Shell Thickness Dependent Photocatalytic Properties of ZnO/CdS Core–Shell Nanorods

Abstract

Core/shell nanorod arrays of ZnO/CdS have been synthesized with varying shell thickness and their shell thickness dependent photocatalytic properties have been investigated. Core/shell nanorod arrays of core diameter of 100 nm with variable shell thickness (10–30 nm) are synthesized by varying the concentration of the citric acid. XRD analysis reveals that tensile strain is obtained for ZnO nanorods and the compressive strain is obtained for core/shell nanorods. The UV–visible absorption spectra of the core/shell nanorod arrays show a red shift of the band edge of uncoated ZnO with shell growth. Steady-state photoluminescence (PL) spectra of the core/shell nanorod arrays show red shift of emission band with the increase in shell thickness. Decay kinetics indicate that the average lifetime (⟨τ⟩) of the core/shell nanorod arrays is larger than that of the uncoated ZnO nanorods due to charge separation. I–V studies show a 16-fold enhancement in current using the ZnO/CdS core/shell nanorod arrays having CdS shell thickness of 30 nm as compared to bare ZnO nanorods. The photocatalytic studies confirmed that the ZnO/CdS core/shell nanorod arrays exhibit improved degradation efficiency compared to bare ZnO and CdS under simulated solar radiation. The core/shell nanorods having shell (CdS) thickness of 30 nm displays the highest photocatalytic efficiency for the degradation of rhodamine B under simulated solar radiation, indicating efficient separation of electron–hole pairs. The mechanism of the photodegradation of RhB is given to elucidate the efficiency enhancement of ZnO/CdS photocatalysts. These results demonstrate that the ZnO/CdS core/shell nanorod arrays provide a facile and compatible frame for potential applications in nanorod-based solar cells and as efficient photocatalysts.

Rational design of CdS@ZnO core-shell structure via atomic layer deposition for drastically enhanced photocatalytic H2 evolution with excellent photostability

“…nontoxicity and low cost [35][36][37][38][39][40], ZnO has been considered as a very promising semiconductor shell option.…”

“…For example, Wang et al synthesized two ZnO-CdS heterostructures by a thermal replacement method, ZnO disk-CdS nanoparticle and ZnO rod-CdS nanoparticle, respectively [36], and found the ZnO-CdS heterostructures exhibited much higher photocatalytic activity than single ZnO and CdS, respectively. Khanchandani et al synthesized ZnO/CdS core-shell nanorods with CdS as shell by a solution reaction approach [39], which presented improved photocatalytic activity. Interestingly, we realized that most of the reported ZnO-CdS heterojunctions with core-shell structure are based on the structural design of ZnO core and CdS shell, probably due to the fact that ZnO tends to grow preferably along certain facets, which can readily lead to the structure, morphology and distribution of ZnO shell very difficult to control.…”

Core@shell Nanoparticles: Greener Synthesis Using Natural Plant Products

“…Ren et al (in 2017) showed that an increase in the pH values ranging from 4 to 7 leads to 30 times enhancement in the removal efficiency of heavy metals ions by magnetic CoFe 2 O 4 @SiO 2 NPs. Joshi et al [68] showed that increase in shell thickness of Fe 3 O 4 -SiO x core shell NPs led to decreases on r 2 relaxivity in magnetic resonance imaging (MRI). Yang et al studied the influence of shell thickness of Au@Ag core shell NPs on the antimicrobial activity against Escherichia coli and Staphylococcus aureus; Au@Ag NPs with average shell thickness of 8.8 nm showed the higher antibacterial activity when compared with Au@Ag NPs with the shell thickness of 1.5 nm at the same concentration [69].…”

Fabrication of high-performance CuInSe2 nanocrystals-modified TiO2 NTs for photocatalytic degradation applications

“…4(A) and (B). The degradation mechanism elucidated on the basis of the reported ones [47,48] is shown in Scheme 1 with the following equations:…”