Cellulose Thin Films Research Articles

Detection of Hydrogen Peroxide Vapors Using Acidified Titanium(IV)-Based Test Strips

One method for the colorimetric detection of hydrogen peroxide vapor is based on a titanium–hydrogen peroxide complex. A color changing material based on a titania hydroxypropyl cellulose thin film was initially developed. However, as this material dries, the sensitivity of the material is significantly reduced. Thus, an alternative sensing material, based on titanium(IV) oxysulfate, an ionic liquid, and in some cases, triflouromethanesulfonic acid adsorbed onto low-cost silicon thin-layer chromatography (TLC) plates, was developed. TiO2 was heated with concentrated sulfuric acid in a controlled environment, usually at temperatures ranging from 100 °C to 250 °C. These sensors are disposable and single-use and are simple and inexpensive. When the resulting thin-film sensors are exposed to ppm levels of hydrogen peroxide vapor, they turn from a white reflective material to an intense yellow or orange. Ti(IV) oxysulfate combined with an acid catalyst and an ionic-liquid-based material provides an opportunity to enhance the sensor activity towards the peroxide vapor and decreases the detection limit. Kinetic measurements were made by the quantification of the intensity of the reflected light as a function of the exposure time from the sensor in a special cell using a low-cost web camera and a tungsten lamp. The measured rate of the color change indicates high sensitivity and first-order kinetics over a hydrogen peroxide concentration range of approximately 2 to 31 ppm. These new materials are a starting point for the preparation of more active sensor materials for hydrogen peroxide and organic peroxide vapor detection.

Thickness‐dependent glass transition temperature of hydroxyethyl cellulose thin films based on dielectric properties

AbstractHydroxyethyl cellulose (HEC) thin films with a molecular weight of 720,000 g/mol deposited by thermal evaporation in a thickness range of 250, 500, and 750 nm were measured in a frequency range of 1–105 Hz and a temperature range of 233–373 K for dielectric characterization with increments of 10 K. Dielectric results were used to derive and evaluate the glass transition temperature and ductility, which are essential parameters for structural analysis. Results showed that the thickness of HEC thin films was an effective parameter on dielectric and structural properties. Because of the increasing thickness, the dielectric constant has values between 22 and 143 at 1 kHz, and glass transition temperature and ductility change between 211–175 K and 15–20, respectively. Based on the literature and the compatible results, the main effect of these variations could be dead layers and voids in structure. The effect of the dead layer gave an important idea about the adjustability of mechanical properties of HEC thin films depending on the thickness. In this way, it would be possible to use these thin films deposited from HEC with 720,000 g/mol molecular weight, especially in drug delivery, electrophoresis technologies, biomedical devices, and coverage applications.

PH-dependent pressure-sensitive colonic capsules for the delivery of aqueous bacterial suspensions

Microbiome-based therapies hold great promise for treating various diseases, but the efficient delivery of live bacteria to the colon remains a challenge. Furthermore, current oral formulations, such as lyophilized bacterial capsules or tablets, are produced using processes that can decrease bacterial viability. Consequently, high dosages are required to achieve efficacy. Herein, we report the design of pressure-sensitive colonic capsules for the encapsulation and delivery of aqueous suspensions of live bacteria. The capsules consisted of 2 functional thin-films (hydrophobic and enteric) of ethyl cellulose and Eudragit S100 dip-coated onto hydroxypropyl methylcellulose molds. The capsules could be loaded with aqueous media and provide protection against acidic fluids and, to some extent, oxygen diffusion, suggesting their potential suitability for delivering anaerobic bacterial strains. Disintegration and mechanical studies indicated that the capsules could withstand transit through the stomach and upper/proximal small intestinal segments and rupture in the ileum/colon. In vitro studies showed that bacterial cells (anaerobic and aerobic commensals) remained highly viable (74–98%) after encapsulation and exposure to the simulated GI tract conditions. In vivo studies with a beagle dog model revealed that 67% of the capsules opened after 3.5 h, indicating content release in the distal gastrointestinal tract. These data demonstrate that live aqueous bacterial suspensions comprised of both aerobic and anaerobic commensals can be encapsulated and in the future might be efficiently delivered to the distal gastrointestinal tract, suggesting the practical applications of these capsules in microbiome-based therapies.

Fabrication of hybrid tin oxide‐cellulose nanocomposite as the flexible and thin supercapacitor

AbstractMicrofibrillated cellulose (MFC) with reinforcing effects is a useful building block in the fabrication of flexible and thin supercapacitors. Herein, a hybrid tin oxide‐cellulose nanocomposite was hydrothermally produced and coated on MFC thin films to form a supercapacitor. The hybrid tin oxide‐cellulose thin films were structurally analyzed using scanning electrode microscopy, Fourier transform infrared spectroscopy and x‐ray diffraction. The cellulose thin film with the highest loading of hybrid tin oxide‐cellulose nanocomposite exhibited a specific capacitance of 225.88 F g−1 at 100 mV s−1 and 486.38 F g−1 at 20 mV s−1 in the three‐electrode electrochemical system. In addition, it revealed good cyclic stability up to 40 cycles run continuously with 95% cyclic retention. The high specific capacitance and superior cyclic stability could be related to the enhanced charge mobility and ion diffusion between the solid and electrolyte interface. The cellulose thin film coated with flower‐like hybrid nanocomposite showed great potential in energy storage.

Porous Cellulose Thin Films as Sustainable and Effective Antimicrobial Surface Coatings.

In the present work, we developed an effective antimicrobial surface film based on sustainable microfibrillated cellulose. The resulting porous cellulose thin film is barely noticeable to human eyes due to its submicrometer thickness, of which the surface coverage, porosity, and microstructure can be modulated by the formulations and the coating process. Using goniometers and a quartz crystal microbalance, we observed a threefold reduction in water contact angles and accelerated water evaporation kinetics on the cellulose film (more than 50% faster than that on a flat glass surface). The porous cellulose film exhibits a rapid inactivation effect against SARS-CoV-2 in 5 min, following deposition of virus-loaded droplets, and an exceptional ability to reduce contact transfer of liquid, e.g., respiratory droplets, to surfaces such as an artificial skin by 90% less than that from a planar glass substrate. It also shows excellent antimicrobial performance in inhibiting the growth of both Gram-negative and Gram-positive bacteria (Escherichia coli and Staphylococcus epidermidis) due to the intrinsic porosity and hydrophilicity. Additionally, the cellulose film shows nearly 100% resistance to scraping in dry conditions due to its strong affinity to the supporting substrate but with good removability once wetted with water, suggesting its practical suitability for daily use. Importantly, the coating can be formed on solid substrates readily by spraying, which requires solely a simple formulation of a plant-based cellulose material with no chemical additives, rendering it a scalable, affordable, and green solution as antimicrobial surface coating. Implementing such cellulose films could thus play a significant role in controlling future pan- and epidemics, particularly during the initial phase when suitable medical intervention needs to be developed and deployed.

Quartz crystal microbalance with dissipation (QCM-D) as a way to study adsorption and adsorbed layer characteristics of hemicelluloses and other macromolecules on thin cellulose films: A Review

Cellulose and hemicellulose are abundant renewable resources. Thus, studying the adsorption mechanism of hemicellulose adsorption onto cellulose will contribute to further understanding of the fiber network, promote the development of new materials, and improve the utilization rate of resources. Quartz crystal microbalance with dissipative (QCM-D) is a research tool that can monitor quality changes at nanograms level; it is often used in the field of adsorption. Starting from the interaction between cellulose and hemicellulose, this paper outlines research on the principle, influencing factors, and kinetics of hemicellulose adsorption onto cellulose by QCM-D and expounds the research methods and means in the field of adsorption of similar biomass that can be used for reference. It provides a reference for further study of adsorption mechanism.

Xylan-cellulose thin film platform for assessing xylanase activity

Enzymatic degradation of plant polysaccharide networks is a complex process that involves disrupting an intimate assembly of cellulose and hemicelluloses in fibrous matrices. To mimic this assembly and to elucidate the efficiency of enzymatic degradation in a rapid way, models with physicochemical equivalence to natural systems are needed. Here, we employ xylan-coated cellulose thin films to monitor the hydrolyzing activity of an endo-1,4-β-xylanase. In situ surface plasmon resonance spectroscopy (SPRS) revealed a decrease in xylan areal mass ranging from 0.01 ± 0.02 to 0.52 ± 0.04 mg·m−2. The extent of digestion correlates to increasing xylanase concentration. In addition, ex situ determination of released monosaccharides revealed that incubation time was also a significant factor in degradation (P > 0.01). For both experiments, atomic force microscopy confirmed the removal of xylans from the cellulose thin films. We provide a new model platform that offers nanoscale sensitivity for investigating biopolymer interactions and their susceptibility to enzymatic hydrolysis.

Supramolecular modulation of the mechanical properties of amino acid-functionalized cellulose nanocrystal films

Cellulose nanocrystal (CNC) is a promising building block for the bottom-up assembly of novel lightweight renewable materials. The ability to engineer the interfacial properties of CNC is of paramount importance to develop assembled materials for various applications; yet it remains a challenge to manipulate the supramolecular interactions within the cellulosic nanomaterials in a controlled manner. In this context, we demonstrate in this article how the assembly and mechanical properties of cellulose thin films can be controlled by manipulating the interfacial interactions of TEMPO-oxidized cellulose nanocrystals (TOCNCs) grafted with two different amino acids, arginine and tryptophan. The amino acid grafting onto the cellulose scaffold was confirmed in aqueous solutions by 1H NMR spectroscopy and in solid form by FTIR and XPS techniques. The surface functionalization of TOCNCs with simple cationic and aromatic groups provides a strategy for tuning the assembly of the nanostructures based on different supramolecular cross-linking interactions, including hydrogen bonds, π–π stacking, and cation–π interactions. In particular, we show that nanocellulose chains cross-linked by the non-covalent cation–π interactions lead to the formation of a laminated superstructure with high deformation and load standing capabilities. Our work provides a versatile strategy for tuning the surface properties of nanocellulose and represents an important step toward the development of sustainable materials with tailored mechanical properties, which will enable a wider application range of this building block all the way from tissue-engineering scaffolds to flexible devices.

The Interaction of Cellulose Thin Films With Small Organic Molecules-Comparability of Two Inherently Different Methods.

Paper is the material of choice for a large range of applications because it has many favorable environmental and economic characteristics. Especially in the packaging sector of dry goods and food products, paper has found unique applications. For that purpose, it has to fulfill certain requirements: Primarily it should protect the packaged goods. In order to ensure the compliance of a paper packaging, its interactions with the packaged goods should be investigated. Therefore, it is of utmost importance to understand how the paper interacts with chemicals of different nature and what factors influence these interactions—be that the nature of the paper or the characteristics of the substances. In this study, we investigated the surface interactions of cellulose thin films with n-decane and deuterated methanol using two different analytical methods: headspace solid-phase microextraction with gas chromatography and flame ionization detection (HS-SPME-GC/FID) and temperature-programmed desorption (TPD). Cellulose thin films were characterized with contact angle and FT-IR measurements and successfully applied as model systems for real paper samples. Regarding the interactions of the cellulose films with the model compounds, the two inherently different methods, HS-SPME-GC/FID and TPD, provide very comparable results. While the nonpolar n-decane was readily released from the cellulose films, the polar model compound deuterated methanol showed a strong interaction with the polar cellulose surface.

Extraction of cellulose from oil palm empty fruit bunch using eco-friendly solvents for preparation of transparent cellulose thin film

The purpose of this research is to extract the cellulose using eco-friendly reagents of hydrogen peroxide and formic acid and determine the optimum reaction time for delignification process. The extracted cellulose and characterised using FTIR, TGA and PSA. The percentage yield of extracted cellulose were calculated. The highest yield was found to be 65.78 % at reaction time 120 min. The FTIR spectral studies confirm the removal of lignin from the delignified cellulose at peak 1613 cm−1 and the TGA result shows the thermal degradation of extracted cellulose at 329.04, 329.92 and 330.99 °C at reaction time 60, 90 and 120 min. The PSA studies provided the evidence of extracted particle size of the cellulose become finer as the reaction time increase. The particle size observed for delignified cellulose at 60, 90 and 120 min are 68.4, 64.6 and 57.3 μm. The extraction of cellulose and characterization to determine the optimum reaction time was able to obtain. From the result obtained, it can be concluded that the longer the reaction time, the higher the percentage yield of cellulose extracted. Film formation was later carried out using the extracted cellulose from different reaction time.

Investigation of brightness and decay characteristics of YAG:Ce3+, Ca-α-Sialon:Eu2+ and CaAl12O19:Mn4+ phosphors incorporated with Ni-doped SnO2 particles

In this study, we investigated the enhancement in the optical and decay properties of three phosphors, Ce3+-doped yttrium aluminium garnet (YAG:Ce3+), Eu2+-doped yellow oxynitride phosphor (Ca-α-SiAlON:Eu2+), Mn4+-doped aluminate-based phosphor (CaAl12O19:Mn4+), as a result of the interactions of the light-harvesting Ni-doped SnO2 additive. When the YAG:Ce3+ encapsulated in the presence of the nanoscale metal oxide in ethyl cellulose (EC) thin film, exhibited a 59% increase in its brightness as against its non-additive form. Similarly, when excited by 466 nm, the individual blends of Ca-α-SiAlON:Eu2+ and CaAl12O19:Mn4+ phosphors with Ni-doped SnO2 particles demonstrated 65% and 93% improvement in the intensity values, respectively. Decay characteristics of the phosphors and their Ni-doped SnO2 blends were measured in microsecond and nanosecond time scales. When they are in close proximity in a polymeric matrix, the emission- and lifetime-based results have approved that Ni-doped SnO2 particles and phosphors act as donor and acceptor, respectively. Furthermore, the thermal stabilities, quantum efficiencies and CIE chromaticity coordinates of all phosphors and their blends with Ni-doped SnO2 additive were investigated. In parallel with the increase in emission-based intensities and decay time kinetics, we enhanced the internal quantum efficiencies to 94.1%, 86.2% and 80.4%, with the blending of Ni-doped SnO2 particles to YAG:Ce3+, Ca-α-SiAlON:Eu2+, and CaAl12O19:Mn4+ phosphors, respectively. Notably, all of the phosphor composites along with additive indicated higher thermal stability in the temperature range of 303–503 K with respect to the additive-free forms. In the light of these results, the proposed composites can bring a new approach for the existing problems of yellow, orange, and red phosphors concerning the brightness and color rendering index and can be considered as potential candidates on LED technologies.

Influence of Calcium Silicate and Hydrophobic Agent Coatings on Thermal, Water Barrier, Mechanical and Biodegradation Properties of Cellulose.

Thin films of cellulose and cellulose–CaSiO3 composites were prepared using 1-ethyl-3-methylimidazolium acetate (EMIMAc) as the dissolution medium and the composites were regenerated from an anti-solvent. The surface hydrophilicity of the resultant cellulose composites was lowered by coating them with three different hydrophobizing agents, specifically, trichloro(octadecyl)silane (TOS), ethyl 2-cyanoacrylate (E2CA) and octadecylphosphonic acid (ODPA), using a simple dip-coating technique. The prepared materials were subjected to flame retardancy, water barrier, thermal, mechanical and biodegradation properties analyses. The addition of CaSiO3 into the cellulose increased the degradation temperature and flame retardant properties of the cellulose. The water barrier property of cellulose–CaSiO3 composites under long term water exposure completely depends on the nature of the hydrophobic agents used for the surface modification process. All of the cellulose composites behaved mechanically as a pure elastic material with a glassy state from room temperature to 250 °C, and from 20% to 70% relative humidity (RH). The presence of the CaSiO3 filler had no effect on the elastic modulus, but it seemed to increase after the TOS surface treatment. Biodegradability of the cellulose was evaluated by enzyme treatments and the influence of CaSiO3 and hydrophobic agents was also derived.

Characterization and optical gas sensing properties of BaSnO3 synthesized by novel technique: flame spray pyrolysis

Barium stannate (BaSnO3) particles were synthesized using a one-step flame spray pyrolysis (FSP) method. The fabricated ceramic powders were investigated in terms of the structural, morphological, and optical properties by using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), zeta particle size analyzer, UV–Visible spectroscopy (UV–Vis) and photoluminescence spectroscopy (PL). The XRD results showed the structure of BaSnO3 crystals has been obtained when the powders were exposed at high temperatures, specifically at 1200 °C. The synthesized particles in the submicron size in a range of 70–980 nm were produced. The optical bandgap value of the synthesized crystals was calculated using reflectance spectra with the Kubelka–Munk method and found as 3.14 eV. When the powders were excited at 375 nm, they exhibited emission bands in the visible and near-infrared region (NIR) of the electromagnetic spectrum. In this study, the intensity- and decay time-based gas sensing properties of nanoscale BaSnO3 embedded in ethyl cellulose (EC) thin films when exposed to the vapors of different solvents were also measured. The optical sensitivities (I-I0/I0) of the sensing materials for the NH3, acetone, and EtOH solvent vapors were calculated as 0.835, 0.672, and 0.521, respectively.

Real-time adsorption of optical brightening agents on cellulose thin films

Optical brightening agents (OBAs) are commonly used in textile and paper industry to adjust product brightness and color appearence. Continuous production processes lead to short residence time of the dyes in the fiber suspension, making it necessary to understand the kinetics of adsorption. The interaction mechanisms of OBAs with cellulose are challenging to establish as the fibrous nature of cellulosic substrates complicates acquisition of real-time data. Here, we explore the real-time adsorption of different OBAs (di, tetra- and hexasulfonated compounds) onto different cellulose surfaces using surface plasmon resonance spectroscopy. Ionic strength, surface topography and polarity were varied and yielded 0.76–11.35 mg m−2 OBA on cellulose. We identified four independent mechanisms governing OBA-cellulose interactions. These involve the polarity of the cellulose surface, the solubility of the OBA, the ionic strength during adsorption and presence of bivalent cations such as Ca2+. These results can be exploited for process optimization in related industries as they allow for a simple adjustment and experimental testing procedures including performance assessment of novel OBAs.

Photoelectrochemical Complete Decomposition of Cellulose for Electric Power Generation

AbstractA photo‐assisted fuel cell (photofuel cell; PFC) consisting of a porous TiO2 photoanode and a Pt cathode in an aqueous electrolyte containing an organic fuel has been developed to generate an electric power by photoelectrochemically decomposing the fuel. Although direct utilization of cellulose as a fuel should be preferable, photocatalytic direct decomposition of cellulose, polymeric macromolecules, has been rarely reported. In the present study, a cellulose thin film deposited onto the TiO2 photoanode was used as the fuel. It was revealed that the cellulose was decomposed into CO2 through small carbonyl hydrocarbon intermediates. The complete decomposition of cellulose into CO2 implies that almost all the Gibbs free energy of cellulose can be converted into an electric power with the assistance of the photon energy. The PFC composed of the cellulose‐deposited TiO2 and Pt‐deposited Ni foam exhibited excellent photovoltaic performances (1.1 V of photovoltage and quantum efficiency up to 52 %). The present study should represent a potential means of electric power generation based on renewable energy sources by effectively treating waste biomass.

Interactions and Dissociation Constants of Galactomannan Rendered Cellulose Films with Concavalin A by SPR Spectroscopy.

Interactions of biomolecules at interfaces are important for a variety of physiological processes. Among these, interactions of lectins with monosaccharides have been investigated extensively in the past, while polysaccharide-lectin interactions have scarcely been investigated. Here, we explore the adsorption of galactomannans (GM) extracted from Prosopis affinis on cellulose thin films determined by a combination of multi-parameter surface plasmon resonance spectroscopy (MP-SPR) and atomic force microscopy (AFM). The galactomannan adsorbs spontaneously on the cellulose surfaces forming monolayer type coverage (0.60 ± 0.20 mg·m−2). The interaction of a lectin, Concavalin A (ConA), with these GM rendered cellulose surfaces using MP-SPR has been investigated and the dissociation constant KD (2.1 ± 0.8 × 10−8 M) was determined in a range from 3.4 to 27.3 nM. The experiments revealed that the galactose side chains as well as the mannose reducing end of the GM are weakly interacting with the active sites of the lectins, whereas these interactions are potentially amplified by hydrophobic effects between the non-ionic GM and the lectins, thereby leading to an irreversible adsorption.

Fabrication of regenerated cellulose films by DMAc dissolution using parenchyma cells via low-temperature pulping from Yunnan-endemic bamboos

In this study, regenerated cellulose (RC) thin films were obtained using parenchyma cellulose from large clustered bamboos which were endemic to Xishuangbanna area in Yunnan province, China. The bamboo parenchyma cells were separated from their low-temperature (140 ℃ of the maximum temperature) kraft pulps through multi-screening. The cellulose was dissolved in N,N-dimethyl acetamide (DMAc) solvent with LiCl amount from 6 % to 10 %, then regenerated in the glycerol-water solution. X-ray diffraction analysis indicated the crystalline forms of RC films were transited from cellulose I to cellulose II. TGA analysis suggested that lower LiCl usage take an advantage on the higher thermal stability of the RC films. The DMAc-related solvent with a relatively lower LiCl dosage displayed a stronger capacity of cellulose dissolution, shed light on its considerable industrial application prospects and facilitated the high value-added utilization of waste biomass resources.

Influence of cellulose on the thermal conductivity of cellulose based composite thin films

A simplified method using spin coating to prepare cellulose thin film composite has been introduced for insulating materials and thermal conductivity applications. Cellulose was derived from olive pomace and cotton (cellulose triacetate). These two sources were deposited on a silica and glass substrate, to obtain a smooth film based on cellulose (100 μm thick)). A hybrid system based on cellulose thin films was presented to study the effect of additives and the type of cellulose source on the thermal conductivity: silica SiO2, dioxide titan TiO2, olive pomace and cellulose triacetate. The different combinations of cellulose composites offer relative thermal performance, depending on the thickness, the materials processing method, the substrate, the additive and the type of cellulose source. The thermal conductivity was measured using the hot plate technic evolving in a non-stationary regime. The films were characterized by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and also by the Energy Dispersive X-Ray Analyzer (EDX) to determine the chemical structure of the layers. The optical behavior was investigated by Ultraviolet–Visible Spectroscopy (UV–VISIBLE).

Chelator-mediated biomimetic degradation of cellulose and chitin

Non-enzymatic degradation of wood via a chelator-mediated Fenton (CMF) system is the primary method for initial attack in brown rot fungal decomposition of wood, the most common type of fungal degradation of terrestrial carbon biomass on the planet. In this study, the degradation of thin films of cellulose and chitin by a CMF system was investigated and compared to enzymatic hydrolysis. The kinetics of the rapid cellulose and chitin deconstruction and the morphologies of the degraded cellulose and chitin surfaces were studied by quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM), respectively. The QCM-D results quantitatively indicated that ~90 wt% of the regenerated cellulose or chitin was capable of being deconstructed by CMF action alone. While enzymatic degradation was consistent with stripping of layers from the surface of the cellulose or chitin films, the CMF process exhibited a pronounced two stage process with a rapid initial depolymerization throughout the films. The initial degradation rates for both model surfaces by the CMF system were faster than enzyme action. This research suggests that the CMF process should be applicable for the deconstruction of a wide variety of polysaccharides over Fenton chemistry alone.

Amorphous cellulose thin films

Amorphous cellulose thin films with thicknesses of 8–100 nm and sub-nanometer roughness have been fabricated by spin-casting from molecular solutions of cellulose in mixtures of ionic liquids and organic solvents. Combining X-ray, optical and scanning probe measurements, cellulose films have been found to be fully amorphous, and their mass densities are comparable to that of the bulk amorphous cellulose. Full amorphization of cellulose films is achieved through sequential removal of solvents, successive diffusion of ionic liquid molecules out of cellulose films, and simultaneous formation of hydrogen bonding among cellulose chains.