Plasmonic Ag nanoparticles decorated NiAl-layered double hydroxide/graphitic carbon nitride nanocomposites for efficient visible-light-driven photocatalytic removal of aqueous organic pollutants

Tonda, Surendar,Jo, Wan-Kuen Elsevier 2018 CATALYSIS TODAY - Vol.315 No.-

<P><B>Abstract</B></P> <P>Ag nanoparticles decorated NiAl-layered double hydroxide/graphitic carbon nitride (Ag/LDH/g-C<SUB>3</SUB>N<SUB>4</SUB>) nanocomposites were synthesized for the first time by an <I>in situ</I> hydrothermal method, followed by photoreduction. The visible-light-driven Ag/LDH/g-C<SUB>3</SUB>N<SUB>4</SUB> nanocomposites exhibited enhanced performance for the photocatalytic degradation of aqueous Rhodamine B and 4-chlorophenol. Notably, the Ag/LDH/g-C<SUB>3</SUB>N<SUB>4</SUB> nanocomposite with LDH and Ag contents of 15 wt% and 1 wt%, respectively, showed the highest photocatalytic performance, which was far superior to that observed for pure g-C<SUB>3</SUB>N<SUB>4</SUB>, LDH, and the binary Ag/g-C<SUB>3</SUB>N<SUB>4</SUB> and LDH/g-C<SUB>3</SUB>N<SUB>4</SUB> composites. The enhanced photocatalytic efficiency was mainly attributed to rapid charge transfer at the Ag/LDH/g-C<SUB>3</SUB>N<SUB>4</SUB> interfaces and the surface plasmon resonance of the Ag nanoparticles, which promotes the separation efficiency of photogenerated charge carriers and improves optical absorption. Additionally, the Ag/LDH/g-C<SUB>3</SUB>N<SUB>4</SUB> nanocomposites exhibited excellent photostability during successive experimental runs, with no significant change in degradation performance. These findings are expected to provide new mechanistic insights into the design and construction of efficient visible-light-driven photocatalysts for application in solar energy conversion and environmental remediation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ag/LDH/g-C<SUB>3</SUB>N<SUB>4</SUB> were prepared by an <I>in-situ</I> hydrothermal followed by photoreduction. </LI> <LI> Ag/LDH/g-C<SUB>3</SUB>N<SUB>4</SUB> exhibits stronger light absorption in the visible light region. </LI> <LI> Ag/LDH/g-C<SUB>3</SUB>N<SUB>4</SUB> showed high photocatalytic performance for RhB and 4-CP degradation. </LI> <LI> Rapid charge transfer at interfaces and SPR of Ag contribute to enhanced activity. </LI> <LI> The Ag/LDH/g-C<SUB>3</SUB>N<SUB>4</SUB> nanocomposites exhibited excellent photostability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Application of Cu-loaded One-dimensional TiO2 Nanorods for Elevated Photocatalytic Environmental Friendly Hydrogen Production

김동진,Surendar Tonda,조완근 한국환경과학회 2021 한국환경과학회지 Vol.30 No.1

Photocatalytic green energy H2 production utilizing inexhaustible solar energy has been considered as a potential solution to problems of energy scarcity and environmental contamination. However, the design of a cost-effective photocatalyst using simple synthesis methodology is still a grand challenge. Herein, a low-cost transition metal, Cu-loaded one-dimensional TiO2 nanorods (Cu/TNR) were fabricated using an easy-to-use synthesis methodology for significant H2 production under simulated solar light. X-ray photoelectron spectral studies and electron microscopy measurements provide evidence to support the successful formation of the Cu/TNR catalyst under our experimental conditions. UV-vis DRS studies further demonstrate that introducing Cu on the surface of TNR substantially increases light absorption in the visible range. Notably, the Cu/TNR catalyst with optimum Cu content, achieved a remarkable H2 production with a yield of 39,239 μmol/g after 3 h of solar light illumination, representing 7.4- and 27.7-fold enhancements against TNR and commercial P25, respectively. The notably improved H2 evolution activity of the target Cu/TNR catalyst was primarily attributed to its excellent separation and efficiently hampered recombination of photoexcited electron-hole pairs. The Cu/TNR catalyst is, therefore, a potential candidate for photocatalytic green energy applications.

Novel CoAl-LDH/g-C₃N₄/RGO ternary heterojunction with notable 2D/2D/2D configuration for highly efficient visible-light-induced photocatalytic elimination of dye and antibiotic pollutants

Jo, Wan-Kuen,Tonda, Surendar Elsevier 2019 Journal of hazardous materials Vol.368 No.-

<P><B>Abstract</B></P> <P>In this study, we fabricate a novel ternary heterojunction comprising CoAl-layered double hydroxide, g-C<SUB>3</SUB>N<SUB>4</SUB>, and reduced graphene oxide (LDH/CN/RGO) with a notable 2D/2D/2D configuration using a simple one-step hydrothermal method. The visible-light-induced LDH/CN/RGO ternary heterojunctions displayed significantly enhanced photocatalytic performance towards the degradation of aqueous Congo red (CR, dye) and tetracycline (TC, antibiotic) contaminants, which is far superior to that observed for pristine CN (base material), LDH, P25 (reference), and binary CN/RGO and LDH/CN heterojunctions. In particular, the LDH/CN/RGO ternary heterojunction with RGO and LDH contents of 1 wt.% and 15 wt.%, respectively, exhibited the highest degradation activity among all the fabricated catalysts, and it also displayed exceptional stability during recycling experiments. The significant enhancement in the photocatalytic performance and good stability of existing LDH/CN/RGO ternary heterojunctions were primarily attributed to the large intimate interfacial contact between constituent CN, LDH, and RGO prompted by their exceptional 2D/2D/2D arrangement, which accelerates the interfacial charge-transfer processes to effectively hinder the recombination of photoexcited charge carriers. The present study provides new insights into the rational design and fabrication of novel g-C<SUB>3</SUB>N<SUB>4</SUB>-based 2D/2D/2D layered ternary heterojunctions as high-performance photocatalysts, and promotes their application in addressing diverse energy and environmental issues.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CoAl-LDH/g-C<SUB>3</SUB>N<SUB>4</SUB>/RGO 2D/2D/2D ternary heterojunction was fabricated for the first time. </LI> <LI> Ternary heterojunction showed excellent performance for CR and TC photodegradation. </LI> <LI> Greater charge separation owing to large interfacial contact contributed to high activity. </LI> <LI> Ternary heterojunctions displayed high photostability during recycling experiments. </LI> <LI> Possible degradation pathways of CR and TC were proposed based on LC/MS/MS results. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Altered Autonomic Functions and Distressed Personality Traits in Male Adolescents with Internet Gaming Addiction

Kim, Nahyun,Hughes, Tonda L,Park, Chang G.,Quinn, Laurie,Kong, In Deok MARY ANN LIEBERT 2016 CyberPsychology, Behavior and Social Networking Vol. No.

Resting-State Peripheral Catecholamine and Anxiety Levels in Korean Male Adolescents with Internet Game Addiction

Kim, Nahyun,Hughes, Tonda L.,Park, Chang G.,Quinn, Laurie,Kong, In Deok MARY ANN LIEBERT 2016 CyberPsychology, Behavior and Social Networking Vol. No.

<P><B>Abstract</B></P><P>The purpose of this study was to compare the resting-state plasma catecholamine and anxiety levels of Korean male adolescents with Internet game addiction (IGA) and those without IGA. This cross-sectional comparative study was conducted with 230 male high school students in a South Korean city. Convenience and snowball sampling methods were employed, and data were collected using (1) participant blood samples analyzed for dopamine (DA), epinephrine (Epi), and norepinephrine (NE) and (2) two questionnaires to assess IGA and anxiety levels. Using SPSS 15.0, data were analyzed by descriptive analysis, χ<SUP>2</SUP>-tests, <I>t</I>-tests, and Pearson's correlation tests. The plasma Epi (<I>t</I> = 1.962, <I>p</I> < 0.050) and NE (<I>t</I> = 2.003, <I>p</I> = 0.046) levels were significantly lower in the IGA group than in the non-IGA group; DA levels did not significantly differ between the groups. The mean anxiety level of the IGA group was significantly higher compared with the non-IGA group (<I>t</I> =−6.193, <I>p</I> < 0.001). No significant correlations were found between catecholamine and anxiety levels. These results showed that excessive Internet gaming over time induced decreased peripheral Epi and NE levels, thus altering autonomic regulation, and increasing anxiety levels in male high school students. Based on these physiological and psychological effects, interventions intended to prevent and treat IGA should include stabilizing Epi, NE, and anxiety levels in adolescents.</P>

Construction of Bi₂WO₆/RGO/g-C₃N₄ 2D/2D/2D hybrid Z-scheme heterojunctions with large interfacial contact area for efficient charge separation and high-performance photoreduction of CO₂ and H<sub>2</

Jo, Wan-Kuen,Kumar, Santosh,Eslava, Salvador,Tonda, Surendar Elsevier 2018 Applied Catalysis B Vol.239 No.-

<P><B>Abstract</B></P> <P>We have rationally constructed a hybrid heterojunction comprising of Bi<SUB>2</SUB>WO<SUB>6</SUB>, reduced graphene oxide, and g-C<SUB>3</SUB>N<SUB>4</SUB> (BWO/RGO/CN) with a 2D/2D/2D configuration for efficient photoreduction to generate solar fuels. These heterojunctions displayed dramatically improved performance towards CO<SUB>2</SUB> reduction to generate CO and CH<SUB>4</SUB> under visible-light irradiation, compared to the base material (CN), P25 as reference, as well as binary BWO/CN and RGO/CN heterojunctions. Particularly, the BWO/RGO/CN heterojunctions with 1 wt. % RGO and 15 wt. % BWO achieved record performance in the yields of carbonaceous products (CO + CH<SUB>4</SUB>) compared to other synthesized catalysts, with a selectivity of 92% against H<SUB>2</SUB>. The remarkable photocatalytic performance was mainly attributed to the unique 2D/2D/2D architecture that creates large interfacial contact between the constituent materials for rapid charge transfer, to hinder the direct recombination of photoinduced electrons and holes. Notably, RGO played two significant roles: as a supporter to capture the electrons from CN, and as a redox mediator to promote the Z-scheme charge transfer between CN and BWO. The result is a greater extent of charge separation in the present BWO/RGO/CN heterojunction system, as evidenced by the photoluminescence, photocurrent responses, and electron microscopy findings. More importantly, the heterojunctions displayed excellent stability during recycling tests with no obvious loss in the generation of CO and CH<SUB>4</SUB> from photoreduction of CO<SUB>2</SUB>. This interesting interfacial engineering approach presented herein offers a promising route for the rational design of a new class of layered multicomponent heterojunctions with 2D/2D/2D architecture for various applications in environmental protection and solar energy conversion.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bi<SUB>2</SUB>WO<SUB>6</SUB>/RGO/g-C<SUB>3</SUB>N<SUB>4</SUB> hybrid heterojunctions with 2D/2D/2D configuration were fabricated. </LI> <LI> Heterojunctions showed excellent CO<SUB>2</SUB> photoreduction activity to generate solar fuels. </LI> <LI> RGO plays dual roles as a supporter and a redox mediator to promote charge separation. </LI> <LI> Rapid charge transfer due to large interfacial contact contributed to high activity. </LI> <LI> Hybrid heterojunctions exhibited high photostability during recycling experiments. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Hierarchical flower-like NiAl-layered double hydroxide microspheres encapsulated with black Cu-doped TiO₂ nanoparticles: Highly efficient visible-light-driven composite photocatalysts for environmental remediation

Jo, Wan-Kuen,Kim, Yeong-Gyeong,Tonda, Surendar Elsevier 2018 Journal of hazardous materials Vol.357 No.-

<P><B>Abstract</B></P> <P>Herein, highly efficient composite photocatalysts comprising black Cu-doped TiO<SUB>2</SUB> nanoparticles (BCT) encapsulated within hierarchical flower-like NiAl-layered double hydroxide (LDH) microspheres were fabricated via a one-step hydrothermal route. Cu-doping and subsequent reduction treatment led to extended visible-light absorption of TiO<SUB>2</SUB> in the resulting composites, as confirmed by ultraviolet-visible diffuse reflectance spectral analysis. Moreover, thorough investigations confirmed the strong interactions between LDH and BCT in the resulting BCT/LDH composites. Notably, the BCT/LDH composites exhibited remarkable performance in the degradation of hazardous materials (methyl orange and isoniazid), superior to that of the individual components, reference P25, and P25/LDH under visible-light irradiation. Moreover, the BCT/LDH composite containing 30 wt% of BCT displayed the highest photocatalytic performance among the synthesized photocatalysts and also exhibited high stability during recycling tests with no obvious change in the activity. The superior photodegradation activity of the BCT/LDH composites was primarily attributed to efficient transfer and separation of the photoinduced charge carriers, resulting from the intimate contact interfaces between LDH and BCT. This approach represents a promising route for the rational design of highly efficient and visible-light-active LDH-based composite photocatalysts for application in energy harvesting and environmental protection.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Novel and highly efficient black Cu-doped TiO<SUB>2</SUB>/NiAl-LDH composites were fabricated. </LI> <LI> Both components in the composite system exhibited strong visible-light absorption. </LI> <LI> Composite system showed excellent performance for MO and isoniazid photodegradation. </LI> <LI> Rapid charge transfer at the interface contributed to remarkable photo-activity. </LI> <LI> The composite system exhibited high photostability during recycling experiments. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

In situ phase transformation synthesis of unique Janus Ag₂O/Ag₂CO₃ heterojunction photocatalyst with improved photocatalytic properties

Jo, Wan-Kuen,Kumar, Santosh,Yadav, Poonam,Tonda, Surendar Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.445 No.-

<P><B>Abstract</B></P> <P>Herein, Ag<SUB>2</SUB>O/Ag<SUB>2</SUB>CO<SUB>3</SUB> nanocomposite with unique Janus morphology was synthesized by a facile ion-exchange followed by an in situ phase transformation method with precise control of its nucleation and growth processes. Contrary to conventional synthetic procedures of Janus architectures, the present Janus system was constructed without the need for surfactants or toxic chemicals. Most importantly, the visible-light-absorbing Janus Ag<SUB>2</SUB>O/Ag<SUB>2</SUB>CO<SUB>3</SUB> nanocomposite exhibits a remarkable performance toward the degradation of Rhodamine B and 4-chlorophenol, far superior to that observed for bare Ag<SUB>2</SUB>CO<SUB>3</SUB>. The obvious enhancement of the photocatalytic performance of this nanocomposite is mainly attributed to the intimate Ag<SUB>2</SUB>O/Ag<SUB>2</SUB>CO<SUB>3</SUB> interface created by its exceptional Janus architecture, which in turn allows for rapid charge transfer processes. Additionally, the Janus system exhibited a high photostability during recycling experiments with no significant change in the degradation activity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A Janus system was constructed without the need for conventionally used surfactants. </LI> <LI> Facile ion-exchange followed by an in situ phase transformation method was used. </LI> <LI> Rapid charge transfer at Ag<SUB>2</SUB>O/Ag<SUB>2</SUB>CO<SUB>3</SUB> interface contributed to enhanced activity. </LI> <LI> Janus nanocomposite exhibited excellent photostability in recycling experiments. </LI> <LI> Janus system prepared using less harmful chemicals showed high photoactivity. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Review of Liquid Crystal Spatial Light Modulators at Thales Research & Technology;Technology and Applications

Lee, Mane-Si Laure,Loiseaux, Brigitte,Dolfi, Daniel,Tonda, Sylvie,Huignard, Jean-Pierre The Korean Infomation Display Society 2002 Journal of information display Vol.3 No.3

Liquid Crystal Spatial Light Modulators (LC-SLMs) provide many interesting applications in laser optics and opto-el ectronic systems, in addition to displays. Among them, three topics developed at Thales Research & Technology are reviewed: wavefront correction for laser beam control, microwave processing in radar systems and holography for TN-LCDs viewing angle compensation.