Excellent detection of H₂S gas at ppb concentrations using ZnFe₂O₄ nanofibers loaded with reduced graphene oxide

Van Hoang, Nguyen,Hung, Chu Manh,Hoa, Nguyen Duc,Van Duy, Nguyen,Park, Inkyu,Van Hieu, Nguyen Elsevier Sequoia 2019 Sensors and actuators. B Chemical Vol.282 No.-

<P><B>Abstract</B></P> <P>Cost-effective fabrication of sensors and detection of ultralow concentrations of toxic gases are important concerns for environmental monitoring. In this study, the reduced graphene oxide (RGO)-loaded ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofibers (ZFO-NFs) were fabricated by facile on-chip electrospinning method and subsequent heat treatment. The multi-porous NFs with single-phase cubic spinel structure and typical spider-net morphology were directly assembled on Pt-interdigitated electrodes. The diameters of the RGO-loaded ZFO-NFs were approximately 50–100 nm with many nanograins. The responses to H<SUB>2</SUB>S gas showed a bell-shaped behaviour with respect to RGO contents and annealing temperatures. The optimal values of the RGO contents and the annealing temperatures were found to be about 1.0 wt% and 600 °C, respectively. The response of the RGO-loaded ZnFe<SUB>2</SUB>O<SUB>4</SUB> NFs to 1 ppm H<SUB>2</SUB>S gas was as high as 147 at 350°C while their cross-gas responses to SO<SUB>2</SUB> (10 ppm), NH<SUB>3</SUB> (100 ppm), H<SUB>2</SUB> (250 ppm), C<SUB>3</SUB>H<SUB>6</SUB>O (1000 ppm), and C<SUB>2</SUB>H<SUB>5</SUB>OH (1000 ppm) were rather low (1.8−5.6). The high sensor response was attributed to formation of a heterojunction between RGO and ZnFe<SUB>2</SUB>O<SUB>4</SUB> and due to the fact that NFs consisted of many nanograins which resulted in multi-porous structure and formation of potential barriers at grain boundaries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> rGO-loaded ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofibers have simply prepared by electrospinning. </LI> <LI> rGO-loaded ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofiber sensors can detect H<SUB>2</SUB>S gas down to ppb level. </LI> <LI> The loading rGO can result in an enhancement of H<SUB>2</SUB>S gas ensing performance. </LI> </UL> </P>

A facile thermal evaporation route for large-area synthesis of tin oxide nanowires: Characterizations and their use for liquid petroleum gas sensor

Nguyen Van Hieu,Le Thi Ngoc Loan,Nguyen Duc Khoang,Nguyen Tuan Minh,Do Thanh Viet,Do Cong Minh,Tran Trung,Nguyen Duc Chien 한국물리학회 2010 Current Applied Physics Vol.10 No.2

In this paper, a very simple procedure was presented for the reproducible synthesis of large-area SnO2nanowires (NWs) on a silicon substrate by evaporating Sn powders at temperatures of 700, 750, and 800 ℃. As-obtained SnO2 NWs were characterized by field emission scanning electron microscopy (FESEM),transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy. They revealed that the morphology of the NWs is affected by growth temperature and the SnO2 NWs are single-crystalline tetragonal. The band gap of the NWs is in the range of 4.2–4.3 eV as determined from UV/visible absorption. The NWs show stable photoluminescence with an emission peak centered at around 620 nm at room-temperature. The sensors fabricated from the SnO2 NWs synthesized at 700 ℃ exhibited good response to LPG (liquefied petroleum gas) at an operating temperature of 400 ℃.

Analytical Asymptotic Expressions for the Green’s Function of the Electron in a Single-Level Quantum Dot at the Kondo and the Fano Resonances

Nguyen Van Hieu,Nguyen Bich Ha,V. P. Gerdt,O. Chuluunbaatar,A. A. Gusev,Yu. G. Palii,Nguyen Van Hop 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6

The Kondo and the Fano resonances in the two-point Green’s function of the single-level quantum dot were found and investigated in many previous works by means of different numerical calculation methods. In this report, we present a derivation of the analytical forms of the resonance terms in the expression of the two-point Green’s function. For that purpose, the system of Dyson equations for the two-point nonequilibrium Green’s functions in the complex-time Keldysh formalism was established to the second order in the tunneling coupling constants with the mean field approximation for the statistical averages of the products of four electron creation and destruction operators. This system of Dyson equations was solved exactly by means of the computer algebra and the analytical expressions for the resonance terms are derived. The conditions for the existence of the Kondo or the Fano resonances were found.

Determinants Influencing Housing-Option Decision of Gen Y: The Case of Vietnam

Ha Thu LUONG(Ha Thu LUONG ),Dung Manh TRAN(Dung Manh TRAN ),Dan Linh Ngoc NGUYEN(Dan Linh Ngoc NGUYEN ),Van Bao NGUYEN(Van Bao NGUYEN ),Anh Thuc LE(Anh Thuc LE ),Hieu Van PHAM(Hieu Van PHAM ) 한국유통과학회 2023 유통과학연구 Vol.21 No.7

An innovative method to improve the performance of Extended Kalman filter for system identification

Nguyen Van Hieu,Lee Jin Ho 대한토목학회 2022 대한토목학회 학술대회 Vol.2022 No.10

<i>In situ</i> growth of flower-like V₂O₅ arrays on graphene@nickel foam as high-performance electrode for supercapacitors

Van Hoa, Nguyen,Quyen, Tran Thi Hoang,Nghia, Nguyen Huu,Van Hieu, Nguyen,Shim, Jae-Jin Elsevier 2017 Journal of alloys and compounds Vol.702 No.-

<P><B>Abstract</B></P> <P>Hierarchical flower-like V<SUB>2</SUB>O<SUB>5</SUB> growth on graphene and nickel foam electrodes was fabricated by using chemical vapor deposition and hydrothermal methods for electrochemical capacitors. Taking advantages of the high conductivity of graphene, high capacitance of well-defined V<SUB>2</SUB>O<SUB>5</SUB> flower-like structure and open framework of three-dimensional nickel foam, the resulting electrodes exhibited rapid electron and ion transport, large electroactive surface area, and excellent structural stability. The specific capacitance was as high as 1235 F g<SUP>−1</SUP> at a current density of 2 A g<SUP>-1</SUP>, suggesting its potential as a high performance electrode for supercapacitors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hierarchical flower-like V2O5/graphene/nickel foam electrodes was fabricated. </LI> <LI> The electrodes exhibited rapid electron and ion transport, large electroactive surface area. </LI> <LI> The specific capacitance was as high as 1235 A g−1 at a current density of 2 A g−1. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Numerical simulation-based performance improvement of the separation of circulating tumor cells from bloodstream in a microfluidic platform by dielectrophoresis

Nguyen Ngoc-Viet,Van Manh Hoang,Van Hieu Nguyen 한국유변학회 2022 Korea-Australia rheology journal Vol.34 No.4

Circulating tumor cells (CTCs) detection has become one of the promising solutions for the early diagnosis of cancers. Thus, the separation of CTCs is of great importance in biomedical applications. In addition, microfluidic technology has been an attractive approach to the manipulation of biological cells. This study presents the parametric investigations relevant to the volumetric throughput of a microfluidic platform with the dielectrophoresis (DEP)-based cell manipulation technique for the continuous CTCs separation. A low potential voltage at an appropriate frequency was applied to slanted planar electrodes to separate CTCs from normal cells in blood samples due to mainly the cell size difference. The performance of the separation process was analyzed by evaluating the cell trajectories, purity, and recovery rates. Several inlet flow rates of buff er and cell sample fluid streams were examined. Various channel configurations with different outlet and height dimensions were also investigated to enhance the isolation of CTCs. During the simulation, the size and shape of cells were assumed as fixed-sized, solid spheres. The results showed that CTCs could be separated from blood cells, including white blood cells (WBCs), red blood cells (RBCs), and platelets (PLTs) with recovery and purity factors up to 100% at the cell sample throughput of 10 μL/ min by utilizing a suitable microchannel design. The current study significantly contributes valuable insights into the design of the microchip devices to effectively and selectively isolate different cancerous cells in biofluids.

Television Programs for the Youth in Vietnam (A View from Popular Culture) -Case Study of Reality Show “So You Think You Can Dance” Broadcasted by HCMC Television Station-

( Nguyen Van Hieu ),( Truong Van Minh ) 전북대학교 인문학연구소 2014 건지인문학 Vol.11 No.-

This study is to investigate the relationship between TV and popular culture by analyzing a TV program on HTV targeting young people, on the basis of a recent study of the HTV(HCM Television Station), Vietnamese broadcasting company targeting young people. Also, it studies Vietnamese young generation`s desire of culture and characteristics of their acceptance. Vietnamese TV has made very meaningful advancement since 1997. Appearance and popularity of a reality show entitled "So You Think You Can Dance", to be intensively analyzed in this research, is also placed amid this process. From the 1990s, especially from 1997 when Vietnamese government began to announce policies which emphasize socialization of medicine, culture and education, Vietnamese TV met transition period, and particularly development of programs targeting young generation was conspicuous. This phenomenon became a sign of showing association between TV and development of popular culture in Vietnam. And at the same time, this is showing strong integration with the whole world appeared in the stream of Vietnamese globalization. Young people show their own characteristic evidently in their communication mode and messages they accept from TV programs. They are not controlled by unclear messages and have their own thought clearly in watching programs which include the aim at true values, so-called "goodness and beauty", giving them strong messages and coming up to their expectations.

Gas sensor based on nanoporous hematite nanoparticles: Effect of synthesis pathways on morphology and gas sensing properties

Nguyen Duc Cuong,Tran Thai Hoa,Dinh Quang Khieu,Nguyen Duc Hoa,Nguyen Van Hieu 한국물리학회 2012 Current Applied Physics Vol.12 No.5

The development of a low cost and scalable gas sensor for the detection of toxic and flammable gases with fast response and high sensitivity is extremely important for monitoring environmental pollution. In this work, we introduce two different synthesis pathways for the preparation of scalable Fe2O3nanoparticles for gas sensor applications. One is co-precipitation and the other is hydrothermal method. The gas sensing properties of the a-Fe2O3 nanoparticles (NPs) fabricated by different synthesis pathways were studied and compared. The performance of the NPs in the detection of toxic and flammable gases such as carbon dioxide, ammonia, liquefied petroleum gas, ethanol, and hydrogen was evaluated. The Fe2O3 NP-based gas sensors exhibited high sensitivity and a response time of less than a minute to analytic gases. However, the NPs fabricated by the one-step direct method exhibited higher sensitivities than those generated by the a-Fe2O3 NPs obtained by co-precipitation synthesis possibly because of their nanoporous structure. This performance is attributed to the large specific surface area of the NPs, which results in higher sensitivity. The development of a low cost and scalable gas sensor for the detection of toxic and flammable gases with fast response and high sensitivity is extremely important for monitoring environmental pollution. In this work, we introduce two different synthesis pathways for the preparation of scalable Fe2O3nanoparticles for gas sensor applications. One is co-precipitation and the other is hydrothermal method. The gas sensing properties of the a-Fe2O3 nanoparticles (NPs) fabricated by different synthesis pathways were studied and compared. The performance of the NPs in the detection of toxic and flammable gases such as carbon dioxide, ammonia, liquefied petroleum gas, ethanol, and hydrogen was evaluated. The Fe2O3 NP-based gas sensors exhibited high sensitivity and a response time of less than a minute to analytic gases. However, the NPs fabricated by the one-step direct method exhibited higher sensitivities than those generated by the a-Fe2O3 NPs obtained by co-precipitation synthesis possibly because of their nanoporous structure. This performance is attributed to the large specific surface area of the NPs, which results in higher sensitivity.

Detection of pathogenic microorganisms using biosensor based on multi-walled carbon nanotubes dispersed in DNA solution

Nguyen Thi Thuy,Phuong Dinh Tam,Mai Anh Tuan,Anh-Tuan Le,Le Thi Tam,Vu Van Thu,Nguyen Van Hieu,Nguyen Duc Chien 한국물리학회 2012 Current Applied Physics Vol.12 No.6

The present paper introduces a facile and cost-effective route for the direct dispersion of multi-walled carbon nanotubes (MWCNTs) in DNA solution. Their application in detecting Escherichia coli O157:H7using DNA biosensorwas demonstrated. The dispersion state of theMWCNTswas characterized via UVeVis spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy. The interaction between DNA sequence and the MWCNTs was investigated using Raman spectroscopy and Fourier transform infrared spectroscopy. As-obtainedMWCNT solutionwas used in the preparation of DNA sensor. Results revealed that the developed DNA sensor can detect a DNA target as low as 1 nM in a buffer solution. The sensitivity of the DNA sensor reached approximately 0.19 nM/mV. The effect of dispersion parameters, including pH values, DNA concentration, ion strength, and sonication time, on sensor response was also studied. TheDNA sensor can respondwell to 120 min of sonication time, a pH value of 9, and 20 mM of DNA sequence concentration. The results of the present study showed a potential application of the DNA sensor in the detection of Escherichia coli O157:H7.