Recent progress of metal-graphene nanostructures in photocatalysis

Khan, Mohammad Ehtisham,Khan, Mohammad Mansoob,Cho, Moo Hwan The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.20

<P>Metal-graphene nanostructures (NSs) as photocatalysts, prepared using simple and scalable synthesis methods, are gaining heightened attention as novel materials for water treatment and environmental remediation applications. Graphene, the unique few layers sheet-like arrangement of sp<SUP>2</SUP> hybridized carbon atoms, has an inimitable two-dimensional (2D) structure. The material is highly conductive, has high electron mobility and an extremely high surface area, and can be produced on a large scale at low cost. Accordingly, it has been considered as an essential base component for producing various metal-based NSs. In particular, metal-graphene NSs as photocatalysts have attracted considerable attention because of their special surface plasmon resonance (SPR) effect that can improve their performance for the removal of toxic dyes and other pollutants. This review summarizes the recent and advanced progress for the easy fabrication and design of graphene-based NSs as photocatalysts, as a novel tool, using a range of approaches, including green and biogenic approaches.</P>

Visible light-induced enhanced photoelectrochemical and photocatalytic studies of gold decorated SnO₂ nanostructures

Khan, Mohammad Mansoob,Ansari, Sajid Ali,Khan, Mohammad Ehtisham,Ansari, Mohd Omaish,Min, Bong-Ki,Cho, Moo Hwan The Royal Society of Chemistry 2015 NEW JOURNAL OF CHEMISTRY Vol.39 No.4

<P>This paper reports a novel one-pot biogenic synthesis of Au–SnO<SUB>2</SUB> nanocomposite using electrochemically active biofilm. The synthesis, morphology and structure of the as-synthesized Au–SnO<SUB>2</SUB> nanocomposite were in-depth studied and confirmed by UV-vis spectroscopy, photoluminescence spectroscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. It was observed that the SnO<SUB>2</SUB> surface was decorated homogeneously with Au nanoparticles. The photoelectrochemical behavior of the Au–SnO<SUB>2</SUB> nanocomposite was examined by cyclic voltammetry, differential pulse voltammetry, electrochemical impedance spectroscopy, and linear sweep voltammetry in the dark and under visible light irradiation. Visible light-induced photoelectrochemical studies confirmed that the Au–SnO<SUB>2</SUB> nanocomposite had enhanced activities compared to the P–SnO<SUB>2</SUB> nanoparticles. The Au–SnO<SUB>2</SUB> nanocomposite was also tested for the visible light-induced photocatalytic degradation of Congo red and methylene blue, and showed approximately 10 and 6-fold higher photocatalytic degradation activity, respectively, compared to P–SnO<SUB>2</SUB>. These results showed that the Au–SnO<SUB>2</SUB> nanocomposite exhibits excellent and higher visible light-induced photoelectrochemical and photocatalytic activities than the P–SnO<SUB>2</SUB> nanoparticles, and can be used for a wide range of applications.</P> <P>Graphic Abstract</P><P>Visible light-induced photocatalytic degradation of colored dyes using Au–SnO<SUB>2</SUB> nanocomposite. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4nj02245a'> </P>

Defected graphene nano-platelets for enhanced hydrophilic nature and visible light-induced photoelectrochemical performances

Khan, Mohammad Ehtisham,Khan, Mohammad Mansoob,Cho, Moo Hwan Elsevier 2017 The Journal of physics and chemistry of solids Vol.104 No.-

<P><B>Abstract</B></P> <P>This paper reports an optimized electron beam irradiation (60kGy and 90kGy) approach for defects-related engineering of graphene nano-platelets for optical and structural properties dependent photoelectrochemical performances. The defects in the electron beam irradiated pristine graphene nano-platelets were studied, analyzed and confirmed using standard characterization techniques such as, diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), high resolution-transmission electron microscopy (HR-TEM) and contact angle measurements. DRS clearly revealed the increment in the absorption band using electron beam irradiation doses of 60kGy and 90kGy. Contact angle measurements confirm the additional hydrophilic nature of the defects engineered graphene nano-platelets in comparison with pristine graphene. The photoelectrochemical performances such as linear sweep voltammetry and electrochemical impedance spectroscopy further confirms the enhancement in the optical, spectroscopic, and photoelectrochemical properties of the 90kGy defected graphene in comparison to pristine graphene nano-platelets. Therefore, the proposed method is a reliable way of fine-tuning the properties (optical, spectroscopic and photoelectrochemical) of pristine graphene nano-platelets using electron beam irradiation for enhanced photoelectrochemical performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Electron beam irradiated (60 kGy and 90 kGy) pristine graphene. </LI> <LI> Defects engineered graphene for visible light induced photoelectrochemical performances. </LI> <LI> Detailed analysis of defects engineered graphene with standard characterization techniques. </LI> <LI> Defects engineered pristine graphene used as a photoelectrode. </LI> <LI> Defects engineered graphene as an enhanced hydrophilic in nature. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Proposed electron transfer mechanism of defect engineered graphene nano-platelets under visible light irradiation.</P> <P>[DISPLAY OMISSION]</P>

Potentials of <i>Costus woodsonii</i> leaf extract in producing narrow band gap ZnO nanoparticles

Khan, Mohammad Mansoob,Saadah, Nurin Hayatus,Khan, Mohammad Ehtisham,Harunsani, Mohammad Hilni,Tan, Ai Ling,Cho, Moo Hwan Elsevier 2019 Materials science in semiconductor processing Vol.91 No.-

<P><B>Abstract</B></P> <P>Narrow band gap zinc oxide (ZnO) nanoparticles (NPs) were synthesized using unboiled and boiled leaf extracts of <I>Costus woodsonii</I>. The as-synthesized NPs were characterized using a range of techniques. The as-synthesized ZnO NPs were crystalline with a hexagonal wurtzite structure similar to the commercial ZnO (ZnO-C). The maximum absorbance was observed at ~390 nm for ZnO-C and the as-synthesized ZnO NPs (ZnO-UL and ZnO-BL) showed a red shift, i.e. ~448 nm to ~462 nm, hence, a lower band gap of ~2.68–2.77 eV. The band gap energy of the as-synthesized ZnO NPs was lower than that of commercial ZnO. The surface of ZnO was coated/modified with the components of the leaf extract. The as-synthesized ZnO NPs showed similar particle sizes and were spherical in shape. These studies confirmed the green synthesis of ZnO NPs using <I>Costus woodsonii</I> and the significantly reduced band gap (E<SUB> <I>g</I> </SUB> = ~2.68 eV to ~2.77 eV) of the as-synthesized ZnO NPs compared to the ZnO-C (E<SUB> <I>g</I> </SUB> = 3.18 eV).</P>

Biogenic synthesis of a Ag–graphene nanocomposite with efficient photocatalytic degradation, electrical conductivity and photoelectrochemical performance

Khan, Mohammad Ehtisham,Khan, Mohammad Mansoob,Cho, Moo Hwan The Royal Society of Chemistry 2015 New journal of chemistry Vol.39 No.10

<P>This paper reports an environmentally benign, simple, cost efficient, one-step, surfactant free, and biogenic synthesis of a silver–graphene (Ag–graphene) nanocomposite using an electrochemically active biofilm (EAB). The EAB was used for the reduction of Ag<SUP>+</SUP> to Ag<SUP>0</SUP> onto the graphene sheets. The morphology, structure, composition, and optical properties and contact angle of the Ag–graphene were obtained using a range of techniques which confirmed the anchoring/presence of silver nanoparticles (AgNPs) onto the graphene sheets. The photocatalytic activity of Ag–graphene was evaluated by the degradation of methylene blue and Congo red dye in aqueous solution at an ambient temperature in the dark and under visible-light irradiation. The results showed that the photocatalytic activity of the Ag–graphene nanocomposite was enhanced significantly by the loading of AgNPs in the graphene sheets. Contact angle measurements confirm the hydrophilic nature of the Ag–graphene nanocomposite which is very helpful in photocatalysis. The electrical conductivity and photocurrent measurements of the Ag–graphene nanocomposite exhibited a much better performance than P–graphene. This study highlights the design of a novel facile synthetic route for a new photocatalyst using the SPR of Ag and graphene as a support. The as-synthesized Ag–graphene nanocomposite has potential applications in photocatalytic degradation, photoelectrodes and optoelectronic devices.</P> <P>Graphic Abstract</P><P>Visible light-driven photocatalytic degradation of organic pollutants using the Ag–graphene nanocomposite. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5nj01320h'> </P>

Graphite-like carbon nitride (C₃N₄) modified N-doped LaTiO₃ nanocomposite for higher visible light photocatalytic and photo-electrochemical performance

Rakibuddin, Md,Kim, Haekyoung,Ehtisham Khan, Mohammad Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.452 No.-

<P><B>Abstract</B></P> <P>A novel g-C<SUB>3</SUB>N<SUB>4</SUB>/N doped-LaTiO<SUB>3</SUB> organic-inorganic hybrid (CLT) is synthesized via a sol–gel polymerized complex method followed by a facile solid state transformation route. The as synthesized hybrid is characterized using powder X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, UV–visible diffuse reflectance spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis. The results show that the band gap of LaTiO<SUB>3</SUB> is narrowed and also could absorb visible light after doping of N into the LaTiO<SUB>3</SUB> lattice. It is observed that N-doped LaTiO<SUB>3</SUB> nanoparticles are wrapped with the g-C<SUB>3</SUB>N<SUB>4</SUB> nano-sheet layers, forming a heterojunction structure, in the CLT hybrid. The CLT hybrid exhibits not only longer wavelength absorption in the visible region but also an enhancement in the photocatalytic and photocurrent activity under visible light compared to pure N-doped LaTiO<SUB>3</SUB> and g-C<SUB>3</SUB>N<SUB>4</SUB>. Moreover, the hybrid is photo-stable and reusable. The improved visible light photocatalytic activity of the CLT hybrid is ascribed to its suitable band edge potential, better separation of photoinduced charge carriers owing to the heterojunction, and the synergistic effect of g-C<SUB>3</SUB>N<SUB>4</SUB> and N-LaTiO<SUB>3</SUB>. Based on the results of photoluminescence, electrochemical impedance, and radical scavenger studies, a possible photocatalytic mechanism for the hybrid is also proposed. The g-C<SUB>3</SUB>N<SUB>4</SUB>/N-LaTiO<SUB>3</SUB> hetero-structure is expected to provide new insight for the application of rare-earth-metal based perovskite oxides in environmental remediation and could be suitable for water splitting and other energy related applications as well.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel g-C<SUB>3</SUB>N<SUB>4</SUB>/N doped-LaTiO<SUB>3</SUB> hybrid was synthesized via a facile sol–gel method. </LI> <LI> N-doped LaTiO<SUB>3</SUB> were wrapped with g-C<SUB>3</SUB>N<SUB>4</SUB>, forming a heterojunction structure. </LI> <LI> CLT hybrid exhibits an improved catalytic activity and photocurrent performance. </LI> <LI> The enhanced activity is due to the heterojunction pf CLT. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>A novel g-C<SUB>3</SUB>N<SUB>4</SUB>/N doped-LaTiO<SUB>3</SUB> organic-inorganic hybrid (CLT) is synthesized via a sol–gel polymerized complex method followed by facile solid state transformation route, which exhibits an improved visible light catalytic and photocurrent activity of LaTiO<SUB>3</SUB>.</P> <P>[DISPLAY OMISSION]</P>

Photocatalyticdegradation activity of goji berry extract-mediated green synthesized antibacterialsilver-zinc oxide nanocomposites under simulated solar light irradiation

( Abdulrahman ),( Kannan Badri Narayanan ),( Mohammad Ehtisham Khan ),한성수 한국공업화학회 2022 한국공업화학회 연구논문 초록집 Vol.2022 No.-

Sustainable fabrication of silver-titania nanocomposites using goji berry (Lycium barbarum L.) fruit extract and their photocatalytic and antibacterial applications

한성수,( Abdulrahman Ahmed Sharwani ),( Kannan Badri Narayanan ),( Mohammad Ehtisham Khan ) 한국공업화학회 2021 한국공업화학회 연구논문 초록집 Vol.2021 No.1