysis. 

The molecular weight distribution of the peptides could be partially controlled by choice of the sensitizer diglycine was formed twice as efficiently on platinized titanium dioxide as on platinized cadmium sulfide, whereas the yield of pentaglycine was four times higher on CdS/Pt than on Ti02/Pt. 

The three basic types are photoconductive, photovoltaic, and photo-emissive, and all are sensitive to both heat and light. The resistance of a photoconductive cell is lowered when it is illuminated and, over a small range, its response is linear. Cells containing lead sulfide, which is sensitive at wavelengths greater than 700 nm, and cadmium sulfide or selenide, with a sharp response maximum at 710 nm, have been used but may not give a stable response and are largely restricted to specialized applications in other fields. Silicon photodiodes and transistors are sensitive from 340 to 1200 nm with a peak at 900 nm. 

Lead sulfide transducers arc sensitive in the region between 0.8 and 3 pm (12,500 to 3300 cm ). A thin layer of this eompound is deposited on glass or quartz plates to form (he cell. The cm ire assembly is then sealed in an evacuated container to protect the semiconductor from reaction with the atmosphere. The sensitivity of cadmium sulfide, cadmium seicnide.and lead sulfide transducers is shown by curves B. D, and O in Figure 7-27,... 

The effects of chemicals can vary strongly, depending on the incorporation route. The acidic environment in some parts of the stomach and gastrointestinal tract (pH = l to 5) can cause hydrolysis-sensitive chemicals to be decomposed on oral incorporation. Chemical transformations can lead to more toxic or less toxic compounds. In the stomach, acidic compounds are preferentially absorbed, while the absorption of alkaline and lipophilic chemicals occurs particularly in the intestinal tract The body excretes chemicals which are not directly resorbed either in the stomach or in the intestinal tract so that a possibly available toxic property may not become effective, e.g., in the case of cadmium sulfide or barium sulfate. 

Yellow and orange Cadmium sulfide produces orange-yeUow or similar shades when combined with zinc or selenium, but it contains the problematic heavy metal and is mainly used in engineering applications. Lead chromate produces bright yellows, but is light-sensitive and must be treated. Lead chromate, sulfite, and molybdate combined can create a stable orange color. Newer non-toxic compounds based on rare earth elements, such as cerium sulfide, reportedly offer the same shades as toxic chromates. 

Steele, M. C., Hile, J. W. Maclver, B. A. (1976). Hydrogen-sensitive palladium gate MOS capacitors.. Appl. Phys., Vol. 47, pp. 2537-2538 Steele, M. C. Maclver, B. A. (1976). Palladium/cadmium-sulfide Schottky diodes for hydrogen detection. AppL Phys. Lett., Vol. 28, pp. 687-688... 

Most intrinsic photoconductors are made of indium antimonide (InSb), cadmium sulfide (CdS), or lead sulfide (PbS). Figure 4.79 shows the spectral sensitivity of these materials. While PbS detectors can be used also at room temperature with detectivities of 5x 10 cm Hz W InSb detectors... 

Numnuam et al. (2008) reported the first potentiometric aptasensor nsing ion-selective microelectrodes for THR detection. In the sandwich design, the THR was captured by a thiolated aptamer attached to the surface of the gold electrode and the measurements were based on cadmium sulfide quantum dot (CdS-QDs) label of the secondary aptamer. The potentiometric aptasensor presented good sensitivity allowing the detection of up to 28fmol of THR in PBS buffer solutions (detection limit of 0.14 nM). 

Among the long afterglow alkaline-earth sulfides, only (Ca, Sr)S Bi3+, CaS Bi3+, and CaS Eu2+, Tm2+ still have any real importance because their respective blue, violet, and red luminescence cannot yet be achieved with the less hydrolysis-sensitive zinc sulfide phosphors. The last-mentioned phosphor gives an intensive red afterglow and can substitute the red zinc-cadmium phosphor. 

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