Gel Spin Research Articles

Polyacrylonitrile Interactions with Carbon Nanotubes in Solution: Conformations and Binding as a Function of Solvent, Temperature, and Concentration

AbstractPolyacrylonitrile (PAN) is among the most promising precursor polymers to produce strong and lightweight carbon fiber. Conformations in solution and the extent of binding to carbon nanotubes (CNTs) are critical during gel spinning and for alignment of graphitic layers upon carbonization. Here, quantitative insights into these processes are reported using molecular dynamics simulations at the atomic scale including virtual π electrons and comparisons to experimental data. Common solvents for fiber spinning induce significant differences in PAN conformation in dilute solutions at 25 °C with persistence lengths between 0.5 and 2 nm. Variations in conformation become smaller at 75 °C, in the presence of CNTs, and at higher PAN concentration. “Aging” of PAN conformations in dimethylformamide and dimethylsulfoxide at higher temperature is explained and a correlation between extended polymer conformations and increased binding to CNTs is identified in dilute solutions. PAN is overall barely attracted to CNTs under common solution conditions and enters significant surface contact only at higher concentration as solvent is physically removed. The impact of temperature is small, whereby binding increases at lower temperatures. The results provide guidance to control interactions of polymers with CNTs to induce distinct conformations and specific binding at the early stages of assembly.

FABRICATION of n-ZnO:Mn/p-Si HETEROJUNCTION DIODES and ITS I-V, C-V CHARACTERISTICS

To investigate the effects of Mn dopant on n-ZnO/p-Si device performance, ZnO films were produced in different Mn dopant by the sol gel spin coating method. Morphological properties of the films were studied by emission scanning electron microscopy (FESEM). Then, the n-ZnO:Mn/p-Si heterojunction diodes were fabricated. The diode parameters were determined by current-voltage (I-V) measurements. The values of the diodes were found to be 8.38, 6.84 and 3.87, respectively, for the diodes produced using undoped, 1% Mn doped and 3% Mn doped ZnO films. At the same time, electrical parameters were determined to compare by using Cheung and Norde methods. According to the evaluation of values obtained by different methods, an improvement on the rectifying properties of the ZnO diode with Mn dopant has been observed. In the continuation of the study, the photovoltaic properties of the heterojunction diodes have been studied. The results obtained at different illumination intensities showed that the diodes are sensitive to light. Capacitance-voltage (C-V) measurements of the fabricated diodes are also investigated in detail.

Superhydrophilicity of photocatalytic ZnO/SnO2 heterostructure for self-cleaning applications

Sol–gel spin coating technique was used to deposit thin films of ZnO, SnO2, and ZnO/SnO2 on a borosilicate glass substrate. The films were characterized using XRD, FESEM, EDX, HRTEM, AFM, UV-Vis spectrophotometer, and contact angle meter. X-ray diffraction confirms the presence of both hexagonal wurtzite and tetragonal phase of ZnO and SnO2 respectively in ZnO/SnO2. Wettability studies reveal that ZnO/SnO2 film is superhydrophilic with water contact angle of 3.4°. The photocatalytic performance of the films is evaluated by measuring the degradation of an aqueous solution of methylene blue, methyl orange, and their mixture. The degradation of stearic acid adsorbed on the film’s surface is measured by tracking the water contact angle after UV irradiation as a function of time. The excellent photocatalytic activity of ZnO/SnO2 thin films is attributed to formation of type-II heterostructure between ZnO and SnO2, which inhibits the charge recombination between photogenerated electrons and holes. The ZnO/SnO2 shows good photocatalytic activity after five recycling runs. ZnO/SnO2 thin films being excellent photocatalyst along with its superhydrophilic nature will have potential application in self-cleaning and antifogging.

Preparation of calcium alginate/polyethylene glycol acrylate double network fiber with excellent properties by dynamic molding method

In order to greatly reduce the viscosity of sodium alginate (SA) gel solution and improve the properties of calcium alginate (CA) fiber, SA/polyethylene glycol acrylate (PEGDA) gel spinning solution with interpenetrating network structure was prepared by using one-pot method firstly. Then the solution was extruded continuously into the coagulation bath. CA/PEGDA composite fiber with double network was prepared by ionic crosslinking SA macromolecules with Ca2+ during the dynamic molding process of solidification, stretch and curl. Rheological results indicated that the spinning solution’s apparent viscosity was 92.8% smaller than that of the pure SA solution at PEGDA content of 20 wt%. As the PEGDA content increased, the storage modulus G' and the loss modulus G" both decreased. FTIR results showed that PEGDA content had an obvious influence on hydrogen bond in CA/PEGDA system. The tensile strength of composite fiber reached maximum of 2.91cN/dtex at PEGDA of 10%.

Synthesis and investigation of some physical properties of pure and Ho-loaded ZnO nano-rods

In this research, pure and Ho-loaded zinc oxide nano-rods have been synthesized with the sol–gel spin coating way. The impact of holmium-loading content changed between 0–4 at.% in step of 1 at.% on the structural, vibrational, surface, and optical characters was inquired. The hexagonal ZnO nano-rods with (002) and (101) preferential orientations were seen from SEM and XRD analyses. It was found that the surface character of ZnO nano-rods depended on Ho-loading content. The UV and green emission bands were observed from PL analysis. A blue shift with low-content Ho level was seen from UV/Vis spectrophotometer and PL measurements. The optical band-gap value primarily raised from 3.32 to 3.40 eV for low Ho content, and then, it went down for more Ho loading. The present study gives that the physical features of zinc oxide are greatly healed with holmium loading.

Structural, optical, and photoluminescence properties of erbium doped TiO2 films

TiO2 thin films doped with low percentages (3, 7, and 10 at.%) of Er3+ have been synthesized by sol gel spin coating technique. The influence of erbium concentration on the physical properties was analyzed using different characterization techniques such as X-ray diffraction, Raman spectroscopy, TEM analysis, EDS-SEM, AFM, UV–Visible transmittance spectroscopy, photoresponse and photoluminescence. The doped films exhibited significant modifications on the structural, optical and electrical properties due to the incorporation of erbium ions. The band gap energy was red shifted by Er doping indicating an improvement in visible light absorption. Intense Er3+-based emission peaks in the range 520–560 nm were observed for all samples. It was observed that Er-dopant concentration had direct impact on photoluminescence intensity.

Characterization of TiN Oxide Doping Antimony Thin Layer with Sol- Gel Spin Coating Method for Electronic Device

Antimony tin oxide coating research has been carried out using a spin sol gel coating method with different doping concentrations (0, 5, 10, 15, 20)%. The results of the study on the morphological structure (SEM) of thin films that have been carried out showed more cracks on the surface of the morphology of thin layers without doping compared to thin layers with doping antimony. The Results of crystal structure of XRD in thin antimony doping tin oxide layer shows the grinding index of tin oxide crystals, 101, 110, 211, 220. In grain size, with increasing antimony doping percentage, the average grain size decreases. The optical properties using UV-Vis in thin films of antimony tin oxide doping show samples including semiconductor materials that can be used as electronic devices as seen from the reduction of this energy gap (3,680 - 3,574) eV. Also seen is an increase in the percentage of antimony doping and repetition of layers, the lower the transmissions value, but the value of absorbance of the thin layer increases.

Mesoporous Structure of Doped and Undoped PEG on Ag/TiO2 Thin Film

In this reaserch, photocatalyst silver titanium dioxide was doped and modified by Polyethylene Glycol (PEG). The purpose of the present study was to analyse the synthesized Ag/TiO2 thin film doped and undoped PEG. Ag/TiO2 thin films on silicon wafer have been prepared by sol–gel spin coating. The samples were characterized by Grazing Incidence X-ray diffraction (GIXRD), Field Emission Scanning Electron Microscopy (FESEM) and Atomic Force Microscope (AFM). The doped and undoped PEG Ag/TiO2 thin films showed a mesoporous TiO2 matrix which includes TiO2 crystallites of 10-20 nm in size and small Ag nanoparticles (white spots) with various sizes ranging from 10 to 30 nm. However, doped PEG Ag/TiO2 thin film showed the Ag nanoparticles became agglomerates but still remained roughly uniform on the surface.

P085 Pre-treatment of patient sera with melon™ gel spin column yields better results in solid phase immunoassays

P085 Pre-treatment of patient sera with melon™ gel spin column yields better results in solid phase immunoassays

The role of etching current density and porous structure on enhanced photovoltaic performance of ZnO/PS heterojunction solar cells

The paper reports the fabrication of zinc oxide/porous silicon (ZnO/PS) heterojunction solar cells based on porous material and the effects of etching current density and porous structure on the performance of these solar cells. PS samples were produced by electrochemical etching on a p-type crystalline-silicon (c-Si) wafer with boron (B) doped and (111) orientation. The etching process was carried out in a HF:C2H5OH (1:3) electrolyte solution at different etching current densities of 5, 10, 15, and 25 mA/cm2 for 15 min at room temperature (RT). ZnO nanoparticles synthesized by sol–gel method were coated on PS layers by the sol–gel spin coating technique at a speed of 300 rpm for 20 s at RT for fabrication of ZnO/PS heterojunction solar cells. The structural analyses were performed using a field emission scanning electron microscope. Depending on the increase of etching current density, the pore diameter and porosity in the etched structures increased approximately from 200 to 920 nm and from 19 to 62%, respectively. Reflection characteristics of ZnO/PS heterojunction solar cells were determined using reflection measurements. The lowest optical reflection was obtained in ZnO/PS heterojunction solar cell with PS layer formed at high etching current density. The dark I–V measurements indicated that all the solar cells exhibited a typical rectifying behavior, and the ideality factor increased with the increase of etching current density. Light I–V measurements were performed under AM1.5G conditions. The short circuit current, open circuit voltage, and energy conversion efficiency (η) increased with the increase of etching current density. The best photovoltaic performance was obtained in ZnO/PS heterojunction solar cell having the PS layer produced at high etching current density of 25 mA/cm2. The highest energy conversion efficiency of 6.05% was obtained in this solar cell. It was determined that the etching current density and porous structure are important parameters affecting the photovoltaic performance of ZnO/PS heterojunction solar cells.

Correction to: Effect of film thickness on structural, morphological, and optical properties of Cu2ZnSnS4 thin films prepared by sol–gel spin coating

The author found a spelling mistake in reference no. 46.

Investigation on the optical transmission in UV range of sol-gel spin coated zinc oxide nanofilms deposited on glass

Physical properties of semiconductor thin films change when reducing their thicknesses from micro- to nanoscales. Indeed, zinc oxide (ZnO) microfilms absorb ultraviolet (UV) light; however, the optical transmission of the ZnO nanofilms shows double transmission edges in the same range of wavelengths. In the present work, we deposited ZnO nanofilms on glass substrates by sol–gel spin coating method. We carried out grazing incidence X-ray diffraction (GIXRD), where results showed that elaborated ZnO nanofilms have wurtzite structure, with dominance along (100), (002) and (101). A bruker profilometer gives a thickness about 119 nm. The photoluminescence at room temperature of films carried out with Horiba iHR 550 shows a strong luminescence in visible range. The ZnO nanofilms showed high optical transmission in the UV and the visible ranges with a drop of about 50% in the wavelengths range of 300-400 nm. The high optical transmission observed in the UV range was explained by photoluminescence.

Investigation of Optimum Mg Doping Content and Annealing Parameters of Cu2MgxZn1-xSnS4 Thin Films for Solar Cells.

Cu2MgxZn1−xSnS4 (0 ≤ x ≤0.6) thin films were prepared by a simple, low-temperature (300 °C) and low-cost sol–gel spin coating method followed by post-annealing at optimum conditions. We optimized the annealing conditions and investigated the effect of Mg content on the crystalline quality, electrical and optical performances of the Cu2MgxZn1−xSnS4 thin films. It was found that the Cu2MgxZn1−xSnS4 film annealed at 580 °C for 60 min contained large grain, less grain boundaries and high carrier concentration. Pure phase kesterite Cu2MgxZn1−xSnS4 (0 ≤ x ≤ 0.6) thin films were obtained by using optimal annealing conditions; notably, the smaller Zn2+ ions in the Cu2ZnSnS4 lattice were replaced by larger Mg2+ ions. With an increase in x from 0 to 0.6, the band gap energy of the films decreased from 1.43 to 1.29 eV. When the ratio of Mg/Mg + Zn is 0.2 (x = 0.2), the grain size of Cu2MgxZn1−xSnS4 reaches a maximum value of 1.5 μm and the surface morphology is smooth and dense. Simultaneously, the electrical performance of Cu2MgxZn1−xSnS4 thin film is optimized at x = 0.2, the carrier concentration reaches a maximum value of 3.29 × 1018 cm−3.

Investigation on the Selenization Treatment of Kesterite Cu2Mg0.2Zn0.8Sn(S,Se)4 Films for Solar Cell.

High-selenium Cu2Mg0.2Zn0.8Sn(S,Se)4 (CMZTSSe) films were prepared on a soda lime glass substrate using the sol–gel spin coating method, followed by selenization treatment. In this work, we investigated the effects of selenization temperature and selenization time on the crystal quality, and electrical and optical properties of CMZTSSe films. The study on the micro-structure by XRD, Raman, X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS) analysis showed that all CMZTSSe samples had kesterite crystalline structure. In addition, the crystalline quality of CMZTSSe is improved and larger Se takes the site of S in CMZTSSe with the increase of selenization temperature and selenization time. When increasing the selenization temperature from 500 to 530 °C and increasing the annealing time from 10 to 15 min, the morphological studies showed that the microstructures of the films were dense and void-free. When further increasing the temperature and time, the crystalline quality of the films began to deteriorate. In addition, the bandgaps of CMZTSSe are tuned from 1.06 to 0.93 eV through adjusting the selenization conditions. When CMZTSSe samples are annealed at 530 °C for 15 min under Se atmosphere, the crystal quality and optical–electrical characteristics of CMZTSSe will be optimal, and the grain size and carrier concentration reach maximums of 1.5–2.5 μm and 6.47 × 1018 cm−3.

Effects of Al dopant on XRD, FT-IR and UV–vis properties of MgO films

Undoped and Al doped MgO films have been prepared by a sol–gel spin coating method. The crystalline structural, optical, vibrational and morphological properties of the Al doped MgO films were characterized by different techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–vis absorption spectra, and Fourier transform infrared (FT-IR) measurements. XRD patterns confirm that the films were polycrystalline cubic nature. The crystallite size of the films slightly changed with increasing the Al dopant content. The optical band gap of the films was found to decrease from 3.92 to 3.84 eV by Al incorporation. The FT-IR spectroscopy confirms the presence of MgO. The observed vibrational bands at 679 and 862 cm−1 revealed the existence of the cubic MgO bonds. Surface morphology of the films was significantly affected by Al doping.

Effect of Organic Additives on the Characteristics of Al/Organic Additive:ZrO2/p-Si Metal–Insulator-Semiconductor (MIS) Type Schottky Barrier Diodes

In this work, zirconium dioxide (ZrO2) thin films were prepared on glass substrates with organic additives such as polyethylene glycol-6000 (PEG), polysorbate-80 (P80), triton X-100 (T100), citric acid (CA), tartaric acid (TA), and oxalic acid (OA) by sol–gel spin coating technique. The prepared thin films were annealed at 600 °C and their structural, morphological, optical and dc electrical properties were studied. From the XRD pattern, the crystal structure of the ZrO2 films was found to be monoclinic. The SEM micrographs of PEG:ZrO2 and CA:ZrO2 thin films exhibited rod-shaped and square-shaped grains, respectively. The EDX analysis confirmed the presence of Zr and O elements in the ZrO2 films. The UV–Vis analysis showed a higher transmittance for the PEG:ZrO2 and T100:ZrO2 films. The optical band gap (Eg) varied in the range of 5.66–5.83 eV. DC electrical conductivity (σdc) increased with a decrease of activation energy (Ea) for organic additive:ZrO2 thin films compared to pure ZrO2. A maximum value of σdc was noticed for the PEG:ZrO2 thin film. Metal–insulator-semiconductor type Schottky barrier diodes (Al/organic additive:ZrO2/p-Si) were fabricated and their electrical characteristics were studied. Results showed that the barrier height (ΦB), series resistance (Rs) and ideality factor (n) decreases for Al/organic additive:ZrO2/p-Si SBDs from that of the Al/Pure ZrO2/p-Si.

A comparative study on the electrical and dielectric properties of Al/Cd-doped ZnO/p-Si structures

We have reported on the electrical and dielectric properties of Al/CdxZn1-xO/p-Si structures. The cadmium-doped zinc oxide (CdxZn1−xO) thin films with various Cd dopants (x = 0.10, 0.20 and 0.30) were deposited on p-Si wafers via sol–gel spin coating method. The admittance (Y = Gm + iωCm) measurements were performed at 1 MHz. The C−2–V plots were used to extract the main electrical parameters such as the diffusion potential (VD), the concentration of acceptor atoms (NA), depletion region width (WD) and barrier height (ΦB). The experimental results reveal that the capacitance increases with higher Cd dopant concentration due to the presence of interfacial charges while an opposite behaviour is observed in conductance. The lower values of conductance in the sample with high Cd content can be attributed to increase in series resistance. The dielectric measurements also confirm the effect of Cd substitution in ZnO on the device performance.

Superhydrophobic ZnO/TiO2 heterostructure with significantly enhanced photocatalytic activity

ZnO/TiO2 and TiO2/ZnO thin films were prepared on borosilicate glass slide (BSG) by cost effective sol–gel spin coating technique. The films were characterized using X-ray diffraction, FESEM and FT-IR. The X-ray diffraction reveals the existence of both hexagonal ZnO and anatase TiO2 phases for ZnO/TiO2 and TiO2/ZnO thin films. In the present work, an effort has been made to systematically study the wettability and photocatalytic activity of ZnO/TiO2 and TiO2/ZnO thin films. The wettability of the films was assessed by measuring the water contact angle (WCA). The WCA of ZnO/TiO2 and TiO2/ZnO was 43.6o and 26.3o respectively. The WCA of the films increases by modifying with octadecanoic acid (OA) where ZnO/TiO2 shows superhydrophobic nature having WCA of 151.0o. The photocatalytic activities of the films were evaluated by measuring the degradation of methylene blue (MB) and octadecanoic acid under UV light. The photocatalytic efficiency of ZnO/TiO2 was higher because of the formation of heterostructure which inhibits the charge recombination.

Development of pure rutile $$\hbox {TiO}_{2}$$ TiO 2 and Magneli titanium sub-oxide microstructures over titanium oxide-seeded glass substrates using surfactant-free hydrothermal process

Titanium oxide seed layer was coated over glass substrates by sol–gel spin coating method. Single-step surfactant-free hydrothermal process developed titanium oxide microstructures over the titanium oxide-seeded glass substrates. Various morphologies of titanium oxide microstructures, varying from coral reefs to flower-like morphology were evolved by changing HCl concentration (1 and 3 M) in the precursor solution and growth temperature (GT) (120, 150 and \(180{^{\circ }}\hbox {C}\)) of the hydrothermal process. Structural studies confirmed the formation of rutile \(\hbox {TiO}_{2,} \hbox { TiO}_{2}+\hbox {Ti}_{2}\hbox {O}_{3}\) and \(\hbox {Ti}_{4}\hbox {O}_{7}\) microstructures due to varying the concentration of HCl (1 and 3 M) in the solution and GTs. Morphological studies revealed the possibility of engineering coral reefs, cauliflower, flowers, ball, cactus and jasmine flower-shaped microstructures of titanium oxide films by tuning the growth parameters. The indirect band gap of the titanium oxide microstructures derived from UV–Vis absorption spectra lies in the range of 2.9–3.02 eV.

Polyacrylonitrile sheath and polyacrylonitrile/lignin core bi-component carbon fibers

Polyacrylonitrile (PAN) sheath and PAN/lignin core bi-component fibers have been processed using gel spinning and subsequently carbonized by batch process. By varying the sheath-core volume fraction in the bi-component fibers, solid-sheath/solid-core or solid-sheath/porous-core low density carbon fibers have been manufactured. The solid core fiber, with a lignin content of ∼31 wt%, can be stabilized and carbonized to carbon fiber with a tensile modulus as high as 274 GPa. Carbon fibers with a porous, honeycomb-structured core is reported with a tensile modulus value of 242 GPa. While the lignin incorporation enhances the cost-effectiveness and renewability of carbon fibers, the methods and results in this work demonstrate an approach to harness the design and manufacturing of robust PAN/lignin blend carbon fibers and porous low-density carbon fibers enabled by lignin utilization.