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The auspicious merits of polysaccharides make them eminent choices in numerous fields, particularly water remediation. Nonetheless, polysaccharides like chitosan (CTS) suffer from low adsorbability. Meanwhile, the recent revolution in material science has produced substances with supreme adsorbability, such as metal-organic frameworks (MOFs). Consequently, the Fe/MOF-5@CTS composite film was synthesized by doping a low amount (5 wt%) of Fe/MOF-5 into the CTS film. The crystallinity, morphology, composition, and surface charge of the Fe/MOF-5@CTS composite film were identified using multiple characterization analyses. Furthermore, the adsorption property of Fe/MOF-5@CTS was examined for the removal of Congo red (CR). Surprisingly, the Qmax of CR onto Fe/MOF-5@CTS reached 219.78 mg/g. Additionally, the composite film only lost 18.54% of its capacity after ten cycles. The selectivity test demonstrated the higher selectivity of the positively charged-rich composite film towards anionic dyes, especially CR, compared to the cationic dyes. Based on the practical experiments and analysis tools, the adsorption mechanism of CR onto Fe/MOF-5@CTS is presumed to occur via electrostatic, host-guest, π-π interaction, and coordination bonds.

Consumer demands and requirements by regulatory agencies to use more environmentally friendly and less polluting packaging have directed researchers to consider packaging materials that are naturally derived or made from renewable resources to replace or reduce use of synthetic polymers. Biodegradable and/or edible films have the potential to reduce some traditional synthetic polymeric packaging materials for specific applications. In recent years, biodegradable films prepared with animal and vegetable proteins have received increasing attention and are increasingly being used in the food-packaging industry due to their relative abundance, film-formation capacity, biodegradability, and nutritional value. However, the ideal protein films for food-packaging application should be strong, be elastic, and have very low permeability. The aim of this review is to offer a comprehensive view of recent state-of-the-art protein-based films as biodegradable materials applicable to food packaging with special reference to the application and combination of technological advances. Such advances include plasticization, cross-linking techniques, nanotechnology, and composite films. The results indicate that the functional properties of protein films are still not comparable with those of synthetic films, but there are promising potential methodologies that might further improve the mechanical and barrier properties of protein-based films. Nanocomposite films with well-controlled structures comprise an up-and-coming area of research. Research into nanocomposite film includes the opportunity to design biofilms and packaging materials with the precisely desired functional properties. By employing natural agents with antimicrobial and antioxidant properties, these materials promise to provide maintenance during storage time and to increase the shelf life of food products.

In this study, hydrophobic polymer composite films based on polyurethane (PU) were prepared for oil-water separation. Hydrophilic fumed silica (nano-SiO 2 ) was introduced as reinforcing filler, and silane coupling agent (KH550) was used to crosslink PU with nano-SiO 2 in situ for enhancing the nano-SiO 2 dispersion in the films. The microscopic morphology, crystalline structure, and hydrophobic properties of the films were characterized by using scanning electron microscopy, X-ray diffraction, FTIR spectroscopy, water contact angle, and water absorption tests. The results showed that the hydrophobicity of the nano-SiO 2 /PU composite films increased with the addition of nano-SiO 2 . KH550 not only significantly promoted the crosslink action between PU and nano-SiO 2 but also enhanced the dispersion of nano-SiO 2 in the composite films. Moreover, the pore structure of the prepared films was changed with the addition of nano-SiO 2 and KH550, which greatly improved the hydrophobicity. The test results for oil-water separation performance showed that the prepared composite films can efficiently separate the oil from oil-water mixtures with good repeatability.

Cellulose is lack of UV-blocking and antibacterial properties, which have limited its application. In this work, the nanoscale lignin with high content of hydroxyl groups and small particle size in prehydrolysate was isolated and used as a green reinforcement ingredient for fabrication of cellulose nanofibril (CNF) films with excellent mechanical properties, as well as UV protection and antibacterial capabilities. Cryogenic transmission electron microscopy (Cryo-TEM) and nuclear magnetic resonance analyses showed that the resulting lignin was in the form of nanoparticles (6–12 nm) with high phenolic hydroxyl contents (4.9 mmol/g). The optimum lignin inclusion rate of 5% allowed it to reinforce CNF composite film, increasing its tensile strength from 108.5 to 143.3 MPa. In addition, the film exhibited excellent UV protection capabilities. It blocked 91.5% of UV-A and 99.9% of UV-B light. Finally, the resulting lignin-based CNF films exhibited antibacterial activities against both Escherichia coli and Streptococcus hemolyticus. This work demonstrates the utility of nanoscale lignin from prehydrolysate can be used to produce cellulose-based composite films with valuable properties.

Ethyl cellulose (EC) was filled with bentonite (Bent) particles by mechanical dispersion to produce composite film materials that were studied using various methods. According to X-ray diffraction (XRD) analysis, the inter-chain separation length was larger in EC/Bent composite then those in pure polymer. Infrared spectrometry indicated a formation of hydrogen bonds between the hydroxyl groups of EC and the silanol groups of clay. Tests showed an increase in tensile strength of the polymer material (by 35–40%) when doped with bentonite. It was found that modification of polymer with bentonite resulted in increasing of the adsorption efficiency of methylene blue (MB): the equilibrium concentration of MB ions in adsorbent phase increased 2.5 times. The MB adsorption kinetics obeyed the pseudo-first-order mechanism. Isotherms were in good agreement with Langmuir model. For the composite, the maximum monolayer adsorption capacity was 4 times higher than that for pure polymer.

The waste valorization of spent coffee grounds (SCGs), which are obtainable in large amounts worldwide for new non-wood source has been considered. Cellulose nanofibers derived from SCGs have been successfully produced by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation of SCGs containing 10% cellulose (dry weight). The TEMPO-oxidized cellulose nanofibers (TOCNFs) are 20–35 nm wide observed by scanning electron microscopy. X-ray diffraction showed that TOCNFs are present in a cellulose crystal form I. The average crystal size corresponding to a fiber width was 4.2 nm, as determined from the diffraction pattern. Solid-state NMR shows that hemicellulose and lignin were mostly removed from SCGs via TEMPO-mediated oxidation, but small amounts of triacylglycerols remained in the TOCNFs. Thermogravimetric analysis of TOCNFs showed two major steps of thermal decomposition at 251 °C and 267 °C, which were higher than the coffee roasting temperature range. Furthermore, in order to investigate an interaction of these TOCNFs with a polymer, a SCG-derived TOCNF composite film with poly(vinyl alcohol) as a water-soluble polymer was prepared. We found the TOCNFs were successfully integrated into the polymer. The outcome of this study indicated that SCGs could be used as well as wood as an alternative source for producing TOCNFs, thus contributing to the development of sustainable green chemistry.Graphic abstract

In this present work, a PVA/PVP-blend polymer was doped with various concentrations of neodymium oxide (PB-Nd+3) composite films using the solution casting technique. X-ray diffraction (XRD) analysis was used to investigate the composite structure and proved the semi-crystallinity of the pure PVA/PVP polymeric sample. Furthermore, Fourier transform infrared (FT-IR) analysis, a chemical-structure tool, illustrated a significant interaction of PB-Nd+3 elements in the polymeric blends. The transmittance data reached 88% for the host PVA/PVP blend matrix, while the absorption increased with the high dopant quantities of PB-Nd+3. The absorption spectrum fitting (ASF) and Tauc’s models optically estimated the direct and indirect energy bandgaps, where the addition of PB-Nd+3 concentrations resulted in a drop in the energy bandgap values. A remarkably higher quantity of Urbach energy for the investigated composite films was observed with the increase in the PB-Nd+3 contents. Moreover, seven theoretical equations were utilized, in this current research, to indicate the correlation between the refractive index and the energy bandgap. The indirect bandgaps for the proposed composites were evaluated to be in the range of 5.6 eV to 4.82 eV; in addition, the direct energy gaps decreased from 6.09 eV to 5.83 eV as the dopant ratios increased. The nonlinear optical parameters were influenced by adding PB-Nd+3, which tended to increase the values. The PB-Nd+3 composite films enhanced the optical limiting effects and offered a cut-off laser in the visible region. The real and imaginary parts of the dielectric permittivity of the blend polymer embedded in PB-Nd+3 increased in the low-frequency region. The AC conductivity and nonlinear I-V characteristics were augmented with the doping level of PB-Nd+3 contents in the blended PVA/PVP polymer. The outstanding findings regarding the structural, electrical, optical, and dielectric performance of the proposed materials show that the new PB-Nd+3-doped PVA/PVP composite polymeric films are applicable in optoelectronics, cut-off lasers, and electrical devices.

The choice of cathode and anode materials for electrochromic devices plays a key role in the performance of electrochromic smart windows. In this research, WO 3/Ag and TiO 2/NiO composite thin films were separately prepared by the hydrothermal method combined with electrodeposition. The electrochromic properties of the single WO 3 thin film were optimized, and TiO 2/NiO composite films showed better electrochromic performance than that of the single NiO film. WO 3/Ag and TiO 2/NiO composite films with excellent electrochromic properties were respectively chosen as the cathode and the anode to construct a WO 3/Ag‒TiO 2/NiO electrochromic device. The response time ( t c = 4.08 s, t b = 1.08 s), optical modulation range (35.91 %), and coloration efficiency (30.37 cm 2·C −1) of this electrochromic device are better than those of WO 3‒NiO and WO 3/Ag‒NiO electrochromic devices. This work provides a novel research idea for the performance enhancement of electrochromic smart windows.

In this work, citric acid (CA) modified starch/gelatin composite films were prepared by mixing modified starch and gelatin in different proportions (1:0, 1:1, 1:4, 4:1 and 0:1). Blending of chemically modified starch with food grade CA and gelatin as second polymers were studied as a new and novel approach for fabrication of eco-friendly composite films with excellent packaging properties. Taking considerations of improvement in functional properties of the films, a series of starch films were derived using CA–starch and gelatin using solution casting approach. Influence of CA (0.5%, 1%, 3%, 5% and 7% w/w of total starch) on functional properties (moisture content, solubility, swelling index, moisture migration rate, moisture absorption, opacity and mechanical properties) were studied. FTIR and SEM analysis were utilized to characterize the interaction between the starch chains and surface morphology of films. Findings revealed that functional properties (aqueous solubility, swelling index, and moisture barrier properties) significantly (p < 0.05) improved as CA content increased. Composite films with CA–starch/gelatin of the ratio (4:1) revealed excellent functional properties. FTIR spectra illustrated strong interaction between the starch chains in the starch films. SEM analysis showed that gelatin exhibited good compatibility in the composite films. Therefore obtained composite films possessed a homogenious, dense and compact networks. In conclusion, CA and gelatin made better starch film properties and broadened the potential applications in the food packaging.

Thin-film nanocomposite (TFN) forward osmosis (FO) membranes have attracted significant attention due to their potential for solving global water scarcity problems. In this study, we investigate the impact of titanium oxide (TiO 2 ) and titanium oxide/reduced graphene (TiO 2 /rGO) additions on the performance of TFN-FO membranes, specifically focusing on water flux and reverse salt diffusion. Membranes with varying concentrations of TiO 2 and TiO 2 /rGO were fabricated as interfacial polymerizing M-phenylenediamine (MPD) and benzenetricarbonyl tricholoride (TMC) monomers with TiO 2 and its reduced graphene composites (TiO 2 /rGO). The TMC solution was supplemented with TiO 2 and its reduced graphene composites (TiO 2 /rGO) to enhance FO performance and reverse solute flux. All MPD/TMC polyamide membranes are characterized using various techniques such as scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle measurements. The results demonstrate that incorporating TiO 2 /rGO into the membrane thin layer improves water flux and reduces reverse salt diffusion. In contrast to the TFC membrane (10.24 L m −2 h −1 and 6.53 g/m 2 h), higher water flux and higher reverse solute flux were detected in the case of TiO 2 and TiO 2 /rGO-merged TFC skin membranes (18.81 and 24.52 L m −2 h −1 and 2.74 and 2.15 g/m 2 h, respectively). The effects of TiO 2 and TiO 2 /rGO stacking on the skin membrane and the performance of TiO 2 and TiO 2 /rGO skin membranes have been thoroughly studied. Additionally, being investigated is the impact of draw solution concentration. Graphical Abstract