Zinc oxide nanoparticles-chitosan composite film for cholesterol biosensor

Zinc oxide nanoparticles (NanoZnO) uniformly dispersed in chitosan (CHIT) have been used to fabricate a hybrid nanocomposite film onto indium-tin-oxide (ITO) glass plate. Cholesterol oxidase (ChOx) has been immobilized onto this NanoZnO-CHIT composite film using physiosorption technique. Both NanoZnO-CHIT/ITO electrode and ChOx/NanoZnO-CHIT/ITO bioelectrode have been characterized using Fourier transform-infrared (FTIR), X-ray diffraction (XRD), cyclic voltammetry (CV), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) techniques, respectively. The ChOx/NanoZnO-CHIT/ITO bioelectrode exhibits linearity from 5 to 300 mg dl⁻¹ of cholesterol with detection limit as 5 mg dl⁻¹, sensitivity as 1.41 × 10⁻⁴ A mg dl⁻¹ and the value of Michaelis-Menten constant (K_m) as 8.63 mg dl⁻¹. This cholesterol biosensor can be used to estimate cholesterol in serum samples.     

Ferrocene-functionalized graphene electrode for biosensing applications

A novel ferrocene-functionalized reduced graphene oxide (rGO)-based electrode is proposed. It was fabricated by the drop casting of ferrocene-functionalized graphene onto polyester substrate as the working electrode integrated within screen-printed reference and counter electrodes. The ferrocene-functionalized rGO has been fully characterized using FTIR, XPS, contact angle measurements, SEM and TEM microscopy, and cyclic voltammetry. The XPS and EDX analysis showed the presence of Fe element related to the introduced ferrocene groups, which is confirmed by a clear CV signal at ca. 0.25 V vs. Ag/AgCl (0.1 KCl). Mediated redox catalysis of H₂O₂ and bio-functionalization with glucose oxidase for glucose detection were achieved by the bioelectrode providing a proof for potential biosensing applications.     

Epitaxial oxide thin films by pulsed laser deposition: Retrospect and prospect

Pulsed laser deposition (PLD) is a unique method to obtain epitaxial multi-component oxide films. Highly stoichiometric, nearly single crystal-like materials in the form of films can be made by PLD. Oxides which are synthesized at high oxygen pressure can be made into films at low oxygen partial pressure. Epitaxial thin films of highT _c cuprates, metallic, ferroelectric, ferromagnetic, dielectric oxides, superconductor-metal-superconductor Josephson junctions and oxide superlattices have been made by PLD. In this article, an overview of preparation, characterization and properties of epitaxial oxide films and their applications are presented. Future prospects of the method for fabricating epitaxial films of transition metal nitrides, chalcogenides, carbides and borides are discussed.     

Compressed matrix thin film (CMTF)-assisted laser desorption ionization mass spectrometric analysis

The inhomogeneous re-crystallization process of matrix materials is the major concerns associated with matrix assisted laser desorption/ionization (MALDI) analysis. We describe here the approach termed compressed matrix thin film (CMTF) in order to make a uniform matrix deposition. In this approach, solid matrix particles are compressed under 10 MPa of pressure by a compressor that is regularly used in infrared spectroscopic analysis. Then aqueous samples can be deposited on the surface of the matrix film. Major advantages of the CMTF approach are summarized as follows. (1) Reproducible sample preparation procedure. Size and thickness of matrix thin films can be controlled by using a fixed mold.force and known amount of matrix materials. (2) Significantly decreased shot-to-shot variations and enhanced reproducibility. (3) Tolerance for in situ salt washing. Because matrix materials are hydrophobic, salts can be washed away while proteins or peptides are retained on the surface of matrix thin films through hydrophobic interactions. (4) Improved sensitivity. The hydrophobic coating of MALDI sample plate by matrix thin films prevents the spreading of samples across the plate and confines analytes to a small area, leading to increased local concentration. (5) A new means for tissue analysis. Tissue sections can be directly transferred to the uniform surface of matrix materials for reproducible and quantitative comparison of different molecules in different localization. The proposed CMTF should be an enabling technique for mass spectrometric analysis with improved correlations between signal intensities and sample quantities.     

Thin film composite optical waveguides for sensor applications: a review

We review the design and fabrication of thin-film composite optical waveguides (OWG) with high refractive index for sensor applications. A highly sensitive optical sensor device has been developed on the basis of thin-film, composite OWG. The thin-film OWG was deposited onto the surface of a potassium-ion-exchanged (K⁺) glass OWG by sputtering or spin coating (5–9 mm wide, and with tapers at both ends). By allowing an adiabatic transition of the guided light from the secondary OWG to the thin-film OWG, the electric field of the evanescent wave at the thin film was enhanced. The attenuation of the guided light in the thin film layer was small, and the guided light intensity changed sensitively with the refractive index of the cladding layer. Our experimental results demonstrate that thin-film, composite OWG gas sensors or immunosensors are much more sensitive than sensors based on other technologies.     

Direct formation of silver nanoparticles in cuttlebone-derived organic matrix for catalytic applications

Development of biologically derived materials for the construction of materials with new functions is a crucial intersection of materials science and biotechnology, which is currently a topic of research interest. In this paper, we report on the use of cuttlebone-derived organic matrix (CDOM) as scaffold and reducer for the formation of silver nanoparticles (AgNPs). The experiment was carried out by simple immersing of CDOM in tollen’s reagent and incubating at 80 °C. UV–vis spectra and TEM were utilized to characterize the AgNPs and investigate their formation process. Results demonstrate that the size and distribution of AgNPs are influenced by the incubation time and protein component in CDOM. Furthermore, the AgNPs–CDOM composite was applied to catalyze the reduction of 4-nitrophenol in the presence of NaBH₄, and it can be easily separated from the liquid-phase reaction system during the reusing cycles.     

Novel polyethersulfone-cellulose composite thin film using sustainable empty fruit bunches from Elaeis guineensis for methylene blue removal

The consumption of the polymeric membrane is increased over the years due to the high demand from the industries. This work attempts to evaluate the performance of polyethersulfone (PES) membrane incorporated with cellulose nanofibrils (CNF), which can be extracted from empty fruit bunches generated from palm oil mills. PES/CNF/polyvinylpyrrolidone (PVP) blend membranes were fabricated using phase inversion method under the following conditions: 16 to 24 wt% PES, 0.2 to 1.2 wt% CNF and 0.3 to 1.0 wt% PVP. Response Surface Methodology (RSM) was employed to optimize the composition of this composite membrane. 80.9 L/m².hr permeate flux and 62.3% MB rejection were obtained at a composition of 18.0202 wt% PES, 0.2000 wt% CNF, and 0.4980 wt% PVP. ANOVA for the models showed that the Prob.>F values for permeate flux and MB rejection were 0.0011 and 0.001, which indicated the significant effect of CNF on the performance of the PES composite membrane.     

Electrode modified with a composite film of ZnO nanorods and Ag nanoparticles as a sensor for hydrogen peroxide

A conducting fluorine-doped tin oxide (FTO) electrode, first modified with zinc oxide nanorods (ZnONRs) and subsequently attached with photosynthesized silver nanoparticles (AgNPs), designated as AgNPs/ZnONRs/FTO electrode, was used as an amperometric sensor for the determination of hydrogen peroxide. The first layer (ZnONRs) was obtained by chemical bath deposition (CBD), and was utilized simultaneously as the catalyst for the photoreduction of Ag ions under UV irradiation and as the matrix for the immobilization of AgNPs. The aspect ratio of ZnONRs to be deposited was optimized by controlling the number of their CBDs to render enough surface area for Ag deposition, and the amount of AgNPs to be attached was controlled by adjusting the UV-irradiation time. The immobilized AgNPs showed excellent electrocatalytic response to the reduction of hydrogen peroxide. The resultant amperometric sensor showed 10-fold enhanced sensitivity for the detection of H₂O₂, compared to that without AgNPs, i.e., only with a layer of ZnONRs. Amperometric determination of H₂O₂ at −0.55 V gave a limit of detection of 0.9 μM (S/N = 3) and a sensitivity of 152.1 mA M⁻¹ cm⁻² up to 0.983 mM, with a response time (steady-state, t₉₅) of 30-40 s. The selectivity of the sensor was investigated against ascorbic acid (AA) and uric acid (UA). Energy dispersive X-ray (EDX) analysis, transmission electron microscopic (TEM) image, X-ray diffraction (XRD) patterns, cyclic voltammetry (CV), and scanning electron microscopic (SEM) images were utilized to characterize the modified electrode. Sensing properties of the modified electrode were studied both by CV and amperometric analysis.     

Cuttlebone-derived organic matrix as a scaffold for assembly of silver nanoparticles and application of the composite films in surface-enhanced Raman scattering

Biologically derived materials provide a rich variety of approaches toward new functional materials because of their fascinating structures and environment-friendly features, which is currently a topic of research interest. In this paper, we show that the cuttlebone-derived organic matrix (CDOM) is an excellent scaffold for the one-step synthesis and assembly of silver nanoparticles (AgNPs), which can be further used as substrate for surface-enhanced Raman scattering (SERS). Formation of AgNPs–CDOM composite was accomplished by the reaction of CDOM with AgNO₃ and NH₃·H₂O solution at 80 °C without using any other stabilizer and reducing agents. UV–vis spectra and TEM were utilized to characterize the AgNPs and investigate their formation process. Results demonstrate that the size and distribution of AgNPs can be partly regulated by changing incubation time; the concentration of NH₃·H₂O is critical to the formation rate of AgNPs. As a proof of principle, we show that the AgNPs–CDOM composite can be employed in trace analysis using SERS.     

Fabrication of tri-polymers composite film with high cyclic stability and rapid degradation for cardiac tissue engineering

In this communication, biodegradable and highly elastic silk fibroin/poly(lactide-co-ε-caprolactone)/polyethylene oxide (SF/PLCL/PEO) tri-polymers composite film was fabricated by sol–gel casting technology. The tri-polymers composite film exhibited a high cycle performance and rapid degradation rate by regulating the content of blending of the three polymer contents. The viability of cardiomyocyte cells was demonstrated for both SF/PLCL and SF/PLCL/PEO composite films after 1 day of culture, although the tri-polymers composite film demonstrated superior cell growth, attachment and spreading after culturing for 7 days. Study findings support the potential application of this biocompatible tri-polymers composite film as a heart patch substitute with multi-functionalities.     

Functionalized gold nanoparticles as additive to form polymer/metal composite matrix for improved DNA sequencing by capillary electrophoresis

A new matrix additive, poly (N,N-dimethylacrylamide)-functionalized gold nanoparticle (GNP-PDMA), was prepared by “grafting-to” approach, and then incorporated into quasi-interpenetrating network (quasi-IPN) composed of linear polyacrylamide (LPA, 3.3 MDa) and PDMA to form novel polymer/metal composite sieving matrix (quasi-IPN/GNP-PDMA) for DNA sequencing by capillary electrophoresis. Without complete optimization, quasi-IPN/GNP-PDMA yielded a readlength of 801 bases at 98% accuracy in about 64 min by using the ABI 310 Genetic Analyzer at 50 °C and 150 V/cm. Compared with previous quasi-IPN/GNPs, quasi-IPN/GNP-PDMA can further improve DNA sequencing performances. This is because the presence of GNP-PDMA can improve the compatibility of GNPs with the whole sequencing system, enhance the entanglement degree of networks, and increase the GNP concentration in system, which consequently lead to higher restriction and stability, higher apparent molecular weight (MW), and smaller pore size of the total sieving networks. Furthermore, the composite matrix was also compared with quasi-IPN containing higher-MW LPA and commercial POP-6. The results indicate that the composite matrix is a promising one for DNA sequencing to achieve full automation due to the separation provided with high resolution, speediness, excellent reproducibility, and easy loading in the presence of GNP-PDMA.     

A nano-porous CeO(2)/Chitosan composite film as the immobilization matrix for colorectal cancer DNA sequence-selective electrochemical biosensor

CeO₂/Chitosan (CHIT) composite matrix was firstly developed for the single-stranded DNA (ssDNA) probe immobilization and the fabrication of DNA biosensor related to the colorectal cancer gene. Such matrix combined the advantages of CeO₂ and chitosan, with good biocompatibility, nontoxicity and excellent electronic conductivity, showing the enhanced loading of ssDNA probe on the surface of electrode. The preparation method is quite simple and inexpensive. The hybridization detection was accomplished by using methylene blue (MB), an electroactive lable, as the indicator. The differential pulse voltammetry (DPV) was employed to record the signal response of MB and determine the amount of colorectal cancer target DNA sequence. The experimental conditions were optimized. The established biosensor has high detection sensitivity, a relatively wide linear range from 1.59 × 10⁻¹¹ to 1.16 × 10⁻⁷ mol L⁻¹ and the ability to discriminate completely complementary target sequence and four-base-mismatched sequence.     

The improved performance of MALDI‐TOF MS on the analysis of herbal saponins by using DHB‐GO composite matrix

Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) is an excellent analytical technique for rapid analysis of a variety of molecules with straightforward sample pretreatment. The performance of MALDI‐TOF MS is largely dependent on matrix type, and the development of novel MALDI matrices has aroused wide interest. Herein, we devoted to seek more robust MALDI matrix for herbal saponins than previous reported, and ginsenoside Rb1, Re, and notoginsenoside R1 were used as model saponins. At the beginning of the present study, 2,5‐dihydroxybenzoic acid (DHB) was found to provide the highest intensity for saponins in four conventional MALDI matrices, yet the heterogeneous cocrystallization of DHB with analytes made signal acquisition somewhat “hit and miss.” Then, graphene oxide (GO) was proposed as an auxiliary matrix to improve the uniformity of DHB crystallization due to its monolayer structure and good dispersion, which could result in much better shot‐to‐shot and spot‐to‐spot reproducibility of saponin analysis. The satisfactory precision further demonstrated that minute quantities of GO (0.1 μg/spot) could greatly reduce the risk of instrument contamination caused by GO detachment from the MALDI target plate under vacuum. More importantly, the sensitivity and linearity of the standard curve for saponins were improved markedly by DHB‐GO composite matrix. Finally, the application of detecting the Rb1 in complex biological sample was exploited in rat plasma and proved it applicable for pharmacokinetic study quickly. This work not only opens a new field for applications of DHB‐GO in herbal saponin analysis but also offers new ideas for the development of composite matrices to improve MALDI MS performance.     

Comparative study of LiMn2O4 thin film cathode grown at high, medium and low temperatures by pulsed laser deposition

LiMn₂O₄ thin films with different crystallizations were respectively grown at high, medium and low temperatures by pulsed laser deposition (PLD). Structures, morphologies and electrochemical properties of these three types of thin films were comparatively studied. Films grown at high temperature (?873 K) possessed flat and smooth surfaces and were highly crystallized with different textures and crystal sizes depending on the deposition pressure of oxygen. However, films deposited at low temperature (473 K) had rough surfaces with amorphous characteristics. At medium temperature (673 K), the film was found to consist mainly of nano-crystals less than 100 nm with relatively loose and rough surfaces, but very dense as observed from the cross-section. The film deposited at 873 K and 100 mTorr of oxygen showed an initial discharge capacity of 54.3 μAh/cm² μm and decayed at 0.28% per cycle, while the amorphous film had an initial discharge capacity of 20.2 μAh/cm² μm and a loss rate of 0.29% per cycle. Compared with the highly crystallized and the amorphous films, nano-crystalline film exhibited higher potential, more capacity and much better cycling stability. As high as 61 μAh/cm² μm of discharge capacity can be achieved with an average decaying rate of only 0.032% per cycle up to 500 cycles. The excellent performance of nano-crystalline film was correlated to its microstructures in the present study.     

On-wafer thermomechanical characterization of a thin film polyimide formed by vapor deposition polymerization for through-silicon via applications: Comparison to plasma-enhanced chemical vapor deposition SiO2

Thin-film polyimides were prepared by solvent-less vapor deposition polymerization (VDP) from pyromellitic dianhydride and 4,4′-oxydianiline at 200 °C for liner dielectric formation of vertical interconnects called through-silicon vias (TSVs) used in three-dimensionally stacked integrated circuit (3DICs). FTIR, synchrotron XPS, and TDS were employed for determining the imidization ratio, and in addition, the mechanical properties, coefficient of thermal expansion and Young's modulus, of the VDP polyimide were characterized on Si wafers. The VDP polyimide exhibited extremely high conformality, beyond 75%, toward high-aspect-ratio deep Si holes, compared with conventional SiO₂ prepared by plasma-enhanced chemical vapor deposition. The adhesion between the VDP polyimide and Si wafer was enhanced by an Al-chelate promotor. Remarkably, the VDP polyimide TSV liner dielectrics showed much less thermomechanical stresses applied to the Si surrounding the TSVs than the plasma-chemical vapor deposition SiO₂. The small keep-out zone is expected for scaling down highly reliable 3DICs for the upcoming real artificial intelligence society.