Quantum Size Effects in Semiconductor Photocatalysis

Stroyuk, A. L.; Kryukov, A. I.; Kuchmii, S. Ya.; Pokhodenko, V. D.

doi:10.1007/s11237-005-0042-8

Cited by 73 publications

(58 citation statements)

References 150 publications

(232 reference statements)

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“…Moreover, a limiting factor that controls the efficiency of photocatalysis is the rapid recombination of photogenerated electrons and holes in semiconductor particles [57]. Recombination of the electron-hole pair within the semiconductor particle is drastically reduced with decreasing particle size [58]. Hence, due to smaller size, recombination rate of electron and hole for the ZnO nanocrystallines prepared in the presence of the RTIL with longer microwave irradiation time and higher RTIL content is lower than the prepared sample in other conditions.…”

Section: Rtil [Emim][etso 4 ] Consists Of [Emim] + Cations and [Etsmentioning

confidence: 99%

Preparation and characterization of ZnO nanocrystallines in the presence of an ionic liquid using microwave irradiation and photocatalytic activity

Esmaili

Habibi‐Yangjeh

2010

JICS

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Fast, simple and template-free method is proposed for preparation of ZnO nanocrystallines in the presence of 1-ethyl-3-methylimidazolium ethyl sulfate, [EMIM][EtSO 4 ], a room-temperature ionic liquid (RTIL) under microwave irradiation. The powder X-ray diffraction (XRD) studies display that products are excellently crystallized in the form of wurtzite hexagonal structure. Energy dispersive X-ray spectroscopy (EDX) investigations reveal that the products are extremely pure. The results obtained by scanning electron microscopy (SEM) demonstrate that mean size of ZnO nanocrystallines decreases with microwave irradiation time and the RTIL content of media. Diffuse reflectance spectra (DRS) of the ZnO nanocrystallines shows blue shift relative to the bulk ZnO, which can be attributed to quantum confinement effect of ZnO nanocrystallines. A possible formation mechanism of the ZnO nanocrystallines in aqueous solution of the RTIL is presented. Photocatalytic activity of the ZnO nanocrystallines towards photodegradation of methylene blue (MB) was carried out. The results demonstrate that photocatalytic activity of the ZnO nanocrystallines increases with microwave irradiation time and the RTIL content of media.

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Section: Rtil [Emim][etso 4 ] Consists Of [Emim] + Cations and [Etsmentioning

confidence: 99%

Preparation and characterization of ZnO nanocrystallines in the presence of an ionic liquid using microwave irradiation and photocatalytic activity

Esmaili

Habibi‐Yangjeh

2010

JICS

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“…Moreover, a limiting factor that controls the efficiency of photocatalysis is the rapid recombination of photogenerated electrons and holes in the nanoparticles [61]. Recombination of electronhole pair within the semiconductor particle is drastically reduced with decreasing particle size [62].…”

Section: Results and Disscusionmentioning

confidence: 99%

Simple and low temperature preparation and characterization of CdS nanoparticles as a highly efficient photocatalyst in presence of a low-cost ionic liquid

Taghvaei

Habibi‐Yangjeh

Behboudnia

2010

JICS

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A simple and low temperature method is proposed for preparation of CdS nanoparticles in presence of 1-ethyl-3-methylimidazolium ethyl sulfate, [EMIM] [EtSO 4 ], a room-temperature ionic liquid (RTIL). The powder X-ray diffraction (XRD) studies display that the products are excellently crystallized in the form of cubic structure and size of the nanparticles prepared in presence of the RTIL is smaller than that prepared in water. Energy dispersive X-ray spectroscopy (EDX) investigations reveal that the products are very pure and nearly stoichiometric. The results obtained by scanning electron microscopy (SEM) demonstrate that the CdS nanoparticles prepared in presence of the RTIL have lower tendency for aggregation relative to the prepared sample in water. Diffuse reflectance spectra (DRS) of the product prepared in the neat RTIL, shows 1.52 eV blue shift relative to bulk CdS, which can be attributed to quantum confinement effect of the CdS nanoparticles. A possible formation mechanism for CdS nanoparticles in presence of the RTIL is presented. Photocatalytic activity of the CdS nanoparticles towards photodegradation of methylene blue (MB) using UV and visible lights was performed. The results demonstrate that observed firstorder rate constant for photodegradation of MB on CdS nanoparticles prepared in the neat RTIL are about 20 and 6 times greater than the prepared sample in water using visible and UV lights, respectively.

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“…It is known that the consumption of h VB + in reactions (4) and (6) occurs much more rapidly than the consumption of e CB − in the reaction with oxygen (process (5)) [3,10]. As a result the CdS NP appear to be enriched in negative charge, which leads to the Burshtein-Moss effect, the reversible hypsochromic shift of l tr , the analysis of which permits information to be obtained on the dynamics of reaction (5) in the microsecond domain [3,10,11].…”

mentioning

confidence: 99%

“…As a result the CdS NP appear to be enriched in negative charge, which leads to the Burshtein-Moss effect, the reversible hypsochromic shift of l tr , the analysis of which permits information to be obtained on the dynamics of reaction (5) in the microsecond domain [3,10,11]. For example, using the Burshtein-Moss effect the authors of [11] showed that the rate of reaction (5) increased by an order of magnitude with a decrease in the size of CdS NP from 7.2 to 3.2 nm.…”

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confidence: 99%

Photoinduced variations in the size of nanoparticles of CdS in colloidal solutions

et al. 2007

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The possibility of decreasing the size of colloidal nanoparticles of CdS in the oxidative photocorrosion reaction in the presence of methylviologen and of increasing their size during photocatalytic reduction of sulfur in ethanol in the presence of cadmium acetate. A dependence of the quantum yield of the latter reaction on the initial size of CdS nanoparticles was observed, which was interpreted as a result of quantum size effects.The unique luminescent, non-linear optical and photochemical properties of semi-conductor (SC) nanoparticles (NP), the character and intensity of which in many cases are functions of the size of the NP [1-5] has stimulated considerable interest in the methods of synthesis which permit purposeful and gradual variation in size of the SC NP [4,5]. Among the approaches to obtain "homologous" series of SC NP, the dimensions and optical properties of which, at constant chemical composition, change over a wide range, the most successful are methods based on formation of the SC NP in a structured medium (e.g. micellar), and also the use of Ostwald ripening of SC NP at high temperatures in high boiling solvents [4,5]. In addition to this the possibility of using such SC NP, for example, in photochemical reaction is very limited since such methods require carrying out difficult procedures to extract the NP from the micellar medium or an organic oil and then to stabilize them in solution. In the case of cadmium sulfide and a series of other photoactive SC which take part in photochemical conversions which may be used for "photopoisoning" of the SC NP which permits changes of the size and distribution of the NP with respect to size [6].In the present work it is shown that the size of CdS NP can be gradually changed photochemically -either a decrease in size during oxidative photocorrosion in aqueous solution in the presence of methylviologen or an increase in size in the photocatalytic process of formation of cadmium sulfide by reduction of elemental sulfur in the presence of NP of CdS and cadmium acetate in ethanol solutions. EXPERIMENTALIn this work the following chemicals were used: CdCl 2 , Cd(CH 3 COO) 2 , Na 2 S·9H 2 O, methylviologen chloride (MV 2+ ), sodium polyphosphate (NaPP) (chemically pure) (Aldrich), and sulfur (very pure). Ethanol was dehydrated by boiling with calcined calcium oxide and redistilled twice. Nanoparticles of CdS were obtained in aqueous solutions of sodium polyphosphate (3·10 -3 mol/L) by the interaction of cadmium chloride and sodium sulfide (1·10 -3 mol/L), and also in anhydrous 184 0040-5760/07/4303-0184

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Quantum Size Effects in Semiconductor Photocatalysis

Cited by 73 publications

References 150 publications

Preparation and characterization of ZnO nanocrystallines in the presence of an ionic liquid using microwave irradiation and photocatalytic activity

Preparation and characterization of ZnO nanocrystallines in the presence of an ionic liquid using microwave irradiation and photocatalytic activity

Simple and low temperature preparation and characterization of CdS nanoparticles as a highly efficient photocatalyst in presence of a low-cost ionic liquid

Photoinduced variations in the size of nanoparticles of CdS in colloidal solutions

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