Anyarat Watthanaphanit

A novel one-step synthesis of gold nanoparticles in an alginate gel matrix by solution plasma sputtering

We report a novel strategy to produce stable colloidal gold nanoparticles (AuNPs) in alginate aqueous solution which can be done in one step and without any chemicals. The AuNPs were produced by applying a voltage across a pair of gold electrodes which were immersed in alginate aqueous solution. Since the generation of AuNPs was caused by the sputtering of gold electrodes, the process was named the solution plasma sputtering (SPS) process. We utilize the alginate polymer in order to meet three important requirements: (1) to promote the generation of plasma in a liquid environment, (2) to endow biocompatibility to the AuNPs, and (3) to provide colloidal stability to the AuNPs-alginate aqueous suspensions. The alginate concentrations were varied as 0.2, 0.5, and 0.9 %w/v. The concentration-dependent effect on the particle size of AuNPs, the physical absorption property and the stability of the AuNPs-alginate suspensions were studied. Results indicate that preparation of chemical-free colloidal AuNPs-alginate aqueous suspension is successful by the SPS process. The obtained colloidal suspensions were stable and able to retain their strong plasmon absorption bands within a reasonable time period. As a consequence, this is a high-potential technique to produce AuNPs suspended in alginate aqueous solution appropriate for biomedical applications.

Enhanced degradation of chitosan by applying plasma treatment in combination with oxidizing agents for potential use as an anticancer agent

Solution plasma (SP) treatment in combination with oxidizing agents, i.e., hydrogen peroxide (H2O2), potassium persulfate (K2S2O8) and sodium nitrite (NaNO2) were adopted to chitosan degradation in order to achieve fast degradation rate, low chemicals used and high yield of low-molecular-weight chitosan and chitooligosaccharide (COS). Among the studied oxidizing agents, H2O2 was found to be the best choice in terms of appreciable molecular weight reduction without major change in chemical structure of the degraded products of chitosan. By the combination with SP treatment, dilute solution of H2O2 (4-60mM) was required for effective degradation of chitosan. The combination of SP treatment and dilute solution of H2O2 (60mM) resulted in the great reduction of molecular weight of chitosan and water-soluble chitosan was obtained as a major product. The resulting water-soluble chitosan was precipitated to obtain COS. An inhibitory effect against cervical cancer cell line (HeLa cells) of COS was also examined.

Synthesis of colloidal MnO2 with a sheet-like structure by one-pot plasma discharge in permanganate aqueous solution

Stable colloidal MnO2—consisting of MnO2 with a sheet-like structure—was synthesized by solution plasma process (SPP). The synthesis was completed in one-step by discharging the plasma in potassium permanganate (KMnO4) aqueous solution without using any dispersants or stabilizers. An alteration of the manganese oxide oxidation state, from MnO4− to MnO2 as a function of the discharge time, was investigated by UV-vis spectroscopy. Morphology and elemental constituents were observed by TEM and EDS mapping. Results indicated that the discharge time was an important feature for the formation of MnO2 in the SPP system. Specifically at neutral pH (pH = 7), MnO4− was completely reduced to MnO2 within a discharge time of 18 min. After that the obtained MnO2 was converted rapidly to Mn2+. To better understand the possible pathways of MnO2 formation by the SPP, we compared aspects of the reaction under different pH conditions. Formation of MnO2 under additional, controlled pH conditions, i.e. 2 and 12, was studied. Results suggested that hydrogen species played a key role for the reduction of MnO4− in the water-based SPP system. In comparison to the existing routes for the synthesis of MnO2 nanosheets with a single or low number of layers, the SPP holds excellent promise as an effective alternative means regarding its simplicity, time-energy preserving, and scalability.

Verification of Radicals Formation in Ethanol-Water Mixture Based Solution Plasma and Their Relation to the Rate of Reaction.

Our previous research demonstrated that using ethanol-water mixture as a liquid medium for the synthesis of gold nanoparticles by the solution plasma process (SPP) could lead to an increment of the reaction rate of ∼35.2 times faster than that in pure water. This drastic change was observed when a small amount of ethanol, that is, at an ethanol mole fraction (χethanol) of 0.089, was added in the system. After this composition, the reaction rate decreased continuously. To better understand what happens in the ethanol-water mixture-based SPP, in this study, effect of the ethanol content on the radical formation in the system was verified. We focused on detecting the magnetic resonance of electronic spins using electron spin resonance spectroscopy to determine the type and quantity of the generated radicals at each χethanol. Results indicated that ethanol radicals were generated in the ethanol-water mixtures and exhibited maximum quantity at the xethanol of 0.089. Relationship between the ethanol radical yield and the rate of reaction, along with possible mechanism responsible for the observed phenomenon, is discussed in this paper.

Conversion of cellulose into reducing sugar by solution plasma process (SPP)

In the present study, cellulose colloids are treated with the solution plasma process in order to prepare reducing sugar. The investigated parameters are treatment time, type of electrodes, and applied pulse frequency of the bipolar supply. The reducing sugar was characterized by DNS method and the%yield of total reducing sugar (TRS) was then calculated. The crystal structure and chemical structure of plasma-treated cellulose was measured by XRD and FT-IR, respectively. The%yield of TRS was greatly enhanced by solution plasma treatment using Fe electrode. SEM and TEM micrograph indicated that Fe electrode yield the incidental Fe nanoparticles, hypothesized to catalyze the cellulose degradation during SPP treatment. The crystal structure of cellulose was destroyed. Solution plasma treatment of cellulose using Fe electrode at the high applied frequency pulse provided the highest%TRS.

Sericin-binded-deprotenized natural rubber film containing chitin whiskers as elasto-gel dressing

Here, we aims to demonstrate a simple concept in biomaterials design by using natural resources solely as raw materials to fabricate elastic wound care dressing. Elasto-gel films comprise of silk sericin (SRC), natural rubber (NR), and chitin whisker (CTW) were developed. A glue-like protein SRC found in silk cocoons is beneficial for the treatment of wounds due to its superior skin moisturizing ability. However, the pure SRC film is generally difficult to be fabricated because of its weak structural feature. This limitation was overcome by using NR as a binder which consecutively rendered elasticity and strength of the films. CTW was chosen as another component to promote ability of the films for tissue restoration. Before the film formation, protein in the natural rubber latex (NRL) was removed to avoid allergic and cytotoxic problems. The enzyme-treated NR/SRC (ETNR/SRC) films having different blend compositions were fabricated by solution casting technique. The highest amount of the SRC to gain an easy to handle ETNR/SRC film was 30%. The ETNR/SRC/CTW films having 20% SRC were fabricated and studied in comparison. Essential properties of the films as elastic wound care dressings were investigated and effect of the materials chemistry on the observed properties were discussed.

Simple introduction of carboxyl head group with alkyl spacer onto multiwalled carbon nanotubes by solution plasma process

A simple method of fabricating carboxyl-terminated multiwalled carbon nanotubes (MWCNTs) with alkyl spacers was developed to improve the dispersion quality of MWCNTs in aqueous solutions using solution plasma (SP) in a 6-aminocaproic acid solution. The formation of SP in the solution led to better dispersion of MWCNTs in aqueous solutions. Fourier transform infrared spectroscopy (FT-IR) results indicate that a carboxyl group with an alkyl spacer can be introduced by SP treatment in the 6-aminocaproic acid solution. Sedimentation tests show that the SP-treated MWCNTs in the 6-aminocaproic acid solution retained their good dispersion quality in aqueous solutions of pHs 5, 6, and 9. The alkyl spacer plays an important role in the preservation of dispersion states particularly at pH 6.