1D and 2D NMR of nanocellulose in aqueous colloidal suspensions

Novel Acryloylated and Methacryloylated Nanocellulose Derivatives with Improved Mucoadhesive Properties

In this work, three nanocellulose derivatives are synthesized with the aim of preparing new mucoadhesive materials. Nanocellulose is reacted with glycidyl methacrylate in dimethylsulphoxide, and with acryloyl and methacryloyl chloride in dimethylacetamide in the presence of 4-(N,N-dimethylamino)pyridine as a catalyst. These reactions are carried out under heterogeneous conditions, and the reaction products are characterized using various spectroscopic techniques, X-ray diffraction, atomic force microscopy, and thermogravimetric analysis. The Fourier-transform infrared spectra showed all the characteristic absorption bands typical for cellulose and also new peaks at 1720 cm-1 for the carbonyl group (C═O) and 1639, 812 cm-1 for the double bond (C═C). It is established that the crystal structure of the nanocellulose is slightly changed with derivatisation and the thermal stability of these derivatives increased. Mucoadhesive properties of nanocellulose and its derivatives is evaluated using the tensile test, rotating basket method, and fluorescence flow-through method. The retention of these polymers is evaluated on sheep oral mucosal tissue ex vivo using artificial saliva. Test results demonstrated that the new derivatives of nanocellulose have improved mucoadhesive properties compared to the parent nanocellulose.

Jahim J, Sajab MS, Ibrahim Z. Synergistic sequential oxidative extraction for nanofibrillated cellulose isolated from oil palm empty fruit bunch

This research presents a comprehensive study of sequential oxidative extraction (SOE) consisting of alkaline and acidic oxidation processes to extract nanocellulose from plant biomass. This proposed process is advantageous as its operation requires a minimum process with mild solvents, and yet successfully isolated high-quality nanofibrillated cellulose (NFC) from raw OPEFB. The SOE involved ammonium hydroxide (NH4OH, 2.6 M) and formic acid (HCOOH, 5.3 M) catalyzed by hydrogen peroxide (H2O2, 3.2 M). This approach was used to efficiently solubilize the lignin and hemicellulose from Oil Palm Empty Fruit Bunch (OPEFB) at the temperature of 100°C and 1 h extraction time, which managed to retain fibrous NFC. The extracted solid and liquor at each stage were studied extensively through physiochemical analysis. The finding indicated that approximately 75.3%dwb of hemicellulose, 68.9%dwb of lignin, and 42.0%dwb of extractive were solubilized in the first SOE cycle, while the second SOE cycle resulted in 92.3%dwb, 99.6%dwb and 99.8%dwb of solubilized hemicellulose, lignin, and extractive/ash, respectively. High-quality NFC (75.52%dwb) was obtained for the final extracted solid with 76.4% crystallinity, which is near the crystallinity of standard commercial NFC. The proposed process possesses an effective synergy in producing NFC from raw OPEFB with less cellulose degradation, and most of the degraded hemicellulose and lignin are solubilized in the liquor.

Multifunctional self-healing hydrogels via nanoengineering of colloidal and polymeric cellulose

The unique features of self-healing hydrogels hold great potential for biomedical applications including injectable hydrogels for cancer treatment, procedures for tumor removal or resection. However, the fabrication of durable and multifunctional self-healing hydrogels composed of biocompatible, green building blocks via versatile synthetic methodology continues to pose a significant challenge. Here, we engineered dialdehyde cellulose (DAC, as a macromolecular bio-crosslinker), and electrosterically stabilized nanocrystalline cellulose (ENCC, as a ligand-targeted drug carrier) to facilitate a strategy for the construction of self-healing hydrogels. Benefiting from its high carboxyl group density, ENCC was functionalized with folic acid (FA) using a non-toxic DMTMM coupling agent and loaded with doxorubicin (DOX, a model drug) through electrostatic interactions. A natural self-healing hydrogel was prepared from carboxymethyl chitosan (CCTS) and DAC mixed with DOX-loaded FA-ENCC using dynamic Schiff-base and hydrogen linkages. A combination of active supramolecular and vital covalent junctions led to a soft (storage modulus ∼500 Pa) and durable material, with rapid (< 5 min) reconstruction of molecular structure from fractured and injected to intact forms. The DAC-CCTS hydrogel showed an appreciable loading capacity of ∼5 mg g-1. Biocompatibility of the hydrogels was evaluated using cell viability and metabolic activity assays, showing lower metabolic activity due to sustained release of its cargo. These materials offer a versatile, sustainable, and green platform for the efficient construction of hydrogels, based on macro- and nano-engineered cellulose, the most abundant and easily accessible biopolymer.

Tunable poly(lauryl methacrylate) surface grafting via SI-ATRP on a one-pot synthesized cellulose nanofibril macroinitiator core as a shear-thinning rheology modifier and drag reducer

The optimally one-pot synthesized 2-bromoproponyl esterified cellulose nanofibril (Br-CNF) has been validated as a robust macroinitiator for self-surface-initiated atom transfer radical polymerization (SI-ATRP) of lauryl methacrylate (LMA) in tunable graft lengths and high conversions of up to 92.7%. SI-ATRP of LMA surface brushes on Br-CNF followed first order kinetics in lengths at up to 46 degree of polymerization (DP) based on mass balance or 31 DP by solution-state 1H NMR in DMSO-d6. With increasing PLMA graft lengths, Br-CNF-g-PLMA cast films exhibited increasing hydrophobicity with water contact angles from 80.9° to 110.6°. The novel Br-CNF-g-PLMA exhibited dual shear thinning behavior of the Br-CNF core as evident by n < 1 flow behavior index and drag reducing properties of PLMA grafts with increased viscosity at up to 21 071×. Br-CNF-g-PLMA with 46 DP could be fully dispersed in silicon pump oil to function as a drag reducer to enhance viscosity up to 5× at 25, 40, and 55 °C. The novel macroinitiator capability of Br-CNF in SI-ATRP of vinyl monomers and the bottlebrush-like LMA surface grafted Br-CNF as highly effective viscosity modifier and drag reducer further demonstrate the versatile functionality of Br-CNF beyond hydrophobic coatings and reactive polyols previously reported.

Synthesis and property of superabsorbent polymer based on cellulose grafted 2-acrylamido-2-methyl-1-propanesulfonic acid

An eco-friendly superabsorbent polymer (SAP) was prepared by grafting 2-acrylamido-2-methyl-1-propanesulfonic acid onto microcrystalline cellulose in lithium chloride/N, N-dimethylacetamide system. The synthesized SAP (cellulose-g-PAMPS) was characterized by FTIR, TGA, SEM, ¹H NMR, ¹³C NMR and XRD. The water absorption equilibrium of cellulose-g-PAMPS could be achieved within 10 min in distilled water. Moreover, the maximum water absorption capacities of cellulose-g-PAMPS in distilled water, 0.9 wt% NaCl solution and 3.2 wt% Na₂CO₃ solution were 648.9, 298.4 and 207.3 g·g^-1, respectively. The water absorption behavior of cellulose-g-PAMPS was interpreted by the pseudo-second-order model. Furthermore, cellulose-g-PAMPS could be used in some extreme conditions due to its high acid and alkali resistance. The water retention rate of cellulose-g-PAMPS could be maintained above 90 % at 25 °C for 6 h. As a consequence, the synthesized SAP can be applied to increase the plant growth and survival time under drought conditions, even under saline alkali conditions.

Surfactant Assisted In Situ Synthesis of Nanofibrillated Cellulose/Polymethylsilsesquioxane Aerogel for Tuning Its Thermal Performance

Nanofibrillated cellulose (NFC) and polymethylsilsesquioxane (PMSQ) based aerogel are prepared by the sol-gel method. The objective of this work is to study the impact of surfactant and base catalyst on the thermal and mechanical performance of the corresponding aerogel. The rheological premonitory assists in predicting the bulk properties of the aerogel. The chemical structure of the aerogel is studied by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and solid-state nuclear magnetic resonance (NMR). X-ray microtomographic (XMT) analysis confirms the homogeneous and monolithic structure of the aerogel. The lowest thermal conductivity is achieved as 23.21 mW m^-1 K^-1 with V-0 and HBF rating through UL-94 test. Thermal performance of aerogels is cross-verified through modeling and simulation in COMSOL multiphysics platform. The mechanical properties of aerogel are evaluated by monolithic compression test in axial and radial compression test up to 90% strain, cyclic compression loading-unloading, and reloading test, flexural test, and dynamic mechanical analysis. The time-temperature analysis has shown around 5 °C temperature difference in the middle of the room after using the aerogel panel at the exposed surface, which assists in the practical application of the synthesized aerogel panel.

Influence of filler material on properties of fiber-reinforced polymer composites: A review

The current day target for material scientists and researchers is developing a wholesome material to satisfy the parameters such as durability, manufacturability, low cost, and lightweight. Extensive research studies are ongoing on the possible application of polymer matrix composites in engineering and technology, since these materials have an edge over conventional materials in terms of performance. Hybridization of reinforcements is considered to be a better option to enhance the efficiency and performance of composite materials. Accordingly, research studies focus on the surface treatment of natural fibers and the addition of nanofillers (natural or synthetic) by industry and academia to take the properties and application of composites to the next level. This review purely focuses on the influence of fillers on the properties of composites along with the probable application of filler-based polymer composites.

One-step synthesis of gold nanoparticles for catalysis and SERS applications using selectively dicarboxylated cellulose and hyaluronate

Properties and applications of gold nanoparticles (AuNPs) depend on their characteristics which are intrinsically connected to the reducing and capping agents used in their synthesis. Although polysaccharides are commonly used for Au salt reduction, the control over the result is often limited. Here, the selectively dicarboxylated cellulose (DCC) and hyaluronate (DCH) with adjustable composition and molecular weight are used for the first time as reducing and capping agents for AuNPs preparation in an environmental friendly one-step synthesis. Mechanism of reduction and structure-function relationships between the composition of oxidized polysaccharides and properties of formed AuNPs are elucidated and the variances in the macromolecular architecture of dicarboxypolysaccharides are applied to guide the growth of AuNPs. While the homogenous structure and high density of carboxyl groups of fully-oxidized DCC induced isotropic growth of small and uniform AuNPs with good catalytic performance (d = ~20 nm, TOF = 7.3 min^-1, k = 1.47 min^-1), the lower stabilizing potential and slower reduction rates of the DCH induced the anisotropic growth of larger polyhedral ~50 nm nanoparticles, which increased the Surface-Enhanced Raman Scattering efficacy (9× stronger Raman signals on average compared to AuDCC). The use of dicarboxypolysaccharides with adjustable composition and properties thus introduced a new degree of freedom for the preparation of AuNPs with desired properties.

Development of Cellulose Nanofibril/Casein-Based 3D Composite Hemostasis Scaffold for Potential Wound-Healing Application

Excessive bleeding in traumatic hemorrhage is the primary concern for natural wound healing and the main reason for trauma deaths. The three-dimensional (3D) bioprinting of bioinks offers the desired structural complexity vital for hemostasis activity and targeted cell proliferation in rapid and controlled wound healing. However, it is challenging to develop suitable bioinks to fabricate specific 3D scaffolds desirable in wound healing. In this work, a 3D composite scaffold is designed using bioprinting technology and synergistic hemostasis mechanisms of cellulose nanofibrils (TCNFs), chitosan, and casein to control blood loss in traumatic hemorrhage. Bioinks that consist of casein bioconjugated TCNF (with a casein content of 104.5 ± 34.1 mg/g) using the carbodiimide cross-linker chemistry were subjected to bioprinting for customizable 3D scaffold fabrication. Further, the 3D composite scaffolds were in situ cross-linked using a green ionic complexation approach. The covalent conjugation among TCNF, casein, and chitosan was confirmed by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and X-ray diffraction (XRD) studies. The in vitro hemostasis activity of the 3D composite scaffold was analyzed by a human thrombin-antithrombin (TAT) assay and adsorption of red blood cells (RBCs) and platelets. The 3D composite scaffold had a better swelling behavior and a faster whole blood clotting rate at each time point than the 3D TCNF scaffold and commercial cellulose-based dressings. The TAT assay demonstrated that the 3D composite scaffold could form a higher content of thrombin (663.29 pg/mL) and stable blood clot compared to a cellulosic pad (580.35 pg/mL), 3D TCNF (457.78 pg/mL), and cellulosic gauze (328.92 pg/mL), which are essential for faster blood coagulation. In addition, the 3D composite scaffold had a lower blood clotting index (23.34%) than the 3D TCNF scaffold (41.93%), suggesting higher efficiencies for RBC entrapping to induce blood clotting. The in vivo cytocompatibility was evaluated by a 3D cell culture study, and results showed that the 3D composite scaffold could promote growth and proliferation of NIH 3T3 fibroblast cells, which is vital for wound healing. Cellulase-based in vitro deconstruction of the 3D composite scaffold showed significant weight loss (80 ± 5%) compared to the lysozyme hydrolysis (22 ± 5%) after 28 days of incubation, suggesting the biodegradation potential of the composite scaffold. In conclusion, this study proposes efficient prospects to develop a 3D composite scaffold from bioprinting of TCNF-based bioinks that can accelerate blood clotting and wound healing, suggesting its potential application in reducing blood loss during traumatic hemorrhage.

One-pot synthesis of 2-bromopropionyl esterified cellulose nanofibrils as hydrophobic coating and film

Bromo-esterified cellulose nanofibrils have been one-pot synthesized by direct heterogeneous 2-bromopropionyl esterification and in situ ultra-sonication to serve as versatile hydrophobic nm thick coating or 100 μm thick film.

Distribution and Quantification of Diverse Functional Groups on Phosphorylated Nanocellulose Surfaces

Phosphorylated cellulose nanofiber (CNF) is attracting attention as a newly emerged CNF with high functionality. However, many structural aspects of phosphorylated CNF remain unclear. In this study, we investigated the chemical structures and distribution of ionic functional groups on the phosphorylated CNF surfaces via liquid-state nuclear magnetic resonance measurements of colloidal dispersion. In addition to the monophosphate group, polyphosphate groups and cross-linked phosphate groups were introduced in the phosphorylated CNFs. The proportion of polyphosphate groups increased as the phosphorylation time increased, reaching ∼30% of all phosphate groups. Only a small amount of cross-linked phosphate groups existed in the phosphorylated CNF after a prolonged reaction time. Furthermore, phosphorylation of cellulose using urea and phosphoric acid was found to be regioselective at the C2 and C6 positions. There existed no significant difference between the surface degrees of substitution at the C2 and C6 positions of the phosphorylated CNFs.

Nanocellulose: Resources, Physio-Chemical Properties, Current Uses and Future Applications

The growing environmental concerns due to the excessive use of non-renewable petroleum based products have raised interest for the sustainable synthesis of bio-based value added products and chemicals. Recently, nanocellulose has attracted wide attention because of its unique properties such as high surface area, tunable surface chemistry, excellent mechanical strength, biodegradability and renewable nature. It serves wide range of applications in paper making, biosensor, hydrogel and aerogel synthesis, water purification, biomedical industry and food industry. Variations in selection of source, processing technique and subsequent chemical modifications influence the size, morphology, and other characteristics of nanocellulose and ultimately their area of application. The current review is focused on extraction/synthesis of nanocellulose from different sources such as bacteria and lignocellulosic biomass, by using various production techniques ranging from traditional harsh chemicals to green methods. Further, the challenges in nanocellulose production, physio-chemical properties and applications are discussed with future opportunities. Finally, the sustainability of nanocellulose product as well as processes is reviewed by taking a systems view. The impact of chemicals, energy use, and waste generated can often negate the benefit of a bio-based product. These issues are evaluated and future research needs are identified.

Generating biomembrane-like local curvature in polymersomes via dynamic polymer insertion

Biomembrane curvature formation has long been observed to be essential in the change of membrane morphology and intracellular processes. The significant importance of curvature formation has attracted scientists from different backgrounds to study it. Although magnificent progress has been achieved using liposome models, the instability of these models restrict further exploration. Here, we report a new approach to mimic biomembrane curvature formation using polymersomes as a model, and poly(N-isopropylacrylamide) to induce the local curvature based on its co-nonsolvency phenomenon. Curvatures form when poly(N-isopropylacrylamide) becomes hydrophobic and inserts into the membrane through solvent addition. The insertion area can be fine-tuned by adjusting the poly(N-isopropylacrylamide) concentration, accompanied by the formation of new polymersome-based non-axisymmetric shapes. Moreover, a systematic view of curvature formation is provided through investigation of the segregation, local distribution and dissociation of inserted poly(N-isopropylacrylamide). This strategy successfully mimicks biomembrane curvature formation in polymersomes and a detailed observation of the insertion can be beneficial for a further understanding of the curvature formation process. Furthermore, polymer insertion induced shape changing could open up new routes for the design of non-axisymmetric nanocarriers and nanomachines to enrich the boundless possibilities of nanotechnology.

Investigating biomembrane curvature formation is important for studying intracellular processes, but the instability of liposome models mimicking these membranes restricts exploration of membrane processes. Here, the authors demonstrate control over the curvature formation in polymersome membranes by insertion of PNIPAm as stimuli responsive polymer.

Preparation of alpha cellulose from sugarcane bagasse and its cationization: Synthesis, characterization, validation and application as wet-end additive

Paper industry uses cationic polymers for imparting strong bonds with pulp furnish to enhance strength properties. Due to environmental reasons, emphasis is on utilization of biobased polymers in place of synthetic. Sugarcane bagasse, an agro-industrial waste, was processed for extraction of alpha cellulose and preparation of cationic derivative. Reaction conditions were optimized to achieve highly substituted cationic derivative with insertion of 2-hydroxy-3-(trimethylammonium) propyl group. Artificial neural network (ANN) was applied to analyze the experimental data for cationization modeling. Maximum degree of substitution 0.66, was achieved at 5.0 M NaOH/anhydro glucose unit (AGU), 20 °C alkalization temperature, 8 min alkalization time, 3.5 M/AGU etherification agent concentration, 45 min time and 60 °C etherification reaction temperature. The experimental results showed that mean square error values for input parameters were significantly low. The ANN based regression values of the output, and computed values of target were close to unity. ANN based fitting indicates better performance level to predict the degree of substitution. The synthesized cationic cellulose was characterized through FTIR, XRD, NMR, FESEM and TGA. The activity of cationized cellulose as wet-end additive was tested for bagasse, wheat straw and recycled pulps due to their shorten fiber and feeble pulp characters than wood pulp.

Tuning of Ag Nanoparticle Properties in Cellulose Nanocrystals/Ag Nanoparticle Hybrid Suspensions by H2O2 Redox Post-Treatment: The Role of the H2O2/AgNP Ratio

Hybrid nanoparticles involving 10-nm silver nanoparticles (AgNPs) nucleated on unmodified rod-like cellulose nanocrystals (CNCs) were prepared by chemical reduction. H2O2 used as a post-treatment induced a size-shape transition following a redox mechanism, passing from 10-nm spherical AgNPs to 300-nm triangular or prismatic NPs (AgNPrisms), where CNCs are the only stabilizers for AgNPs and AgNPrisms. We investigated the role of the H2O2/AgNP mass ratio (α) on AgNPs. At α values above 0.20, the large amount of H2O2 led to extensive oxidation that produced numerous nucleation points for AgNPrisms on CNCs. On the contrary, for α below 0.20, primary AgNPs are only partially oxidized, releasing a reduced amount of Ag+ ions and thus preventing the formation of AgNPrisms and reforming spherical AgNPs. While XRD and EXAFS reveal that the AgNP fcc crystal structure is unaffected by the H2O2 treatment, the XANES spectra proved that the AgNP-AgNPrism transition is always associated with an increase in the metallic Ag fraction (Ag0). In contrast, the formation of new 15-nm spherical AgNPs keeps the initial Ag0/Ag+ ratio unmodified. For the first time, we introduce a complete guide map for the fully-controlled preparation of aqueous dispersed AgNPs using CNC as a template.

A luminescent cellulose ether with a regenerated crystal form obtained in tetra(n-butyl)ammonium hydroxide/dimethyl sulfoxide

Cellulose-based luminescent materials are usually formed via either covalent attachment or combination with luminogens. In this work, three luminescent cellulose ethers without conventional luminophores have been homogeneously synthesized in a mixed solvent of tetra(n-butyl)ammonium hydroxide (TBAH)/dimethyl sulfoxide (DMSO). The one obtained by etherifying microcrystalline cellulose (MCC) with 4-bromomethylbenzoic acid (BBA), i.e., MCC-BBA, exhibits a regenerated crystal form of IV_II, whereas the other two are amorphous. The large difference of crystalline properties might be due to the formation of a new hydrogen bond network in MCC-BBA derived from the intermolecular interactions of COOH and their adjacent C2/C3OH groups. Such structural deviations might result in luminescence variations. Indeed, MCC-BBA can give brighter luminescence, which might be derived from crystallization-induced luminescence as well as photo-induced charge transfer effect. The presented work provides new insights into the rational synthesis of cellulose ethers, paving the way toward the design of non-conventional cellulose-based luminescent materials.

Understanding heat driven gelation of anionic cellulose nanofibrils: Combining saturation transfer difference (STD) NMR, small angle X-ray scattering (SAXS) and rheology

A novel mechanism of heat-triggered gelation for oxidised cellulose nanofibrils (OCNF) is reported. We demonstrate that a synergistic approach combining rheology, small-angle X-ray scattering (SAXS) and saturation transfer difference NMR (STD NMR) experiments enables a detailed characterisation of gelation at different length scales. OCNF dispersions experience an increase in solid-like behaviour upon heating as evidenced by rheological studies, associated with enhanced interfibrillar interactions measured using SAXS. Interactions result in an increased fibrillar overlap and increased population of confined water molecules monitored by STD NMR. In comparison, cationic cellulose nanofibrils (produced by reaction of cellulose with trimethylglycidylammonium chloride) were found to be heat-unresponsive.

Assembling and redispersibility of rice straw nanocellulose: effect of tert-butanol

Self-assembling of sulfuric-acid-hydrolyzed cellulose nanocrystals (CNCs, 6.4 nm wide) and TEMPO oxidized cellulose nanofibrils (CNFs, 2.1 nm wide) from aqueous suspensions was induced by rapid freezing (-196 °C, 10 min) and slow lyophilization (-50 °C, 0.05 mbar, 2 days). The assembled structures contain submicron (200-700 nm) wide and tens of micrometer long fibers at up to 0.1-0.5% and 0.01-0.05%, the critical fiber-to-film transformation concentrations for CNCs and CNFs, respectively. The assembled fiber widths were significantly reduced to ∼40 nm, that is, by 1 order of magnitude, when 10% of the aqueous media was replaced with tert-butanol. Further increasing tert-butanol contents in the media to 93/7 (CNCs) and 50/50 (CNFs) tert-butanol/water, both at 0.1% nanocellulose concentration, reduced longitudinal assembling for CNCs and lateral assembling for CNFs as well as increased critical fiber-to-film transformation concentration for CNFs. While all assembled structure could be redispersed in water, those from tert-butanol/water could also be easily redispersed in DMF aided with brief 2 min ultrasonication. None of the assembled structures could be redispersed in the lower dielectric constant ethanol, acetone or chloroform.

Synthesis of cellulose nanofibril bound silver nanoprism for surface enhanced Raman scattering

Silver nanoprisms (AgNPs) were robustly synthesized using TEMPO-oxidized cellulose nanofibrils (CNFs) as a dual capping and shape-regulating agent for the first time. Reducing AgNO3 with NaBH4 in CNF suspensions produced smaller but more uniform Ag nanospheres (AgNSs) with increasing Ag(+)/CNF ratios. CNF bound AgNSs were facilely transformed to AgNPs by etching with H2O2, supporting the capping and shape-regulating capability of CNFs. AgNPs could also be synthesized directly in a one-shot reduction reaction with NaBH4 in the presence of both CNFs and H2O2. The AgNPs transformed from CNF bound AgNSs are similar to those synthesized directly, but more stable against H2O2. Successful synthesis of AgNPs with 80-320 nm truncated edges was confirmed by light blue solution color, sharp out-of-plane quadruple resonance peak at 334 nm and prominent in-plane dipole resonance peaks at 762-900 nm. The [111] lattice plane of AgNP was clearly evident by its predominant XRD peak at 38°, confirming the unique shape-regulating ability of the nearly fully surface carboxylated CNFs. The CNF surface bound AgNPs were easily fabricated into freestanding CNF/AgNPs films that showed excellent surface enhanced Raman scattering of Rhodamine 6G with analytical enhancement factor of 5 × 10(3) in contrast to none from the CNF/AgNSs film.