Meng-Yun Chung

Bacteriostatic Substrate by Conductivity Method and Electric Spark Discharge Method Combined with Electrospinning for Silver Dressing

This study uses the conductivity method, Electric Spark Discharge Method, and the electrospinning technique to develop a better silver-based antibacterial agent. The preparation process is free of chemical substances and also conforms to the green energy-saving process. The silver iodide was prepared in an iodine agar medium by using the conductivity method. Multiple bacteriostasis experiments showed that the molds grew in the position with iodine of the culture medium after 6 days, as well as in the position with silver iodide after 10 days. The results prove that silver iodide has better bacteriostatic ability than povidone iodine. The nanosilver colloid was prepared in the PVA solution by using the Electric Spark Discharge Method. UV-Vis, Zetasizer, and SEM-EDX analyses proved that the PVA solution contained nanosilver colloid with good suspension stability. Finally, the electrospinning technique was used to spin the PVA solution with nanosilver colloid into the PVA nanofibrous membrane. According to UV-Vis analysis, the absorption peak of this nanofibrous membrane is about 415 nm, meaning this nanofibrous membrane contains nucleate nanosilver colloid, and is very suitable for antiseptic dressing.

Parameters for Fabricating Nano-Au Colloids through the Electric Spark Discharge Method with Micro-Electrical Discharge Machining

In this study, the Electric Spark Discharge Method (ESDM) was employed with micro-electrical discharge machining (m-EDM) to create an electric arc that melted two electrodes in deionized water (DW) and fabricated nano-Au colloids through pulse discharges with a controlled on–off duration (TON–TOFF) and a total fabrication time of 1 min. A total of six on–off settings were tested under normal experimental conditions and without the addition of any chemical substances. Ultraviolet–visible spectroscopy (UV–Vis), Zetasizer Nano measurements, and scanning electron microscopy–energy dispersive X-ray (SEM–EDX) analyses suggested that the nano-Au colloid fabricated at 10–10 µs (10 µs on, 10 µs off) had higher concentration and suspension stability than products made at other TON–TOFF settings. The surface plasmon resonance (SPR) of the colloid was 549 nm on the first day of fabrication and stabilized at 532 nm on the third day. As the TON–TOFF period increased, the absorbance (i.e., concentration) of all nano-Au colloids decreased. Absorbance was highest at 10–10 µs. The SPR peaks stabilized at 532 nm across all TON–TOFF periods. The Zeta potential at 10–10 µs was −36.6 mV, indicating that no nano-Au agglomeration occurred and that the particles had high suspension stability.

Antimicrobial Property of Nanosilver Colloid Prepared by Electrical Spark Discharge Method on Aspergillus niger

This study employed an electrical spark discharge method (ESDM) to prepare a nano-Ag colloid as an antifungal solution. The solution was diluted to two concentrations, and the fungal medium prepared in this study was coated with Aspergillus niger. The nano-Ag colloid solution was mixed with A. niger in various concentrations and dripped onto 3M Petrifilm plates. Inhibited growth observed after several days confirmed the antifungal effect of the nano-Ag colloid on A. niger. Because direct washing produced inaccurate quantitation and yielded A. niger in an excessively high concentration, this study employed an inoculation loop method for A. niger quantitation. The concentrations of A. niger ranged from 10−2 to 10−7%. The optimal colony count was observed on day 2. During an experiment regarding the antifungal effect of the ESDM-prepared nano-Ag colloid on A. niger, 3M Petrifilm plates were employed to observe the growth of A. niger. The colony count of 10−2% A. niger without nano-Ag colloid was approximately 60. After the nano-Ag colloid was added, the colony count substantially decreased to approximately 10. The colony count of 10−7% A. niger was reduced to 11 or lower after the nano-Ag colloid was added. The results confirmed the antifungal effect of the nano-Ag colloid on the growth of A. niger.

Fabricating TiO2 nanocolloids by electric spark discharge method at normal temperature and pressure

In this study, TiO2 nanocolloids were successfully fabricated in deionized water without using suspending agents through using the electric spark discharge method at room temperature and under normal atmospheric pressure. This method was exceptional because it did not create nanoparticle dispersion and the produced colloids contained no derivatives. The proposed method requires only traditional electrical discharge machines (EDMs), self-made magnetic stirrers, and Ti wires (purity, 99.99%). The EDM pulse on time (T on) and pulse off time (T off) were respectively set at 50 and 100 μs, 100 and 100 μs, 150 and 100 μs, and 200 and 100 μs to produce four types of TiO2 nanocolloids. Zetasizer analysis of the nanocolloids showed that a decrease in T on increased the suspension stability, but there were no significant correlations between T on and particle size. Colloids produced from the four production configurations showed a minimum particle size between 29.39 and 52.85 nm and a zeta-potential between -51.2 and -46.8 mV, confirming that the method introduced in this study can be used to produce TiO2 nanocolloids with excellent suspension stability. Scanning electron microscopy with energy dispersive spectroscopy also indicated that the TiO2 colloids did not contain elements other than Ti and oxygen.

A Study of Photocatalysis of Methylene Blue of TiO2 Fabricated by Electric Spark Discharge Method

This study used the Electric Spark Discharge Method (ESDM) to prepare nano-Ti colloid. The results showed that the process efficiency increased according to the current and selecting different discharge periods ( - ). The preparation process is pollution-free and very contributive to using TiO2 for photocatalytic reaction to degrade organic compounds. This study used 99.9% pure Ti metal to examine the effects of different discharge parameter settings on the photocatalysis of methylene blue. The experimental results showed that the discharge period ( - ) has an effect on the characteristics of the prepared nano-Ti colloid but affects its concentration. The nano-Ti colloid, as prepared under different parameters, has poor photocatalytic reaction with methylene blue at the concentration of 50 mg/L. The nano-Ti colloid does not have favorable effect on degrading methylene blue above 50 mg/L. For degrading methylene blue at a low concentration of 10 mg/L, the 100-100 nano-Ti parameter is preferable. For degrading methylene blue at a high concentration of 30 mg/L, nano-Ti colloid with exceeding 100 and fixed at 100 is better. As the nano-Ti colloid prepared by ESDM was free of chemical agents, when TiO2 was used in photocatalytic reaction to degrade organic compounds, there was no secondary pollution to the environment.

Developing PC-based servo system of micro-EDM for preparing nanosilver colloid

As the industrial electrical discharge machine (EDM) has the defects of high cost and large volume in preparing nanosilver colloid, this study designs a micro-electrical discharge machine (micro-EDM) for preparing nanosilver colloid. This micro-EDM comprises mechanical structure, a PC-Based real-time control system, and a servo circuit. As the electrode-holder of mechanical structure is made by 3D printer, manufacturing costs and implement volume are greatly reduced. The PC-Based real-time control system can implement electrode gap control, discharge circuit control, and real-time process monitoring through the servo circuit. The PC-Based real-time control system is implemented by VisSim software and the RT-DAC4/PCI card, thus, the partial electronic circuit of EDM can be replaced by software through this card to reduce the circuit size and cost. The nanosilver colloid prepared by this micro-EDM is analyzed by precision instruments. The results prove that the micro-EDM can prepare the same nanosilver colloid as that prepared by industrial EDM. The micro-EDM designed in this study has lower cost and smaller volume than traditional EDM, and the discharge condition in the process can be real-time monitored by computer.