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( Chundi Seshendra Reddy ),( Maddaka Reddeppa ),권빈희,박성민,인인식 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
Pure and N-GQDs (Nitrogen doped graphene quantum dots) incorporated SnO<sub>2</sub> nanotubes (NTs) were fabricated by a one-step electrospinning method. The structure, morphology, chemical state and specific surface area were analyzed. The SnO<sub>2</sub> nanotubes consists of tens of thousands of SnO<sub>2</sub> nanoparticles with an ultra-small grain size. The as-synthesized pure and N-GQDs incorporated SnO<sub>2</sub> nanotubes were used to fabricate gas sensor. It was found that the gas response toward 100 ppm of ammonia was improved from 6.48 to 82.44 at room temperature, through the activation by N-GQDs. And the results indicate that the sensor based on N-GQDs incorporated SnO<sub>2</sub> not only has ultrahigh sensitivity but also possesses good response-recovery properties, linear dependence, repeatability, selectivity and long-term stability, demonstrating the potential to use N-GQDs incorporated SnO<sub>2</sub> nanotubes as ammonia gas sensors. ** 2019년 한국교통대학교 지원을 받아 수행하였음.
( Chundi Seshendra Reddy ),( Akepati Sivasanakara Reddy ),권빈희,박성민,인인식 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
The effect of graphene oxide (GO) on the ethanol sensing and photodetector performance of SnO<sub>2</sub> nanotubes (NTs) were studied. Pristine SnO<sub>2</sub> NTs were produced via electrospinning method, whereas GO-SnO<sub>2</sub> NTs were produced by dipping SnO<sub>2</sub> NTs in a GO solution with a suitable annealing. The pristine and GO-SnO<sub>2</sub> NTs showed higher response, towards ethanol gas compared to other gases with an optimum working temperature of 300°C. Integration of GO on the surface of SnO<sub>2</sub> NTs can be a suitable method to enhance the sensing performance. Then, pure and doped SnO<sub>2</sub> nanotubes based photodetectors were constructed, GO-SnO<sub>2</sub> NTs exhibits good quantum efficiency and short response time compare with pristine SnO<sub>2</sub> nanotubes. The high performance of the doped SnO<sub>2</sub> nanotubes can be attributed to the perfect crystallinity and the special GO-embedded structure. ** 2019년 한국교통대의 지원을 받아 수행하였음.
Chundi Seshendra Reddy,A. Sivasankar Reddy,P. Sreedhara Reddy 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.1
La0.7Ba0.3MnO3 (LBMO) thin films were deposited on Si substrates at various substrate temperatures (Ts) ranging from 823 K to 1023 K using electron beam evaporation (EBE), and studied the structural, composition and electrical properties of the films as a function of deposition temperature were studied. X-ray diffraction (XRD) studies revealed the epitaxial growth in the films. The surface morphology of the films were characterized by atomic force microscopy (AFM). The elemental composition analysis investigated by energy dispersive spectroscopy (EDS) confirmed the stoichiometry. The films deposited at higher substrate temperatures (1023 K), showed lower resistivity with a higher temperature coefficient of resistance (TCR). A TCR of 4.09%/K obtained in the present investigation is suitable for bolometric applications near to the room temperature.
Chundi Seshendra Reddy,Liwen Zhang,Yejun Qiu,Yanan Chen,A. Sivasankar Reddy,P. Sreedhara Reddy,Sreekantha Reddy Dugasani 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.63 No.-
Graphene-based device/sensor made of multifunctional nanomaterials is an emerging technology due to its huge impact on the engineering materials. Herein, we report the synthesis of pristine SnO2, Al-doped SnO2 (Al–SnO2), and graphene-embedded Al–SnO2 (G–Al–SnO2) nanotubes by one-step electrospinning method and studied their physical and gas sensing characteristics. The synthesized tubular structure was confirmed by scanning electron microscope (SEM) and transmission electron microscope (TEM). Structural, chemical binding, pore size, and chemical composition/elemental states were estimated by the X-ray diffraction, Raman, BET, and X-ray photoelectron spectroscopy, respectively. The performance of the gas sensing based on SnO2, Al–SnO2, and G–Al–SnO2 materials for H2 detection was investigated, and the G–Al–SnO2 composite nanotubes exhibit the superior sensitivity at 300 °C. The sensing response reaches about 23.8 at H2 concentration of 100 ppm with a shorter response time of about 2.2 s and recovery time of about 1.4 s. The gas sensing performance of the G–Al–SnO2 nanotubes is much better than that of the pristine SnO2 and Al–SnO2 nanotubes, which is probably attributed to the relatively smaller diameter of about 100 nm, better thermal and electronic conductivity, and relatively high oxygen vacancy, induced by graphene and Al-doping. The prepared H2 sensor is a simple, compact and highly sensitive, which holds high promising in many fields.
TiO<sub>2</sub>-GQDs Nanocomposite for Room Temperature NO Gas Sensing under UV Light Irradiation
( Guntakrinda Murali ),( Chundi Seshendra Reddy ),권빈희,박성민,인인식 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
Nitric oxide (NO) gas sensor has garnered extensive interest considering the NO gas adverse effects on environment and human health. Metal oxides require a high temperature to accelerate the gas interaction with the oxide surface, which is not adequate while detecting the flammable analytes. UV light illumination is observed to enhance the gas interaction with the oxide similar to thermal energy. In this study, we employed UV photoconductive graphene quantum dots(GQDs) and N-doped GQDs(NGQDs) to enhance the room temperature NO gas sensing of TiO<sub>2</sub> nanoplates. In the dark, TiO<sub>2</sub>-GQDs and TiO<sub>2</sub>-NGQDs exhibited 3 and 4 folds response increment to NO gas compared to TiO<sub>2</sub> nanoplates, respectively. Under the UV illumination, TiO<sub>2</sub>-GQDs and TiO<sub>2</sub>-NGQDs exhibited further increased NO gas response, 2 and 3 times higher response is noted compared to their response in the dark, respectively. The TiO<sub>2</sub>-NGQDs sensor shows good selectivity to NO gas. ** 2019년 한국교통대학교 지원을 받아 수행하였음.
Polarized Upconversion Emission from One-dimensional Ultrathin YF3:Yb/Er Nanostructures
( Guntakrinda Murali ),( Chundi Seshendra Reddy ),권빈희,박성민,인인식 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
Upconversion (UC) nanostructures have attracted enormous research interests due to their unique optical properties underpinning their promising applications in various fields. In the present study, ultrathin YF3 nanostructures such as nanowires and nanobelts are synthesized using an oleylamine assisted colloidal chemical strategy. Two-dimensional lamellar assemblies of YF3 clusters are observed to be crucial intermediates in the growth process, which transform to nanobelts and nanowires depending on the reaction temperature. Both ultrathin nanowires and nanobelts exhibited an identical UC emission profiles comprising three emission bands centered at 545 nm (green), 660 nm (red) and 810 nm (infrared). The polarized UC emission studies on the domain of perfectly aligned assembly of parallel ultrathin YF<sub>3</sub>:Yb/Er nanowires revealed 0.32, 0.28 and 0.50 polarization degrees for green, red and infrared emission peaks, respectively. ** 2019년 한국교통대의 지원을 받아 수행하였음.