Tanusri Pal

Synergistic effect of zinc selenide–reduced graphene oxide towards enhanced solar light-responsive photocurrent generation and photocatalytic 4-nitrophenol degradation

Herein, we report the in situ synthesis of zinc selenide (ZnSe)-decorated reduced graphene oxide (RGO) by a simple one-step solvothermal reaction for application in large-area, thin-film photodetector devices and photocatalytic 4-nitrophenol degradation. The photoresponsivity of the RGO–ZnSe photodetector is three orders of magnitude higher than that of controlled ZnSe. The ac transport mechanism in the composite reveals that its electrical conduction is modulated by a temperature-independent universal function. An EIS study confirmed the influence of RGO on the conductivity and charge transfer in the RGO–ZnSe composite. The photocatalytic degradation efficiency of the composite is four times higher than that of controlled ZnSe. In the RGO–ZnSe composite, RGO acts as a solid-state electron mediator, which efficiently collects the photo-induced electrons from the conduction band of ZnSe and subsequently hinders electron–hole recombination in ZnSe. This study explores the role of RGO–ZnSe synergy in achieving better photoresponse and photocatalytic performance. The RGO–ZnSe composite may lead to new possibilities in solar energy-harvesting applications and photocatalytic degradation of different non-self-sensitizing water pollutants.

Morphology dependent photoinduced electron transfer from N,N-dimethylaniline to semiconductor cadmium sulfide

Photoluminescence of large (150–200 nm) colloidal CdS nanoparticles in isopropanol was efficiently quenched by the electron donor molecule N,N-dimethylaniline (DMA). The quenching rates were found to be accelerated with improvement of the crystallinity of the CdS substrates. Electron-transfer from DMA to spherical CdS nanoclusters with 2–4 nm polycrystalline domains inside exhibited the slowest quenching rate (kq ∼ 0.65 × 1010 M−1 S−1). However the quenching rate was enhanced by ∼2 times (kq ∼ 1.2 × 1010 M−1 S−1) when crystal plane alignments were moderately improved. Further improvement of the quenching rate (kq ∼ 3.5 × 1010 M−1 S−1) was successfully achieved when the morphology of the CdS substrates was changed to nanorods. This enhancement is attributed to the single crystalline structure i.e. highly ordered crystal planes along the axis of the nanorod.

Solution processable RGO-CdZnS composite for solar light responsive photocatalytic degradation of 4-Nitrophenol

We report the one pot single step synthesis and characterization of solution processable reduced graphene oxide (RGO) - cadmium zinc sulfide (CdZnS) nanocomposite materials. The composite was characterized structurally and morphologically by XRD and TEM studies. The reduction of GO in RGO-CdZnS composite, was confirmed by XPS and Raman spectroscopy. The photocatalytic activity of the RGO-CdZnS composite was investigated towards the degradation of 4-Nitrophenol. A notable increase of photocatalytic efficiency of RGO-CdZnS compare to controlled CdZnS was observed. Here RGO plays a crucial role to efficient photo induced charge separation from the CdZnS, and decreases the electron-hole recombination probability and subsequently enhanced the photocatalytic activity of the RGO-CdZnS composite material under simulated solar light irradiation. This work highlights the potential application of RGO-based materials in the field of photocatalytic degradation of organic water pollutant.

Solar Light Responsive Photocatalytic Activity of Reduced Graphene Oxide–Zinc Selenide Nanocomposite

Solution processable reduced graphene oxide–zinc selenide (RGO–ZnSe) nanocomposite has been successfully synthesized by an easy one-pot single-step solvothermal reaction. The RGO–ZnSe composite was characterized structurally and morphologically by the study of XRD analysis, SEM and TEM imaging. Reduction in graphene oxide was confirmed by FTIR spectroscopy analysis. Photocatalytic efficiency of RGO–ZnSe composite was investigated toward the degradation of Rhodamine B under solar light irradiation. Our study indicates that the RGO–ZnSe composite is catalytically more active compared to the controlled-ZnSe under the solar light illumination. Here, RGO plays an important role for photoinduced charge separation and subsequently hinders the electron–hole recombination probability that consequently enhances photocatalytic degradation efficiency. We expect that this type of RGO-based optoelectronics materials opens up a new avenue in the field of photocatalytic degradation of different organic water pollutants.

Reduced graphene oxide-CdS nanocomposite with enhanced photocatalytic 4-Nitrophenol degradation

We report the photocatalytic activity of reduced graphene oxide cadmium sulfide (RGO-CdS) composite towards the degradation of 4-Nitrophenol (4-NP) under simulated solar light illumination. The solution processable RGO-CdS composite was synthesized by one pot single step low cost solvothermal process, where the reduction of graphene oxide (GO), synthesis and attachment of CdS onto RGO sheets were done simultaneously. The structural and morphological characterization of the RGO-CdS composite and the reduction of GO was confirmed by X-ray diffractometry, TEM imaging and Fourier transform infrared spectroscopy respectively. The photocatalytic efficiency of RGO-CdS composite is 2.6 times higher in compare to controlled CdS. In RGO-CdS composite the photo induced electrons transfer from CdS nanorod to RGO sheets, which reduces the recombination probability of photo generated electron-hole in the CdS. These well separated photoinduced charges enhanced the photocatalytic activity of the RGO-CdS composite. Our st...

Reduced Graphene Oxide–Cadmium Zinc Sulfide Nanocomposite with Controlled Band Gap for Large-Area Thin-Film Optoelectronic Device Application

Herein, we report the one pot single step solvothermal synthesis of reduced grapheme oxide–cadmium zinc sulfide (RGO–Cd0.5Zn0.5S) composite. The reduction in graphene oxide (GO), synthesis of Cd0.5Zn0.5S (mentioned as CdZnS in the text) nanorod and decoration of CdZnS nanorods onto RGO sheet were done simultaneously. The structural, morphological and optical properties were studied thoroughly by different techniques, such as XRD, TEM, UV–Vis and PL. The PL intensity of CdZnS nanorods quenches significantly after the attachment of RGO, which confirms photoinduced charge transformation from CdZnS nanorods to RGO sheet through the interface of RGO–CdZnS. An excellent photocurrent generation in RGO–CdZnS thin-film device has been observed under simulated solar light irradiation. The photocurrent as well as photosensitivity increases linearly with the solar light intensity for all the composites. Our study establishes that the synergistic effect of RGO and CdZnS in the composite is capable of getting promising applications in the field of optoelectronic devising.

Photo current generation in RGO - CdS nanorod thin film device

Herein, we report the synthesis and characterization of reduced graphene oxide (RGO) - cadmium sulfide (CdS) nanocomposite materials. The reduction of GO, formation of CdS and decoration of CdS onto RGO sheets were done in a one- pot solvothermal process. We have observed that the PL intensity for CdS nanorods remarkably quenched after the attachment of RGO, which established the photo induced charge transformation from the CdS nanorod to RGO sheets through the RGO-CdS interface. The optoelectronic transport properties of our fabricated large area thin film device exhibits excellent photo induced charge generation under simulated solar light illumination. The photo sensitivity of the device increases linearly with the increase of illuminated light intensity. The RGO-CdS composite exhibits enhance photocatalytic dye degradation efficiency in compare to control CdS under simulated solar light illumination.

Opto-electronic transport properties of graphene oxide based devices

Large area, solution-processed, graphene oxide (GO)nanocomposite based photo FET has been successfully fabricated. The device exhibits p-type charge transport characteristics in dark condition. Our measurements indicate that the transport characteristics are gate dependent and extremely sensitive to solar light. Photo current decay mechanism of GO is well explained and is associated with two phenomena: a) fast response process and b) slow response process. Slow response photo decay can be considered as the intrinsic phenomena which are present for both GO and reduced GO (r-GO), whereas the first response photo decay is controlled by the surface defect states. Demonstration of photo FET performance of GO thin film is a significant step forward in integrating these devices in various optoelectronic circuits.