Cs Films Research Articles

Preparation, Characterization, and Antimicrobial Activity of Chitosan/Kaolin Clay Biocomposite Films

AbstractChitosan (CS) is a polycation found in nature that exhibits many good properties. Kaolin (KAO) clay is a natural inorganic filler and is being used in medicine, ceramic, food additives, etc. Therefore, the mixing of two such biomaterials, a natural polycation (CS) and natural filler (KAO clay) may lead to a biocomposite, chitosan/kaolin (CS/KAO) clay, with many interesting properties. In this study, the composites of CS and KAO clay are prepared by mixing the solution of CS (in dilute acetic acid) with KAO clay at various weight ratios. FT‐IR, UV/Vis, X‐Ray diffraction, SEM, UTM, TGA, and DSC analyses are used to investigate these biocomposites thoroughly. Agar well diffusion method has been used to determine the antibacterial activities of different concentrations of the CS‐ KAO clay against gram ‐positive (Bacillus subtilis) and gram‐ negative (Escherichia coli) bacteria. The biocomposites exhibited antibacterial activities against tested microrganisms. In addition, swelling tests of the biocomposites are also carried out. The CS/KAO clay biocomposite films show better tensile strength than CS film. It is observed that dispersed KAO clay improves the thermal stability and enhances the hardness of the matrix systematically with the increase of its loading.

Levan-chitosan blend films: Preparation, structural, physical properties and application in pork packaging

Conventional fossil fuel-based packaging materials often brings of food safety and serious environmental pollution. It is significant to develop an environmentally-friendly packaging material. In this work, a levan-chitosan (LE/CS) blend film was fabricated via the solution casting method. The films were evaluated by Fourier transform infrared spectroscopy and X-ray diffraction, indicating the formation of hydrogen bonds between chitosan and levan. The mechanical properties of LE/CS films demonstrated a mechanical strength higher than CS films, and the best tensile strength appeared at a ratio of LE/CS (1:1) up to 18.78 ± 0.73 MPa. The addition of levan caused a significant increase in absorption of UV light with a reduction in swelling water of the blend films from 29.13 ± 0.53 % of chitosan film to 2.07 ± 0.27 % of LE/CS (1:1) film. A higher contact angle and lower WVP were observed for LE/CS blend films. LE/CS blend films were then used as packaging material for fresh pork and were well maintained the qualities. The study suggested that the new blend film might have a good prospect as a food packaging material.

Multifunctional Ag/ZnO/chitosan ternary bio-nanocomposites synthesized via laser ablation with enhanced optical, antibacterial, and catalytic characteristics

Organic dyes and microorganisms in industrial wastewater have harmed both the environment and human health. Herein, Ag/ZnO/chitosan (Ag/ZnO/Cs) ternary bio-nanocomposites were prepared by anchoring Ag NPs to the ZnO/Cs matrix by the laser ablation method as multifunctional materials. The proposed strategy enables the growth of very fine Ag NPs (2–10 nm) with good dispersion, resulting in the synthesis of Ag/ZnO/Cs composites with antibacterial effectiveness, enhanced UV–visible barrier characteristics, and boosted catalytic reduction properties. The successful formation of nanomaterials (ZnO and Ag) was confirmed by XRD, UV–Vis, HRTEM, and FTIR. The optical studies anticipate that the synthesized Ag/ZnO/Cs films will provide significant photocatalytic capability. TGA confirmed that the composite film had improved thermal stability over the Cs film. Staphylococcus aureus, Bacillus subtilus, Escherichia coli, and Pseudomonas aeruginosa are used to study the antibacterial activity of various Ag/ZnO/Cs hybrids. The influence of Ag NPs on increasing the catalytic potential of nanocomposite films was investigated by methyl orange (MO) reduction. The mechanism of enhanced catalytic reduction activity owing to ZnO/Ag co-sensitization was also discussed. Finally, within 10 min Ag/ZnO/Cs exhibited 90 % removal efficiency after four cycles, demonstrating the efficiency and stability of the composite catalyst in reduction procedures.

Functional Properties and Preservative Effect of P-Hydroxybenzoic Acid Grafted Chitosan Films on Fresh-Cut Jackfruit.

In the present study, p-hydroxybenzoic acid-grafted chitosan (PA-g-CS) conjugates with different grafting degrees were synthesized by a free radical-regulated grafting approach. The conjugates were further developed into films by casting, and their characteristics and preservative effects on fresh-cut jackfruit were evaluated. Compared to the CS film, the PA-g-CS film showed comprehensive performance improvements, including enhancements of water solubility, anti-ultraviolet capacity, antioxidation, and antibacterial activity. Moreover, compared with CS film, some appreciable and favorable changes of physical properties were observed in the PA-g-CS films, which included water vapor permeability, oxygen permeability, surface morphology, moisture content, and mechanical intensity. Furthermore, compared to CS alone, the application of PA-g-CS films to fresh-cut jackfruit exerted a beneficial effect on the quality of products, as indicated by the inhibition of weight loss, softening, and membrane damage, the maintenance of soluble solids and ascorbic acids contents, as well as a reduced bacterial count and a higher sensory score. Among these PA-g-CS films, the best preservation effect was achieved with the highest degree of grafting (PA-g-CS III). The results suggested that the PA-g-CS film has the potential to be explored as a new type of packaging material for the preservation of fresh-cut fruits and vegetables.

Dual Synergistic Effects of MgO-GO Fillers on Degradation Behavior, Biocompatibility and Antibacterial Activities of Chitosan Coated Mg Alloy

The aim of this work was to establish and characterize chitosan/graphene oxide- magnesium oxide (CS/GO-MgO) nanocomposite coatings on biodegradable magnesium-zinc-cerium (Mg-Zn-Ce) alloy. In comparison to that of pure CS coatings, all composite coatings encapsulating GO-MgO had better adhesion strength to the Mg-Zn-Ce alloy substrate. The result depicted that the co-encapsulation of GO-MgO into the CS layer leads to diminish of contact angle value and hence escalates the hydrophilic characteristic of coated Mg alloy. The electrochemical test demonstrated that the CS/GO-MgO coatings significantly increased the corrosion resistance because of the synergistic effect of the GO and MgO inside the CS coating. The composite coating escalated cell viability and cell differentiation, according to cytocompatibility tests due to the presence of GO and MgO within the CS. The inclusion of GO-MgO in CS film, on the other hand, accelerates the formation of hydroxyapatite (HA) during 14 days immersion in SBF. Immersion results, including weight loss and hydrogen evolution tests, presented that CS/GO-MgO coating enables a considerably reduced degradation rate of Mg-Zn-Ce alloy when compared to the bare alloy. In terms of antibacterial-inhibition properties, the GO-MgO/CS coatings on Mg substrates showed antibacterial activity against Escherichia coli (E. coli), with a large inhibition area around the specimens, particularly for the coating containing a higher concentration of GO-MgO. Bacterial growth was not inhibited by the bare Mg alloy samples. The CS/GO-MgO composite coating is regarded as a great film to enhance the corrosion resistance, bioactivity, and antibacterial performance of Mg alloy implants.

Development and characterization of active packaging films based on chitosan and sardinella protein isolate: Effects on the quality and the shelf life of shrimps

The transformation of wastes from food processing industry to value-added products is one of the major challenges in sustainable development. This work aimed to develop active packaging films based on chitosan (Cs) and sardinella protein isolate (SrPI) obtained from blue crab and Sardinella aurita by-products, respectively. The data from fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) indicate an improvement in the structural and thermal properties of the films by incorporating SrPI into the chitosan matrix. In contrast, the composite films exhibited lower mechanical properties than the Cs film. Composite and Cs films were employed to package the shrimp in order to improve their conservation. The results showed that the increased SrPI content in packaging films improved the chemical properties and microbial stability of wrapped shrimps during cold storage. Therefore, these results encourage the use of Cs-SrPI films as active packaging material.

Plasmon-enhanced photoemission from Au nanoparticles covered with cesiated film

The quantum efficiency (QE) and thermal emittance are two main parameters for photocathode, especially for the emission source of free electron laser (FEL) accelerator. It is in challenge how to reduce the rigorous fabrication of cathode and how to enhance the quantum efficiency for photocathode. Facing to the issues in our case, we have investigated plasmon-enhanced photoemission from Au nanoparticles (NPs) covered with Cs film in the microwave electron gun of free electron laser. The large-area preparation and low-cost photocathode are formed by rapid thermal annealing of thin Au films. Cs film covered is found to effectively excite photoelectrons from Au NPs under the visible light (at the 532 nm). The quantum efficiency (QE) of the Au NPs-Cs increases to 2.3 × 10−4 with the pico-second pulsed laser irradiation, and the normalized root mean square (RMS) thermal emittance of the electron beam is about 1.89 mm mrad. It confirms the feasibility for the proposed metallic nanoparticles to be applied to the high brightness electron sources.

Cationized high amylose maize starch films reinforced with borax cross-linked nanocellulose

In this study, a novel strategy for modifying nanocellulose (NC) by borax cross-linking was developed, and the obtained borax modified nanocellulose (BNC) was incorporated into cationized high amylose maize starch (CS) films to evaluate the applicability. Cellulose molecules were successfully cross-linked by boron ester bonds, and the original crystal type and basic chemical structure were not changed. Compared with NC, the relative crystallinity of BNC was slightly increased, and the thermal stability was obviously enhanced. Addition of NC and BNC to CS films significantly improved their tensile strength and water resistance. The dispersion of nanocellulose in CS films was effectively improved by borax cross-linking modification. CS/BNC films showed higher mechanical and water resistance properties compared with CS/NC films. Compared with pure CS film, tensile strength of the composite film with 6 wt% BNC increased about 4.0 times, and its water-vapor permeability decreased about 37%. The novel strategy for preparing BNC by using boron ester bonds will provide a potential approach for the development of starch films with desirable properties.

Development of active packaging films based on chitosan and nano-encapsulated luteolin

Luteolin is a flavone with potent antioxidant and antimicrobial activities. In this study, luteolin was encapsulated in oil-in-water nanoemulsions that were emulsified by glycerol monooleate and Tween 20. Results showed 68 mg luteolin-loaded nanoemulsions had the highest stability (zeta potential of −39.8 mV) and encapsulation efficiency (89.52%). Then, active packaging films were developed by incorporating free or nano-encapsulated luteolin into chitosan-based matrix. The microstructure, physical and functional properties of CS film containing free luteolin (CS-LL) or nano-encapsulated luteolin (CS-LLNEs) were compared. Different from CS film, CS-LL and CS-LLNEs films had compact inner microstructure and strengthened intermolecular interactions. Moreover, CS-LLNEs film was more homogenous and compact than CS-LL film. As a result, CS-LLNEs film presented higher water vapor and oxygen barrier abilities and mechanical properties in comparison with CS-LL film. In addition, CS-LLNEs film showed slower release rate of luteolin in 95% ethanol (fatty food stimulant) as compared with CS-LL film. The controlled release of luteolin from film matrix could guarantee CS-LLNEs film to exert antioxidant activity up to 10 days. Our results suggest CS-LLNEs film can be developed as an emerging active packaging material that has potential applications in food industry.

Immobilized Fe-Loaded Chitosan Film for Methyl Orange Dye Removal: Competitive Ions, Reusability, and Mechanism

Large scale application of solid sorbent for wastewater treatment have been barred with problems associated with its difficulty of filtration and adsorbent recovery from aqueous solution. The use of a solid support could eliminate these problems and offer better adsorption ability and reusability of the adsorbent. In this study, we have fabricated Fe-loaded chitosan (Fe-CS) film immobilized onto a glass support. The prepared Fe-CS film showed greater adsorption capacity of methyl orange (MO) by 22.5% as opposed to an unmodified CS film material. The adsorption isotherms, kinetics, thermodynamics, and reusability of the prepared adsorbent were investigated in detail. The adsorption profile under kinetic conditions adopted a best-fit according to the pseudo-second-order kinetic model, while the adsorption profiles equilibrium conditions were described by both the Langmuir and Temkin isotherm models. The trend for the maximum adsorption capacity (qm) at variable temperature are listed: 97.1 (303 K), 102 (313 K) and 205 mg g−1 (323 K). The binding mechanism of MO adsorption onto the immobilized Fe-CS film was by both electrostatic attractions and chelating interactions. As well, the findings of this study showed that the immobilized Fe-CS film is an effective adsorbent that can be easily recovered from treated water and recycled for multiple adsorption–desorption processes. The properties of the immobilized Fe-CS film demonstrate its excellent ability for the removal of MO dye or any similar pollutants.

Composite films based on chitosan and epigallocatechin gallate grafted chitosan: Characterization, antioxidant and antimicrobial activities

The effect of chitosan-epigallocatechin gallate conjugate (CS-EGCG) at various ratios (10:0, 9:1, 8:2, 7:3, 6:4 and 5:5, w/w) and glycerol (30 and 50%, w/w) on mechanical, barrier and optical properties of CS films and CS/CS-EGCG composite films was studied. CS films added with 30 or 50% glycerol (CS-30G or CS-50G, respectively) had high tensile strength and elongation at break. Generally, CS/CS-EGCG composite films had higher resistance to light transmission than CS films (p < 0.05). With augmenting concentrations of CS-EGCG, films with lower lightness (L*) and higher redness (a*) and yellowness (b*) were obtained. Therefore, among composite films, those with CS/CS-EGCG ratio of 8:2, containing 30 or 50% glycerol, were selected for further analyses in comparison to CS films. Composite films, regardless of glycerol levels, showed higher antioxidant and antimicrobial activities as compared to CS films (p < 0.05). Overall, CS/CS-EGCG (8:2) composite films had satisfactory physical properties with increased antimicrobial and antioxidant activities and could serve as promising packaging for food shelf-life extension.

Functional properties of chitosan films with conjugated or incorporated salicylic acid

The aim of this work to find out the influence of salicylic acid-grafted-chitosan (SA-g-CS) and salicylic acid incorporated chitosan on the properties of chitosan film. The SA-g-CS conjugated films (SA-g-CS Ⅰ, SA-g-CS Ⅱ, and SA-g-CS Ⅲ) and the SA-CS incorporated films (SA-CS Ⅰ, SA-CS Ⅱ, and SA-CS Ⅲ) with equivalent salicylic acid content were prepared, respectively. The physical, mechanical, and biological properties of SA-g-CS conjugated and SA-CS incorporated films were evaluated. The opacity and water solubility were enhanced, thickness and water vapor permeability changed, and moisture content, tensile strength and elongation at break of chitosan film decreased or increased after conjugation or incorporation of SA. Compared with CS film, SA-g-CS conjugated and SA-CS incorporated films showed enhanced antioxidant and antibacterial activities, and these activities increased with the increasing of SA content. SA-g-CS conjugated films possessed better water vapor barrier property, antioxidant and antibacterial properties than SA-CS incorporated films. Therefore, SA-g-CS conjugated films exhibited better functional properties than SA-CS incorporated films. Compared with incorporation, conjugation of SA with CS is a more efficient way to improve properties of CS film.

A facile sol–gel synthesis of chitosan–boehmite film with excellent acid resistance and adsorption performance for Pb(II)

A chitosan–boehmite (CS–boehmite) film with excellent acid resistance for effective Pb(II) removal was successfully synthesized via a facile sol–gel method. The composite, corresponding boehmite and CS films were characterized by XRD, ATR-FT-IR, TG, SEM and XPS. The static adsorption experiment showed that their adsorption well matched the pseudo-second order model on chemisorption adsorption, and the modified Langmuir model on homogenously surface for monolayer adsorption. Especially, the composite film with cross-linking mass ratio of 1:1 did not dissolve after shaking in an acidic solution of pH=2.0 for 1h due to formation of the monodentate C(O−Al)2 ligand, while the boehmite and CS films dissolved 24wt% and 100wt%, respectively. The maximum adsorption capacity of the composite film is 33.00mg/g from the modified Langmuir model which is much higher than 19.57mg/g of the boehmite film and 17.48mg/g of the CS film, respectively, and these values are highly close to their calculated values from the pseudo-second order model and also from the experiment values. Furthermore, the composite film shows strong capability of resisting disturbance for the coexisting cations (Na+, Mg2+, K+ and Ca2+); its adsorption mechanisms involve electrostatic attraction, complexation to form PbOH and the chemical precipitation of Pb3(CO3)2(OH)2.

Functional properties and preservative effect on Penaeus vannamei of chitosan films with conjugated or incorporated chlorogenic acid

The chlorogenic acid-grafted-chitosan conjugates (CA-g-CS) with three grafting ratios were synthesized. Then the CA-g-CS conjugated films (CA-g-CS I, CA-g-CS II, and CA-g-CS III) and the CA-CS incorporated films (CA-CS I, CA-CS II, and CA-CS III) with equivalent chlorogenic acid content were prepared, respectively. The physical, mechanical, and biological properties of CA-g-CS conjugated and CA-CS incorporated films were evaluated. Further, the CA-g-CS III and CA-CS III were chosen to evaluate their preservative effect on shrimp. Compared with CS film, CA-g-CS conjugated and CA-CS incorporated films showed enhanced opacity and water solubility, changed thickness and water vapor permeability, and reduced moisture content, tensile strength and elongation at break. Conjugation or incorporation of CA enhanced antioxidant and antibacterial activities of CS films, and these activities increased with the increasing of CA content. CA-g-CS III showed better preservative effect on shrimp than CA-CS III in terms of weight loss, pH value, total volatile basic nitrogen, total bacterial count and sensory score of shrimp during storage. Therefore, CA-g-CS conjugated films exhibited better bioactivities and preservative effect on shrimp than CA-CS incorporated films. Compared with incorporation, conjugation of CA with CS is a more efficient way to improve properties of CS film.

Massive\xa0and massless charge carriers in an epitaxially strained alkali metal quantum well on graphene

We show that Cs intercalated bilayer graphene acts as a substrate for the growth of a strained Cs film hosting quantum well states with high electronic quality. The Cs film grows in an fcc phase with a substantially reduced lattice constant of 4.9 Å corresponding to a compressive strain of 11% compared to bulk Cs. We investigate its electronic structure using angle-resolved photoemission spectroscopy and show the coexistence of massless Dirac and massive Schrödinger charge carriers in two dimensions. Analysis of the electronic self-energy of the massive charge carriers reveals the crystallographic direction in which a two-dimensional Fermi gas is realized. Our work introduces the growth of strained metal quantum wells on intercalated Dirac matter.

Cellulose Nanocrystal Reinforced Chitosan Based UV Barrier Composite Films for Sustainable Packaging.

In this study, green composite films based on cellulose nanocrystal/chitosan (CNC/CS) were fabricated by solution casting. FTIR, XRD, SEM, and TEM characterizations were conducted to determine the structure and morphology of the prepared films. The addition of only 4 wt.% CNC in the CS film improved the tensile strength and Young’s modulus by up to 39% and 78%, respectively. Depending on CNC content, the moisture absorption decreased by 34.1–24.2% and the water solubility decreased by 35.7–26.5% for the composite films compared with neat CS film. The water vapor permeation decreased from 3.83 × 10−11 to 2.41 × 10−11 gm−1 s−1Pa−1 in the CS-based films loaded with (0–8 wt.%) CNC. The water and UV barrier properties of the composite films showed better performance than those of neat CS film. Results suggested that CNC/CS nanocomposite films can be used as a sustainable packaging material in the food industry.

Enhancing the properties of gelatin–chitosan bionanocomposite films by incorporation of silica nanoparticles

AbstractFunctional enhancement of biopolymer was attempted in this work for food packaging application. Incorporation of chitosan (0–9%) and silica (0–10%) nanoparticles (NP's) into gelatin film (Gel) has been tried and their effects on moisture content, tensile strength (TS), elongation at break (%E), wettability, water vapor permeability (WVP), and antimicrobial activities were studied. Morphology of nanoparticles was studied using scanning electron microscopy and transmission electron microscopy. Chitosan NP's showed agglomeration at higher concentration which leads to lower the mechanical as well as barrier properties of the film. However, silica NP's enhanced the properties of bionanocomposite film. TS was increased from 6.05 MPa of pure gelatin film to a maximum value of 38.91 MPa at CS NP's of 5.8% and Si NP's of 7%; however, %E decreased with addition of nanoparticles resulting in brittleness of film. WVP for pure gelatin film was 25.21 g mm/kPa m2 day, which reduced to 3.30 g mm/kPa m2 day after incorporation of 10% Si NP's. Antimicrobial activity was observed against E. coli and S. aureus. Incorporation of CS NP's improved the antimicrobial activity of gelatin film. Si NP's showed improvement in mechanical and barrier properties of Gel–CS films, however, had no effect on antimicrobial activities.Practical ApplicationResearchers community are more concerned of natural biopolymers to reduce the use of synthetic polymers, especially in food packaging. Gelatin is one of the natural biopolymer and have potential to be used as food packaging material. Problem with gelatin and many other biopolymer based film is their poor mechanical and barrier properties. Present study was framed to overcome these problems by incorporating silica and chitosan nanoparticles in gelatin film. The results observed would be useful to develop a biopolymer based nanocomposite film with improved mechanical, barrier and antimicrobial properties, which can be used for active food packaging.

Antioxidant and antibacterial chitosan film with tea polyphenols-mediated green synthesis silver nanoparticle via a novel one-pot method

In the present study, the antioxidant and antibacterial chitosan/tea polyphenols-silver nanoparticles composite film (CS/TP-AgNPs) was developed via a novel one-pot method. The TP was added to the CS film not only as the reducing agent of AgNPs but also as the cross-linking agent and antioxidant. The AgNPs and nanocomposite films developed were characterized by field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Besides, the physical, mechanical, antioxidant and antibacterial properties of the nanocomposite films were also analyzed. As the content of TP-AgNPs incorporation increased, the color of CS/TP-AgNPs nanocomposite film gradually shifted to brown, accompanied by an increase in opacity and thickness. The decrease in moisture contents and water vapor permeability of CS/TP-AgNPs nanocomposite film indicated that the TP-AgNPs varied the original bond between the CS-CS and CS-water. The denser cross-section of CS/TP-AgNPs nanocomposite film confirmed the enhanced mechanical properties. It is worth noting that CS/TP-AgNPs nanocomposite film exhibited more excellent antioxidant and antibacterial activity than CS film. This study developed the multi-functionality chitosan film by the simultaneous incorporation of AgNPs and TP and revealed the multiple effects of TP acting as reducing agent for AgNPs, cross-linking agent and antioxidant on chitosan film.

Chitosan-based nitric oxide-releasing dressing for anti-biofilm and in vivo healing activities in MRSA biofilm-infected wounds

Bacterial biofilms on wounds impair the healing process and often lead to chronic wounds. Chitosan is a well-known biopolymer with antimicrobial and anti-biofilm effects. S-nitrosoglutathione (GSNO) has been identified as a promising nitric oxide (NO) donor to defend against pathogenic biofilms and enhance wound healing activities. In this study, we prepared NO-releasing chitosan film (CS/NO film) and evaluated its anti-biofilm activity and in vivo wound healing efficacy against methicillin-resistant Staphylococcus aureus (MRSA) biofilm-infected wounds in diabetic mice. The in vitro release study showed sustained release of NO over 3 days in simulated wound fluid. The CS/NO film significantly enhanced antibacterial activity against MRSA by > 3 logs reduction in bacterial viability. Moreover, CS/NO film exhibited a 3-fold higher anti-biofilm activity than the control and CS film. In in vivo MRSA biofilm-infected wounds, the CS/NO film-treated group showed faster biofilm dispersal, wound size reduction, epithelialization rates, and collagen deposition than the untreated and CS film-treated groups. Therefore, the CS/NO film investigated in this study could be a promising approach for the treatment of MRSA biofilm-infected wounds.

Evaluation of physical, mechanical, and biodegradation of chitosan/graphene oxide composite as bone substitutes

ABSTRACTIn this study, a nanocomposite was prepared from chitosan (Cs) and graphene oxide (GO) with different percentages. The results of Fourier-transform infrared spectroscopy, thermal gravity analysis, and X-ray diffraction showed that the presence of GO nanoparticles increased thermal stability and crystallinity of Cs. Tensile test results showed that the presence of 0.3 wt.% GO in Cs film increased the tensile strength and Young’s modulus by 296% and 193%, respectively. The results of bioactivity and biodegradation test showed that the presence of GO in Cs film increased the density of the apatite-like layer on the surface and the degradation time.