Preparation of turmeric-derived sulfur-functionalized carbon dots: antibacterial and antioxidant activity

Journal of Materials Science - The work describes the preparation of carbon dots using turmeric as the carbon source and their functionalization with sulfur to enhance the functionality. The...     

Thermodynamic Analysis of Water Vapor Sorption Isotherms and Mechanical Properties of Selected Paper-Based Food Packaging Materials

ABSTRACT:  Adsorption isotherms of 3 selected paper-based packaging materials, that is, vegetable parchment (VP) paper, Kraft paper, and solid-bleached-sulfate (SBS) paperboard, were determined at 3 different temperatures (25, 40, and 50 °C). The GAB isotherm model was found to fit adequately for describing experimental adsorption isotherm data for the paper samples. The monolayer moisture content of the paper samples decreased with increase in temperature, which is in the range of 0.0345 to 0.0246, 0.0301 to 0.0238, and 0.0318 to 0.0243 g water/g solid for the MG paper, the Kraft paper, and the SBS paperboard, respectively. The net isosteric heats of sorption ( q_st ) for the paper samples decreased exponentially with increase in moisture content after reaching the maximum values of 18.51, 27.39, and 26.80 kJ/mol for the VP paper, the Kraft paper, and the SBS paperboard, respectively, at low-moisture content. The differential enthalpy and entropy of 3 paper samples showed compensation phenomenon with the isokinetic temperature of 399.7 K indicating that water vapor had been adsorbed onto the paper samples with the same mechanism. Depending on the paper material, tensile strength of paper samples was affected by moisture content.     

Water resistance and mechanical properties of biopolymer (alginate and soy protein) coated paperboards

The effect of biopolymer coating on the water barrier and mechanical properties of paperboards used as corrugated fiberboard box liners was studied under several conditions. Paperboards were coated with selected biopolymers, such as alginate and soy protein isolate (SPI) and studied with or without further treatment, such as cross-linking through CaCl₂ or formaldehyde treatment and compositing with organically modified montmorillonite (OMMT). Biopolymer coating increased the thickness of paperboards from 9% to 16%, depending on the coating materials and treatment methods, and resulted in a smoother and more homogeneous surface. Though the tensile strength (TS) of the coated paperboards decreased from 12.5% to 37.5% of the uncoated paperboards by coating, ring crush strength was not decreased. Wetting properties, such as contact angle of water drop, dynamic change in contact angle, water vapor permeability (WVP), and water absorptivity were also affected by biopolymer coating, but the degree of change was dependent on the coating materials as well as treatment methods. For example, the rate of change in contact angle of water on paperboards decreased dramatically from 1.4 to 3.8 times depending on the coating materials as well as treatment methods. Generally, SPI-coated paperboards were more water-resistant than alginate coated ones. However, water resistance of the alginate-coated paperboards post-treated with the CaCl₂ solution was comparable to the SPI coated ones.     

Copper-based nanoparticles for biopolymer-based functional films in food packaging applications

This review summarizes the latest developments in the design, fabrication, and application of various Cu-based nanofillers to prepare biopolymer-based functional packaging films, focusing on the effects of inorganic nanoparticles on the optical, mechanical, gas barrier properties, moisture sensitivity, and functional properties of the films. In addition, the potential application of Cu-based nanoparticle-added biopolymer films for fresh food preservation and the effect of nanoparticle migration on food safety were discussed. The incorporation of Cu-based nanoparticles improved the film properties with enhanced functional performance. Cu-based nanoparticles such as copper oxide, copper sulfide, copper ions, and copper alloys affect biopolymer-based films differently. The properties of composite films containing Cu-based nanoparticles depend on the concentration of the filler, the state of dispersion, and the interaction of the nanoparticles with the biopolymer matrix in the film. The composite film filled with Cu-based nanoparticles effectively extended the shelf life by maintaining the quality of various fresh foods and securing safety. However, studies on the migration characteristics and safety of copper-based nanoparticle food packaging films are currently being conducted on plastic-based films such as polyethylene, and research on bio-based films is limited.     

Water vapor adsorption isotherms of agar-based nanocomposite films

Adsorption isotherms of agar and agar/clay nanocomposite films prepared with different types of nanoclays, that is, a natural montmorillonite (Cloisite Na(+) ) and 2 organically modified montmorillonites (Cloisite 30B and Cloisite 20A), were determined at 3 different temperatures (10, 25, and 40 °C). The water vapor adsorption behavior of the nanocomposite films was found to be greatly influenced with the type of clay. The Guggenheim-Anderson-de Boer (GAB) isotherm model parameters were estimated by using both polynomial regression and nonlinear regression methods and it was found that the GAB model fitted adequately for describing experimental adsorption isotherm data for the film samples. The monolayer moisture content (m(o) ) of the film samples was also greatly affected by the type of nanoclay used, that is, m(o) of nanocomposite films was significantly lower than that of the neat agar film. Nanocomposite films prepared with hydrophobic nanoclays (Cloisite 30B and Cloisite 20A) exhibited lower m(o) values than those prepared with hydrophilic nanoclay (Cloisite Na(+) ).     

Kinetics of the Au-Ni-Sn ternary intermetallic layer redeposition at the solder/under-bump metallurgy interface during aging treatment

The Au-Ni-Sn ternary intermetallic layer redeposition at the interface between the solder and the Au/Ni/Cu under-bump metallurgy (UBM) was measured experimentally and analyzed theoretically. The predicted thicknesses of the layer, assuming Au diffusion in the Sn-3.5Ag solder matrix, were thicker than those measured experimentally. The thicknesses predicted in the Sn-37Pb solder matrix, on the other hand, were thinner than those measured experimentally. The discrepancies between the predicted and measured thicknesses were discussed based on findings, such as formation of the ternary phase and presence of AuSn₄ depletion zones in the solder matrices, and the stoichiometry of the ternary phase.     

Preparation and characterization of agar/clay nanocomposite films: the effect of clay type

Abstract: Agar‐based nanocomposite films with different types of nanoclays, such as Cloisite Na⁺, Cloisite 30B, and Cloisite 20A, were prepared using a solvent casting method, and their tensile, water vapor barrier, and antimicrobial properties were tested. Tensile strength (TS), elongation at break (E), and water vapor permeability (WVP) of control agar film were 29.7 ± 1.7 MPa, 45.3 ± 9.6%, and (2.22 ± 0.19) × 10^?9 g·m/m²·s·Pa, respectively. All the film properties tested, including transmittance, tensile properties, WVP, and X‐ray diffraction patterns, indicated that Cloisite Na⁺ was the most compatible with agar matrix. TS of the nanocomposite films prepared with 5% Cloisite Na⁺ increased by 18%, while WVP of the nanocomposite films decreased by 24% through nanoclay compounding. Among the agar/clay nanocomposite films tested, only agar/Cloisite 30B nanocomposite film showed a bacteriostatic function against Listeria monocytogenes.     

Dehydration characteristics of Maesaengi (Capsosiphon fulvescens) in hot-air drying

Maesaengi (Capsosiphon fulvescens) was dehydrated in a single layer at drying air temperatures ranging from 50–80°C in a laboratory scale convective dryer with an air velocity of 0.26 m/s. The effect of drying air temperature on the drying kinetic characteristics was determined. Maesaengi was dried to equilibrium moisture content within 200–600 min under these drying conditions. Drying rate curves of maesaengi showed an initial short period of a constant drying rate, followed by a falling drying rate period. The moisture decrease in the sample during dehydration was well described by the zero-order kinetic model. An Arrhenius-type equation was used to test the effect of temperature on drying rate according to an activation energy value of 29.36 kJ/mol.