Citric acid crosslinked carboxymethyl cellulose edible films: A case study on preserving freshness in bananas.

The study involves the preparation and characterization of crosslinked-carboxymethyl cellulose (CMC) films using varying amounts of citric acid (CA) within the range 5 %-20 %, w/w, relative to the dry weight of CMC. Through techniques such as Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, carbonyl content analysis, and gel fraction measurements, the successful crosslinking between CMC and CA is confirmed. The investigation includes an analysis of chemical structure, physical and optical characteristics, swelling behavior, water vapor transmission rate, moisture content, and surface morphologies. The water resistance of the cross-linked CMC films exhibited a significant improvement when compared to the non-crosslinked CMC film. The findings indicated that films crosslinked with 10 % CA demonstrated favorable properties for application as edible coatings. These transparent films, ideal for packaging, prove effective in preserving the quality and sensory attributes of fresh bananas, including color retention, minimized weight loss, slowed ripening through inhibiting amyloplast degradation, and enhanced firmness during storage.

Evaluation of Micro- and Nano-Bismuth(III) Oxide Coated Fabric for Environmentally Friendly X-Ray Shielding Materials.

This research focuses on the development of environmentally friendly textile-based shielding composites, from micro-sized and nanosized Bi2O3 particles, against ionizing radiation. Polyester fabric dyne-coated with either micro- or nano-Bi2O3 particles shields some X-rays but the effectiveness is poor. With only ∼58% uptake of micro-sized Bi2O3 particles dyeing on polyester fabric, the insufficient amount of Bi2O3 leaded to the low density of particles, resulting in only 30% of X-ray shielding at 80 kVp. Cotton fabric coated with either micro- or nano-Bi2O3/poly(vinyl alcohol) (PVA) composites, on the other hand, demonstrated the capacity to attenuate X-ray generated by high diagnostic X-ray tube voltages of 70-100 kVp, in compliance with medical protection requirements. The X-ray attenuation performance of cotton fabric coated with either micro-Bi2O3/PVA or nano-Bi2O3/PVA nanocomposite decreased progressively with increasing tube acceleration voltages, however their ionizing radiation-shielding performance enhanced with the number of fabric layers. Interestingly, for all X-ray tube voltages evaluated, the micro-Bi2O3/PVA composite outperformed the nano- Bi2O3/PVA composite in terms of X-ray shielding. At a weight ratio of 66.7% Bi2O3, 10 layers of cotton fabric coated with micro- Bi2O3/PVA composite can attenuate 90, 85, and 80% of X-ray photons at 70, 80, and 100 kVp, respectively. As a result, these less harmful X-ray shielding materials have the potential to replace lead-based composites, which are highly toxic to human health and have negative environmental consequences.

A Simple and Precise Estimation of Water Sliding Angle by Monitoring Image Brightness: A Case Study of the Fluid Repellency of Commercial Face Masks.

Fluid repellency of a hydrophobic surface has been typically demonstrated in terms of water sliding angle. A drop shape analysis method with a written computer algorithm monitoring the image brightness was proposed to precisely estimate the sliding angle. A hydrophobic surface coated with silanized silicon dioxide or polytetrafluoroethylene was selected as a known sample for the method validation. Average pixel brightness in an 8-bit grayscale unit rapidly increased after a water drop rolled off the surface, thus removing its black pixels. The resulting sliding angle was then determined as the tilt angle of the sample stage related to the sliding time at the brightness leap. The optimized angular speed of the rotor at 0.1 degrees per frame was chosen to avoid an overestimation of the sliding angle due to the deceleration. The proposed method yielded accurate sliding angles with an error of less than 0.2 degrees. It was then applied to study the fluid resistance of commercial face masks including disposable surgical masks and reusable fabric masks. It was found that the outermost layer of the single-use surgical masks can moderately repel a water drop with a sliding angle of 49.4 degrees. Meanwhile, the pre-coated fabric masks retained high protection efficiency at a sliding angle of less than 45 degrees after about 20 wash cycles. In addition, a raw muslin fabric coated with a commercial water-repellent spray could be a promising and affordable alternative to the surgical mask during the pandemic with high water repellency even after a few washes. The results suggested that, besides the hydrophobicity indicated by the typical contact angle, the precise sliding angle estimated by the proposed alternative method could additionally provide crucial information that might lead to a detailed discussion of the fluid repellency of rough materials.

Influence of alcohol treatments on properties of silk-fibroin-based films for highly optically transparent coating applications.

Thin films of silk fibroin were prepared by solvent evaporation from calcium chloride/ethanol aqueous solution. The influence of alcohol treatments on thermal, mechanical and optical properties of silk-fibroin-based film is presented. To understand the conformal structure of the alcohol-treated silk fibroin film, the IR spectral decomposition method is employed. The optical properties especially the optical transparency, haze and fluorescence emission of alcohol-treated silk fibroin film is systematically investigated together with the conformal structure to understand the effect of the fibril such as the beta-sheet influencing the optical properties. Monohydric alcohol treatment increased beta-turn content in the regenerated silk fibroin structure. These affected the amount of light diffusion and scattering within silk-fibroin films. With alcohol-treatment, all the silk-fibroin films exhibit exceptional optical transparency (>90%) with different levels of optical haze (2.56-14.17%). In particular, ethanol-treated silk-fibroin films contain the highest content of beta-turns (22.8%). The ethanol-treated silk-fibroin films displayed a distinct interference of oscillating crests and troughs in the UV-Vis transmittance spectra, thereby showing the lowest optical haze of 2.56%. In contrast, the silk-fibroin films treated with methanol and propanol exhibit the highest (14.17%) and second-highest (10.29%) optical transmittance haze, respectively. The beta-turn content of the silk-fibroin films treated with methanol is the lowest (20.5%). These results show the relationship between the beta-turn content and optical haze properties. The results manifestly provide a method to manufacture exceptional optically transparent silk-fibroin films with adjustable light diffusion and scattering which can be designed to meet specific applications with the potential to provide UV-shielding protection via monohydric alcohol treatment.