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Huy, Bui The,Gerelkhuu, Zayakhuu,Chung, Jong Won,Dao, Van-Duong,Ajithkumar, Gangadharan,Lee, Yong-Ill Elsevier 2017 Materials science and engineering B. Advanced Func Vol.223 No.-
<P>Cr3+-doped Nalm(0.70-x)Gd(0.10)F(4):Yb0.18Er0.02Crx nanoparticles were synthesized by one step solvothermal method. The structural, emission properties were studied by XRD, FT-IR, emission spectra. The doping of 15 mol% Cr3+ into NaLu0.70-xGd0.10F4:Yb0.18Er0.02Crx induced cubic-hexagonal phase transition, with a consequent 20 times improvement in the upconversion fluorescence quantum yield. The roles of Cr3+ in the phase transition as well as the mechanism of the multi-photon upconversion process in the material were discussed. The Yb3+-Cr3+ dimer could play the role of as a sensitizer by transferring energy to Er3+. The Cr3+ ions result an asymmetry in the environment surrounding the rare-earth ions, which would favor the hypersensitive transitions. This research may open up a new perspective to prepare high upconversion luminescent materials. (C) 2017 Elsevier B.V. All rights reserved.</P>
Development of a simple method for sensing melamine by SERS effect of Ag particles
Huy, Bui The,Pham, Quoc-Thai,An, Nguyen Thi Thai,Conte, Eric,Lee, Yong-Ill Elsevier 2017 Journal of luminescence Vol.188 No.-
<P><B>Abstract</B></P> <P>A simple and inexpensive procedure for melamine sensing based on surface-enhanced Raman scattering (SERS) of Ag particles was developed. The controllable shape of Ag particles was performed using co-precipitate at room temperature without surfactant. SERS signals were obtained due to the melamine were directly adsorbed on Ag particles without substrate. The enhancement factor of SERS effect depended on the architectural form of Ag particles. Among the three types of Ag nanostructures, the raspberry-like Ag sample displayed the strongest signal. The proposed probe exhibits great potential for melamine detecting and good reproducibility (the relative standard deviation (RSD) =3.7%).</P>
Huy, Bui The,Kumar, Avvaru Praveen,Seo, Min-Ho,Kim, Jan-Di,Lee, Yong-Ill American Scientific Publishers 2014 Journal of Nanoscience and Nanotechnology Vol.14 No.10
<P>Highly luminescent CdTe quantum dots (QDs) were synthesized through a co-precipitation route in aqueous salt solutions using different thiols as stabilizers. The synthetic procedure was simple, efficient, and stable. It could also allow controlling the emission wavelength by varying the experimental conditions such as reaction time and pH values. The strong luminescence of the QDs was observed under UV-excitation and emission colors could be adjusted. The interaction between CdTe QDs and triethylenetetramine dihydrochloride (TETA) which is a candidate treatment for diabetic cardiovascular complication was investigated by fluorescence spectroscopy. Based on the quenching effect on CdTe photoluminescence intensity by TETA, a simple assay system for analyzing the content of TETA in aqueous samples was developed. The linearity was maintained in the range of 0.2 μM to 1.2 μM (R2 = 0.994) with a limit of detection (LOD; S/N = 3) at 28 nM. The results showed that CdTe QDs capped with diverse thiols has a potential for the quantitative analysis of TETA in urine samples.</P>
Huy, Bui The,Jung, Da-som,Kim Phuong, Nguyen Thi,Lee, Yong-Ill Elsevier 2017 CHEMOSPHERE - Vol.184 No.-
<P><B>Abstract</B></P> <P>A novel TiO<SUB>2</SUB>@MgO-Fe<SUB>2</SUB>O<SUB>3</SUB> core-shell structure has been synthesized <I>via</I> a hydrolysis and co-precipitation method followed by calcination at 500 °C and has proven to be an efficient photocatalyst. The obtained TiO<SUB>2</SUB>@MgO-Fe<SUB>2</SUB>O<SUB>3</SUB> core-shell was characterized by scanning electron microscopy, X-ray diffraction, and UV–Vis diffused reflectance techniques. Its photocatalytic activity toward 2,4-dichlorophenoxyacetic acid (2,4-D) was investigated in aqueous solutions with and without visible light irradiation in the presence and absence of hydrogen peroxide. It was revealed that a strong electronic coupling exists between two components within the TiO<SUB>2</SUB>@MgO-Fe<SUB>2</SUB>O<SUB>3</SUB> core-shell structure. The present findings clearly highlight that TiO<SUB>2</SUB>@MgO-Fe<SUB>2</SUB>O<SUB>3</SUB> exhibits excellent photocatalytic activity under visible light irradiation in the presence of H<SUB>2</SUB>O<SUB>2</SUB>. More than 83% degradation of 2,4-D was observed within 240 min, at an initial concentration of 100 mg L<SUP>−1</SUP> with 0.5 g of catalyst per liter. Moreover, the material showed high chemical stability after four consecutive experiments with no significant difference in the rate of photocatalytic degradation. Therefore, the results reported herein offer a green, low cost and highly efficient photocatalyst for environmental remediation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A strong electronic coupling between components within TiO<SUB>2</SUB>@MgO-Fe<SUB>2</SUB>O<SUB>3</SUB> structure. </LI> <LI> Effective transfer of the photogenerated e<SUP>−</SUP> and h<SUP>+</SUP>at the heterojunction interface. </LI> <LI> TiO<SUB>2</SUB>@MgO-Fe<SUB>2</SUB>O<SUB>3</SUB> showed excellent photodegradation of 2,4-D in the presence of H<SUB>2</SUB>O<SUB>2</SUB>. </LI> </UL> </P>
A Vapor Sensor Based on a Porous Silicon Microcavity for the Determination of Solvent Solutions
Huy Bui,Thuy Van Nguyen,The Anh Nguyen,Thanh Binh Pham,Quoc Trung Dang,Thuy Chi Do,Quang Minh Ngo,Roberto Coisson,Van Hoi Pham 한국광학회 2014 Current Optics and Photonics Vol.18 No.4
A porous silicon microcavity (PSMC) sensor has been made for vapors of solvent solutions, and a method has been developed in order to obtain simultaneous determination of two volatile substances with different concentrations. In our work, the temperature of the solution and the velocity of the air stream flowing through the solution have been used to control the response of the sensor for ethanol and acetone solutions. We study the dependence of the cavity-resonant wavelength shift on solvent concentration, velocity of the airflow and solution temperature. The wavelength shift depends linearly on concentration and increases with solution temperature and velocity of the airflow. The dependence of the wavelength shift on the solution temperature in the measurement contains properties of the temperature dependence of the solvent vapor pressure, which characterizes each solvent. As a result, the dependence of the wavelength shift on the solution temperature discriminates between solutions of ethanol and acetone with different concentrations. This suggests a possibility for the simultaneous determination of the volatile substances and their concentrations.
The Impact of COVID-19 Pandemic on Firm Performance: Empirical Evidence from Vietnam
BUI, Trung Huy,NGUYEN, Huong Thu,PHAM, Yen Nhu,NGUYEN, Trang Thu Thi,LE, Linh Thao,LE, Giang Thu Tran Korea Distribution Science Association 2022 The Journal of Asian Finance, Economics and Busine Vol.9 No.7
The outbreak of Coronavirus disease 2019 (COVID-19) has caused serious impacts not only on human health but also on the economies around the world. Enterprises play an important role in the development of every country but it is also one of the most affected sectors during the pandemic. Drawing on panel data of 131 enterprises listed on the Vietnamese stock exchange from 2016Q1 to 2021Q3, this study aims to investigate the impact of the COVID-19 pandemic on firm performance. Enterprises are classified into seven industries including Agriculture, Material, Industry, Real estate and Construction, Energy, Consumer, and Service. The paper also analyzes the variation of the effects among companies, focusing on differences in revenue and capital structure. The results show that the COVID-19 pandemic negatively affects business performance. In addition, the empirical findings indicate that revenue and debt decreasing can cause deterioration of firm performance during the pandemic period. The decrease in revenue has a direct impact on firm profitability. The reduction of debt levels affects the corporate leverage leading to adverse effects on firm performance. The negative effect is more pronounced for companies in some specific sectors including industry, real estate, construction, consumption, and services.
Photoluminescence spectroscopy of Cd-based quantum dots for optosensing biochemical molecules
Huy, Bui The,Kim Phuong, Nguyen Thi,Nguyen, Thu-Thuy T.,Lee, Yong-Ill Taylor Francis 2018 Applied spectroscopy reviews Vol.53 No.2
<P>The size-dependent properties of optical quantum dots (QDs), such as broad excitation spectra; narrow, tunable, and symmetric emission spectra; and high resistance to photo-bleaching lead them to be a promising candidate for optosensing diverse targets, including metal ions, drugs, biochemical compounds, and pathogenic bacteria. Here, we report on the recent developments of synthetic and functionalized methods for preparing cadmium (Cd)-based QDs. We discuss their surface modification and toxicity. In particular, we focus on how optosensing techniques have progressed for biochemical analysis using Cd-based QDs over the years.</P>