Jeyoung Jung

Step-reduced synthesis of starch-silver nanoparticles

In the present process, silver nanoparticles were directly synthesized in a single step by microwave irradiation of a mixture of starch, silver nitrate, and deionized water. This is different from the commonly adopted procedure for starch-silver nanoparticle synthesis in which silver nanoparticles are synthesized by preparing a starch solution as a reaction medium first. Thus, the additional step associated with the preparation of the starch solution was eliminated. In addition, no additional reducing agent was utilized. The adopted method was facile and straight forward, affording spherical silver nanoparticles with diameter below 10nm that exhibited good antibacterial activity. Further, influence of starch on the size of the silver nanoparticles was noticed.

Microwave assisted antibacterial chitosan-silver nanocomposite films.

In the current approach, antibacterial chitosan-silver nanocomposite films were fabricated through microwave irradiation. During the process, by utilizing chitosan as reducing agent, silver nanoparticles were synthesized within 11 min by microwave irradiation. Further, films were fabricated within 90 min. It involved an energy consumption of just 0.146 kWh to synthesize silver nanoparticles. This is many times less than the energy consumed during conventional methods. The silver nanoparticles were examined through UV-vis spectrum and transmission electron microscopy (TEM). The fabricated films were characterized by using scanning electron microscopy coupled with an energy dispersive spectrometer (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and contact angle (CA) measurements. The films exhibited antibacterial properties against both Gram-negative micro-organisms (Escherichia coli; E. coli) and Gram-positive micro-organisms (Staphylococcus aureus; S. aureus). In overall, the procedure adopted for fabricating these antibacterial films is environmental friendly, time-saving and energy-saving.

Development of functional antimicrobial papers using chitosan/starch-silver nanoparticles

In the present work, we report the synthesis of chitosan:starch‑silver nanoparticle (Cht:St-AgNPs) coated papers for antimicrobial packaging applications. The starch-assisted synthesized St-AgNPs are spherical in shape with an average particle size of 7 nm. Chitosan was mixed into the synthesized St-AgNPs solution with different ratios of 9:1, 8:2, 7:3, and 5:5 by weight. Further, the influence of different ratios of Cht:St-AgNPs on the various paper properties such as mechanical properties, water and oil resistance, and antimicrobial activities was investigated. It was observed that the properties of the coated papers were strongly dependent on the composition of Cht:St-AgNPs. The Cht:St-AgNPs-coated paper prepared with the ratio of 9:1 showed excellent mechanical properties and good resistance properties against water and oil. The Cht:St-AgNPs coated papers showed a remarkable enhancement in mechanical strength, oil and water resistance, and antibacterial and antifungal activity, which can make them a potential candidate for functional antimicrobial packaging applications.

One-step synthesis of starch-silver nanoparticle solution and its application to antibacterial paper coating

Antibacterial starch-silver nanoparticles (ST-AgNPs) for use as coating solutions were prepared in a single step by ultrasonicating a mixture of starch, silver nitrate, and distilled water. The starch was used as an eco-friendly and inexpensive reducing agent. UV-vis spectra and transmission electron microscopy indicated that our single-step process was effective for synthesizing starch-based coating solution with AgNPs. Further, the as-prepared coating solution with AgNPs was applied to expand the application of paper for antibacterial packaging. The starch-coated paper with AgNPs showed not only highly enhanced oil resistance, but also excellent antibacterial activity, making our biodegradable starch-coated paper with AgNPs highly feasible for packaging applications.

Chitosan-mediated synthesis of flowery-CuO, and its antibacterial and catalytic properties

In the current investigation, CuO with a flower-like morphology has been successfully synthesized in situ in a chitosan medium (0.0015gmL-1) from copper nitrate (Cu(NO3)2·3H2O) and ammonia solution via a facile microwave-induced method. The as-prepared CuO was characterized by SEM, TEM, EDX, XRD, FTIR and TGA. The antibacterial activity of the flower-CuO against Escherichia coli was examined by analyzing colony forming units, and it was proved that the flower-CuO was able to kill >99% bacteria. Further, the flower-CuO exhibited excellent catalytic activity towards the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4. The reaction kinetics followed a pseudo-first-order rate law with a rate constant of 0.183min-1. To the best of our knowledge, this is the first time that copper oxide with the flower-like morphology has been synthesized by using a chitosan solution.

Improving properties of Hanji by coating chitosan–silver nanoparticle solution

A chitosan-silver nanoparticle solution (CSNS) was applied as a coating material to Hanji (Korean traditional paper), and the properties of the coated paper were investigated as a function of the dilution ratio. The required CSNS was first prepared from AgNO3 (30mmol) by utilizing chitosan as a reducing and stabilizing agent via ultrasonication. The as-prepared CSNS was diluted to various ratios (undiluted, 1/10, 1/100, and 1/1000) and applied to Hanji by a dip-coating method. The tensile, burst, oil resistance, and antibacterial properties of the coated Hanji against Escherichia coli were evaluated. Among the various dilution ratios, the maximum level of dilution that can positively influence the tensile, burst, oil resistance, and antibacterial properties of Hanji was identified as 1/10, 1/100, 1/10 and 1/1000 of the pure CSNS, respectively. These findings are significant because a specific property of Hanji can be economically improved by changing the dilution ratio.