Phuong Dinh Tam

DNA sensor development based on multi-wall carbon nanotubes for label-free influenza virus (type A) detection

This paper describes the DNA immobilization using carbon multi-walled nanotubes (MWCNTs) for direct and label-free detection of influenza virus (type A). The DNA probe was attached on the sensor surface by means of covalent bonding between the amine and phosphate groups of the DNA sequence. The interaction between the DNA probe and the MWCNTs were characterized by Fourier Transform Infrared (FTIR) spectrometry, Raman spectra. The hybridization of the DNA probe and the target DNA were detected by changes in the conductance on the surface of sensors leading to the change in the output signal of the system. The results show that the DNA sensor can detect as low as 0.5 nM of the target DNA samples; the response time of DNA sensor is approximately 4 min.

Novel silver nanoparticles: synthesis, properties and applications

In this paper, we present versatile and effective techniques to synthesise silver nanoparticles (Ag-NPs)-based compounds such as colloidal silver nanoparticles (CSNPs) and silver nanoparticles powders (SNPPs). The CSNPs stabilised by a surfactant oleic acid were produced for the first time through the reduction of [Ag(NH3)2]+(aq) complex by glucose with UV irradiation treatment, while the SNPPs were formed by thermal decomposition of silver-oleate complex at 330°C for 1 h. The CNPPs and CSNPs with average diameters (~9–10 nm) and highly stableaqueous dispersions were obtained. Noticeably, these synthesised Ag-NPs exhibited an excellent antibacterial activity against gram-negative Escherichia coli (ATCC 43888-O157:k-:H7) and methicillin-resistant gram-positive Staphylococcus aureus (ATCC 43300) bacteria. The electron microscopic technique provided deeper insights on the interaction and bactericidal mechanism of the Ag-NPs. Potential applications of the synthesised CSNPs and SNPPs for antibacterial – masterbatchs, acrylic emulsion paint as well as coating layer on cotton textiles were demonstrated.

Biosensor based on nanocomposite material for pathogenic virus detection

This paper introduces a DNA biosensor based on a DNA/chitosan/multi-walled carbon nanotube nanocomposite for pathogenic virus detection. An easy, cost-effective approach to the immobilization of probe DNA sequences on the sensor surface was performed. Cyclic voltammograms were used to characterize the probe DNA sequence immobilization. Complementary sequence hybridization was examined by electrochemical impedance spectroscopy. Results revealed that the developed DNA sensor can detect a target DNA concentration as low as 0.01×10(-12) M. The sensitivity of the prepared sensor was 52.57 kΩ/fM. The reusability and storage stability of the DNA sensor were also investigated. Results showed that the electron-transfer resistance decreased to approximately 35% after 8 weeks and to approximately 80% after 12 weeks of storage.

Label-free electrochemical immunosensor based on cerium oxide nanowires for Vibrio cholerae O1 detection.

This paper developed a label-free immunosensor based on cerium oxide nanowire for Vibrio cholerae O1 detection application. The CeO2 nanowires were synthesized by hydrothermal reaction. The immobilization of Anti-V. cholerae O1 onto CeO2 nanowire-deposited sensor was performed via an amino ester, which was created by using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, and sulfo-N-hydroxysuccinimide. The electrochemical responses of the immunosensor were studied by electrochemical impedance spectroscopy with [Fe (CN) 6] (3-/4-) as redox probe. A linear response in electron transfer resistance for cell of V. cholerae O1 concentration was found in the range of 1.0 × 10(2)CFU/mL to 1.0 × 10(4)CFU/mL. The detection limit of the immunosensor was 1.0 × 10(2)CFU/mL. The immunosensor sensitivity was 56.82 Ω/CFU · mL(-1). Furthermore, the parameters affecting immunosensor response were also investigated, as follows: pH value, immunoreaction time, incubation temperature, and anti-V. cholerae O1 concentration.

A comparative study on the NH3 gas-sensing properties of ZnO, SnO2, and WO3 nanowires

In this work, a large quantity of ZnO, SnO2 and WO3 nanowires (NWs) was successfully synthesised by simple and efficient methods. Their morphology and microstructure were characterised by FE-SEM, TEM, XRD, PL, and Raman. The NH3 gas-sensing properties of these NWs were investigated and compared. It was found that the responses and response-recovery time of SnO2 and WO3 NWs sensors to NH3 gas are relatively comparable, and they have a better NH3 gas-sensing performance than that of ZnO NWs sensor. In addition, the SnO2 NWs sensor has the lowest operating temperature.

Impact parameters investigation of DNA immobilisation process on DNA sensor response

This paper studies impact parameters of DNA sequence immobilisation on DNA sensor response. The parameters were examined including immobilisation time, carbon nanotubes concentration, DNA probe concentration and pH value. The DNA probe sequences were immobilised on surface of microelectrodes by using multi–walled carbon nanotubes (MWCNTs) as mediator. The hybridisation between DNA probe and DNA target was detected by changes in the conductance on the surface of sensors leading to the change in the output signal of the system. The experimental results showed that DNA sensor can well detect E. coli O157:H7 bacteria at optimal parameters including immobilisation time of 120 minute, MWCNTs of 1 mg, 20 µM DNA probe and pH7. Additionally, influence of BSA agent blocking was also studied. The result showed that DNA sensor response was decrease about 15% compared to that obtained in the absence of BSA blocking.

Effect of chromium substituted on structural and magnetic characterization lithium ferrite nanoparticles

In this work, we present a structural, morphology and magnetic study of the Li0.5Fe2.5-xCrxO4 spinel nanoparticles (x = 0, 0.5, 0.75, 1, and 1.25) with mean particle size of 20-30 nm prepared by sol-gel method. The lattice constants and the size of particle decrease with increasing Cr concentration. In these samples, the preference of Cr 3+ and Li + ions in the octahedral sites and a small degree of site-interchange between Li + in the octahedral sites and Fe 3+ in the tetrahedral sites were found which increases with increasing the Cr content. A decrease of magnetization due to the spin disorder in the surface layer of the particles was observed. The spontaneous magnetization at 5K suggests the Néel type of magnetic ordering in these samples. The magnetic coercivity is discussed in terms of particle size, morphology and chromium substitution.

Synthesis of ZnO nanorod for immunosensor application

This paper reported a facile method to synthesize ZnO nanorods for immunosensor application. The ZnO nanorods were synthesized by hydrothermal reaction. Synthesis time affecting on morphology of nanorods was also studied. The immobilization of anti-rotavirus onto ZnO nanorod-deposited sensor was performed via absorption method. The electrochemical responses of the immunosensor were studied by cyclic voltammetry (C-V) method with [Fe(CN) 6 ] 3−/4− as redox probe. A linear decreased response in C-V for cell of rotavirus concentration was found in the range of 7.8×10 5 CFU/mL to 7.8×10 8 CFU/mL. The detection limit of the immunosensor was 7.8×10 5 CFU/mL. The results indicated application of ZnO nanorod sensor for label-free real-time detection of a wide dynamics range of biological species.

Electromagnetic interference shielding effectiveness of Cu powder/carbon black/epoxy resin composite film

A novel composite of carbon black and Cu powder is mixed with epoxy resin in order to produce a composite material suitable for electromagnetic shielding applications. The microstructure of the composite material is investigated by mean of field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared spectroscopy (FTIR). The electromagnetic interference shielding effectiveness (EMI-SE) of composite material is tested over frequency range of 8-12 GHz. According to the experimental results the maximum value of EMI-SE obtained at room temperature is approximately 4 dB and 7 dB for carbon black / epoxy resin sample and Cu powder / carbon black/epoxy resin sample with thinkness 500 µm, respectively. The influence of Cu powder mass and the thick film is also studied. The results indicate that the EMI-SE can reach approximately 25 dB at Cu powder 10 mass %.

Novel portable electrical detection system for DNA SENSOR application

A novel, portable, electrical detection system was constructed for DNA sensor application to detect DNA hybridisation. The read-out circuit consists of an analogue circuit and a digital circuit. The analogue circuit with an IC MAX038 generates a sine wave with a constant frequency (10 kHz), which serves as the input for the DNA sensor. The DNA sensor consists of active and reference sensors. DNA hybridisation between the DNA probe and the target sequences causes changes in the conductance of the conductive membrane (DNA/MWCNTs) on the sensor surface, which lead to changes in the amplitude of the sine wave from the sensor output compared with that of the reference signal output (input sine wave). We used a digital circuit with a microprocessor (PIC33FJ256MC710) to determine the change in the amplitude of the sine wave signal of the sensor. From these digital data, the difference in the amplitudes of the active and reference sensors was calculated and displayed on the liquid crystal display. Measurement results show that the portable electrical detection system can detect DNA target concentrations as low as 0.16 µM. The detection of the amplified polymerase chain reaction sample and the reproducibility of the DNA sensor results were also determined using the designed readout circuit. The proposed electrical detection system is suitable for DNA sensor application.