Author
Krishna Gopakumar Warrier
Other affiliations: Academy of Scientific and Innovative Research, Council of Scientific and Industrial Research
Bio: Krishna Gopakumar Warrier is an academic researcher from National Institute for Interdisciplinary Science and Technology. The author has contributed to research in topics: Boehmite & Anatase. The author has an hindex of 36, co-authored 219 publications receiving 4589 citations. Previous affiliations of Krishna Gopakumar Warrier include Academy of Scientific and Innovative Research & Council of Scientific and Industrial Research.
Topics: Boehmite, Anatase, Sol-gel, Specific surface area, Photocatalysis
Papers published on a yearly basis
Papers
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TL;DR: In this paper, the photocatalytic activity of nanocrystalline titania (TiO2) powders has been investigated as a function of processing and material parameters through the decomposition of the methylene blue (MB) dye under exposure to ultraviolet (UV) radiation (λ = 200−400 nm) in an aqueous solution.
Abstract: Nanocrystalline titania (TiO2) powders have been synthesized via sol−gel, using an alkoxide precursor, under different processing conditions, and their photocatalytic activity has been investigated as a function of processing and material parameters through the decomposition of the methylene blue (MB) dye under exposure to the ultraviolet (UV) radiation (λ = 200−400 nm) in an aqueous solution. The nanocrystalline TiO2 powders with different morphology, crystallinity, average nanocrystallite size, surface area, and phase structure are obtained by controlling the ratio of molar concentrations of water and alkoxide (R) within the range of 5−60 and calcining the as-synthesized amorphous powders at higher temperatures (400−800 °C). The nanocrystalline TiO2 powders have been characterized using the scanning electron microscope (SEM), X-ray diffraction (XRD), and the Brunauer, Emmett, and Teller (BET) surface area measurement techniques while their photocatalytic activity was monitored using a UV−visible spectro...
162 citations
TL;DR: In this paper, the photocatalytic activity of mixed-phase nanocrystalline titania (TiO 2) processed via sol−gel SMC is measured by monitoring the degradation of the methylene blue dye in an aqueous solution, under UV-radiation exposure, using the UV−vis absorption spectroscope.
Abstract: Mixed-phase nanocrystalline titania (TiO 2) with varying rutile content has been synthesized via solvent mixing and calcination (SMC) treatment of sol−gel-derived nanocrystalline anatase-TiO 2 and rutile-TiO 2 precursors. The mixed-phase nanocrystalline TiO 2 processed via sol−gel SMC has been characterized using X-ray diffraction, the scanning electron microscope, high-resolution transmission electron microscope, and ultraviolet−visible (UV−vis) diffuse reflectance spectroscope for analyzing its morphology, phase contents, nanocrystallite size distribution, and band gap. The photocatalytic activity of mixed-phase nanocrystalline TiO 2 processed via sol−gel SMC is measured by monitoring the degradation of the methylene blue dye in an aqueous solution, under the UV-radiation exposure, using the UV−vis absorption spectroscope. It is demonstrated that the photocatalytic activity of mixed-phase nanocrystalline TiO 2 processed via sol−gel SMC is a function of rutile content with the maximum photocatalytic acti...
156 citations
TL;DR: In this paper, the structural changes and coordination of Al and Si in the mullite system as a function of temperature (60-1400°C) were studied. But the results of the FTIR spectral patterns of the gel and the gel calcined at 200°C show bands corresponding to Al-O−Al and Si−O−Si vibrations, while at higher temperatures hydroxyl groups and organics present have been removed.
145 citations
138 citations
TL;DR: In this article, a simple aqueous spray drying process was used to obtain high surface area porous architecture of C3N4 nanosheets by using 2 wt% poly vinyl alcohol as binder.
Abstract: Environmental remediation employing semiconducting materials offer a greener solution for pollution control. Herein, we report the development of high surface area porous architecture of C3N4 nanosheets by a simple aqueous spray drying process. g-C3N4 nanosheets obtained by the thermal decomposition of urea-thiourea mixture are spray granulated to microspheres using 2 wt% poly vinyl alcohol (PVA) as binder. The post granulation thermal oxidation treatment resulted in in situ doping of carbon leading to improved photophysical properties compared to pristine g-C3N4. The C3N4 granules with surface area values of 150 m2/g rendered repetitive adsorption of tetracycline antibiotic (∼75% in 60 min) and the extended absorption in the visible region facilitated complete photocatalytic degradation upon sunlight irradiation (>95% in 90 min). The delocalized π bonds generated after carbon doping and the macro-meso porous architecture created by the granulation process aided high adsorption capacity (70 mg/g). The pho...
120 citations
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TL;DR: It is anticipated that this review can stimulate a new research doorway to facilitate the next generation of g-C3N4-based photocatalysts with ameliorated performances by harnessing the outstanding structural, electronic, and optical properties for the development of a sustainable future without environmental detriment.
Abstract: As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...
5,054 citations
TL;DR: In this paper, photo-induced superhydrophilicity was used on the surface of a wide-band gap semiconductor like titanium dioxide (TiO 2 ) for photocatalytic activity towards environmentally hazardous compounds.
4,241 citations
TL;DR: The mechanical properties of nanocrystalline materials are reviewed in this paper, with emphasis on their constitutive response and on the fundamental physical mechanisms, including the deviation from the Hall-Petch slope and possible negative slope, the effect of porosity, the difference between tensile and compressive strength, the limited ductility, the tendency for shear localization, fatigue and creep responses.
3,828 citations
TL;DR: A comprehensive analysis of the reported effects of dopants on the anatase to rutile phase transformation and the mechanisms by which these effects are brought about is presented in this article, yielding a plot of the cationic radius versus the valence characterised by a distinct boundary between inhibitors and promoters.
Abstract: Titanium dioxide, TiO2, is an important photocatalytic material that exists as two main polymorphs, anatase and rutile. The presence of either or both of these phases impacts on the photocatalytic performance of the material. The present work reviews the anatase to rutile phase transformation. The synthesis and properties of anatase and rutile are examined, followed by a discussion of the thermodynamics of the phase transformation and the factors affecting its observation. A comprehensive analysis of the reported effects of dopants on the anatase to rutile phase transformation and the mechanisms by which these effects are brought about is presented in this review, yielding a plot of the cationic radius versus the valence characterised by a distinct boundary between inhibitors and promoters of the phase transformation. Further, the likely effects of dopant elements, including those for which experimental data are unavailable, on the phase transformation are deduced and presented on the basis of this analysis.
2,570 citations
TL;DR: UV-Visible ار راد ن .د TiO2 ( تیفرظ راون مان هب نورتکلا یاراد لماش VB و ) رگید اب لاقتنا VB (CO2) .
Abstract: UV-Visible ار راد ن .د TiO2 ( تیفرظ راون مان هب نورتکلا یاراد یژرنا زارت لماش VB و ) رگید زارت ی یژرنا اب ( ییاناسر راون مان هب نورتکلا زا یلاخ و رتلااب VB یم ) .دشاب ت ود نیا نیب یژرنا توافت یژرنا فاکش زار ، پگ دناب هدیمان یم .دوش هک ینامز زا نورتکلا لاقتنا VB هب VB یم ماجنا دریگ ، TiO2 اب ودح یژرنا بذج د ev 2 / 3 ، نورتکلا تفج کی دیلوت یم هرفح .دیامن و نورتکلا هرفح ی نا اب هدش دیلوت یم کرتشم حطس هب لاقت ثعاب دناوت شنکاو ماجنا اه یی ددرگ . TiO2 دربراک ،دراد یدایز یاه هلمج زا یم ناوت اوه یگدولآ هیفصت یارب (CO2) و بآ و ... نآ زا هدافتسا درک .
2,055 citations