Number Of Bilayers Research Articles

Assessing the Layer-by-Layer Assembly of Cellulose Nanofibrils and Polyelectrolytes in Pancreatic Tumor Spheroid Formation.

Three-dimensional (3D) tumor spheroids are regarded as promising models for utilization as preclinical assessments of chemo-sensitivity. However, the creation of these tumor spheroids presents challenges, given that not all tumor cell lines are able to form consistent and regular spheroids. In this context, we have developed a novel layer-by-layer coating of cellulose nanofibril-polyelectrolyte bilayers for the generation of spheroids. This technique builds bilayers of cellulose nanofibrils and polyelectrolytes and is used here to coat two distinct 96-well plate types: nontreated/non-sterilized and Nunclon Delta. In this work, we optimized the protocol aimed at generating and characterizing spheroids on difficult-to-grow pancreatic tumor cell lines. Here, diverse parameters were explored, encompassing the bilayer count (five and ten) and multiple cell-seeding concentrations (10, 100, 200, 500, and 1000 cells per well), using four pancreatic tumor cell lines-KPCT, PANC-1, MiaPaCa-2, and CFPAC-I. The evaluation includes the quantification (number of spheroids, size, and morphology) and proliferation of the produced spheroids, as well as an assessment of their viability. Notably, our findings reveal a significant influence from both the number of bilayers and the plate type used on the successful formation of spheroids. The novel and simple layer-by-layer-based coating method has the potential to offer the large-scale production of spheroids across a spectrum of tumor cell lines.

Polyelectrolyte multilayers modification of nanofiltration membranes to improve selective separation of mono- and multivalent cations in seawater brine

Nowadays, brine produced in the Reverse Osmosis (RO) seawater desalination plants is a significant and largely untapped source of critical minerals and metals, which is usually discharged into the seas as wastewater. As a front face stage in the brine mining process, nanofiltration (NF) membranes can be used to separate brine stream into monovalent and multivalent ion-rich streams. Since high separation factors are required in seawater RO brine, polyelectrolyte multilayers with Layer-by-Layer (LbL) technique were used in this study to modify commercial polyamide NF membranes and improve their performance. Two common polyelectrolytes, poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium 4-styrenesulfonate) (PSS) were coated onto two poly-piperazine polyamide NF membranes (NF270 and Desal-5 DL). The effects of the bilayers number and the outer layer charge on membranes’ performance were studied using two crossflow filtration setups with two different membrane sizes to find the membrane with the higher monovalent/multivalent separation factor. Desal-5 DL membrane coated with 5.5 bilayers provided the highest selectivity factors for mono/multivalent cations (> 21), the highest average rejection of multivalent cations group (about 95.7%) for short-term experiments. Another interesting result was the increase in water permeance of the Desal-5 DL membrane after it was coated with 5.5 bLs (indicating more than 20% improvement in pure water permeance). In addition, the stability test with brines at 20 bar showed that this membrane was stable over an extended period of filtration (22 hours) with an even higher selectivity factor of 34 and multivalent cations rejection of 97.7% on average.

Unveiling the effects of the surface and in-depth nanostructure on the far-UV optical reflectance of thin fluoride multilayer coatings

Developing high-quality optical components for far ultraviolet (FUV) spectrum is gaining significance in space observations. Optical elements designed for a narrowband FUV response rely on coatings made of thin multilayers (MLs), alternating between two materials with low optical absorption and significantly contrasting refractive indices. Recent research shows that (AlF3/LaF3) systems outperform (MgF2/LaF3) coatings in FUV optical reflectance due to two critical factors: 1) AlF3′s lower refractive index compared to MgF2, and 2) structural properties resulting from a trade-off between the number of bilayers, contributing to higher reflectance, and the tendency for roughness to increase with the total coating thickness, limiting FUV optical performance. This study conducts a comprehensive examination of the nano-microstructure of these MLs, using three techniques: AFM for surface characterization, cross-sectional SEM micrographs with backscattered electrons, and Rutherford Backscattering Spectrometry (RBS) for in-depth structural and compositional analysis. A strong correlation is observed between roughness, grain size, composition, and intermixing, impacting the optical response in the FUV range. Nanometer-scale intermixing between layers is estimated using RBS. These findings provide a foundation for modeling FUV optical reflectance in MLs, enabling the optimization of their design through materials engineering to achieve more efficient optical devices for FUV applications in space observations.

Structural and corrosion Evaluation for multilayer system conformed by TiCN/TiVCN

Development of more complex hard coatings that can be implemented in increasingly severe and complex conditions is necessary for the evolution of the metalworking industry. Therefore, this research focuses on the synthesis and corrosion study of the [TiCN/TiVCN]n system as a function of the bilayers number. Thus, the structural resulted determined that the quaternary TiVCN coating, which presents very little information so far, presents an FCC structure as the conventional TiCN system, and the inclusion of vanadium atoms that compete with titanium atoms in Wyckoff 4a positions causes a distortion of the crystal lattice that increase with the bilayers number. An increase of 64.3% in the polarization resistance of the multilayers coating with n = 70 bilayers when compared to the n = 1 bilayer. Corrosion rate decreased by 57% when comparing the 70 bilayers coatings with the 1 bilayer coating. The results obtained show that this new multilayer system presents optimum properties to be used as protective coating on engineering devices exposed to high corrosion conditions.

Minimum Number of Si-C Bilayers Needed in Polytypes of SiC Semiconductor to Exhibit Bandgaps of Bulk Materials

Minimum Number of Si-C Bilayers Needed in Polytypes of SiC Semiconductor to Exhibit Bandgaps of Bulk Materials

Omnidirectional antireflective coatings prepared with chitin nanofibers via layer-by-layer self-assembly

Antireflective coatings play an important role in various optical devices. Herein, we developed omnidirectional antireflective coatings fabricated with charged chitin nanofibers (ChNFs) through layer-by-layer (LbL) self-assembly technology. The charged ChNFs were prepared from chitin with modifications of esterification (negatively charged) and esterification followed partial deacetylation (positively charged), respectively, through ultrasonic treatment. The effects of concentration of the ChNF suspensions and number of bilayers on thickness, refractive index and antireflective capacity of the ChNF coatings were investigated. Refractive index of the ChNF coatings can be manipulated by changing concentration of the ChNF suspensions. Thickness of the ChNF coatings depends on number of bilayers and concentration of the ChNF suspensions. The ChNF coating on a glass substrate with 5 bilayers fabricated using the suspensions with concentration 0.1% had a refractive index of 1.36 and yielded 4% gain in transmittance compared to the glass at the wavelength of 550 nm. This work demonstrates that charged ChNFs are promising building blocks to fabricate antireflective coatings on large size substrates with high efficiency and low cost through LbL self-assembly.

Optimizing microstructure of polyelectrolyte ion exchange membrane for electrodialysis

In electrodialysis process, polyelectrolyte multilayer membranes (PEMMs) are introduced as a novel ion exchange membrane (IEM), as they can adjust different membrane structures according to the requirement. However, due to the influence of membrane structure on ion permeability and its mechanism have not been deeply studied, it is difficult to select the optimal structure under service conditions, resulting in low separation efficiency or increased energy consumption. Herein, a theoretical method is proposed to establish the structure–activity relationship of PEMMs, and then select the optimal membrane structure. The fixed charge was described by a specific trigonometric function to simulate the PEMMs. The effects of different membrane structures and charges on ion permeability and flux were studied by the modified Poisson-Nernst-Planck (MPNP) equations, and the competitive control relationship between the bilayers number and the charge density of each layer on the membrane performance was found. With our theoretical model, the selectivity and efficiency of PEMMs in electrodialysis can be comprehensively evaluated to guide its design and application.

Modification Approaches of Polyphenylene Oxide Membranes to Enhance Nanofiltration Performance.

Presently, water pollution poses a serious threat to the environment; the removal of organic pollutants from resources, especially dyes, is very important. Nanofiltration (NF) is a promising membrane method to carry out this task. In the present work, advanced supported poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) membranes were developed for NF of anionic dyes using bulk (the introduction of graphene oxide (GO) into the polymer matrix) and surface (the deposition of polyelectrolyte (PEL) layers by layer-by-layer (LbL) technique) modifications. The effect of PEL combinations (polydiallyldimethylammonium chloride/polyacrylic acid (PAA), polyethyleneimine (PEI)/PAA, and polyallylamine hydrochloride/PAA) and the number of PEL bilayers deposited by LbL method on properties of PPO-based membranes were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle measurements. Membranes were evaluated in NF of food dye solutions in ethanol (Sunset yellow (SY), Congo red (CR), and Alphazurine (AZ)). The supported PPO membrane, modified with 0.7 wt.% GO and three PEI/PAA bilayers, exhibited optimal transport characteristics: ethanol, SY, CR, and AZ solutions permeability of 0.58, 0.57, 0.50, and 0.44 kg/(m2h atm), respectively, with a high level of rejection coefficients-58% for SY, 63% for CR, and 58% for AZ. It was shown that the combined use of bulk and surface modifications significantly improved the characteristics of the PPO membrane in NF of dyes.

Asymmetric polyelectrolyte multilayer nanofiltration membranes: Structural characterisation via transport phenomena

One promising application of polyelectrolyte multilayers (PEMs) is their use as selective layers in nanofiltration (NF). Especially encouraging are the simplicity of fabrication, controlled layer thickness in the nanometer range, and versatility. In addition to commonly used tuning parameters such as pH, ionic strength, and choice of polyelectrolytes, combining two different PEMs in a so-called asymmetric PEM enables further optimisation of the selective membrane layer. Experimental characterisation of these PEMs is complex, and therefore, the knowledge of the exact layer structure is limited. In this work, we combine filtration experiments and theoretical transport models to describe the effective structure of an asymmetric PEM made of a bottom layer of poly(allylamine hydrochloride) (PAH)/poly(sodium 4-styrenesulfonate) (PSS) and a top layer of PAH/poly(acrylic acid) (PAA). Obtained membrane properties suggest the formation of a distinct layer structure with individual layer properties close to the single symmetric PEM after a minimum number of layers. There is, however, a fundamental difference in the retention of salt and polyethylene glycol molecules. While salt retention properties of the asymmetric PEM are stable already after only one bilayer of PAH/PAA, a gradual transition in the retention of polyethylene glycol molecules from the more open PAH/PSS system to the dense PAH/PAA system is observed. This is attributed to the different exclusion mechanisms dominating solute transport (size- vs charge-based). A gradual decrease in molecular weight cut-off (MWCO) with increasing bilayer (BL) number of PAH/PAA is observed, resulting in a minimum MWCO of around 120g mol−1 after 5 BLs. Theoretical transport models assuming an ideal layer structure in series predict this value as well. At the same time, high mono- to divalent salt selectivity is observed after 1 BL of PAH/PAA already. Single salt retention of NaCl is around 20% versus Na2SO4, MgCl2 and MgSO4 being above 95%. Although this trend is qualitatively predicted by the theoretical transport model, again assuming ideal layers in series, deviations indicate variations in charge distribution within these layers.

Versatile sensing capabilities of layer-by-layer deposited polyaniline-reduced graphene oxide composite-based sensors

Precise temperature, humidity, and organic pollutants monitoring are required for industrial, environmental and medical applications. The interesting properties of polyaniline for sensors, such as environmental responsiveness and stability, combined with the large surface area and tunable properties of graphene oxide, offer excellent prospects for the development of sensor materials. In this paper, we show that HCl-doped polyaniline/reduced graphene oxide (PANI/rGO) layer-by-layer deposition and subsequent reduction can be used as resistive sensors for temperature, humidity, acetone, and electrochemical sensors for organophosphate detection in aqueous solutions. Sensors were characterized using atomic force and scanning electron microscopies and energy-dispersive x-ray and Raman spectroscopies, and impedance spectroscopy complemented by semi-empirical quantum chemical calculations. Reduction temperature and bilayer numbers influence PANI/rGO sensor characteristics significantly. The results show that only one PANI/rGO bilayer is needed to provide a temperature coefficient of resistance of − 0.758 °C−1 and 37% sensitivity at 95% relative humidity. PANI/rGO shows potential for electrochemical detection of dimethoate affected by the number of bilayers and reduction temperature. The response to acetone vapor is linear from 1 to 60 ppm and detectable at 1 ppm. The sensors do not respond to methanol and some other volatile organic compounds (VOCs) at the same concentration. Food monitoring with total VOCs detection was successfully demonstrated. PANI/rGO sensors feature versatile sensing capabilities, making them feasible due to their rapid production and low cost.

Spray-assisted LBL assembly of chitosan/nanocellulose as coatings of commercial membranes for oil-in-water emulsion separation

Owing to the limitation of their wettability and pore size, lab filter membranes could not separate oil/water emulsions. Herein, we present surface modification of commercial membranes with chitosan/nanocellulose coatings via a spray-assisted layer-by-layer (LBL) assembly technology. By alternate spraying chitosan (CS) solution and TEMPO-oxidized tunicate cellulose nanofiber (TCNF) suspension, (CS/TCNF)n multilayers were obtained, where n denotes the number of bilayers. The (CS/TCNF)6 coated membrane possessed superhydrophilicity, underwater superoleophobicity, and outperforming anti-oil-fouling properties, which could effectively separate various oil-in-water emulsions. Importantly, the (CS/TCNF)6 coated membrane not only had stable permeate flux with nearly 100 % recovery ratio for the separation of pump oil-in-water emulsion, but also exhibited good harsh-environment-tolerant property. This work provided a novel strategy for designing and preparing stable anti-oil-fouling membranes for oily wastewater treatment.

Eco-friendly preparation, characterization, evaluation of anti-melanogenesis/antioxidant effect and in vitro/in vivo safety profile of kojic acid loaded niosome as skin lightener preparation

In the current study, an ultrasonic approach (as green method) was utilized to prepared kojic acid niosome (kojisome) which aimed to increase the dermal delivery and improving anti-melanogenesis properties. The study’s findings demonstrated that increasing cholesterol enhanced the mean particle size from 68.333 ± 5.686 nm to 325.000 ± 15.099 nm and entrapment efficiency 0% to 39.341 ± 4.126% of the kojisome. Cholesterol may enhance the number and rigidity of bilayers that induced a size enhancement and entrapment efficiency. The skin permeability test revealed that kojisome gel had more kojic acid in dermal layers (437.563 ± 29.857 μg/cm2 or 16.624 ± 1.379%) than kojic acid plain gel (161.290 ± 14.812 μg/cm2 or 6.128 ± 0.672%). The niosome’s lipophilicity allowed for gradual penetration, possibly due to better contact with the skin layers. Also, the extended-release behavior of improved kojisome exhibited high safety profile and low side effect in In vitro cytotoxicity assay, dermal irritation test, and Histo-pathological evaluation. Furthermore, optimum kojisome inhibited melanin formation (53.093 ± 2.985% at 1000 µM) higher than free kojic acid (62.383 ± 1.958%) significantly (p < 0.05). In addition, Kojisome 6 inhibited L-dopa auto-oxidation greater extent (94.806 ± 2.411%) than pure kojic acid solution (72.953 ± 2.728%). Kojisome by delivering and targeting large amount of kojic acid on specific site causes high efficacy in inhibition of melanin synthesis. The observations of this study revealed that the produced kojisome might be used as a potential nano-vehicle for kojic acid dermal administration, thereby opening up innovative options for the treatment of hyperpigmentation problems.

Impact of support pore properties on the performance of layer-by-layer self-assembly nanofiltration membrane

This paper investigates the impact of the porous structure of the support on the permselectivity and backwash resistance of Layer-by-Layer (LBL) nanofiltration (NF) membranes. Four different polyethersulfone (PES) hollow fiber membranes with varying pore sizes were coated with poly(allylamine hydrochloride)/poly(sodium-4-styrenesulfonate) (PAH/PSS) polyelectrolyte pairs. The study found that adjusting the number of bilayers in the coating process enabled the production of LBL membranes with similar molecular weight cut-off (MWCO) around 250 Da and high Mg2+ rejection of 95 %. However, Na2SO4 rejection decreased as the number of bilayers increased, as the positively charged PAH overcompensated. The study also found that the pore size of the support did not significantly impact the backwash resistance of the LBL membranes, indicating that the polyelectrolyte chains can penetrate through the pores of the supports regardless of pore size. This finding can guide the design of suitable supports for LBL NF membranes with tailored performances.

Structural and Optical Properties of Tungsten Disulfide Nanoscale Films Grown by Sulfurization from W and WO3.

Tungsten disulfide (WS2) was prepared from W metal and WO3 by ion beam sputtering and sulfurization in a different number of layers, including monolayer, bilayer, six-layer, and nine-layer. To obtain better crystallinity, the nine-layer of WS2 was also prepared from W metal and sulfurized in a furnace at different temperatures (800, 850, 900, and 950 °C). X-ray diffraction revealed that WS2 has a 2-H crystal structure and the crystallinity improved with increasing sulfurization temperature, while the crystallinity of WS2 sulfurized from WO3 (WS2-WO3) is better than that sulfurized from W-metal (WS2-W). Raman spectra show that the full-width at half maximum (FWHM) of WS2-WO3 is narrower than that of WS2-W. We demonstrate that high-quality monocrystalline WS2 thin films can be prepared at wafer scale by sulfurization of WO3. The photoluminescence of the WS2 monolayer is strongly enhanced and centered at 1.98 eV. The transmittance of the WS2 monolayer exceeds 80%, and the measured band gap is 1.9 eV, as shown by ultraviolet-visible-infrared spectroscopy.

Self-Assembly of Glycerol-Amphiphilic Janus Dendrimers Amplifies and Indicates Principles for the Selection of Stereochemistry by Biological Membranes.

The principles for the selection of the stereochemistry of phospholipids of biological membranes remain unclear and continue to be debated. Therefore, any new experiments on this topic may help progress in this field. To address this question, three libraries of constitutional isomeric glycerol-amphiphilic Janus dendrimers (JDs) with nonsymmetric homochiral, racemic, and symmetric achiral branching points were synthesized by an orthogonal-modular-convergent methodology. These JDs amplify self-assembly, and therefore, monodisperse vesicles known as dendrimersomes (DSs) with predictable dimensions programmed by JD concentration were assembled by rapid injection of their ethanol solution into water. DSs of homochiral JD enantiomers, racemic, including mixtures of different enantiomers, and achiral exhibited similar DS size-concentration dependence. However, the number of bilayers of DSs assembled from homochiral, achiral, and racemic JDs determined by cryo-TEM were different. Statistical analysis of the number of bilayers and coarse-grained molecular dynamics simulations demonstrated that homochiral JDs formed predominantly unilamellar DSs. Symmetric achiral JDs assembled only unilamellar DSs while racemic JDs favored multilamellar DSs. Since cell membranes are unilamellar, these results indicate a new rationale for nonsymmetric homochiral vs racemic selection. Simultaneously, these experiments imply that the symmetric achiral lipids forming more stable membrane, probably had been the preferable assemblies of prebiotic cell membranes.

Modification of Cellulose Acetate Microfiltration Membranes Using Graphene Oxide-Polyethyleneimine for Enhanced Dye Rejection.

Pressure-based membrane processes represent excellent water resource recovery prospects from industrial waste streams. In contrast with conventional pretreatment technologies, studies have shown that membrane pretreatment applications, such as microfiltration (MF), are more cost-effective and improve the results of the overall treatment processes. Hence, enhancing rejection efficiency of MF will enhance the performance of any downstream treatment processes. In this study, 0.45 µm cellulose acetate (CA) microfiltration membranes were modified by vacuum filtration-assisted layer-by-layer deposition of bilayers composed of negatively charged graphene oxide (GO) and positively charged polyethyleneimine (PEI). The performance of 1-, 2-, and 4-bilayer GO-PEI-modified membranes were investigated for their dye-rejection of anionic eriochrome black T (EBT) dye and cationic methylene blue (MB) dye in a cross-flow membrane module. As the number of bilayers on the membrane increased, the membrane thicknesses increased, and the deionized (DI) water flux through the membranes decreased from 4877 LMH/bar for the control (no bilayer) membrane to 2890 LMH/bar for the 4-bilayer membrane. Conversely, the dye-rejection performance of the modified membranes increased as increasing bilayers of GO-PEI deposited on the membranes. The anionic EBT dye saw superior rejection (~90% rejection) compared to the cationic MB dye (~80% rejection), which can be attributable to the electrostatic repulsion between the negatively charged GO surface and anionic EBT dye. After 50% recovery of the saline and dye-laden feed water, there was an observed drop in DI water fluxes of ~40-41% and 36%, respectively. There was also a slight increase in EBT dye-rejection during the composite feed-water experiments, attributed to the precipitation of salts on the membrane feed side or pore spaces, which subsequently reduce the membrane pore sizes.

PRODUCTION AND PROPERTIES OF A PHOTOLUMINESCENT COATING BASED ON SEMICONDUCTOR QUANTUM DOTS IN A HOLLOW CORE OF MICROSTRUCTURED GLASS

Microstructured optical fibers (MOF) are a promising tool for improving biosensors, optical sensing, biomedical research, and clinical imaging. Approaches to the modification of the inner surface of microstructured optical fibers with a hollow core (MOF-HC) with polymer and photoluminescent materials using layer-by-layer deposition technology was developed. The method allows not only varying the thickness and charge of the layers, but also controllably introduce functional structures into the layers, in particular nanoparticles. The layer-by-layer deposition of polydiallyldimethylammonium chloride (PDDA) cationic polyelectrolyte with an average molecular weight (200 - 350 kDa) and negatively charged fluorescent nanoparticles - cadmium-free quantum dots (QD) of the AgInS2/ZnS structure, luminescent red (625 nm), orange (606 nm), yellow (570 nm) and green (556 nm) was investigated. QDs of the AgInS2/ZnS core/shell structure were obtained by the one-pot aqueous synthesis and selectively separated by successive deposition into fractions according to the size and color of the luminescence. This ensured the similarity of the properties of QDs with different luminescence colors. It was found that with an increase in the number of bilayers PDDA/QD from 1 to 5, the long-wave shift of the HC-MOF transmittance spectrum is: for layers based on red QD - 10 nm, orange QD - 11 nm, yellow 7 nm and green 8 nm relative to the spectrum of the original HC-MOF. When QD is included in the composition of the photoluminescent coating in the HC-MOF, a decrease in the wavelength of the maximum emission of QD is recorded, while the application of a subsequent layer of PDDA leads to its increase. For citation: Kochergin T.P., Ponomaryova T.S., Goryacheva I.Y. Production and properties of a photoluminescent coating based on semiconductor quantum dots in a hollow core of microstructured glass. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 2. P. 85-91. DOI: 10.6060/ivkkt.20236602.6615.

Preparation of Small Unilamellar Vesicle Liposomes Using Detergent Dialysis Method.

Small unilamellar liposomes are commonly used as model biomembranes and carriers for drug and gene delivery. Although methods which employ mechanical forces or organic solvents can be used to reduce the liposome size and the number of lipid bilayers, they are not suitable options when the purpose is to incorporate biologically active proteins into lipid bilayers or to encapsulate nucleic acid into liposomes. Detergent dialysis is a simple and inexpensive procedure to produce homogeneous small unilamellar vesicles (SUVs). Lipids are solubilized by detergent at a concentration much higher than its critical micellar concentration (CMC) in an aqueous dispersion medium. Free monomer detergent molecules in the dispersion medium are removed during dialysis, while the supramolecular detergent-lipid mixed micelles (MMs) are kept inside the dialysis tubing, leading to dissociation of detergent molecules from MMs. SUVs are formed after the micelle to vesicle transition (MVT).

Graphene oxide-based layer-by-layer nanofiltration membrane using inkjet printing for desalination

Nanofiltration (NF) membrane was prepared using inkjet printing assisted layer-by-layer (LBL) assembly of polyethylenimine (PEI) and graphene oxide (GO) on a polyketone (PK) substrate surface then cross-linked with glutaraldehyde (GA). The membrane characterizations confirmed the successful formation of cross-linked multilayer PEI/GO membranes. PEI/GO membrane prepared with three bilayer numbers was found to have the optimal separation performances with the highest permeability and selectivity. The NF performances of the (PEI/GO)3 membrane were evaluated using different molecular weight dyes and different salts. Results revealed that the (PEI/GO)3 membrane exhibited rejections of 99.9 %, 98.1 %, 94.7 %, and 85.1 % for Rose Bengal (RB), Brilliant blue R (BBR), Eosin Y (EY), and methylene blue (MB), respectively. The selectivity of (PEI/GO)3 membrane for salts followed a sequence of MgSO4 > Na2SO4 > MgCl2 > NaCl. The influences of PEI and GO concentrations on membrane performances were investigated. The stability of (PEI/GO)3 was evaluated by chlorination test and long-term filtration test. The (PEI/GO)3 membrane exhibited desirable chlorine resistant property and excellent long-term filtration stability. Overall, our work provided new ways for the preparation of LBL membranes with good NF performances and excellent stability property.

Development of Polyethersulfone Nanofiltration Membrane with Layer-by-Layer Method for Xylitol Purification

This work is aimed to develop polyethersulfone (PES) nanofiltration (NF) membrane with layer-by-layer (LBL) polyelectrolytes of chitosan (CHI) and poly(acrylic acid) (PAA) for xylitol purification from fermentation broth. Different number of bilayers and type of terminating layer were manipulated for producing more hydrophilicity, negatively charged with improved performance compared to pristine PES membrane. Successful deposition of polyelectrolyte layers onto PES membrane was able to be proven using various tests such as contact angle, Zetasizer and FT-IR. The results obtained have proven that LBL can develop PES membrane with higher resistance to fouling. From Zeta potential analysis, the value of pristine PES membrane's negativity confirmed the theory of negatively charged substrate for LDL. The negative value of PES membrane increased from -16.5 mV to -32.7 mV after being modified to PES (CHI/PAA)6. From FT-IR spectra, the formation of CHI/PAA complexes on the membrane's surface is confirmed through the presence of stretching peaks of -COOH, -NH3+ and -NH2+ groups The pure water flux reduces from 47.40 ±6.30 L⁄m2.h to 7.40 ±1.64 L⁄m2.h after being modified to PES (CHI/PAA)2. The rejection performance of xylitol for PES (CHI/PAA)2 is higher (84.95%) than pure PES membrane (66.17%), while (CHI/PAA)4 offered the lowest selectivity towards xylitol than arabinose and thus able to obtain higher purity of xylitol as retentate. LBL surface modification using CHI/PAA can develop PES membrane with higher hydrophilicity, negatively charge, and is able to give better xylitol rejection compared to pure PES.