Compact Film Structure Research Articles

Influence of 3-chloropropyl) triethoxysilane and pH on the properties of modified guar gum film

Guar gum (GG) as a polymer biopolymer is widely used in the field of bio-based packaging. However, its poor mechanical properties, barrier properties and high viscosity greatly hinder its use as an effective packaging material. Therefore, this study introduced CPTES to improve the mechanical (16.58–27.39 MPa) and tensile properties (26.80 %–30.67 %). The FTIR and XRD results indicated a strong interaction between the biofilm fractions modified by CPTES, CPTES bound to the hydroxyl groups on GG and formed a dense polysiloxane network through adsorption and grafting. OM and AFM reflect a denser and flatter film structure on the surface of the G30 film, which has the best film formation. Based on this, the pH of the solution was further adjusted to reach an alkaline environment, disrupting the intermolecular binding through electrostatic repulsion. The rheological behavior indicates that the viscosity and viscoelasticity of film solution gradually decrease with the increase in pH. OM and AFM results show that the G30/8 film has the best compact properties, while the nonporous compact film structure further improves the mechanical, barrierand and thermodynamic properties of the film. Accordingly, the findings of this study had a certain value for regulating the low viscoelasticity of GG emulsion and enhancing the stability of film formation.

Characterization of multilayer bacterial cellulose-chitosan films loaded with grape bagasse antioxidant extract: Insights into spectral and water properties, microstructure, and antioxidant activity

This work explores the development and characterization of composite multilayer films comprising bacterial cellulose (BC) and chitosan enriched with antioxidant compounds from grape bagasse extract (GE) and glycerol. SEM images revealed a compact structure with successful interactions between BC and chitosan, confirmed by FT-IR analysis. Equilibrium moisture content, water vapor permeability (WVP), swollen capacity, and solubility were systematically investigated, unveiling the influence of glycerol and GE concentrations. Moisture content increased with elevated glycerol and GE levels, attributed to their hydrophilic nature. WVP rose with higher concentrations of hydrophilic compounds, affecting the films' permeability. Swollen capacity decreased, and solubility increased with the addition of GE and glycerol, indicating a more compact film structure. The incorporation of GE conferred antioxidant properties to the films, as evidenced by DPPH and ABTS+ assays, and Total Phenolic Content (TPC) determination. TPC values varied from 0 to 1.75 mg GAE/g dried film, depending on GE. Fourier Transform Infrared Spectroscopy (FT-IR) highlighted polymeric associations, and UV–Vis spectra demonstrated enhanced UV-blocking properties. Overall, these multilayer films offer promising applications in food packaging, leveraging natural antioxidant sources for an enhanced functionality.

Edible film preparation by anthocyanin extract addition into acetylated cassava starch/sodium carboxymethyl cellulose matrix for oxidation inhibition of pumpkin seeds

In this study, an edible film was fabricated by incorporating anthocyanin extract from black rice (AEBR) into acetylated cassava starch (ACS)/carboxymethyl-cellulose (CMC) to enhance the shelf life of pumpkin seeds. The effects of AEBR on the rheological properties of film-forming solutions, as well as the structural characterization and physicochemical properties of the film, were evaluated. Rheological properties of solutions revealed that AEBR was evenly dispersed into polymer matrix and bound by hydrogen bonds, as confirmed by Fourier transform infrared spectroscopy analysis. The appropriate AEBR addition could be compatible with polymer matrix and formed a compact film structure, improving the mechanical properties, barrier properties, and opacity. However, with further addition of AEBR, the tensile strength and water vapor permeability decreased and the tight structure was destroyed. After being stored separately under thermal and UV light accelerated conditions for 20 days, the peroxide value and acid value of roasted pumpkin seeds coated with the AEBR film showed a significant reduction. Moreover, the storage stability of AEBR was improved through the embedding of ACS/CMC biopolymers. These results indicated that AEBR film could effectively delay pumpkin seeds oxidation and prolong their shelf life as an antioxidant material.

Development, characterization and application of colorimetric active packaging based on soy protein isolate, trehalose and Oxalis triangularis extract

Colorimetric active packaging based on soy protein isolate (SPI)/trehalose (TRE) and Oxalis triangularis extract (OTE) was developed for monitoring pork spoilage and preserving Actinidia arguta. The formation of intermolecular hydrogen bonds among TRE, OTE, and the SPI matrix resulted in a more compact film structure and improved mechanical, barrier and water resistance properties. The addition of OTE greatly increased the antibacterial and antioxidant activities of the films. The stability of the films improved due to their dense network structure and good barrier and antioxidant capacity. Among all samples, SPI films containing both TRE and OTE (ST-OTE) exhibited the best barrier and mechanical properties after 45 days of storage and maintained a high level of antioxidant activity after heating and UV irradiation. SPI-OTE and ST-OTE films showed good pH sensitivity and responsiveness and exhibited visible color changes during the monitoring of pork spoilage. Compared to the control group, ST-OTE effectively prolonged the storage period of A. arguta.

Design of corrosion-resistant absorbers with a core @ compact film structure based on the “dissolution-redeposition” theory

Chemical stability is the key factor of magnetic metal powder absorbers for their practical applications in the marine environment. Herein, a strategy of phosphating conversion coating (PCC) preparation based on the “dissolution-redeposition” theory which can regulate the surface dissolution reaction and deposition process of metal powder absorber was constructed reasonably. The TA/pH value of the phosphate conversion solution could be adjusted to reduce the hydrogen evolution rate and increase the nucleation rate of CaHPO4 to prepare compact PCC with a certain thickness on the surface of iron powder. Results show that among the different samples, the sample fabricated in TA/pH = 11.37 solution has the best corrosion resistance with the lowest corrosion current density (Icorr = 0.12 μA/cm2) and the highest corrosion potential (Ecorr = -0.453 V) due to the excellent compactness of PCC, and best microwave absorption performance due to the retained conductivity loss and improved impedance matching of the relatively thin thickness of PCC. The minimum reflection loss was -51.31 dB at 16.6 GHz and the effective bandwidth (RL < -10 dB) up to 5.4 GHz with a matching thickness of 2.28 mm. This work provides a useful reference for the design of integrated materials with microwave absorption and corrosion protection for practical applications.

Physicochemical, mechanical and barrier properties of semi‐refined carrageenan packaging films incorporated with germinated fenugreek seed extract

This work investigates the physicochemical, mechanical and barrier properties of edible packaging films based on semi‐refined κ‐carrageenan (SRC) plasticized with sorbitol and enriched with a water extract of germinated fenugreek seeds (W‐GeFS). The results showed that the incorporation of W‐GeFS into SRC films did not change their water solubility, but their moisture content increased when W‐GeFS was added at 1525 %. The incorporation of 120 % W‐GeFS increased significantly the tensile strength, reaching values comparable to or higher than those reported for conventional nonbiodegradable plastic films. A significant increase in the elongation at break was observed in SRC film containing 15 % W‐GeFS. Besides that, with the addition of 110 % W‐GeFS, Young’s modulus of SRC films significantly increased, indicating an increase in their stiffness. Significant enhancement on water vapor-barrier ability was achieved with the addition of 1 % W‐GeFS. Interestingly, light and oil barrier properties were remarkably improved after W‐GeFS incorporation. Microstructural studies of selected SRC films indicated that W‐GeFS is compatible with the SRC matrix and formed a compact film structure. In conclusion, SRC films containing W‐GeFS could be ideal candidates for sustainable food packaging.

Organic Acids Modified Starch–CMC Based Biodegradable Film: Antibacterial Activity, Morphological, Structural, Thermal, and Crystalline Properties

A novel organic acid-modified starch and carboxymethyl cellulose (CMC) based films plasticized with glycerol were prepared from unconventional tikhur starch (Curcuma angustifolia) by solution casting. Wet milling was used in the laboratory to extract starch from the tikhur rhizome. Carboxymethyl cellulose, at a concentration of (0.2 g−1 starch dry basis) was blended with the starch to improve its film-forming properties. Three different treatments with varying organic acids (lactic, citric, and acetic acid) with a concentration of 5% w/w of starch (2 ppm) in a film-forming solution were given. The effect of organic acid incorporation on the antibacterial, morphological, structural, thermal, and crystalline properties of developed films was studied. The minimum inhibitory concentration values of the three organic acids against gram-negative (E. coli) and gram-positive (S. aureus) bacteria were measured using the tube dilution method. The MIC results revealed that lactic acid and citric acid are effective against both gram-negative and gram-positive bacteria, while acetic acid showed more effectiveness against gram-negative bacteria (E. coli). MBC results revealed that organic acids have potent bactericidal activity. Citric acid resulted in higher inhibition for gram-positive bacteria (S. aureus) compared to gram-negative bacteria (E. coli.). While acetic acid showed higher inhibition for E. coli. than S. aureus. Lactic acid displayed similar inhibition against both S. aureus and E. coli. Among different organic acids, lactic acid incorporation resulted in a more homogeneous, transparent, and thermally stable film. As evidenced by the micrographs, the lactic acid incorporation resulted in a compact film structure without any visible cracks. While X-ray diffraction showed an increase in crystalline properties due to organic acid modification. In this study, it was indicated that modification with organic acids (polycarboxylic acids) effectively improved the overall properties of developed films depending on the type of organic acid used. The developed films have the potential to replace harmful synthetic films in food packaging.

Chitosan films with tunable droplet size of Pickering emulsions stabilized by amphiphilic konjac glucomannan network

In this work, chitosan (CS) emulsion films were prepared with grapefruit essential oil (GEO) Pickering emulsions (OGEOs) stabilized by amphiphilic octenyl succinic anhydride (OSA) konjac glucomannan (OSA-KGM) network. The droplet size of emulsion was regulated by altering oil content in OGEOs (10 %, 20 %, 30 % and 40 %, w/w). The structural and physicochemical properties of CS films with tunable emulsion droplets (OGEOs) were investigated. The droplet size of OGEOs increased with the increasing content of GEO. FT-IR revealed that the formation of CS-OGEOs films was attributed to hydrogen bonding. CS-OGEOs films with large droplets presented smoother surface, enhanced water resistance, UV-shielding property, mechanical properties, but increased water vapor permeability (WVP) compared with CS-OGEOs films with small droplets. In addition, CS-OGEOs films with large droplets also presented compact film structure, controlled release of GEO, high efficiency of DPPH free radical scavenging and antibacterial activity. To sum up, incorporation of emulsion droplets was a good strategy for improving the structural and physicochemical properties of CS films.

Electrochemical Impedance Spectroscopic Investigations of Nanocomposite Thin-Film Formation at an Electrified Micro Liquid-Liquid Interface

Herein, the interface between two immiscible electrolyte solutions (ITIES) has been exploited as a pristine platform for electropolymerization of the 2D and 3D nanocomposite materials, i.e., metal nanoparticles (NPs) embedded within a conductive polymer matrix that are electrogenerated/electropolymerized simultaneously The free-standing conductive thin film can be prepared with an adjustable loading of metallic NPs, to be tailored for a variety of applications, including as catalytic electrodes in fuel cells, or act as a bioreceptor in a biosensor. Electrochemical impedance spectroscopy (EIS) has been used to investigate mechanistic aspects of film growth through two types of charge transfer processes, ion and electron transfer, that occur during electropolymerization. The thermodynamics of a heterogeneous electron transfer (HET) between redox centers, KAuCl4(aq) and terthiophene (TT, org), across the interface governs the electropolymerization reaction, including the rate, which is itself affected by the rate of diffusion of reactants toward the interface, ohmic resistance of the two electrolyte solutions, distance between reactants due to arrangement of ions at the interface, and reorganization energy of the involved species in the reaction. Electropolymerization is controlled through application of an applied external potential difference and monitored voltammetrically as well as by EIS. Curve fitting of EIS data was performed using an equivalent circuit incorporating a phase constant element (CPE) parallel to a resistor for non-ideal interfacial capacitance, and HET resistance across the film as it forms at the ITIES. Next, those elements are parallel to a resistor (R), and a Warburg element (W) to approximate ion transfer across the ITIES/porous thin-film as it grows (Fig. 1). Data suggest that the films electronic conductivity improves with increasing the [TT]:[KAuCl4] ratio. Increased capacitance was hypothesized to be linked to an increase in the effective surface area of the polymer film during its growth phase versus the molecularly smooth ITIES. Higher [TT]:[KAuCl4] ratios elicited higher capacitance as well as diffusion resistance which can be attributed to formation of a more compact film structure. Cyclic voltammetric and potential step methods are compared and discussed, highlighting the formed films final properties, including film thickness and conductivity. Figure 1

Preparation, physicochemical characteristics and bioactivity evaluation of pitaya peel extract/soy protein nanocomposite film containing zinc oxide nanoparticles by photocatalysis

Interactions between components in film-forming solution affected the physicochemical properties of active packaging. A series of soy protein isolate (SPI)-based nanocomposite films reinforced with zinc oxide nanoparticles and different pitaya peel extract (PPE) levels were fabricated by photocatalysis. Results showed that the tensile strength, oxygen and water vapor barrier properties, thermal stability and DPPH scavenging activity were substantially improved, but the elongation at break and transmittance decreased with the proportion of PPE increased due to the formation of a more compact film structure caused by the crosslinking of PPE and SPI, particularly at the SPI/PPE ratio of 1:2. However, excessive PPE was not conducive to the integrity and continuity of film structures. The SPI/PPE films had more favorable anti-bacterial activities against Staphylococcus aureus than Vibrio parahaemolyticus. Therefore, our finding suggested that photocatalytic SPI/PPE nanocomposite film is an interesting alternative to obtain materials with antimicrobial and antioxidant properties. Novelty impact statement Pitaya peel extract (PPE) was added into soy protein isolate (SPI)/ZnO film matrix through photocatalysis. Addition of PPE resulted in compact inner microstructures of the films. SPI-PPE conjugate greatly improved the antibacterial and antioxidant properties of the films.

Insight into the formation mechanism of soy protein isolate films improved by cellulose nanocrystals

This study aimed to evaluate the effects of cellulose nanocrystals (CNC) on the basic properties of soy protein isolate films, and especially to propose the corresponding formation mechanism. Tensile strength, barrier properties, and water resistance were effectively improved after the formation of nanocomposite films. Incorporating CNC could restrict water mobility and improve the viscoelastic properties of films. Appropriate content of CNC (0.50% and 0.75%) promoted the construction of a more homogeneous and compact film structure, which may be attributed to the CNC-induced conformational modifications and the enhanced hydrophobic and hydrogen-bond interactions. While excessive CNC (1.00%) was not conducive to the integrity and continuity of film structures, resulting in the weakened functional properties. The obtained films were able to decrease total viable counts and total volatile basic nitrogen of stored pork, and extend the shelf-life of strawberry. This work offers a theoretical basis for the application of CNC in packaging industry.

Effect of Cellulose Nanocrystal Addition on the Physicochemical Properties of Hydroxypropyl Guar-Based Intelligent Films.

As an important functional material in food industry, intelligent packaging films can bring great convenience for consumers in the field of food preservation and freshness detection. Herein, we fabricated pH-sensing films employing hydroxypropyl guar (HPG), 1-butyl-3-methylimidazolium chloride (BmimCl), and anthocyanin (Anth). Besides, the effects of adding cellulose nanocrystals (CNC) into the composite films upon the films’ structures and physicochemical properties are elucidated. The addition of CNC promoted more compact film structures. Moreover, CNC dramatically improved several properties of the pH-sensing films, including the distinguishability of their color changes, sensitivity to pH, permeability to oxygen and water vapor, solvent resistance, durability, and low-temperature resistance. These results expand the application range of pH-sensing films containing CNC in the fields of food freshness detection and intelligent packaging.

Optimization, characterization and evaluation of papaya polysaccharide-corn starch film for fresh cut apples

In this study, we prepared corn starch (CS) and papaya polysaccharide (PPs) films using the solution casting technique. A Box-Behnken experimental design was used to determine the effect of ethanol concentration, extraction duration, and material concentration during PPs extraction. The resulting films were characterized in terms of structural changes, physical, optical, mechanical, Fourier-transform infrared (FTIR) spectroscopy, and thermal properties. The results show that PPs-CS composite films have good antioxidant and moisturizing properties and general antibacterial performance. These results revealed that after adding PPs, the films exhibited a significant increase in swelling and tensile strength, while depicted a reduction in thickness, transparency, and solubility. SEM images revealed that PPs and CS are highly compatible; moreover, FTIR spectroscopy showed that intermolecular hydrogen bonding existed between CS and PPs, forming a compact film structure. Finally, the incorporation of PPs and CS influenced the shelf-life of fresh cut apples, with the edible film incorporated with PPs positively improving sensory acceptance of combined materials.

Electrochemical degradation of neutral red on PbO2/α-Al2O3 composite electrodes: Electrode characterization, byproducts and degradation mechanism

PbO2/α-Al2O3 composite electrodes were successfully synthesized using composite electrodeposition technology and applied for the electrocatalytic degradation of neutral red (NR). The effect of α-Al2O3 particles on the surface morphology, structure, stability and electrochemical properties of PbO2/α-Al2O3 composite electrodes were characterized. The results showed that the incorporation of α-Al2O3 particles can fine the crystal size of lead dioxide and form compact film structure. PbO2/α-Al2O3 composite electrodes exhibited larger electrochemical active surface area, stronger hydroxyl radical generation ability and longer service lifetime than PbO2 electrodes. Electrochemical oxidization experiments showed that PbO2/α-Al2O3 composite electrodes had the higher neutral red and COD removal efficiency, lower energy consumption and minimum Pb dissolution than PbO2 electrodes. Finally, hypothetical electrocatalytic degradation pathway of neutral red on PbO2/α-Al2O3 composite electrode was proposed, which was dominated by hydroxyl radical mediated oxidization reaction. Under reaction with hydroxyl radicals, neutral red was gradually de-functionalized and hydroxylized to form π-delocalization shrink byproducts, which were transformed to multiple organic acids and then to inorganic substances H2O and CO2 ultimately.

Toward wearable electronics: A lightweight all-solid-state supercapacitor with outstanding transparency, foldability and breathability

Wide applications of smart wearable electronics have triggered tremendous needs for energy storage devices featuring lightweight, transparency, foldability and breathability. However, conventional supercapacitor electrodes are always substrate-supported with a compact film structure, which strongly limits their air permeability, flexibility and transparency. In this report, we demonstrate the use of a freestanding, ultrathin (∼ 6 μm), highly conductive (4 × 105 S/m), highly transparent (> 91%), air permeable (2600 mm/s at 10 Pa) and foldable metallic mesh electrode, decorated with active MnO2 microstructures, as a breathable, transparent and foldable supercapacitor electrode. By introducing Au nanoparticles as the “nanoglue” between Ni and MnO2, excellent electrochemical performances including large areal capacitance (268 mF/cm2) and high cycling stability (90.1% capacitance retention after 10000 cycles) are obtained in the MnO2-Au-Ni mesh electrode. Furthermore, the assembled all-solid-state supercapacitor device delivers high optical transparency (∼83.6%), high air permeability (45.4 mm/s at 100 Pa), superior electrochemical performances and can withstand various deformations including bending, folding, and crumpling. The present freestanding mesh structure electrode could be further explored and applied in more potential applications, such as ion batteries, wearable sensors, and conformal healthcare devices.

Interfacial rheology of a novel dispersed particle gel soft heterogeneous combination flooding system at the oil-water interface

The interfacial phenomena reflected by the thickness of oil films and the stability of oil-in-water emulsions were observed in the soft heterogeneous combination (SHC) flooding process, which were closely linked with the oil recovery. In this work, the effects of tetradecyl hydroxyl sulfo betaine (THSB) concentration and dispersed particle gel (DPG) concentration on the interfacial rheology were investigated; the adsorption performance at different temperatures, salinities and aging times were also systematically evaluated to determine the impact of external factors. The results show that three interactions appeared between the surfactant molecules and DPG particles. The adsorption process presents four stages. At a low THSB concentration and low DPG concentration, some DPG particles can adsorb on the interface together with the surfactant molecules, which markedly increase the adsorption film strength. When the THSB concentration increases, the surfactant molecules tend to interact with each other and aggregates of the surfactant molecules with DPG particles also appear, thereby damaging the compact film structure. As DPG particles are continuously added, the aggregates between particles enhance the strength of the adsorption film. Additionally, interfacial properties were maintained at high-temperatures, high-salinities and long aging times, which indicates the promising application of the SHC flooding system in reservoirs.

Bio-Inspired &lt;i&gt;In Situ &lt;/i&gt;Fabrication of 11-Mercaptoundecanoic Acid Coating on Stainless Steel 304 for Corrosion Protection

Bio-inspired in situ fabrication of 11-Mercaptoundecanoic Acid was proposed to prepare self-assembled coating of alkanethiolates on SS304 alloy. In this method, the SS304 was coated with a reactive biopolymer – Polydopamine (PDA) by dispersing them in a dopamine solution and mildly stirring at room temperature with subsequent covalent attachment of 11-Mercaptoundecanoic Acid molecules through the interaction between thiol groups and Polydopamine. The formation and surface structure of the coating were characterized by water contact angle measurement, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The electronic properties of such obtained functional film were studied by potentiodynamic polarization curve and EIS in 3.5% NaCl solution. Corrosion protection efficiency near 99 % was evaluated, and the excellent corrosion resistance property could be ascribed to the compact film structure and good seawater stability for modified SS304 surface, especially in limiting the infiltration of Cl-.

Antibacterial and photocatalytic properties of Cu2O/ZnO composite film synthesized by electrodeposition

The high antibacterial and photocatalytic activities of Cu2O/ZnO composite films were synthesized through the electrodeposition method. The crystalline phase and microstructure of the film samples were analyzed based on X-ray diffraction and scanning electron microscopy. The Cu2O/ZnO composite film-50 min has uniform and compact film structure with a large surface area. Compared with neat Cu2O film, the spectral response range of Cu2O/ZnO composite film was clearly enlarged to 265–560 nm, indicating that it had stronger spectral response ability in both UV and visible light. Among all the photocatalytic film samples, the Cu2O/ZnO composite film-50 min showed a better antibacterial activity against Escherichia coli (90.23 %) and Staphylococcus aureus (88.78 %) under fluorescent light. In addition, the Cu2O/ZnO composite film-50 min also exhibited the optimal photocatalytic property for the degradation of formaldehyde (80.33 %) under LED light irradiation. Moreover, the high photocatalytic and antibacterial stability in the cycle experiment indicate that Cu2O/ZnO composite film-50 min could be an excellent semiconductor photocatalytic material with high usability in practical applications.

The effect of thermal treatment on polymer-dispersed single-walled carbon nanotube transparent conductive film

Thermal treatment was performed on polymer-dispersed single-walled carbon nanotube (SWCNT) transparent conductive films (TCFs). By using differential scanning calorimetry, thermogravimetry analysis, Fourier transform infrared and Raman spectroscopies, the proper heating temperature and time were determined, resulting in films with the minimum sheet resistance. The post treatment with proper heating temperature and time was used to decrease the sheet resistance from 1100 to 500 Ω/cm−2 with no change in transparency at 250 °C for 1.5 h. The film thickness and surface roughness were reduced significantly, whereas the hardness increased as a result of the more compact film structure. During the heating, the residual polymeric dispersant acquired considerable fluidity causing morphological changes in the SWCNT TCFs. Furthermore, the polymer content on the film was reduced when the thermal treatment was performed above the decomposition temperature of the polymer, as confirmed by the X-ray photoelectron spectroscopy analysis.

Structural and surface characterization of magnetron sputtered In1−xAlxN films grown on GaAs substrates

This paper reports the structural and surface features of In1−xAlxN films grown on GaAs substrates with ZnO buffer layer by using reactive magnetron co-sputtering of Al and In targets in Ar–N2 at 100°C. The Al sputtering power was varied between 100W and 300W with respect to the fixed In power (50W) to obtain different compositions of the films. X-ray diffraction (XRD) studies revealed the formation of nanostructured In1−xAlxN films along (0002) and (101¯1) planes with composition ‘x’ ranging from 0.4 to 0.9. Intensity of the diffraction peaks and crystallite size were decreased with increase of the Al contents in the film. Field emission scanning electron microscopy (FESEM) results indicated that a compact film structure changes into a relatively loose structure by increasing the Al power.