Structure Of Composite Films Research Articles

High-sensitivity fiber temperature sensor based on composite film structure and lossy mode resonance

In this work, we proposed and demonstrated a high-sensitivity optical fiber temperature sensor based on lossy mode resonance (LMR). The sensor is composed of a D-shaped fiber and a thin composite film. The composite film consists of tin dioxide (SnO2) and polydimethylsiloxane (PDMS). PDMS is inserted as an intermediate layer between D-shaped fiber and SnO2 layer, realizing the separation of TM and TE polarization to reduce polarization crosstalk, while also serving as a temperature sensitive layer. The polarization state of the excited LMR can be freely controlled by adjusting the thickness of the composite film. The proposed sensor exhibits a high temperature sensitivity of −1.1883 nm/°C with a measurement range of 10–90 °C. Meanwhile, a fast response time of ∼ 109 ms was observed due to the ultra-thin PDMS interlayer.

Novel electrochromic-supercapacitor device based on P(TPACz)/WO3-PDA nanocomposite film

Organic–inorganic composites of (E)-3,5-di(9 H-carbazol-9-yl)-N-(4-(diphenylamino)benzylidene)aniline/dopamine-modified WO3 (P(TPACz)/WO3-PDA) were prepared by electrochemical polymerisation. The as-prepared P(TPACz)/WO3-PDA composites showed good electrochromic and electrochemical performance. The prominent electrochemical performance of P(TPACz)/WO3-PDA represents a high areal capacitance (32.15 mF cm−2 at 0.1 mA cm−2) and wide range of potential windows (-2.0−1.6 V). Additionally, symmetric supercapacitor devices based on P(TPACz)/WO3-PDA composite films were successfully constructed, which exhibited a high specific capacitance (13.88 mF cm−2 at 0.02 mA cm−2) and an energy density of 7.71 × 10−3 mWh cm−2 in n-doped station. The remarkable electrochromic and electrochemical performances are due to the synergy between the organic polymer and WO3-PDA. A complete large-area composite film structure with high conductivity promises fast electronic transport. This study provides a method for preparing multifunctional composite electrode materials, offering technical support for intelligent displays and energy storage technologies.

Preparation and Keep-Refreshing Effect of Chitosan/Sea Buckthorn Polysaccharide Composite Film on the Preservation of Yellow Cherry Tomatoes.

In this study, sea buckthorn polysaccharides (SBP) were added as functional substances to chitosan (CS), and chitosan/sea buckthorn polysaccharide (SCS) composite films were prepared using the casting method. The effects of SBP addition on the optical properties, physical properties, mechanical properties, structure, antioxidant activity, and antibacterial activity of the SCS composite films were studied, and the prepared SCS composite films were used to preserve yellow cherry tomatoes. The results showed that SCS composite films exhibited good UV resistance, water solubility, and antioxidant activity, but its apparent structure, hydrophobicity, and mechanical properties needed further improvement. Meanwhile, SBP has inhibitory effects on all 8 experimental strains. In addition, the SCS composite film with the addition of 200 mg/L SBP could reduce the weight loss rate of yellow cherry tomatoes, maintain hardness, delay the decrease of total soluble solids, titratable acid, and Vitamin C content, and inhibit the accumulation of malondialdehyde. SCS composite films are beneficial for enhancing the quality of yellow cherry tomatoes during storage, and their application in fruit and vegetable preservation has development prospects.

Cascaded dual-parameter SPR fiber sensor for RI and pH simultaneous detection based on Ag film and an Ag/self-assembled nanofilm structure

To achieve more accurate analysis and detection of changes in liquid parameters, we propose a dual-parameter surface plasmon resonance (SPR) sensor that can measure refractive index (RI) and pH simultaneously. In this paper, we compare and analyze the transmission spectrum when the SPR effect is excited by the cladding mode of a photonic crystal fiber (PCF) and the core mode of the no-core fiber. The results show that the SPR effect excited using the cladding mode is stronger and the sensor has better loss peaks, which is more conducive to realizing the detection of the external environment. Therefore, the sensor uses PCF as the substrate and utilizes a cascade composite film structure, and the area where a silver film is deposited on the surface of the PCF is selected as the RI sensing area. Another part of the PCF, after the silver film is deposited, uses a high-sensitivity polyacrylic acid/chitosan self-assembled nanofilm as the pH-sensitive film. Experimental results show that the maximum sensitivity is 4122.44 nm/RIU and -57.82 nm/pH when the RI range is between 1.333 and 1.385 and the pH range is between 3.11 and 8.63, respectively. In addition, we experimentally verified that the sensor had good stability and repeatability. The design of the sensor provides new possibilities for real-time monitoring and precise control, helping to advance scientific research and the development of industry.

Ultrahigh stability photovoltaic performance of M-Mo6+ (M=Fe3+, Co2+, Ni2+) co-doped BiVO4 films

BiVO4 has been widely studied in photovoltaic conversion. However, as a paraelectric material, BiVO4 lacks an internal electric field for efficient carrier separation, resulting in low photocurrent and limited practical use. Enhancing the photovoltaic performance of thin films through simple methods is challenging. In this paper, M-Mo6+ (M=Fe3+, Co2+, Ni2+) ions were used to co-doped BiVO4 films, which were then composited with NiO to construct composite film structures. The NiO/Bi0.985Co0.015V0.985Mo0.015O4 film achieved a photocurrent density (Jsc) of 2.33 mA/cm2 and an open-circuit voltage (Voc) of 0.39 V. The film also demonstrated a specific detection rate of 2.67 × 1011 jones at an optical power density of 165 mW/cm2 and maintained 1.94 × 1011 jones at 103.7 mW/cm2. At an optical power density of approximately 140 mW/cm2, the specific detection rate begins to decrease. The photovoltaic conversion performance of the film exhibits high stability over a long period of time (＞10,000 s). The thin films maintain good photovoltaic performance at high temperatures. This work provides an approach for the application of BiVO4 in photovoltaics.

High performance composite phosphor-in-glass film for laser-driven warm white light on patterned sapphire substrate

Phosphor-in-glass film (PiF) based on sapphire substrate (SS) is a promising laser-driven color converter. Herein, by using an optimized silicon borate glass component, high-performance Y3Al5O12:Ce3+ PiFs are successfully prepared on both flat sapphire substrate (FSS) and patterned sapphire substrate (PSS) surfaces. Compared with planar structure of FSS, PSS has a periodic arrangement of conical structures on its surface, which effectively increases the contact area between the PiF and the substrate by approximately 56%, thereby forming a more robust film composite structure. The blue laser light is affected by the structure of PSS and produces a typical diffraction effect, which realizes the dispersion of the convergent beam. This significantly expands the laser spot on PSS-PiF and improves the uniformity of light. The saturation power density of PiF-PSS (6.29 W/mm2) is found to be 91% higher than that of PiF-FSS, while maintaining a high luminous efficiency (220 lm/W) and a low correlated color temperature (4500 K). Finally, the thermal quenching mechanism of PiF with different substrate surface morphologies is compared and analyzed. The present results provide important support for designing the interface structure between SSs and PiF to achieve higher efficiency and higher saturation threshold for warm white light.

Hydrophilicity and Pore Structure Enhancement in Polyurethane/Silk Protein-Bismuth Halide Oxide Composite Films for Photocatalytic Degradation of Dye.

Polyurethane/silk protein-bismuth halide oxide composite films were fabricated using a blending-wet phase transformationin situsynthesis method. The crystal structure, micromorphology, and optical properties were conducted using XRD, SEM, and UV-Vis DRS characterize techniques. The results indicated that loaded silk protein enhanced the hydrophilicity and pore structure of the polyurethane composite films. The active species BiOX were observed to grow as nanosheets with high dispersion on the internal skeleton and silk protein surface of the polyurethane-silk protein film. The photocatalytic efficiency of BiOX/PU-SF composite films was assessed through the degradation of Rhodamine B under visible light irradiation. Among the tested films, the BiOBr/PU-SF composite exhibited the highest removal rate of RhB at 98.9%, surpassing the removal rates of 93.7% for the BiOCl/PU-SF composite and 85.6% for the BiOI/PU-SF composite. Furthermore, an active species capture test indicated that superoxide radical (•O2-) and hole (h+) species played a predominant role in the photodegradation process.

SiO2/WO3/ZnO based self-cleaning coatings for solar cells

The accumulation of pollution and any kinds of contamination on the glass cover of the solar cell affects the efficiency of the photovoltaic (PV) systems. The contamination on the glass cover can absorb and reflect a certain part of the sunlight irradiation, which can decrease the intensity of the light coming in through the glass cover. With the study, it was planned to develop self-cleaning coatings for the PV systems. It was aimed to prevent or reduce the contamination-induced efficiency loss of the existing PV systems. In the scope of the project, SiO2/WO3 and SiO2/WO3/ZnO composites were coated from their solutions on the glass substrates using a dip-coating technique. WO3 was selected as a photocatalyst semiconductor. Under the UV light irradiation, WO3 could absorb the photons of the UV light, generating the photoinduced charge carriers. The photoexcited charge carriers provide both the photoinduced hydrophilicity on the surface of the coating and the photocatalytic degradation of the organic contaminants accumulated on the surface of the coating, which allows water droplets to spread and flow on the surface of the cover glass to remove the contaminations. However, the recombination rate of the photoexcited charge carriers on the WO3 film was high. In order to suppress the recombination of the photoinduced charge carriers, WO3 was coupled with SiO2 and ZnO. Both of these semiconductors improved the photocatalytic activity of the WO3 film. Although SiO2 has superior features in terms of the light transmission, it was not very effective under UV light as a photocatalyst alone. The widely preferred photocatalyst ZnO was added into the composite film structure to enhance the photocatalytic activity. The self-cleaning mechanism of the film coatings on a solar cell was investigated through the photocatalytic dye removal efficiency on the as-prepared film samples. There was a slight decrease in the light transparency and the solar cell efficiency because of the WO3 content of the composite film. On the other hand, coupling the SiO2/WO3 film with ZnO enhanced the photocatalytic activity, and it suppressed the reduction effect of the WO3 phase on both the light transparency and the solar cell efficiency. The photocatalytic dye removal efficiency was increased to over 90% after 240 min of UVA light irradiation. In addition, the solar cell coated with the SiO2/WO3/ZnO film provided almost the same solar cell efficiency as the uncoated solar cell. The water contact angle measurement also exhibited the photocatalytic degradation of the model contamination on the glass cover of the solar cell under the UVA light irradiation.Graphical

Tuning the structure and physiochemical properties of sodium alginate and chitosan composite films through sodium tripolyphosphate (STPP) crosslinking

Sodium tripolyphosphate (STPP), an inorganic and non-toxic polyphosphate, has potential applications as a crosslinking agent in the fabrication of edible films. This study utilized STPP in the development of sodium alginate-chitosan composite films, with a focus on their suitability for food packaging applications. The results indicate that the incorporation of STPP led to an increase in film thickness (from 0.048 ± 0.004 to 0.078 ± 0.008 mm), elongation at break (from 11.50 ± 1.49 % to 15.88 ± 2.14 %), water permeation (from 0.364 ± 0.010 to 0.521 ± 0.021 gmm/(m2h*kPa)), and moisture content (from 25.98 ± 0.20 % to 28.12 ± 0.17 %). In contrast, there was a decrease in tensile strength (from 30.23 ± 2.08 to 25.60 ± 1.22 MPa) and swelling index (from 752.9 ± 17.1 to 533.5 ± 8.9 %). Scanning electron microscopy (SEM) analysis revealed the formation of distinctive needle-like microcrystals with the incorporation of STPP. Fourier-transform infrared spectroscopy (FTIR) analysis indicated intermolecular interactions between STPP and the film-forming biopolymers. The data obtained from Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) demonstrated enhanced thermal stability of STPP-loaded films at elevated temperatures. Furthermore, the films exhibited increased DPPH scavenging activity with the addition of STPP. This study underscores the potential of STPP as a crosslinking agent for the development of composite edible films, suggesting applications in the field of food packaging.

Preparation and characterization of corn straw core-based composite films with excellent antioxidant, water vapor barrier, and mechanical properties

Corn straw core (CSC)/cellulose nanofibers (CNF) composite is researched as a food packaging material because of its better anti-ultraviolet (UV) and water vapor barrier properties. However, there are still some challenges, such as insufficient toughness, many gaps or pores inside the film, and a lack of antioxidant properties. To improve these properties, the composite films (CCP-VAE), with excellent anti-UV, antioxidant, blocking bacteria, water vapor barrier, and mechanical properties, were prepared by applying Vernonia anthelmintica (L.) Willd extract (VAE) and poly (ethylene oxide) (PEO). The interaction of the raw materials and the structure of composite films were analyzed by FTIR, XRD, SEM, TG, and DSC. Compared to LDPE, PBAT, or PBSeT, the tensile strength of CCP-VAE-1 composite film was improved by 1.17 times, 1.37 times, or 2.75 times, respectively; compared with CNF/CSC, PP, LDPE, PBAT or PBSeT, the puncture load of this film was advanced by 2.59 times, 0.72 times, 0.64 times, 0.81 times or 2.54 times, respectively; the tearing strength of this film, compared with CNF, PP, LDPE, PBAT or PBSeT, was enhanced by 1.49 times, 2.59 times, 4.00 times, 0.89 times or 3.48 times, respectively; furthermore, compared with CNF, PBAT and PLA, the water vapor transmission coefficient (Pwv) of CCP-VAE-1.5/2 films had a lower value. All CCP-VAE composite films also presented excellent UV barriers and wonderful antioxidant properties. In practical packaging tests with fresh garlic and milk, the weight loss and spoilage caused by external influences were effectively prevented by CCP-VAE composite films, which indicated the potential as food packaging.

Effect of TEMPO-oxidized bacterial cellulose nanofibers stabilized Pickering emulsion of cinnamon essential oil on structure and properties of gelatin composite films

Pure gelatin film often exhibits high hydrophilicity and a lack of antibacterial activity, hindering its practical application in the field of food preservation. To address these issues, we incorporated 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized bacterial cellulose (TOBC) nanofibers stabilized cinnamon essential oil (CEO) Pickering emulsions into the gelatin matrix to develop active food packaging films. The study revealed that the good distribution of emulsion droplets in the film matrix. While with increasing Pickering emulsion proportion, the microstructures of composite films were more heterogeneous, showing some pores or cavities. In addition, the insertion of TOBC-stabilized CEO emulsions could improve the elongation at break (EAB), water-resistance, UV blocking ability, and antibacterial activity of film, but reduced its tensile strength (TS) and water vapor barrier properties (WVP). Notably, the film prepared with 4 % TOBC-stabilized CEO Pickering emulsion demonstrated enhanced preservation of strawberries. Overall, the as-prepared gelatin-based active composite films have considerable potential for food packaging.

Intelligent carboxymethyl cellulose composite films containing Garcinia mangostana shell anthocyanin with improved antioxidant and antibacterial properties

In this study, anthocyanin from Garcinia mangostana shell extract (Mse) was used as pH indicator to prepare intelligent carboxymethyl cellulose (CMC) based composite films. The structure and properties of the CMC-based composite films were characterized and discussed in detail. Results showed that the CMC-based composite films with Mse had excellent mechanical, antibacterial and antioxidant abilities. Especially, the carboxymethyl cellulose/corn starch/Garcinia mangostana shell extract (CMC/Cst/Mse) composite film had best mechanical properties (20.62 MPa, 4.06 % EB), lowest water vapor permeability (1.80 × 10−12 g·cm/(cm2·s·Pa)), excellent ultraviolet (UV) blocking performance, and the best antibacterial and antioxidant abilities. The pH sensitivity of composite films which had Mse obviously changed with time when the fish freshness was monitored at 25 °C. Given the good pH sensitivity of the composite films, it had significant potential for application of intelligent packaging film as a food packaging material to indicate the freshness of fish.

Effect of structure of ZnO and SiO2 core-shell composite nanoparticles as lubricant additive on tribological properties of greases

Nano-additives can enhance the tribological properties of greases. In particular, core-shell composite nanoparticles, which combine multiple nanoparticles, have been the subject of recent research due to their superior properties. In this study, based on the friction pairs material, GCr15, by choosing ZnO with low hardness and SiO2 with high hardness, core-shell composite nanoparticles with soft shell hard core SiO2@ZnO and hard shell soft core ZnO@SiO2 were prepared by chemical deposition and calcination methods. The impact of different structural forms of these composite nanoparticles as grease additives were investigated for the first time by adding them into lithium grease. The results show that ZnO@SiO2 have good tribological properties under light load, reducing the COF by 18 % and decreasing the WSD by 22 %. SiO2@ZnO exhibit the best anti-friction effect under heavy load conditions, reducing the COF by 15 % and decreasing the WSD by 28 %. The GCr15-ZnO-SiO2 surface composite film structure is the key to improve the performance of grease in the two composite nanoparticles. It not only has good wear resistance, but also can increase the bearing capacity of the oil film. The two core-shell structure nano-additives provide a new idea for the design of lubricants under special conditions.

Design of broadband gradient resistive film metamaterial absorber based on genetic algorithm

In recent years, electromagnetic (EM) wave absorbing devices based on metamaterials have attracted widespread attention, due to their advantages such as broadband, easy preparation, and flexibility to tailor EM waves. Nevertheless, a review of the existing research reveals that the inherent sub-wavelength characteristics of metamaterials and metasurfaces impose certain constraints on their applications in low-frequency ranges. In order to achieve low detectability that takes into account both low-frequency and broadband absorbing performance, this work, presents a metamaterial absorber based on 5-layer gradient resistance film and dielectric composite structure, as shown in <xref ref-type="fig" rid="FigureAbstract">Fig. (a)</xref>. To begin with, we introduce the structural design of the initial element, and based on this, the transmission line theory and impedance matching principle are used to analyze the strong wave absorption conditions of the absorber element. In terms of the element structure optimization, the genetic algorithm is adopted to globally search for the optimal solution in the multi-variable domain, resulting in the rapid determination of metamaterial elements’ configurations and resistance parameters that meet the design goals. In the simulation, the wave absorption performance and mechanism of the designed absorbing element are also investigated in an in-depth manner. Simulation results show that the designed metamaterial absorber can achieve more than 90% EM wave absorption in a frequency range of 1.62–19.16 GHz (with a relative bandwidth of 168.8%) under normal incidence of linearly polarized plane waves, which effectively expands the absorption bandwidth to the L band and K band. In addition, the simulations for oblique incidence at different polarizations provide strong evidence for the device’s insensitivity to both polarization and angle. The radar cross section (RCS) curves obtained by the time domain (TD) simulation illustrate that the novel structure can achieve more than 10 dB RCS reduction in a frequency range of 1.7–20 GHz. In the device's performance verification process, a metamaterial absorber with 20 × 20 elements and dimensions of 1.566<inline-formula><tex-math id="M1">\begin{document}$ {\lambda }_{l} $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20231781_M1.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20231781_M1.png"/></alternatives></inline-formula>×1.566<inline-formula><tex-math id="M2">\begin{document}$ {\lambda }_{l} $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20231781_M2.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20231781_M2.png"/></alternatives></inline-formula>× 0.113<inline-formula><tex-math id="M3">\begin{document}$ {\lambda }_{l} $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20231781_M3.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20231781_M3.png"/></alternatives></inline-formula> is fabricated and tested by using the bow method reflectivity test system. The absorptivity curves under 5° oblique incidence of different polarizations, show that the proposed metamaterial absorber can realize more than 80% EM absorption in an entire frequency range from 2 to 18 GHz, the test results of different polarizations are basically consistent. The test results at oblique incidence (<i>θ</i> ≥ 30°) show that although the measured and simulated curves exhibit discrepancies in certain frequency bands due to human error or material dispersion characteristics, the overall experimental results are consistent with our expectations, which fully proves that the designed metamaterial absorber has potential application value in the field of low-frequency and broadband EM absorption.

Development of Carbon Nanotubes–Graphene–Polydimethylsiloxane Composite Film with Excellent Electrothermal Performance

Low power density and low heating rate are the key constraints for the development of conductive polymer materials in the field of electric heating. The carbon nanotubes (CNTs)–graphene (GR)–polydimethylsiloxane (PDMS) composite film was prepared by vacuum filtration and spin coating to solve the problem in this study. Moreover, an AC electric field was used to orient the CNTs to enhance the electrothermal performance. The structure and properties of composite films were analyzed. The results show that the composite film with CNT:GR = 2:1 has the lowest permeation threshold, and can heat up within 30 s and stabilize at 260 °C at 10 V. The electric field-oriented CNTs reduced the insulating polymer layer, increasing the heating rate of the composite film by 1.2 times, and increasing the theoretical thermal conductivity. The flexible electrothermal composite film prepared in this study can be used in thermal insulation, deicing, and wearable electronic devices.

Fabrication of Glycine-Chitosan/TiO2 film for metanil yellow removal from water

This study focused on the modification of chitosan with glycine and TiO2 to improve its performance for adsorption application. It is the first study to use a combination of chitosan, glycine, and TiO2 in the preparation of composite films. The obtained chitosan-glycine/TiO2 composite films were extensively characterized using various techniques, including FT-IR, SEM, XRD, DSC, and tensile tests to study the functional groups, morphology, structure, thermal stability, and mechanical properties of composite films, respectively. FT-IR analysis confirmed the successful formation of the chitosan-glycine/TiO2 film, where chemical interaction occurred between the carboxyl groups of glycine and NH2 of chitosan through a condensation process and physical interaction occurred between chitosan-glycine and TiO2. SEM images revealed that the surface of chitosan-glycine/TiO2 composite films exhibited a rougher texture compared to the unmodified chitosan, indicating structural changes due to the addition of glycine and TiO2. XRD analysis indicated alterations in the crystallinity properties of chitosan upon the incorporation of glycine and TiO2. The DSC results demonstrated that the presence of glycine and TiO2 influences the thermal stability of chitosan. The tensile test revealed the improvement of tensile strength in the chitosan-glycine/TiO2 film, related to the existence of glycine and TiO2. The adsorption process of metanil yellow by the chitosan-glycine/TiO2 film was in accordance with the Langmuir isotherm model. In conclusion, the modification of chitosan with glycine and TiO2 resulted in the development of a promising adsorbent material with improved thermal stability, enhanced tensile strength, and a higher adsorption capacity for metanil yellow. These findings contribute to the potential application of chitosan-glycine/TiO2 films in various adsorption processes.

A thin film resistive humidity sensor based on polymer and carbon black nanoparticle composites

This paper proposes a resistive humidity sensor that uses a carbon-black and polyvinyl alcohol composites thin film, fabricated with a unique film coating method for thinner thickness and higher sensitivity. Improving the sensitivity of sensing films is still of great importance in the research field of gas sensors. The humidity sensor devices with thin composite film and microelectrode structure are fabricated on the glass substrate for a low cost and a simple fabrication process. The sensor gives a rapid response for humidity levels from 10.9% relative humidity (RH) to 73.7% RH, and the response time is about 5.77 s. Experimental results reveal that the sensor has good sensitivity, reproducibility, fast reaction time, and wide range. In addition to humidity, the sensor also responds well to gases such as ethanol. The proposed gas sensor in this paper can be applied to the other combinations of polymers and nanoparticles to form new gas sensors, which have the potential to be used as a gas sensor array for detecting the composition of complex gases such as volatile organic components.

Modulation of the sensing bandwidth of dual-channel SPR sensors by TiO2 film

Facing the diversity and complexity of the types of parameters to be measured, multi-channel surface plasmon resonance (SPR) fiber sensors provide an excellent solution. However, the sensing bandwidth is a key factor affecting the sensor performance. In this paper, we explore a method to modulate the sensing bandwidth using the TiO2 film. A dual-channel SPR sensor with a wide sensing bandwidth is proposed. In this sensor, no-core fiber (NCF) is used as the sensing probe, and multimode fibers are used for the transmission of optical signals. The sensor has a cascaded composite film structure, the region coated with Ag film as the refractive index sensing region and the region coated with Ag/TiO2/PDMS as the temperature sensing region. The experimental results show that the sensing bandwidth of the sensor varies for different TiO2 coating times. It indicates that the TiO2 film can regulate the sensing bandwidth flexibly. Therefore, to achieve the optimal sensing effect, the TiO2 coating time can be flexibly adjusted according to the RI characteristics of the environment. The maximum sensitivity of this dual-channel sensor is 4.5 nm/°C and 3151 nm/RU when the temperature range is between 10 and 80 °C and the RI range is between 1.333 and 1.385, respectively. In addition, we discuss the repeatability and stability of this dual-channel sensor.

Graphene Nanoplatelet and Multiwalled Carbon Nanotube Doping Effect on the Structural and Physical Properties of PolyVinyl Alcohol Composites

Polyvinyl alcohol (PVA) composite thin films were prepared using graphene nanoplatelets (GNPs) and multiwalled carbon nanotubes (MWCNTs) as carbon fillers (CFs). The resulting electrical, optical, mechanical, and structural changes caused by adding the CFs to the pure PVA matrix were characterized. The improvement of electrical, optical, and mechanical properties was interpreted in terms of the percolation theory. Depending on this interpretation, the percolation threshold values, and the critical exponential values of the related properties were calculated. It turns out that the measured mechanical and optical changes were compatible with the site percolation theory while the electrical conductivity was compatible with the classical percolation theory. X-ray diffraction (XRD) measurements were performed to correlate the physical properties with the structure of the PVA composite films. They revealed that the degree of crystallinity of the composites increased with the CF reinforcement and that MWCNT was more effective in improvement of the crystallinity of the PVA composites than GNP.

Investigation of Multi‐Phase Structure and Optoelectronic Performance of Bi‐Doped (Cu−Zn) Oxide Composite Thin Films

AbstractIn this research, thin film composite structures were used to prepare optoelectronic devices from bare and Bi‐substituted p‐CuO/n‐ZnO systems. The p‐CuO/n‐ZnO composite thin film structures were prepared by the SILAR technique, and the influences of two different Bi contents on the structure and main physical performances of the samples were investigated. The X‐ray diffraction (XRD) technique showed that the composited thin film materials were multiphased in rutile hexagonal (wurtzite) phase (ZnO) and monoclinic tenorite phase (CuO) type crystal structure. The obtained surface morphological results presented that the structure exhibits an almost homogeneous, plate‐like surface distribution, and depending on the increase of Bi concentration, the plate‐like sheet area widens from ~2.5 μm to 10 μm and the layer boundaries decrease. FT‐IR and Raman spectroscopy were used to investigate the various vibration and Raman active phonon modes of Bi:p‐CuO/n‐ZnO nanostructured heterostructures. For a comprehensive analysis of the optical bandgap of the fabricated composite samples, the estimated values were obtained from the Tauc plot. Produced samples exhibited an Ohmic behavior and dc resistivity values of films can be determined via Ohm′s Law. The adjusted sheet resistance value of 11.51 MΩ/sq when the content of Bi 3.0 % in the growth bath.