Cellulose Acetate Thin Films Research Articles

A compact bipolar electrochemistry device utilizing a liquid free catholyte and eye visual indication of the reporting event for the determination of antioxidant capacity in real-world samples

Here we report for the first time the development of a compact, closed bipolar electrochemistry (BPE) device for the determination of antioxidant capacity in real-world samples by recording the onset driving voltage at which an eye-visible reporting event at the cathode pole of bipolar electrode (BE) occurs. The BPE cell consists of two distinct anode and cathode compartments that are electrically connected through a platinum wire BE. The anode pole of the BE is covered by a cellulose acetate thin film to prevent the fouling of the surface, while the cathode pole is embedded into an agarose hydrogel containing phenolphthalein, i.e., an acid-base indicator. The method relies on the oxidation of the reducing compounds in the sample by a fixed amount of H2O2 and the electro oxidation of the remaining H2O2 in the anode pole of the BE. This reaction triggers the reduction of water at the cathodic pole accompanied by the production of hydroxyl ions at different, H2O2 concentration-dependent onset driving voltages. The resulting increase of pH at the cathode pole results in the formation of a pink spot (reporting event), which is visible by the unaided eye. The applicability of the BPE device for the determination of antioxidant capacity in fruit juices and sodas is demonstrated. The analytical results, expressed as Trolox (TEAC) or Vitamin C (CVEAC) equivalent antioxidant capacity, correlate well with those obtained by the CUPRAC method.

Preparation of thin films of cellulose acetate-nitrocellulose blend for solid state nuclear track detection using spin coating technique

This paper describes preparation of composite thin films of 12 ± 1 µm from cellulose acetate (CA) and cellulose acetate (CA) -cellulose nitrate (CN) blend on a polyester support for solid state nuclear track detection (SSNTD) application. Films were prepared using a spin coater and their experimentally observed film thickness was compared with theoretically predicted film thickness using Damon and Meyerhofer equations. Effect of RPM of spin coater on cellulose nitrate and cellulose acetate thin films is reported for the first time. Track detection properties of CA + CN are tested and compared with indigenous CN and imported LR-115™ film.

Flexible transparent electrode based on PANi nanowire/nylon nanofiber reinforced cellulose acetate thin film as supercapacitor

Highly uniform, flexible, and transparent electrodes based on in situ polymerization of PANi nanowires on nylon nanofiber-reinforced cellulose acetate thin film substrates were reported in this study. At first, the nylon nanofibers were electrospun followed by infiltration with cellulose acetate to get highly transparent substrate. Then PANi nanowires were grown uniformly on the transparent substrate by an in situ polymerization technique. The resulting thin films showed transparency from 39% to 82% and sheet resistivity between 188 and 8700Ω/sq depending on the aniline monomer concentration. In addition, the transparent electrode exhibited outstanding toughness during bending cycles. Further, the transparent electrode showed excellent capacitive performance with specific capacitance of 402F/g. These promising results highlight the importance of PANi nanowires and nylon reinforced cellulose acetate film as potential materials for optoelectronic devices.

Antifouling coating of cellulose acetate thin films with polysaccharide multilayers.

In this investigation, partially deacetylated cellulose acetate (DCA) thin films were prepared and modified with hydrophilic polysaccharides with the layer-by-layer (LbL) technique. As polysaccharides, chitosan (CHI) and carboxymethyl cellulose (CMC) were used. DCA thin films were manufactured by exposing spin coated cellulose acetate to potassium hydroxide solutions for various times. The deacetylation process was monitored by attenuated total reflectance-infrared spectroscopy, film thickness and static water contact angle measurements. A maximum of three bilayers was created from the alternating deposition of CHI and CMC on the DCA films under two different conditions namely constant ionic strengths and varying pH values of the CMC solutions. Precoatings of CMC at pH 2 were used as a base layer. The sequential deposition of CMC and CHI was investigated with a quartz crystal microbalance with dissipation, film thickness, static water contact angle and atomic force microscopy (AFM) measurements. The versatility and applicability of the developed functional coatings was shown by removing the multilayers by rinsing with mixtures containing HCl/NaCl. The developed LbL coatings are used for studying the fouling behavior of bovine serum albumin (BSA).

DEVELOPMENT OF REACTOR-TYPE "DIP CATALYST" FOR TRANSITION METAL NANOPARTICLE-EMBEDDED POLYMER THIN FILMS

This article describes the development of a new catalytic reactor designed to operate with nanoparticle-embedded polymer thin films. Stabilization of metal nanoparticles in films that serve as catalysts in organic reactions is relatively new; therefore, the development of reactors to facilitate their use is necessary. We describe in detail the preparation of the GDCR reactor-type dip catalyst and its evaluation in the Suzuki - Miyaura cross-coupling reaction of phenylboronic acid and 4-bromoanisole catalyzed by palladium nanoparticle-embedded cellulose acetate thin film (CA/PD(0)). Compared with earlier prototypes, GDCR reactor showed excellent results when operating with CA/PD(0) thin films.

Room-temperature development of thin film composite reverse osmosis membranes from cellulose acetate with antibacterial properties

A cellulose acetate thin film composite (CA TFC) membrane was developed by direct casting of CA onto an ultrafiltration membrane support. The flux through the CA TFC membrane was, as expected, inversely proportional to the selective layer thickness. The membrane with the lowest thickness of the CA film (217nm) initially had poor salt rejection (~55%) but relatively high permeability (~0.5lm−2h−1bar−1). In contrast to asymmetric CA reverse osmosis membranes that are developed in 4°C water baths, the CA TFC membranes were developed by subsequent swelling in room temperature water baths, thermal annealing at 81°C, and with room-temperature incorporation of silver nanoparticles onto CA TFC surfaces by chemical reduction. The change in the physical properties as a result of the swelling process was examined with ellipsometry, grazing incidence X-ray scattering and contact angle measurements. A combined swelling and annealing treatment was found to improve salt rejection to an acceptable reverse osmosis salt rejection level (~94%) without significant deterioration of flux. The swelling time was found to generally improve the membrane performance in terms of flux and surface roughness whilst the silver nanoparticle treatment reduced bacterial surface coverage by four orders of magnitude.

Vertical-cavity surface-emitting laser in the long-wavelength (700 nm) region in the visible by energy transfer between organic dyes

In this work, organic vertical-cavity surface-emitting lasers (VCSELs) with single-mode laser output in the long-wavelength region (~700 nm) of the visible were reported based on the energy transfer between dye pairs consisting of pyrromethene 597 (PM597) and rhodamine 700 (LD700). By co-doping PM597 into the polymeric hosts, the fluorescence intensity of LD700 was enhanced by 30-fold and the photophysical parameters of the donor–acceptor pairs were investigated, indicating the involvement of non-radiative resonance energy transfer processes between PM597 and LD700. Active distributed Bragg reflectors (DBR) were made by alternately spin-coating dye-doped polyvinylcarbazole and cellulose acetate thin films as the high and low refractive index layers, respectively. By sandwiching the active layer with 2 DBR mirrors, VCSEL emission at 698.9 nm in the biological first window (650–950 nm) was observed under the 532-nm laser pulses. The laser slope efficiency and threshold were also measured.

The Effect of Curing Temperature on the Performance of Thin Film Composite Membrane

Kesan suhu rawatan pada prestasi membran komposit dikaji menggunakan dua jenis membran penyokong polimer iaitu selulosa asetat dan polisulfona. Larutan fasa akuas disediakan dengan melarutkan m–fenildiamina, tetrabutilammonium bromida, natrium hidroksida dan hidroquinon berdasarkan komposisi di dalam air suling. Larutan fasa organik disediakan dengan melarutkan trimesil klorida dalam n–heksana. Membran komposit disediakan dengan menggunakan kaedah pempolimeran antara muka. Pempolimeran berlaku dalam fasa organik melalui tindak balas antara muka antara m–fenildiamina, hidrokuinon dan trimesil klorida untuk menghasilkan rangkaian poliesteramida. Suhu rawatan di dalam julat 40°C hingga 100°C digunakan dalam oven semasa proses tindakbalas antara muka. Penilaian prestasi membran komposit terhadap kadar penyingkiran garam dan fluks dilakukan menggunakan sel penelapan ringkas. Hasil uji kaji menunjukkan membran komposit selulosa asetat dengan suhu rawatan 60°C menunjukkan kadar penyingkiran terbaik sebanyak 76% manakala membran komposit polisulfona dengan suhu rawatan 80°C memberikan kadar penyingkiran yang terbaik sebanyak 80%. Kata kunci: Membran lapisan komposit, fasa organik, fasa akuas, suhu rawatan The effect of curing temperature on the performance of thin film composite membranes was studied using two different kinds of polymeric membrane supports, i.e. cellulose acetate and polysulfone. Aqueous phase solution was prepared by dissolving m–phenyldiamine, tetrabutylammonium bromide, sodium hydroxide and hydroquinone based on the composition in distilled water. Organic phase was prepared by dissolving trimesoyl chloride in n–hexane. Polymerization occurred in the organic phase by interfacial reaction of m–phenyldiamine with the presence of trimesoyl chloride to form polyesteramides. Curing temperatures ranging from 40° to 100°C were used in the air–circulated oven during the interfacial reaction process. The performances of the thin film composite membranes in terms of salt rejection and permeation rate were evaluated using the permeation cell. The results showed that cellulose acetate thin film composite membrane cured at 60°C gives the best rejection rate of 76% whilst polysulfone thin film composite membrane cured at 80°C gives the highest rejection rate of 80%. Key words: Thin film composite membrane, aqueous phase, organic phase, curing temperature

Thin functionalized films on cylindrical microelectrodes for electrochemical determination of Hg(II)

Cylindrical carbon fiber microelectrodes (CFMEs) were used for the determination of Hg(II) in aquatic solutions using anodic stripping voltammetry (ASV). Optimizing the parameters, such as the potential and time of deposition, resulted in linear response of the fiber over a large range of Hg(II) concentrations (5 × 10 −8–1 × 10 −5 M). Furthermore, three methods of modification of glassy carbon and CFMEs with thiol or other Hg(II)-complexing groups, have also been examined. Electrodes were modified by electrochemically reducing 4,4′-disulfanediyldibenzenediazonium, followed by reduction of the disulfide bond, by electrodepositing sol–gel based on 3-mercaptopropyltrimethoxysilane and by spin-coating or adsorbing cellulose acetate thin films in which 4,13-didecyl-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (Kryptofix® 22DD) was incorporated. We found that all modified glassy carbon electrodes extracted Hg(II) under open-circuit potential, however, only the cylindrical microelectrode modified via the electrochemical reduction of the diazonium was capable of extracting mercuric ions. The interference of Pb(II), Cd(II), and Cu(II) with the determination of Hg(II) with 4,4′-disulfanediyldibenzenediazonium modified CFME was also studied.

Nanofabrication in cellulose acetate

We have demonstrated nanofabrication with commercialized cellulose acetate. Cellulose acetate is used for bulk nanofabrication and surface nanofabrication. In bulk nanofabrication, cellulose acetate reacts with an e-beam and permanent patterns are formed in it instead of being transferred to other substrates. We have studied the nano relief modulation performance of cellulose acetate before and after development. The depth of the nanopatterns is magnified after development, and is varied by exposing dosage and line width of the pattern. The thinnest 65 nm wide line is achieved in the bulk fabrication. We also demonstrate a binary phase Fresnel lens array which is directly patterned in a cellulose acetate sheet. Because of its unique mechanical and optical properties, cellulose is a good candidate for a template material for soft imprinting lithography. In the surface nanofabrication, cellulose acetate thin film spin-coated on silicon wafers is employed as a new resist for e-beam lithography. We achieved 50 nm lines with 100 nm pitches, dots 50 nm in diameter, and single lines with the smallest width of 20 nm. As a new resist of e-beam lithography, cellulose acetate has high resolution comparable with conventional resists, while having several advantages such as low cost, long stock time and less harmfulness to human health.

Dielectric properties of solution grown cellulose acetate thin films

The dielectric capacitance and loss behaviour of solution grown cellulose acetate thin films were studied as a function of temperature (range 300–420 K) in the frequency range 50 Hz–15 kHz. The capacitance versus temperature plots show a single peak around 345 K which shifts towards higher temperatures with increasing frequency. The loss behaviour exhibits two peaks, occurring at 312 and 345 K. The low-temperature peak is interpreted in terms of small-scale movements of the dipole groups while the high-temperature peak is attributed to the dipole-segmental loss.