High-contrast green luminescence was obtained from molybdenum (Mo)-doped beta-phase gallium oxide (β-Ga2O3) by a sol-gel spin coating method. The X-ray diffraction, atomic force microscopy, and ...ultraviolet–visible–near infrared transmission results revealed that the Mo dopants did not significantly affect the fabricated films’ crystal structure, surface morphology, and energy bandgap (Eg). All spin-coated Mo-doped films formed a beta phase structure and exhibited smooth surface morphology with a root-mean-square surface roughness of less than 7 nm. The thickness of the coated film increased gradually with Mo doping concentration. In the photoluminescence measurements, a green luminescence band associated with the Mo ion dxz-dyz band transition slowly appeared, which hindered the original emission from the recombination of electron–hole pairs in β-Ga2O3 but increased overlapped green color luminescence. Compared with the undoped β-Ga2O3, the CIE chromaticity diagram showed that luminescence changed from blue to green, and the contrast of the green luminescence significantly improved from 0.33 to 0.73.
•Mo-doped gallium oxide was prepared by spin coating for the first time.•Smooth film with root-mean-square surface roughness around 4 nm by spin coating.•High quality crystal structure of Ga2O3 even with heavy dopant concentration.•High contrast single green color emission.
Display omitted
•P-type Ga-doped SnO2 semiconductor films were prepared by sol–gel spin coating.•Optical bandgaps of the SnO2:Ga films are narrower than that of the SnO2 film.•SnO2:Ga films exhibited ...p-type conductivity as Ga doping content higher than 10%.•A p–n heterojunction composed of p-type SnO2:Ga and n-type ZnO:Al was fabricated.
P-type transparent tin oxide (SnO2) based semiconductor thin films were deposited onto alkali-free glass substrates by a sol–gel spin-coating method using gallium (Ga) as acceptor dopant. In this study, we investigated the influence of Ga doping concentration (Ga/Sn+Ga=0%, 5%, 10%, 15%, and 20%) on the structural, optical and electrical properties of SnO2 thin films. XRD analysis results showed that dried Ga-doped SnO2 (SnO2:Ga) sol–gel films annealed in oxygen ambient at 520°C for 1h exhibited only the tetragonal rutile phase. The average optical transmittance of as-prepared thin film samples was higher than 87.0% in the visible light region; the optical band gap energy slightly decreased from 3.92eV to 3.83eV with increases in Ga doping content. Hall effect measurement showed that the nature of conductivity of SnO2:Ga thin films changed from n-type to p-type when the Ga doping level was 10%, and when it was at 15%, Ga-doped SnO2 thin films exhibited the highest mean hole concentration of 1.70×1018cm−3. Furthermore, a transparent p-SnO2:Ga (Ga doping level of 15%)/n-ZnO:Al (Al doping level of 2%) heterojunction was fabricated on alkali-free glass. The I–V curve measurement for the p–n heterojunction diode showed a typical rectifying characteristic with a forward turn-on voltage of 0.65V.
The solubility problem of conjugated polymers in nonhalogenated solvents limits the application of nonhalogenated solvents in Organic solar cells (OSCs). By combining with a hot spin‐coating process, ...efficient PM6:BTP‐BO‐4F:GS‐ISO ternary OSCs are prepared by employing o‐xylene as a solvent. After adding 10 wt% content of GS‐ISO to PM6:BTP‐BO‐4F, the surface morphology in the active layers is improved and the charge extraction, transport, and collection in OSCs are enhanced. Compared with the efficiency of PM6:BTP‐BO‐4F OSCs (16.25%), an efficiency of 18.63% is achieved for PM6:BTP‐BO‐4F:GS‐ISO ternary OSCs. Moreover, PM6:BTP‐BO‐4F:GS‐ISO ternary OSCs with an efficiency of 14.13% are prepared in air. The work provides a new strategy for preparing efficient and environmentally friendly OSCs using green solvents.
Addition of 10 wt% GS‐ISO to PM6:BTP‐BO‐4F improves the surface morphology of the active layer by employing a green solvent (O‐xylene) and a hot spin‐coating process, resulting in enhanced charge extraction, transport, and collection. The final result is the simultaneous enhancement of VOC, JSC, and FF as well as the realization of 18.63% efficiency.
Hydroxyapatite (HA) is widely used in bone repair and regeneration because of its composition and structure similar to human bone. However, the artificially synthesized HA has poor mechanical ...properties, so it is often necessary to add a second phase to the powder as a supporting phase to enhance its mechanical properties. Strontium (Sr) has the properties of promoting the growth of bone cells, which can increase bone formation in the body and reduce bone self-absorption. Nevertheless, Sr-doped HA composites have been rarely reported in the literature in recent years. In this paper, Sr-doped HA was employed to be complexed with chitosan (CS) for the first time to prepare a composite coating that is dense and uniform, with good adhesion and ductility, in order to expand its clinical applications. Therefore, a series of HA samples doped with different Sr mole fraction (0 mol% (pure HA), 0.5 mol%, 1 mol%, 2 mol%, 4 mol%) were prepared by chemical precipitation method. Then the HA/CS composite coating doped with Sr was prepared on the stainless steel substrate by spin-coating technology. The results showed that Sr2+ ions had replaced part of Ca2+ ions and have been successfully doped into the HA lattice. The synthesized HA particles showed a shortrod-like morphology, and the substitution of Sr ions promoted the growth of Sr-doped HA crystals and increased its grain size. In addition, the synthesized Sr-doped HA/CS composite coating is dense and uniform. In vitro cell culture experiments showed that all composite coatings have good biocompatibility. The HA/CS coating with 4 mol% Sr ion doping is more conducive to cell proliferation, adhesion and osteogenic differentiation.
Display omitted
•Sr-doped HA was employed to be complexed with chitosan (CS) for the first time to prepare a composite coating.•The results of XRD, EDX and XPS showed Sr2+ ions had replaced partial Ca2+ ions and been doped into HA crystal lattice successfully.•The synthetic Sr-doped HA/CS composite coatings were dense and uniform.•In vitro cell culture experiments showed that all Sr-doped HA/CS composite coatings have good biocompatibility.
Herein, heavy rare‐earth substituted bismuth ferrite thin films were prepared using a low‐temperature sol–gel‐assisted spin coating method. The substitution of heavy rare‐earth ions for Bi3+ leads to ...structural transformation from rhombohedral (R3c) for x = 0.05 to orthorhombic (Pnma) symmetry for x = 0.05, which was found to have a great effect on the surface morphology, optical band‐gap energy, and photocatalytic activity of a BiFeO3(BFO) thin film. Moreover, the optical properties of prepared films were investigated via UV–visible spectroscopy. For all samples, the bandgap energy values were between 1.18 and 1.65 eV. Moreover, the refractive index and extinction coefficient of samples were about 1.14–1.40 and 0.1–0.6, respectively. Photocatalytic properties of the samples were investigated by measuring the degradation of methylene blue dye under simulated solar irradiation. We found that the heavy rare‐earth substituted BFO thin films have better photocatalytic activity compared to pure BiFeO3 thin film. It was observed that prepared thin films could remove between 37.18% and 77.24% of dye after 180 min irradiation. This study confirms that prepared thin films are a suitable candidate for photocatalytic applications.
Display omitted
•Co doped ZnO thin films were deposited by sol–gel spin coating method.•FESEM images revealed that the films possess granular morphology without any crack.•Enhanced photocatalytic ...activity was observed for Co doped ZnO films than pure ZnO.•Co doping improved the antibacterial activity of the ZnO film.
Nanostructured cobalt doped ZnO thin films were deposited on glass substrate by sol–gel spin coating technique and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and UV–Vis spectroscopy. The XRD results showed that the thin films were well crystalline with hexagonal wurtzite structure. The results of EDAX and XPS revealed that Co was doped into ZnO structure. FESEM images revealed that the films possess granular morphology without any crack and confirm that Co doping decreases the grain size. UV–Vis transmission spectra show that the substitution of Co in ZnO leads to band gap narrowing. The Co doped ZnO films were found to exhibit improved photocatalytic activity for the degradation of methylene blue dye under visible light in comparison with the undoped ZnO film. The decrease in grain size and extending light absorption towards the visible region by Co doping in ZnO film contribute equally to the improved photocatalytic activity. The bactericidal efficiency of Co doped ZnO films were investigated against a Gram negative (Escherichia coli) and a Gram positive (Staphylococcus aureus) bacteria. The optical density (OD) measurement showed better bactericidal activity at higher level of Co doping in ZnO.
Strain engineering is a promising method to manipulate the electronic and optical properties of two-dimensional (2D) materials. However, with weak van der Waals interaction, severe slippage between ...2D material and substrate could dominate the bending or stretching processes, leading to inefficiency strain transfer. To overcome this limitation, we report a simple strain engineering method by encapsulating the monolayer 2D material in the flexible PVA substrate through spin-coating approach. The strong interaction force between spin-coated PVA and 2D material ensures the mechanical strain can be effectively transferred with negligible slippage or decoupling. By applying uniaxial strain to monolayer MoS
, we observe a higher bandgap modulation up to ~300 meV and a highest modulation rate of ~136 meV/%, which is approximate two times improvement compared to previous results achieved. Moreover, this simple strategy could be well extended to other 2D materials such as WS
or WSe
, leading to enhanced bandgap modulation.
Intelligent and controllable circularly polarized absorption and emission switching with high dissymmetric factors have attracted great attention due to the significant potential applications in ...chiral chemistry, chiral photonics, and electronics. However, the lack of examples to achieve freely switchable and adjustable chiroptical properties within a single material, especially in the deformable solid materials, limits the further continuous progress. Herein, an unprecedented, simple, and scalable way to achieve the above goal is presented. A stretchable spin‐coated thin film is fabricated from chiral helical substituted polyacetylene and thermoplastic polyurethane. Macromolecular chains self‐organize into hierarchically chiral superstructures under stretching, facilitating the film to absorb/emit circularly polarized light with opposite handedness from the two faces of the film. The dissymmetry intensity can be adjusted flexibly by controlling the elongation and recovery of the film. The nonreciprocity and chirality adjustability behaviors in stretchable solid materials represent a fundamental advancement and provide new opportunities for the design, preparation, and applications of chiroptical materials.
A general approach is established to produce switchable and adjustable chiroptical materials based on simple spin‐coating. The prepared nonreciprocal flexible film contains hierarchically chiral assemblies and achieves handedness‐switchable circularly polarized absorption and emission in one single object by simply flipping the stretched film. Meanwhile, the dissymmetry intensity is controllable through adjusting the film's elongation.
Poly(vinylidene fluoride) (PVDF) and its copolymers are the polymers with the highest dielectric constants and electroactive responses, including piezoelectric, pyroelectric and ferroelectric ...effects. This semicrystalline polymer can crystallize in five different forms, each related to a different chain conformation. Of these different phases, the β phase is the one with the highest dipolar moment and the highest piezoelectric response; therefore, it is the most interesting for a diverse range of applications. Thus, a variety of processing methods have been developed to induce the formation of the polymer β phase. In addition, PVDF has the advantage of being easily processable, flexible and low-cost. In this protocol, we present a number of reproducible and effective methods to produce β-PVDF-based morphologies/structures in the form of dense films, porous films, 3D scaffolds, patterned structures, fibers and spheres. These structures can be fabricated by different processing techniques, including doctor blade, spin coating, printing technologies, non-solvent-induced phase separation (NIPS), temperature-induced phase separation (TIPS), solvent-casting particulate leaching, solvent-casting using a 3D nylon template, freeze extraction with a 3D poly(vinyl alcohol) (PVA) template, replica molding, and electrospinning or electrospray, with the fabrication method depending on the desired characteristics of the structure. The developed electroactive structures have shown potential to be used in a wide range of applications, including the formation of sensors and actuators, in biomedicine, for energy generation and storage, and as filtration membranes.
•The oxide/hydroxide-free Sb2S3 films were prepared by spin-casting.•Solar cells structure of FTO/TiO2/Sb2S3/P3HT/Al is fabricated.•Photoelectric properties of Sb2S3 films are depended on annealing ...temperature.•The best performance of Sb2S3 based solar cells is obtained at 300 °C annealed.
Antimony sulfide (Sb2S3) thin film was prepared by a simple spin-coating method to fabricate Sb2S3 based inorganic–organic heterojunction solar cells. Annealing temperature impact on the optical absorption and crystallization of Sb2S3 films was studied systematically. The crystallinity and absorption of the Sb2S3 film improved significantly when the annealing temperature increased from 200 °C to 300 °C leading to the power conversion efficiency of Sb2S3-based solar cells increased from 0.02% to 1.91%.
PDF
