Publications

 

(116) Advanced Electronic Materials, 10, 39687-39692 (Q1, IF = 6.593)  

116
Synthesis of 5-hydroxymethylfurfural from monosaccharides catalyzed by superacid VNU-11–SO4 in 1-ethyl-3-methylimidazolium chloride ionic liquid 
 
Linh Ho Thuy Nguyen, Huong Thi Vo, Ha Bich Phan, Minh Huy Dinh Dang, Tan Le Hoang Doan and  Phuong Hoang Tran
 
Abstract: Superacid VNU-11–SO4, a modified metal–organic framework by post-synthetic treatment with a sulfuric acid solution, has been considered as a promising heterogeneous catalyst in the isomerization of glucose to fructose and further dehydration to form 5-hydroxymethylfurfural (HMF) due to its possession of both Lewis and Brønsted acid sites. In this work, we focused on using VNU-11–SO4 for the optimization of the conversion of fructose and glucose into HMF using an ionic liquid as a green solvent. The highest yields of HMF from glucose and fructose could be obtained in 28% (140 °C, 8 h) and 86% (110 °C, 3 h), respectively, with the use of VNU-11–SO4 catalyst in 1-ethyl-3-methylimidazolium chloride ionic liquid. Recycling examination of the catalyst showed only a slight decrease in the HMF yield, implying its potential industrial application in biomass transformation.
 

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(115) Applied Surface Science, 537, 148000 (Q1, IF = 6.707)  

129
Improving memory performance of PVA:ZnO nanocomposite: The experimental and theoretical approaches
 
Nhu Phuong Le Pham Quynh, Tu Uyen Doan Thi, Kim My Tran, Hoang Nam Vu, Hanh Kieu Thi Ta, Cao Vinh Tran, Thang Bach Phan, Ngoc Kim Pham
 
Abstract: The interactions between organic and inorganic components of nanocomposites plays a key role in their microstructure and optoelectrical properties. The comprehensive understanding of these interactions can promote various potential applications of materials, especially in the field of electronic memory devices. In this study, we investigate the interactions of polyvinyl alcohol (PVA) and oxygen vacancy-rich ZnO nanoparticles (NPs) and resistive switching effect of PVA:ZnO nanocomposite. The density functional theory calculation indicates that the PVA chemisorption and the oxygen vacancies of ZnO play a key role in strongly reducing the work function of ZnO NPs of which conduction band can act as a bottom of potential well for trapping electrons in the PVA:ZnO nanocomposite. The oxygen vacancies also increase the stability of the potential well by enhancing chemical bonding between PVA and ZnO. Moreover, we show that at a specific content of ZnO NPs in the PVA matrix, the Ag/PVA:ZnO/FTO memory device has the best resistive switching behavior (operating voltage < 1 V). This implies there exists an optimal average width of the energy barriers between the ZnO NPs in the PVA matrix. The electrical transport mechanisms and resistive switching behavior of this device are also investigated in details.
 

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(114) Journal of Harzard materials, 403, 124104 (Q1, IF = 10.588)  

114
Functionalization of zirconium-based metal-organic frameworks for gas sensing applications
 
Jae-Hyoung Lee,Trang Thi Thu Nguyen, Linh Ho Thuy Nguyen, Thang Bach Phan, Sang Sub Kim, Tan Le Hoang Doan
 
Abstract: The functionalization and incorporation of noble metals in metal-organic frameworks have been widely used as efficient methods to enhance their applicability. Herein, a sulfone-functionalized Zr-MOF framework labeled Zr–BPDC–SO2 (BPDC–SO2 = dibenzo[b,d]-thiophene-3,7-dicarboxylate 5,5-dioxide) and its Pd-embedded composite were efficiently synthesized by adjusting their functional groups. The obtained compounds were characterized to assess their potential for gas sensing applications. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, specific surface area measurements, and thermogravimetric analysis were employed to characterize the new sensor materials. The gas sensing properties of the novel functionalized sensor materials were systematically investigated under various temperature, concentration, and gas type conditions. Owing to the strong hydrogen bonds of the sulfonyl groups and Zr6 clusters in the framework with the hydroxyl groups of ethanol, Zr–BPDC–SO2 emerged as an effective sensor for ethanol detection. In addition, Pd@Zr–BPDC–SO2 exhibited efficient hydrogen sensing performance, in terms of sensor dynamics and response. More importantly, the material showed a higher sensing response to hydrogen than to other gases, highlighting the important role of Pd in the Zr-MOF-based hydrogen sensor. The results of the sensing tests carried out in this study highlight the promising potential of the present materials for practical gas monitoring applications.
 
 

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(113) Molecular Catalysis, accepted (Q1, IF = 5.062)  

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Heterocyclic reaction inducted by Brønsted -Lewis dual acidic Hf-MOF under microwave irradiationư
 
Linh Ho Thuy Nguyen, Trang Thi Thu Nguyen, Minh-Huy Dang Dinh, Phuong Hoang Tran, Tan Le Hoang Doan
 
Abstract: 
 

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(112) Materials Science & Engineering B, 262, 114788 (Q1, IF = )  

112
Experimental combined theoretical study on chemical interactions of graphene oxide with chitosan and its resistive-switching effect 
 
Kim My Tran, Dinh Phuc Do, Hoang Nam Vu, The Toan Nguyen, Kieu Hanh Ta Thi, Bach Thang Phan, Pham Kim Ngoc
 
Abstract: Recently, nanocomposite materials that consist of chitosan (CS) and graphene oxide (GO) have received immense attention in many fields of research, such as biomedicine, environmental studies, energy and electronics. In this paper, we study resistive memory devices in capacitor-like Ag/CS-GO/FTO structures, with the CS-GO nanocomposites acting as the memory layer. The devices showed a bipolar resistive-switching effect under an external electric field, with the endurance of 103 and ON/OFF ratio around 102. The calculated results confirmed by using density-function-theory (DFT) calculations show the stability of CS-GO nanocomposites through the presence of peptide and hydrogen bonds. Moreover, the calculated HOMO–LUMO gap (HLG) of GO is within the HLG of CS, so several unoccupied levels of GO can serve as electron traps in CS-GO nanocomposites. Based on these results above, a resistive-switching mechanism in Ag/CS-GO/FTO devices can be proposed because of the trap/de-trap process of injected electrons under external electric field
 

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(111) RSC Advances, 10, 34690-34701 (Q1, IF = 3.361)  

111
The electronic structures and magnetic properties of mixed-valence Fe-based metal-organic VNU-15 frameworks: a theoretical study from linear response DFT+U calculations
Diem Thi-Xuan Dang, Hieu Cao Dong, Yoshiyuki Kawazoe, Jer-lai Kuo, and Duc Nguyen-Manh
 
Abstract: The crystal symmetries, electronic structures, and magnetic properties of metal–organic VNU-15 frameworks (VNU = Vietnam National University) were investigated using density functional calculations (DFT) with an on-site Coulomb repulsion approximation, Ueff, of 4.30 eV, determined via the linear response method. Two different orientations of dimethylammonium (DMA+) cations in VNU-15 were investigated. Antiferromagnetic configurations were predicted to be the ground states, with Fe ions in high-spin states for both phases. Furthermore, VNU-15 had intrinsic semiconductor electronic behavior with a small band gap of about 1.20 eV. The change in the orientation of DMA+ led to changes in the dispersion of the band structure, the band gap, and the Fe contributions to the valence band and conduction band. A fascinating feature was found involving exchange of oxidation numbers between two adjacent Fe atoms in the two phases. Our results revealed that VNU-15 has strong oxidation activity and predicted the important role of an anisotropic effect on the hole and electron effective masses. The findings presented that the electronic and magnetic properties could be controlled via hydrogen bonds and proved VNU-15 to be a prospective material for photocatalytic applications.
 

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(110) Journal of Electronic Materials, 49, 6510–6518. (Q2, IF = 1.938)  

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Cleavable, Covalently Linked, Affinity Coupling Immune Magnetic Nanoparticles for Specifically Depleting T Cells
 
Kien-Quang Huynh, Duong T Duong, Thuan V Tran, Bich-Tram T Nguyen, Thao-Suong Tran-Nguyen, Thuoc L Tran, Thang B Phan, Kieu-Hanh T Ta, Tran Van Hieu
 
Abstract: Hematopoietic stem cell (HSC) transplantation has become an accepted therapeutic modality for patients with hematopoietic disorders. However, transplant recipients are at high risk of a severe complication known as graft versus host disease (GvHD). To reduce the risk of GvHD, depletion of T cells in donor HSCs prior to transplantation is of vital importance. Magnetic-activated cell sorting (MACS) using immuno-magnetic nanoparticles to selectively deplete T cells presents a potential solution for HSC transplantation. In this study, we presented a complete protocol for the synthesis of immuno-magnetic nanoparticles and characterised their performance for the depletion of Jurkat T cells from cell culture and from a mixture of T cells and HSCs. First, the recombinant protein A/G, an Fc-specific antibody, and magnetic nanoparticles were covalently linked by amine groups on the surface of magnetic nanoparticles and the protein using 3-(2-pyridyldithio) propionic acid N-hydroxysuccinimide ester (SPDP). Then, the anti-Jurkat T antibodies were bound to protein A/G on magnetic nanoparticles via regio-oriented affinity binding. Approximately 85 μg of protein A/G and 25 μg of antibody were bound to 1 mg of magnetic beads. The immuno-magnetic nanoparticles were capable of depleting up to 73% of Jurkat T cells from culture medium and 72% of Jurkat T cells from the mixture. In addition, we showed that our depletion protocol was able to preserve the proliferation and differentiation characteristics of HSCs. In conclusion, our immuno-magnetic nanoparticles provide a potential solution for the depletion of T-cells prior to HSCs transplantation.
 

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(109) Materials Science & Engineering B, 261, 114712 (Q1, IF = 4.051)  

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Dopants and induced residual stress-controlled thermoelectric properties of ZnO thin films
 
Anh Tuan Thanh Pham, Phuong Thanh Ngoc Vo, Hanh Kieu Thi Ta, Ngoc Kim Pham, Hoa  Thi Lai, Hoa Nhu Thi Tran, Vinh Cao Tran, Tan Le Hoang Doan, Sungkyun Park, Thang Bach Phan
 
Abstract: We investigate the structure, optical properties, and thermoelectric power in terms of residual stresses induced in the undoped ZnO and X-doped ZnO (X = Al, Ga) films. The results show that the different native seed layers self-grown during the initial growth cause compressive stress for ZnO and Ga-doped ZnO films and tensile stress for Al-doped ZnO films. The band-gap of the investigated films follows the Burstein–Moss (BM) effect. It is noted that the ZnO film with the lowest compressive stress has a better PF value below 275 °C. The GZO film is more stable at higher temperatures; therefore, it has a better PF value above 275 °C. The residual stress induced in the investigated films is demonstrated through the formation of a self-grown seed layer under the bombardment of high-energy sputtered Ga, Al, Zn, and O species onto the substrate and during film growth.
 

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(108) RSC New Journal of Chemistry, 44, 14529-14535 (Q1, IF = 3.591)  

108
Effect of Fe(iii)-based MOFs on the catalytic efficiency of the tandem cyclooxidative reaction between 2-aminobenzamide and alcohols
 
Minh-Huy Dinh Dang, Trang Thi Minh Nguyen,  Linh Ho Thuy Nguyen, Trang Thi Thu Nguyen, Thang Bach Phan, Phuong Hoang Tran, Tan Le Hoang Doan
 
Abstract: The catalytic properties of metal-organic frameworks (MOFs) containing triangular Fe(III) clusters in the promotion of organic syntheses and photocatalysis applications have been receiving substantial attention for decades. These clusters are appealing due to the strong Lewis acidity afforded by coordinatively unsaturated sites upon the removal of solvent from the framework. In this paper, triangular Fe(III) cluster-based MOFs were shown to be highly efficient heterogeneous catalysts for the solvent-free one-pot condensation of 2-aminobenzamide and alcohols to form quinazolin-4-ones under microwave irradiation. The Fe-MOF catalysts ranging from microporous to mesoporous structures with a variety of geometrical pore structures were investigated. Because of the open accessible spaces for reactants and high density of active sites, MOF-907, built from trimer Fe clusters and a mixture of two linkers, was more effective than other Fe(III)-MOFs. The catalyst can be used for a broad substrate scope and recycled several times without a significant drop-off in its activity.
 

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(107) RSC Advances, 10, 30858-30869 (Q1, IF = 3.361)  

107
The highly sensitive determination of serotonin by using gold nanoparticles (Au NPs) with a localized surface plasmon resonance (LSPR) absorption wavelength in the visible region†                                                                                                                                 
Phuong Que Tran Do, Vu Thi Huong, Nguyen Tran Truc Phuong, Thi-Hiep Nguyen, Hanh Kieu Thi Ta, Heongkyu Ju, Thang Bach Phan, Viet-Duc Phung, Kieu The Loan Trinh and Nhu Hoa Thi Tran
 
Abstract: The development of improved methods for the synthesis of monodisperse gold nanoparticles (Au NPs) is of high priority because they can be used as substrates for surface-enhanced Raman scattering (SERS) applications relating to biological lipids. Herein, Au NPs have been successfully synthesized via a seed-mediated growth method. The LSPR peak is controlled via adjusting the gold nano speed component, and different fabrication methods were studied to establish the effect of sonication time on NP size. The simple, facile, and room-temperature method is based on a conventional ultrasonic bath, which leads to ultrasonic energy effects on the size and morphology of the Au NPs. This research offers new opportunities for the production of highly monodispersed spherical Au NPs without the use of a magnetic stirrer method, as evidenced by ultraviolet-visible reflectance spectra and scanning electron microscopy (SEM) analysis. SEM images indicate that the spherical Au NP colloidal particles are stable and reliable, which paves the way for their use as a nanostructured biosensor platform that can be exploited for multiple applications, for example, in materials science, sensing, catalysis, medicine, food safety, biomedicine, etc. The highest enhancement factor that could be achieved in terms of the SERS enhancement activity of these Au NP arrays was determined using 10−9 M serotonin (5-hydroxytryptamine, 5-HT) as the Raman probe molecules.
 

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(106) ACS Langmuir,, 33, 9967–9976 (Q1, IF = 3.882)  

106
Bimetallic Thin-Film Combination of Surface Plasmon Resonance-Based Optical Fiber Cladding with the Polarizing Homodyne Balanced Detection Method and Biomedical Assay Application                                                                                                                                 
Vu Thi Huong, Vinh Van Tran, Nae Yoon Lee, Dung Van Hoang, Kieu The Loan Trinh, Thang Phan, Nhu Tran
 
Abstract: In this work, we present the optical birefringence properties of the optical fiber cladding that exists as an evanescent field where the refractive index (RI) of the analysis solution is applied for optical sensor aspiration. To enhance the performance of the sensor, we have investigated the sensor with different thicknesses of TiO2 coating and bimetallic (Ag–Al) film alloy combinations by thermal evaporation coating. We described a special balanced homodyne detection method for the intensity difference change between the p- and s-polarization lights in the surface plasmon resonance sensing systems, which is strongly determined by the RI of the test medium. The plasmonic optical fiber can measure a very small change of the RI of a glycerol solution, which is a resolution of 4.37 × 10–8 RI unit (RIU). This method has great advantages of a small-sized optical setup, high stability, high selectivity, easy chemical modification, and low cost. Furthermore, because of the experiment results, we observe that our approach can also eliminate the surrounding noise in the Mach–Zehnder interferometer, which shows the feasibility of this proposed technique. We demonstrate the fluorescence enhancement in detecting the C-reactive protein antibody conjugated with fluorescein isothiocyanate by means of near-field coupling between surface plasmons and fluorophores at spectral channels of emission. This technique can also be extended for application in a biomedical assay and in biochemical science, including molecular diagnostics relying on multichannels that require a small volume of the analyte at each channel which would suffer from the weakness of fluorescence if it were not for the enhancement technology.
 

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(105) ACS Omega, 26, 16139–16148 (Q1, IF = 3.512)  

105
Induced Magnetism of the MoS2 Monolayer during the Transition Metal (Fe/Ni) Bombardment Process: A Nonadiabatic Ab Initio Collision Dynamics Investigation                                                                                                                                 
Thi H. Ho, Hieu T. Hoang, Hieu C. Dong, Yoshiyuki Kawazoe, and Hung M. Le
 
Abstract: The source of induced magnetism in the MoS2 monolayer induced by transition metal (Fe/Ni) collision is investigated using nonadiabatic ab inito molecular dynamics simulations that take into account high-spin and low-spin energy states during trajectory integration. By considering various metal firing angles, a strong interaction between the Fe/Ni atom and the MoS2 surface can be observed because of enormous increase in the kinetic energy of the metal atom. When firing along the Mo-S bond, the Fe bullet is pulled more strongly than when firing along the S-Mo-S bisector. Spin polarization of MoS2 is gradually induced when Fe approaches the surface and eliminated when Fe roams around a potential energy trap on the MoS2 layer. We observe that there is charge transfer between Fe and Mo atoms, which enhances the probability of electron pairing and leads to instantaneous vanishing of total magnetization. The Ni-MoS2 system is found to establish a total magnetization of 1.5-4 μB when Ni is 2.0 Å above the surface. Interestingly, the strong bonding attachment of Ni suppresses the band gap to at least 40%.
 

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(104) RSC Advances, 10, 23899 (Q1, IF = 3.361)  

104
Green synthesis of ZnO nanoparticles using orange fruit peel extract for antibacterial activities                                                                                                                                
Tu Uyen Doan Thi,Trung Thoai Nguyen,Y Dang Thi,Kieu Hanh Thi Ta, Bach Thang Phan and Kim Ngoc Pham
 
Abstract: This paper presents an efficient, environmentally friendly, and simple approach for the green synthesis of ZnO nanoparticles (ZnO NPs) using orange fruit peel extract. This approach aims to both minimize the use of toxic chemicals in nanoparticle fabrication and enhance the antibacterial activity and biomedical applications of ZnO nanoparticles. In this work, an aqueous extract of orange peel was used as the biological reduction agent for the synthesis of ZnO NPs from zinc acetate dihydrate. It was found that the size and morphology of the ZnO NPs significantly depended on physicochemical parameters such as the annealing temperature and pH during NP synthesis. The ZnO NPs exhibited strong antibacterial activity toward Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) without UV illumination at an NP concentration of 0.025 mg mL−1 after 8 h of incubation. In particular, the bactericidal activity towards S. aureus varied extensively with the synthesis parameters. This study presents an efficient green synthesis route for ZnO NPs with a wide range of potential applications, especially in the biomedical field.
 

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(103) Journal of Alloys and Compounds, 844, 156119 (Q1, IF = update)  

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Effects of multi-scale defects on the thermoelectric properties of delafossite CuCr1-xMgxO2 materials                                                                                                                                 
Dung Van Hoang, Anh Tuan Thanh Pham, Hanh Kieu Thi Ta, Truong Huu Nguyen, Ngoc Kim Pham, Lai Thi Hoa, Vinh Cao Tran, Ohtaki Michitaka, Quang Minh Nhat Tran, Jong-Ho Park, Jae-Ki Lee, Su-Dong Park, Tae-Seong Ju, Hongjun Park, Sungkyun Park and Thang Bach Phan
 
Abstract: The thermoelectric performance of CuCr1-xMgxO2 materials in terms of multi-scale defects induced at various Mg dopant concentrations (x = 0–0.3) was thoroughly studied in this paper. At 748 K and for x = 0.05, 0.15, and 0.30, we report the following power factors and thermal conductivities: 175, 213, and 2.3 μW/m K2 and 7.85, 5.60, and 3.82 W/m K, respectively. In the low doping regime (x < 0.15), the thermoelectric performance is mainly dependent on hole carriers originated from point defects via Mg substitution on Cr sites, whereas the thermoelectric properties reduce significantly for x ≥ 0.15 due to nanoscale secondary phases (MgCr2O4, Cu2O and CuO) and mesoscale grain boundaries. At 748 K, our CuCr0.85Mg0.15O2 samples exhibit a high figure of merit ZT = 0.028, which is better than those of other CuCr1-xMgxO2 and related delafossite materials. The correlations between the structural and thermoelectric properties of CuCr1-xMgxO2 materials are also discussed in detail. 
 

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(102) Applied Optics, 55), 5845 (Q2, IF = 1.980)  

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Effects of B2O3 doping on the crystalline structure and performance of DC-magnetron-sputtered, transparent ZnO thin films   
                                                                                                                                
Anh Tuan Thanh Pham, Phuong Ai Thi Nguyen, Yen Kim Thi Phan, Truong Huu Nguyen, Dung Van Hoang, Oanh Kieu Truong Le, Thang Bach Phan, and Vinh Cao Tran
 
Abstract: The thermoelectric performance of CuCr1-xMgxO2 materials in terms of multi-scale defects induced at various Mg dopant concentrations (x = 0–0.3) was thoroughly studied in this paper. At 748 K and for x = 0.05, 0.15, and 0.30, we report the following power factors and thermal conductivities: 175, 213, and 2.3 μW/m K2 and 7.85, 5.60, and 3.82 W/m K, respectively. In the low doping regime (x < 0.15), the thermoelectric performance is mainly dependent on hole carriers originated from point defects via Mg substitution on Cr sites, whereas the thermoelectric properties reduce significantly for x ≥ 0.15 due to nanoscale secondary phases (MgCr2O4, Cu2O and CuO) and mesoscale grain boundaries. At 748 K, our CuCr0.85Mg0.15O2 samples exhibit a high figure of merit ZT = 0.028, which is better than those of other CuCr1-xMgxO2 and related delafossite materials. The correlations between the structural and thermoelectric properties of CuCr1-xMgxO2 materials are also discussed in detail. 
 

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(101) Journal of Electronic Materials, 49, 7420–7426 (Q2, IF = 1.938)  

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Optical Biosensor Using Near Infrared Laser for Enhancement of Detection Accuracy
                                                                                                                                
Nguyen Van Sau, Quang Minh Ngo, Thang Bach Phan, Ngoc Quyen Tran, Tan Tai Nguyen
 
Abstract: This work presents the figures of merit of an optical sensor using a prism based on surface plasmon resonance (SPR). A combination of a prism coated with a thin Ag layer and a wavelength of 1064 nm was used for SPR excitation. The simulated results showed that the sensor coated with a Ag layer of 60 nm yielded good response with a detection accuracy of 14 times that obtained using a wavelength of 633 nm. The sensor using a wavelength of 1064 nm showed a quality factor of around 1027.4° and a penetration depth of 384.4 nm, which were 9.3 times and 3.5 times better, respectively, than those obtained when using a wavelength of 633 nm. The enhancement of the detection accuracy and the penetration depth of the sensor using a wavelength of 1064 nm offer advantages for the detection of bio-targets in biomedical and food applications.
 

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(100) Journal of Polymer Science, 2020, 8127570 (Q1, IF = update)  

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Conjugated Linoleic Acid Grafting Improved Hemocompatibility of the Polycaprolactone Electrospun Membrane
                                                                                                                                
Nam M Tran; Toan L Huynh; Binh N Phan; Nghi T Nguyen; Nhi N Dang, Thang B Phan, Nguyen Thi Hiep
 
Abstract: Polycaprolactone (PCL) is a versatile biomaterial with a wide range of medical applications, but its use in blood-contacting devices is hampered due to insufficient hemocompatibility. In this work, electrospun polycaprolactone (PCL) membranes were chemically grafted with conjugated linoleic acid (CLA) to prevent induced blood coagulation. The density of grafted CLA and its effects on the morphology and wettability of the membranes were examined. The study also investigated how the membrane interacted with human whole blood and platelets to determine its antithrombotic properties. As the results suggested, the grafting caused a negligible effect on the physical properties of the membrane but greatly improved its compatibility with blood, showing that the approach can be investigated further for blood-contacting applications.
 

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(99) J.Photochemistry & Photobiology A: Chemistry, 399, 112639.(Q1, IF = 4.291) 

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Enhancing visible-light-driven water splitting of ZnO nanorods by dual synergistic effects of plasmonic Au nanoparticles and Cu dopants
                                                                                                                                
Nguyen Van Cat Ha, Nguyen Huu Khoa, Tran Cong Khanh, Kim Ngoc Pham, Bach Thang Phan, Heon Lee and Dang Vinh Quang
 
Abstract: Converting solar energy into chemical fuels is important to develop renewable energy. Here, Cu-doped ZnO nanorods (NRs) decorated with Au nanoparticles (NPs) are used as an efficient semiconductor catalyst for visible-light-driven water splitting. Doping Cu into ZnO NRs narrows the bandgap and shifts the absorbance toward red light; decorating Au NPs onto the ZnO:Cu NRs enhances the absorbance in the visible region and improves the solar energy conversion. The band gap of the ZnO:Cu NRs is optimized at 3% Cu doping, which presents a minimum value of 3.09 eV. Furthermore, the surface plasmon resonance effect, which is caused by decorating 10-nm Au NPs on the Cu-doped ZnO NRs, enhances the optical absorption and improves the photoelectrochemical water splitting performance. The presence of Au NPs on the surface of the NRs also reduces charge recombination, increasing the photocurrent. Under visible illumination (λ > 420 nm), the considerable photocurrent density of this device reaches 10.2 μA cm−2 at 0.581 V, which is about 7.3 times higher than that of a pure ZnO NRs sample. The simple and cost-effective fabrication process of this design provides an innovative approach for water splitting and future optoelectronic devices.
 

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(98) Journal of Alloys and Compound, 840, 155680 (Q1, IF = 5.316)

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Effects of Substrate Temperature and Film Thickness on the Structural Behavior of Pulsed Laser Deposited Pb(Mg1/3Nb2/3)O3-PbTiO3(65/35) Epitaxial Thin Films
                                                                                                                                
Van Quang Nguyen, Van Thiet Duong, Thi Huong Nguyen, Rakwon Kang, Anh Tuan Pham, Van Tam Tran, Cao Khang Nguyen, Anh Tuan Duong, Thang Bach Phan, Jungdae Kim, and Sunglae Cho
 
Abstract: Pure perovskite phase 0.65 mol% lead magnesium niobate-0.35 mol% lead titanate (abbreviated as PMN-PT) thin films were grown on a MgO substrate by pulsed laser deposition. The crystal structure and epitaxial orientation of the films were analyzed by means of X-ray diffraction. A θ < eqid1 > 2θ scan and off-axis ϕ scan showed that the PMN-PT films were epitaxially grown with c-axis orientated normal to the surface of the MgO substrate. With increase in substrate temperature, the crystallinity of the film was enhanced for temperature below 660°C. Lattice structure of the film showed a strong dependence on the increase in film thickness. The crystallinity of the film was also enhanced with increasing in the film thickness.
 

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(97) Sensors and Actuators: A Physical, 311, 112085 (Q1, IF = 3.407)  

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The Enhancement of Visible Absorption of Cu Doped ZnO Nanorods on Patterned Substrates
                                                                                                                                
Pham Hoai Nhan, Tong My Hoa, Nguyen Huu Khoa, Dinh Tan Muon, Luong Hoai Nhan, Phan Bach Thang, Tran Cong Khanh, Dang Vinh Quang
 
Abstract: We report the antireflection and light absorption in visible region by new stretchable substrates with patterned structure. Mogul substrates with 3-Dimentional structures were fabricated by using polydimethyl – siloxane that imitate the nanostructures surface. Then, Copper doped ZnO NRs on mogul-patterned surface by hydrothermal method at low temperature. The optical properties, morphology and structures of ZnO:Cu NRs were investigated through out of measurement the scanning electron microscopy, X-Ray diffraction and ultraviolet-visible spectroscopy, respectively. The results show the Cu doped ZnO NRs were uniformly and dense grown on mogul substrates, well oriented in the (002) plane. Additionally, the light absorption can be significantly enhanced to more 10% in a wide spectral range (400-800 nm) due to the reduce reflection. Growing ZnO NRs doping on new stretchable substrates with a mogul-patterned surface were successfully fabricated and applicable in the flexible and stretchable optoelectronic devices.
 

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(96) ACS The Journal of Physical Chemistry C, 124, 8958–8970 (Q1, IF = 4.126)  

96
Effect of Surface States and Breakdown of the Schottky–Mott Limit of Graphene/Silicon van der Waals Heterostructure
                                                                                                                                
Nam Vu, Hieu Le, Thang Phan, Toan Nguyen, Nam Thoai, Thi Cao
 
Abstract: Recent experimental studies have often described the interface of the graphene/semiconductor (G/S) junction in terms of conventional metal/semiconductor (M/S) contact models, but the details of the charge transfer mechanism remain unclear. Here, density functional theory calculations are used to investigate the graphene/silicon (G/Si) interface in the absence and presence of different surface states of the doped Si substrate. It is confirmed that the interaction between graphene and the Si surface is of van der Waals (vdW) type, even though the Si surface is shown to have a high density of dangling bonds. We show that the metallic surface state transfers its spilled-out electron to graphene but prevents the development of a depletion region of free carriers in the subsurface region of the substrate due to strong electrostatic screening property of the metallic surface state, while the hole doping in graphene by the electron-trapping surface states is inhibited by the interfacial potential step of the pillow effect. In the absence of surface states, the behavior of transferred charges is quite free in the interfacial layer; thus, the effective distance of a simple plane capacitor model of the charge transfer potential should be treated as a variable instead of fixing it as in the conventional M/S interface models. More interestingly, the sensitivity of the Schottky barrier height of the G/Si vdW interface can overcome the Schottky–Mott limit and the recently proposed barrier models due to the dependence of the charge transfer potential on the Fermi level shift in graphene.
 

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(95) Advanced Materials and Devices, 5, 199-206.(Q1, IF = 5.469)  

95
Low operating voltage resistive random access memory based on graphene oxide–polyvinyl alcohol nanocomposite thin films
                                                                                                                                
Huu Thoai Ngo, Minh Trang Nguyen Thi, Dinh Phuc Do , Kim My Tran, Bach Thang Phan, Kieu Hanh Ta Thi, Kim Ngoc Pham
 
Abstract: A high-performance non-volatile memory with low power consumption for long battery life and for large data storage is one of the key requirements of the wearable and other electronic Internet of Things (IoT) devices. In this study, we have fabricated and investigated the resistive switching behavior of an RRAM device using the nanocomposite of polyvinyl alcohol (PVA) and graphene oxide (GO) as the switching layer in a hybrid Ag/PVA–GO/FTO structure. The resistive switching behavior of the hybrid Ag/PVA–GO/FTO device depends on the GO amount in the PVA–GO matrix. The optical analysis depicts the good interaction through the hydrogen bonds between the hydroxyl group (–OH) of PVA and Cdouble bondO of GO which play an important role in lowering the power consumption (sweeping voltage −0.5 V to +0.5 V, VSET = −0.28 V, VRESET = 0.34 V, switching ratio ION/IOFF = 104) and switching mechanism of the hybrid Ag/PVA–0.5 wt% GO/FTO device compared to the Ag/PVA/FTO, Ag/GO/FTO and Ag/PVA–1.0 wt% GO/FTO devices. The electrical conduction mechanism is found dominant by the SCLC and the Ohm's law corresponding to the high and low resistance states in which the combination of the trap filling and the delocalization of electrons within π bonding rings switch the device from the high to the low resistance state.
 

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(94) Sensors and Actuators B Chemical, 19, 3323. (Q1, IF = 7.46)