Ag nanowire/ZnO nanobush hybrid structures for improved photocatalytic activity

Thanh Hoai Ta, Qui,Park, Sungho,Noh, Jin-Seo Academic Press 2017 Journal of Colloid and Interface Science Vol. No.

<P><B>Abstract</B></P> <P>Reverse-engineered Ag nanowire/ZnO nanobush hybrid structures have been synthesized for the first time by a combination of polyol method and low-temperature solution method. Through the elaborate control of Ag-to-ZnO weight ratio, vertically aligned ZnO nanobushes grew on the surface of well-faceted Ag nanowires. The Ag/ZnO hybrid nanostructures showed the crystal features of both Ag nanowires and wurtzite ZnO nanostructures. They exhibited strong UV absorption, whereas their photoluminescence spectra were much weaker than pure ZnO nanostructures due to the inhibited carrier recombination. The photocatalytic activity of Ag/ZnO hybrid nanostructures was greatly improved compared to pure ZnO nanostructures. Furthermore, they showed good cyclic performance and easy recovery from the test solution, demonstrating the possibility of their practical use.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Morphological evolution of solution-grown cobalt-doped ZnO nanostructures and their properties

Ta, Qui Thanh Hoai,Namgung, Gitae,Noh, Jin-Seo Elsevier 2018 Chemical physics letters Vol.700 No.-

<P><B>Abstract</B></P> <P>It is demonstrated that the morphology of Co-doped ZnO nanostructures can be easily altered by controlling Co-doping concentration. A facile low-temperature solution method was employed for the nanosynthesis. The morphology of the nanostructures changed from nanorods to nanoparticles, and to needle-like structures as the molar ratio of Co<SUP>2+</SUP> ions increased. No noticeable changes in structural and optical properties were caused by the low concentration of Co-doping, while a magnetic transition was observed. At the very low Co concentrations below 0.3 at%, the nanostructures showed diamagnetism, whereas a paramagnetic behavior was observed at a concentration of 2.5 at%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Co-doped ZnO nanostructures were synthesized by a low-temperature solution method. </LI> <LI> The morphology of the nanostructures could be controlled simply by adjusting the Co<SUP>2+</SUP> concentration. </LI> <LI> No noticeable changes in structural and optical properties were caused by the morphological evolution. </LI> <LI> The Co-doped ZnO nanostructures showed paramagnetism at the Co concentration of 2.5 at%. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Synthesis of Ag@rGO/g‑C3N4 Layered Structures and Their Application to Toxic Gas Sensors: Effect of Ag Nanoparticles

Qui Thanh Hoai Ta,Gitae Namgung,Jin-Seo Noh 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.6

In this work, graphitic carbon nitride (g-C3N4) was synthesized by simple pyrolysis of melamine, and it was hybridized withreduced graphene oxide (rGO) and silver nanoparticles (AgNPs) using a stepwise solution method. AgNPs were randomlydistributed on the surface of rGO/g-C3N4 layered hybrid structure, forming Ag@rGO/g-C3N4 composite. It was disclosedthat the Ag@rGO/g-C3N4 composite responded to both oxidizing and reducing gases at room temperature, and its responsewas greatly enhanced from those of pristine rGO and rGO/g-C3N4. The room temperature responses of the composite wereestimated at − 95% and 8% for 50 ppm of NO2and NH3,respectively. The roles of structural components were discussed, anda gas-sensing mechanism was proposed based on the respective roles. In particular, AgNPs turned out to play an importantrole in the gas-sensing activity.

Versatile role of 2D Ti3C2 MXenes for advancements in the photodetector performance: A review

Adem Sreedhar,Qui Thanh Hoai Ta,Jin-Seo Noh 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.127 No.-

Nowadays, layer-structured two-dimensional (2D) Ti3C2 MXenes have been created a platform as promisingcandidates for developing next-generation photodetectors. Scalable spatial organization of Ti3C2MXenes enables responsive template at the interface of various semiconductors for significant improvementin the photodetector performance. In this review, we provide prospective discussion on geometricalpotentiality of 2D Ti3C2 MXenes to advance the current photodetector device performance. Specifically,we guide the versatility of Ti3C2 MXenes such as a metal electrode, flexible material, transparent nature,and self-power behavior during UV, visible, and broadband photodetector performance. By the excellenceof 2D Ti3C2, we begin to comprehend the Schottky barrier, built-in electric field, and van der Walls heterojunctionformation. It is imperative to understand the vast opportunities of Ti3C2 MXene-based photodetectorseven under flexible conditions, which is higher than conventional gold and graphene. Owing tothe desirable properties, Ti3C2 garnered significant progress in (i) large-size flexible photodetector formationwithout altering the structural and charge carrier properties, (ii) replacing conventional metal electrodesby electrically conductive Ti3C2 in Ti3C2-semiconductor-Ti3C2 (MX-S-MX) photodetector, and (iii)Schottky junction formation at the interface of various semiconductors. Finally, we conclude the status of2D Ti3C2 MXene applicability, challenges, and possible viewpoints for advancement in next-generationphotodetectors.

Stretchable hydrogen sensors employing palladium nanosheets transferred onto an elastomeric substrate

Namgung, Gitae,Ta, Qui Thanh Hoai,Noh, Jin-Seo Elsevier 2018 Chemical physics letters Vol.703 No.-

<P><B>Abstract</B></P> <P>Stretchable hydrogen sensors were fabricated from Pd nanosheets that were transferred onto a PDMS substrate. To prepare the Pd nanosheets, a Pd thin film on PDMS was first biaxially stretched and then PDMS substrate was etched off. The size of Pd nanosheets decreased as the applied strain increased and the film thickness decreased. A transfer technique was utilized to implement the stretchable hydrogen sensors. The stretchable sensors exhibited negative response behaviors upon the exposure to hydrogen gas. Interestingly, the sensors worked even under large strains up to 30%, demonstrating a potential as a high-strain-tolerable hydrogen sensor for the first time.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Palladium (Pd) nanosheets were prepared by a combination of biaxial stretching and PDMS delamination. </LI> <LI> The size of Pd nanosheets could be controlled by adjusting the applied strain and film thickness. </LI> <LI> Stretchable hydrogen gas sensors were fabricated using the Pd nanosheets. </LI> <LI> The stretchable sensors responded to hydrogen gas even under a 30% strain. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Pd nanosheets were prepared by biaxially stretching a Pd film on PDMS and subsequently delaminating the PDMS. It was demonstrated that stretchable hydrogen sensors fabricated from the Pd nanosheets could respond to hydrogen gas even under large strains up to 30%.</P> <P>[DISPLAY OMISSION]</P>

Advancements in the photocatalytic activity of various bismuth-based semiconductor/Ti3C2 MXene interfaces for sustainable environmental management: A review

ADEM SREEDHAR,Qui Thanh Hoai Ta,노진서 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.115 No.-

Rapidly increasing world population and industrialization are difficult to balance our environment. Monitoring water pollution, depletion of fossil fuels, and greenhouse gas emissions is paramount forthe safety of our ecological system. This review is intended to address the environmental monitoringapplications (toxic matter degradation, H2 evolution, CO2 reduction, and N2 reduction) through the possibleinterfacial insights involved between various bismuth (Bi) based semiconductors and 2D Ti3C2MXenes. In this spotlight, we explored strategic point contact (0D/2D) and face contact (2D/2D) interfaceinformation towards superior charge carrier generation, separation, and shortened charge transfer pathunder suppressed recombination. Considering the diverse morphological advancements in Ti3C2 (multilayer,monolayer, QDs, and completely derived C-TiO2), unique interfacial charge transport mechanismswere revealed. Band alignment modulations distinguishably functionalized the charge carrier separationand its participation in photocatalytic activity. With the control on face contact 2D/2D interface, abundantsurface-active sites promoted toxic dye degradation, CO2, and N2 reduction. Overall, this reviewdescribed the concept of advancements in surface interfacial interaction. Finally, challenges and perspectiveson future research are also provided.

Plasmonic Ag nanowires sensitized ZnO flake-like structures as a potential photoanode material for enhanced visible light water splitting activity

Sreedhar, Adem,Neelakanta Reddy, I.,Ta, Qui Thanh Hoai,Namgung, Gitae,Noh, Jin-Seo Elsevier 2019 Journal of Electroanalytical Chemistry Vol.832 No.-

<P><B>Abstract</B></P> <P>Silver nanowires (AgNWs) functionalized ZnO flake-like (ZnO/AgNWs) morphological heterostructures were developed as a promising photoanode by facile RF magnetron sputtering and polyol methods. Herein, we demonstrate the role of rationally tailored AgNWs weight concentration (0, 0.03, 0.05 and 0.07g) on ZnO flake-like morphology for enhanced visible-light-driven photoelectrochemical (PEC) water splitting activity. From XRD studies, ZnO (002) facets were effectively influenced by the selective growth of Ag (111) facets. Notably, XPS studies reveal the strong correlation between AgNWs and ZnO, showing a significant red shift in Zn 2p and O 1s levels and blue shift in Ag 3d level. Whereas, surface hydroxyl groups (OH<SUP>−</SUP>) were originated on ZnO/AgNWs heterostructure, which acts as light trapping states. Interestingly, FESEM images comprise AgNWs distribution on ZnO flake-like morphology, which suggests AgNWs are most accessible networks at the interface of ZnO. As a result, we observed significant variation in the optical transmittance and matching band gap for strong visible light absorption. In conclusion, selective growth of AgNWs-0.05g on ZnO promoted the strong interface reaction kinetics with impressive photoconversion efficiency (0.38%). Thus, developing of unique flake-like/nanowire morphological features underlined to be crucial interest in energy conversion applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Well-defined AgNWs based ZnO flake-like photoanodes reported for the first time. </LI> <LI> Surface interaction between AgNWs and ZnO serves as a key factor for PEC activity. </LI> <LI> Specific surface area of AgNWs achieved for superior visible light harvesting. </LI> <LI> ZnO/AgNWs (0.05g) photoanodes yielded 0.38% photoconversion efficiency. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Insight into anions and cations effect on charge carrier generation and transportation of flake-like Co-doped ZnO thin films for stable PEC water splitting activity

Sreedhar, Adem,Reddy, I. Neelakanta,Hoai Ta, Qui Thanh,Cho, Eunbin,Noh, Jin-Seo Elsevier 2019 Journal of Electroanalytical Chemistry Vol.855 No.-

<P><B>Abstract</B></P> <P>Developing a stable interface interaction between photoelectrode and electrolyte is crucial for achieving superior photoelectrochemical (PEC) water splitting activity. In this aspect, the contribution of anions and cations present in the electrolyte play a decisive role during its interaction with the solvent and surface functional groups on the developed photoelectrode, which greatly determine the charge carrier generation and transportation. Herein, we developed the flake-like Co (1.7 at.%)-doped ZnO (Co-ZnO) thin films by employing simultaneous RF and DC magnetron sputtering, which were post annealed at 250 °C for 2 h. The developed films were used to demonstrate the PEC activity under different aqueous electrolytes (KCl, KOH, NaOH, Na<SUB>2</SUB>SO<SUB>3</SUB> and Na<SUB>2</SUB>SO<SUB>4</SUB>). Most importantly, owing to the promising flake-like features of Co-ZnO, efficient electrode-electrolyte interface interaction has been achieved for stable and improved PEC activity. In turn, detailed PEC activity in KCl, KOH and NaOH electrolytes demonstrated that K<SUP>+</SUP> cations and OH<SUP>−</SUP> anions in KOH greatly influenced the photocurrents than KCl (Cl<SUP>−</SUP>) and NaOH (Na<SUP>+</SUP>) due to the high ionic conductive and diffusion properties. On the other hand, SO<SUB>3</SUB> <SUP>2−</SUP> (Na<SUB>2</SUB>SO<SUB>3</SUB>) anions tailor the charge carrier generation by the advantage of hole scavenging activity compared to SO<SUB>4</SUB> <SUP>2−</SUP> (Na<SUB>2</SUB>SO<SUB>4</SUB>). Comprehensively, our results provide new insight into the selection of aqueous electrolyte to improve the PEC water splitting activity through adopting the ionic conductivity and constructive interaction with photoelectrode.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Flake-like Co (1.7 at.%)-doped ZnO thin films were deposited by RF and DC sputtering. </LI> <LI> Surface interface interaction between Co-ZnO and aqueous electrolytes was explored. </LI> <LI> Ion conductive and diffusion properties highlighted stable and superior PEC activity. </LI> <LI> Photocurrents in KOH (2.3 × 10<SUP>−6</SUP> A/cm<SUP>2</SUP>) > NaOH (2.0 × 10<SUP>−6</SUP> A/cm<SUP>2</SUP>) > KCl (8.7 × 10<SUP>−7</SUP> A/cm<SUP>2</SUP>). </LI> <LI> Na<SUB>2</SUB>SO<SUB>3</SUB> acts as a hole scavenger for superior PEC activity than Na<SUB>2</SUB>SO<SUB>4</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>This study comprehensively explores the anions and cations effect on charge carrier generation and transportation of flake-like Co (1.7 at.%)-doped ZnO thin films for stable PEC water splitting activity under various aqueous electrolytes.</P> <P>[DISPLAY OMISSION]</P>