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Quang Dang, Vinh,Kim, Do-Il,Thai Duy, Le,Kim, Bo-Yeong,Hwang, Byeong-Ung,Jang, Mi,Shin, Kyung-Sik,Kim, Sang-Woo,Lee, Nae-Eung RSC Pub 2014 Nanoscale Vol.6 No.24
<P>Piezoelectric coupling phenomena in a graphene field-effect transistor (GFET) with a nano-hybrid channel of chemical-vapor-deposited Gr (CVD Gr) and vertically aligned ZnO nanorods (NRs) under mechanical pressurization were investigated. Transfer characteristics of the hybrid channel GFET clearly indicated that the piezoelectric effect of ZnO NRs under static or dynamic pressure modulated the channel conductivity (σ) and caused a positive shift of 0.25% per kPa in the Dirac point. However, the GFET without ZnO NRs showed no change in either σ or the Dirac point. Analysis of the Dirac point shifts indicated transfer of electrons from the CVD Gr to ZnO NRs due to modulation of their interfacial barrier height under pressure. High responsiveness of the hybrid channel device with fast response and recovery times was evident in the time-dependent behavior at a small gate bias. In addition, the hybrid channel FET could be gated by mechanical pressurization only. Therefore, a piezoelectric-coupled hybrid channel GFET can be used as a pressure-sensing device with low power consumption and a fast response time. Hybridization of piezoelectric 1D nanomaterials with a 2D semiconducting channel in FETs enables a new design for future nanodevices.</P>
Dang, Quang Vinh,Dao, Hung Cuong,Nguyen, Thuong Korean Chemical Society 2011 대한화학회지 Vol.55 No.6
Surveys on the process of extracting acid from dried rinds of Garcinia oblongifolia Champ. ex Benth (G. oblongifolia) using microwave in terms of time, machine power and solid/liquid rate, have resulted in such findings as: the best time allocation for extracting is 25 minutes; machine power works best at level 2 (microwave power is 400 W); suitable rate of solid/liquid is 0.071 (approximately 150 mL solvent per 10 g of sample). The total amounts acid and (-)-hydroxycitric acid extracted from 100 g dried rinds of G. oblongifolia are 18.592 g and 10.137g respectively. This is the first finding on extraction of (-)-HCA from dried rinds of G. oblongifolia using microwave.
Dang, Vinh Quang,Trung, Tran Quang,Duy, Le Thai,Kim, Bo-Yeong,Siddiqui, Saqib,Lee, Wonil,Lee, Nae-Eung American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.20
<P>A flexible ultraviolet (UV) photodetector based on ZnO nanorods (NRs) as nanostructure sensing materials integrated into a graphene (Gr) field-effect transistor (FET) platform is investigated with high performance. Based on the negative shift of the Dirac point (<I>V</I><SUB>Dirac</SUB>) in the transfer characteristics of a phototransistor, high-photovoltage responsivity (<I>R</I><SUB>V</SUB>) is calculated with a maximum value of 3 × 10<SUP>8</SUP> V W<SUP>–1</SUP>. The peak response at a wavelength of ∼365 nm indicated excellent selectivity to UV light. The phototransistor also allowed investigation of the photocurrent responsivity (<I>R</I><SUB>I</SUB>) and photoconductive gain (<I>G</I>) at various gate voltages, with maximum values of 2.5 × 10<SUP>6</SUP> A W<SUP>–1</SUP> and 8.3 × 10<SUP>6</SUP>, respectively, at a gate bias of 5 V. The UV response under bending conditions was virtually unaffected and was unchanged after 10 000 bending cycles at a bending radius of 12 mm, subject to a strain of 0.5%. The attributes of high stability, selectivity, and sensitivity of this flexible UV photodetector based on a ZnO NRs/Gr hybrid FET indicate promising potential for future flexible optoelectronic devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-20/acsami.5b02834/production/images/medium/am-2015-028343_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b02834'>ACS Electronic Supporting Info</A></P>
Dang, Vinh Quang,Byun, Minseop,Kang, Junjie,Kim, Chaehyun,Jung, Pil-Hoon,Kim, Yang-Doo,Lee, Nae-Eung,Lee, Heon Elsevier 2017 Organic Electronics Vol.50 No.-
<P><B>Abstract</B></P> <P>Our cost-effective approach for hybridizing methylammonium lead iodide and PbS nanoparticles at low temperature (≤100 °C) for photovoltaic devices is introduced. As employed into a perovskite based solar cell platform, effects of PbS on the device performance were investigated. Through experimental observations under simulated air-mass 1.5G illumination (irradiation intensity of 100 mWcm<SUP>−2</SUP>), the efficiency of a perovskite:PbS device is 11% higher than that of a pristine perovskite solar cell under the same fabrication conditions as a result of the broadened absorption range in the infrared region. The highest photovoltaic performance was observed at a PbS concentration of 2% with an open-circuit voltage, short-circuit current density, fill factor, and power-conversion efficiency of 0.557 V, 22.841 mA cm<SUP>−2</SUP>, 0.55, and 6.99%, respectively. Furthermore, PbS NPs could induce hydrophobic modification of the perovskite surface, leading to an improvement of the device stability in the air. Finally, the low-temperature and cost-effective fabrication process of the hybrid solar cells is a good premise for developing flexible/stretchable cells as well as future optoelectronic devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The current density of a pervoskite solar cell got improved by adding PbS NPs due to the widening light absorption. </LI> <LI> With 2% NPs in the active channel, the efficiency of a perovskite:PbS solar cell was about 11% higher than that without PbS NPs. </LI> <LI> Pervoskite:PbS solar cells were more stable in air than ones with only pervoskite. </LI> <LI> The low-temperature fabrication approach is potential to develop wearable solar cells and other applications at low cost. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Solar cells using perovskite:PbS as a co-absorber layer exhibited a higher performance than those using only perovskite. The IR absorption property of PbS NPs widened the absorption range of active materials from the visible region to the IR region, enhancing the current density and the efficiency. More importantly, PbS NPs induced hydrophobic modification on the perovskite surface, causing the co-sensitizer perovskite:PbS device to perform more stably in air. The cell-fabrication process was carried-out at low-temperature that enables the low-cost devices and widen the practical applications.</P> <P>[DISPLAY OMISSION]</P>
Anh Linh Dang,Tuyen Quang Nguyen,Tri Thien Cao,Vinh Quang Dinh,Vinh Dinh Nguyen 제어로봇시스템학회 2021 제어로봇시스템학회 국제학술대회 논문집 Vol.2021 No.10
Traffic detection is a topic of great interest in recent years due to a high demand for better traffic detection systems. Existing traffic detection algorithms work well under ideal driving conditions, however their performance decreases under difficult conditions such as insufficient lighting and illumination. Recently, local patterns have been successfully applied in order to handle complex texture conditions, such as stereo matching, and texture classification. We propose a method that applies Local Tetra Pattern for data preprocessing, so as to improve the performance of deep learning models under said conditions. Our approach achieved better performance than the original raw-models while the changes in inference time are maintained within a negligible interval. By fusing local patterns and raw images, the model gains an acquisition of discriminative information in regions that are highly similar. In challenging conditions, these kinds of information are essential for the model to recover its consciousness of concerned objects which cause many re-cognitional obstructions. Experimental results show a percentage as high as 35.847%, an increase of 12.575% in comparison with the original result on the SKKU data set.
An Omnidirectionally Stretchable Photodetector Based on Organic–Inorganic Heterojunctions
Trung, Tran Quang,Dang, Vinh Quang,Lee, Han-Byeol,Kim, Do-Il,Moon, Sungjin,Lee, Nae-Eung,Lee, Hoen American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.41
<P>Omnidirectionally stretchable photodetectors are limited by difficulties in designing material and fabrication processes that enable stretchability in multiaxial directions. Here, we propose a new approach involving an organic inorganic p-n heterojunction photodetector comprised of free-standing ZnO nanorods grown on a poly(3,4ethylenedioxythiophene)-polystyrene sulfonate transport layer coated on a three-dimensional micropatterned stretchable substrate containing bumps and valleys. This structure allows for efficient absorption of stretching strain. This approach allows the device to accommodate large tensile strain in all of the directions. The device behaves as a photogated p-n heterojunction photodetector in which current modulation was obtained by sensing the mechanisms that rely on photovoltage and photogating effects. The device exhibits a high photoresponse to UV light and reliable electrical performance under applied stretching in uniaxial and omniaxial directions. Furthermore, the device can be easily and conformally attached to a human wrist. This allowed us to investigate the response of the device to UV light during human activity.</P>