Spin-coating Approach Research Articles

Starch-based Janus particles: Proof-of-concept heterogeneous design via a spin-coating spray approach

The asymmetric nature of Janus particles made from synthetic polymers gives them intriguing properties that have found applications in a wide variety of fields, such as drug delivery, emulsion stabilization, and environmental decontamination. The potential of using natural biopolymers as base materials for Janus particles in the food industry, however, has not yet been fully explored. Here we demonstrate for the first time the design of a starch-only-based Janus particle. Using a spin-coating spray approach, we produced both large (12.2 μm) half-porous, waxy cornstarch Janus granules by alpha-amylase treatment and small (1.2 μm) half-hydrophobic, amaranth starch Janus granules by octenyl succinic anhydride esterification. Optical microscopy, scanning electron microscopy, super resolution-structured illumination spectroscopy, and infrared spectroscopy were used to confirm the binary nature of these particles. A methylene blue adsorption test further showed that the untreated (non-porous), half-porous Janus, and fully porous waxy cornstarch granules had five-hour adsorption rates of 20.5, 72.1, and 100%, respectively, and adsorption capacities of 0.82, 2.88, and 3.96 mg/g. Meanwhile, untreated amaranth starch granules were shown not to interact with each other in water, while >68% of the half-hydrophobic granules self-assembled into wormlike strings and micelles, and >66% of the fully hydrophobic granules aggregated into spherical, complex supermicelles. While the low yield typical of Janus particle formation prevents a more detailed characterization of these starch-based Janus particles, the unique properties they displayed here may open exciting, future applications in the food industry as texturants or surface-active agents, as well as in other fields requiring such uncanny materials.

PbS Quantum Dots/2D Nonlayered CdSxSe1–x Nanosheet Hybrid Nanostructure for High-Performance Broadband Photodetectors

Two-dimensional (2D) nonlayered nanomaterials have attracted extensive attention for electronic and optoelectronic applications recently because of their distinct properties. In this work, we first employed a facile one-step method to synthesize 2D nonlayered cadmium sulfide selenide (CdS xSe1- x, x = 0.33) nanosheets with a highly crystalline structure and then we introduced a generic spin-coating approach to fabricate hybrid nanomaterials composed of PbS quantum dots (QDs) and 2D CdS xSe1- x nanosheets and demonstrated their potential for high-performance broadband photodetectors. Compared with pure 2D CdS xSe1- x nanosheet photodetectors, the photoelectric performance of the PbS/CdS xSe1- x hybrid nanostructure is enhanced by 3 orders of magnitude under near-infrared (NIR) light illumination and maintains its performance in the visible (Vis) range. The photodetector exhibits a broadband response range from Vis to NIR with an ultrahigh light-to-dark current ratio (3.45 × 106), a high spectral responsivity (1.45 × 103 A/W), and high detectivity (1.05 × 1015 Jones). The proposed QDs/2D nonlayered hybrid nanostructure-based photodetector paves a promising way for next-generation high-performance broadband optoelectronic devices.

Transparent AgNW-CoNPs conducting film for heat sensor

We have fabricated transparent conducting film (TCF) from silver nanowires (AgNWs) decorated with cobalt nanoparticles (CoNPs) on a thermoplastic polyimide (PI) substrate by solution processed spin-coating approach. AgNWs and CoNPs were produced by modified polyol methods using poly(N-vinylpyrrolidone) PVP (Mw ≈ 1,300,000). The concentration ratio of AgNWs to CoNPs was varied as 1:0, 0.7:0.3, 0.5:0.5, and 0.3:0.7 (in wt%). The results show that increasing the AgNWs/CoNPs concentration up to 0.5: 0.5 raises the TCF temperature interestingly to 350 °C before the Joule heating breakdown occurs at 20 V. However, at a higher content of CoNPs (AgNWs: CoNPs = 0.3:0.7), due to the excessive entanglement of CoNPs in the AgNW network, the temperature further drops down to 65 °C. The optimum transmittance (94%), sheet resistance (52 Ω/□), and thermal stability were obtained at a concentration ratio of AgNWs: CoNPs = 0.5:0.5. The stabilization mechanism is also suggested for the extremely high temperature obtained in this work.

Structure, magnetic and optical behaviors of Zn1-xCoxO (0.01≤x≤0.09) films developed by DMP modified sol-gel spin-coating technique

The opportunity of using electrons' spin rather than electrons charge has shown much eagerness for the future application in information technology. The success to create spin-polarized charge carriers into the semiconductor metal oxides can bring significant advantages in data storage devices. Here, a novel chemical recipe was developed to grow Zn1-xCoxO thin films via Dimethyl pimelimidate dihydrochloride (DMP) modified spin-coating approach. The impact of Co ions (0.01 ≤ x ≤ 0.09) on the lattice constants, bond lengths, residual stress and the volume of unit cell of the ZnO crystal lattice was investigated. The X-ray photoelectron spectroscopy is served for investigating the oxidation states of the Zn and Co ions. It was found that the cobalt ions are incorporated in the ZnO crystals in the form of Co2+. The magnetic hysteresis of the developed thin films was detected by the vibrating magnetometer (VSM). The developed films revealed ferromagnetism with magnetic moment of 1.69μB/Co and coercivity of 135 G at x = 0.03. However, high optical transparency reached to 85% and high photoconductivity exceeded 5 times the un-doped films, was achieved. The developed synthetic method enhanced the magneto-optical behaviors of the Zn1-xCoxO films compared to the used conventional techniques which enable them to be employed as efficient materials for the optical data storage and optical spintronic devices.

Spin-coated planar Sb2S3 hybrid solar cells approaching 5% efficiency.

Antimony sulfide solar cells have demonstrated an efficiency exceeding 7% when assembled in an extremely thin absorber configuration deposited via chemical bath deposition. More recently, less complex, planar geometries were obtained from simple spin-coating approaches, but the device efficiency still lags behind. We compare two processing routes based on different precursors reported in the literature. By studying the film morphology, sub-bandgap absorption and solar cell performance, improved annealing procedures are found and the crystallization temperature is shown to be critical. In order to determine the optimized processing conditions, the role of the polymeric hole transport material is discussed. The efficiency of our best solar cells exceeds previous reports for each processing route, and our champion device displays one of the highest efficiencies reported for planar antimony sulfide solar cells.

Fabrication of phenolic resin based desalting membrane with ordered mesostructure and excellent chlorine resistance

A novel ordered cubic mesostructured phenolic resin (PR)/F127 desalting membrane was fabricated by a spin-coating approach via the self-assembly of PR oligomer and Pluronic F127 triblock copolymer template on a polyacrylonitrile (PAN) ultrafiltration substrate. It has a thin PR/F127 desalting active layer (30nm) and negatively charged membrane surface, and It can reject 83.7% potassium sulphate under 2g/L feed solution and 2.4MPa operating pressure. The rejection to potassium citrate can be elevated to 95.6%, and corresponding permeate flux is 11.0L/m2h, suggesting good separation capability to multivalent-anion salts. Moreover, it was found that this membrane has a good selective passage for non-charged organic species. Additionally, after the membrane was partially carbonized by adding sulphuric acid, the permeate flux can be dramatically improved to 35.9L/m2h with a slight potassium citrate rejection decrease (85.4%). Furthermore, the potassium citrate rejection of the membrane can be still kept at a high level (91.7%) after being treated for 6h in NaClO aqueous solution (pH 4), indicating excellent chlorine resistance performance. This membrane also shows good resistance to acid and alkaline solutions (pH 3–9). The negatively charged membrane surface and F127 templated dense mesostructure play a key role for improving the separation capability of the PR/F127 membrane. This membrane material should have a good application prospect in multi-component separation and reclamation of oxidative waste water.

Multifunctional stannum oxide compact bilayer modified by europium and erbium respectively doped ytterbium fluoride for high-performance dye-sensitized solar cell

Multifunctional stannum oxide compact bilayer modified by europium and erbium respectively doped ytterbium fluoride (SYEu/SYEr) is designed and prepared by a convenient and low-cost spin-coating approach for dye-sensitized solar cell. The most important three functions of the compact bilayer are reducing the recombination rate of electrons as a barrier layer, enlarging the utilization of sunlight as a luminescence material both with down- and up- conversions, and enhancing the long-term stability of the device as a defender of the dye. Besides, the construction of double layer with down- and up- conversion functions has no significant influence on giving rise to quenching effect. Furthermore, these findings offer potential applications for photovoltaic device with a wide range response of sunlight via the variation in rare-earth species and cell structures.

Solution-processed perovskite solar cells using environmentally friendly solvent system

Hybrid inorganic-organic perovskite solar cells have attracted great attention with power conversion efficiencies exceeding 20% using dimethylformamide or dimethyl sulfoxide for the deposition of the perovskite films. Replacing the toxic solvents with non-toxic solvents is one of the key challenges to realize industrial scale commercialization for the perovskite photovoltaics. Here, environmentally friendly solvent systems are employed for processing the perovskite active layer by a two-step spin-coating approach: aqueous Pb(NO3)2 is first spin-coated on mesoporous TiO2 film, and followed by spin-coating of methylammonium iodide in isopropanol. We found that the resulting perovskite was homogeneously covered on the TiO2 surface with relatively high coverage. The best performing perovskite solar cell shows a power conversion efficiency of 13.7% under standard conditions (AM1.5, 100mWcm−2).

New insight into solvent engineering technology from evolution of intermediates via one-step spin-coating approach

The anti-polar solvent technique is an effective way to improve the film quality in a perovskite solar cell. In this work, we reveal the reason why chlorobenzene (CBZ) plays an important role in controlling the crystallization process. By investigating the formation of intermediate phases in the precursor solution, we observed that the CH3NH3I (MAI)-PbI2-dimethylformamide (DMF) or MAI-PbI2-dimethylsulphoxide (DMSO) adducts have not yet formed until washed with non-polar solvent. The accelerated formation of intermediate phase yields high crystalline perovskite layers. Rapid solvent evaporation and retarded perovskite crystallization in one-step method are efficient to obtain high-quality perovskite films. Consequently, MAI-PbI2-DMSO intermediate shows neat rod-like structure with high crystallinity, which eventually transforms extremely dense and uniform perovskite films.

Study of nanomechanical properties of (1-y)BST-yMgO thin films

In the present study thin films of MgO – modified Ba0.6Sr0.4TiO3 (BST60/40) solid solution were prepared by the sol-gel-type chemical solution deposition method on stainless steel substrates. A multilayer spin-coating approach was utilized for the Ba0.6Sr0.4TiO3-MgO thin film deposition with subsequent thermal annealing at T=650-750°C. Dried BST60/40-MgO gel powders were studied with thermogravimetric and differential thermal analysis to determine their thermochemical properties. X-ray diffraction analysis was utilized for thin film characterization in terms of its phase composition and crystal structure. The influence of y=1, 3 and 5 mol.% MgO doping on nanomechanical properties of BST60/40 thin films was studied with nanoindentation. It was found that BST6040 thin films adopted the tetragonal P4mm (99) structure. The volume of the BST60/40 elementary cell, the average hardness as well as the mean value of the Young modulus decreased with an increase in amount of MgO.

Fabrication and characterization of graphene-based hybrid nanocomposite: assessment of antibacterial potential and biomedical application

The present investigation deals with synthesis of graphene oxide (GO) and fabrication of GO-based hybrid nanocomposites (Ncs). Synthesized GO and Ncs were primarily confirmed by UV visible and Fourier transform infrared (FT-IR) spectroscopy. Fabricated Ncs showed potential antimicrobial activity against Gram-positive and Gram-negative bacterial strains. Surface morphology, Elemental analysis, and FTIR imaging analysis were carried out to confirm Ncs formation. The Ncs were impregnated into the pullulan polymeric layer-by-layer (LbL) ultrathin film by using novel spin-coating approach. Mechanical properties were determined using Brookfield texture analyzer, and percentage moisture content confirmed the physicochemical stability of LbL film.

Advanced Fabrication Method for the Preparation of MOF Thin Films: Liquid-Phase Epitaxy Approach Meets Spin Coating Method.

Here, we report a new and advanced method for the fabrication of highly oriented/polycrystalline metal-organic framework (MOF) thin films. Building on the attractive features of the liquid-phase epitaxy (LPE) approach, a facile spin coating method was implemented to generate MOF thin films in a high-throughput fashion. Advantageously, this approach offers a great prospective to cost-effectively construct thin-films with a significantly shortened preparation time and a lessened chemicals and solvents consumption, as compared to the conventional LPE-process. Certainly, this new spin-coating approach has been implemented successfully to construct various MOF thin films, ranging in thickness from a few micrometers down to the nanometer scale, spanning 2-D and 3-D benchmark MOF materials including Cu2(bdc)2·xH2O, Zn2(bdc)2·xH2O, HKUST-1, and ZIF-8. This method was appraised and proved effective on a variety of substrates comprising functionalized gold, silicon, glass, porous stainless steel, and aluminum oxide. The facile, high-throughput and cost-effective nature of this approach, coupled with the successful thin film growth and substrate versatility, represents the next generation of methods for MOF thin film fabrication. Therefore, paving the way for these unique MOF materials to address a wide range of challenges in the areas of sensing devices and membrane technology.

Highly conformal polyimide liner deposition in high‐aspect‐ratio through silicon vias

High-uniformity polyimide liner was successfully achieved in through silicon vias with aspect ratio and density as high as 15:1 and 2.8 × 105 /cm2, respectively. The liner is deposited by vacuum-assisted spin-coating approach, which used vacuum treatment to fully fill the via followed by spin coating to achieve uniform liner. The uniformity along the sidewall of via is evaluated with cross-sectional scanning electron microscopy images, and the results show that the thickness along sidewall from top to bottom has an average value of 530 nm and the achieved step coverage is above 33%. This liner deposition approach is completely compatible with complementary metal-oxide- semiconductor (CMOS) processes, and exhibits excellent uniformity, demonstrating the potential of the proposed technique in future advanced three-dimensional integration applications.

Compact layer influence on hysteresis effect in organic–inorganic hybrid perovskite solar cells

Organic–inorganic hybrid perovskite solar cells have attracted great attention due to their high power conversion efficiency and low cost. However, an anomalous hysteresis effect exists in the perovskite solar cells, especially with TiO2 as the n-type electron extraction layer. In this communication, we prepare two kinds of TiO2 compact layers using Atomic Layer Deposition (ALD) and Spin-Coating (SC) methods and compare their influences on the hysteresis effect. By efficiency comparison and AC impedance spectroscopy study, we find that the thickness and morphology of compact layer have a significant influence on the hysteresis effect. Compared to the SC approach, the ALD prepared compact layer is ultra-thin with uniform morphology and shows small interfacial capacitance and large recombination resistance, meaning reduced interfacial charge accumulation and accelerated electron transport, which would relieve the hysteresis effect.

Wafer-Scale Precise Patterning of Organic Single-Crystal Nanowire Arrays via a Photolithography-Assisted Spin-Coating Method.

A photolithography-assisted spin-coating approach is developed to produce single-crystal organic nanowire (NW) arrays at designated locations with high precision and high efficiency. This strategy enables the large-scale fabrication of organic NW arrays with nearly the same accuracy, reliability, and flexibility as photolithography. The high mobilities of the organic NWs enable the control of the switch of multicolored light-emitting devices with good stability.

Photo-electron double regulated resistive switching memory behaviors of Ag/CuWO4/FTO device

In this work, the CuWO4 film based resistive switching memory capacitors were fabricated with hydrothermal and spin-coating approaches. The device exhibits excellent photo-electron double controlled resistive switching memory characteristics with OFF/ON resistance ratio of ~103. It is believed that the interface of CuWO4 and FTO is responsible for such a switching behavior and it can be described by the Schottky-like barriers model. This study is useful for exploring the multifunctional materials and their applications in photo-electron double controlled nonvolatile memory devices.

SPR enhanced photocatalytic properties of Au-dispersed amorphous BaTiO3 nanocomposite thin films

Aux/BaTiO3 (x = 0, 5, 10, 15, 25, 35, and 45, where x is mol% of Au) composite thin films dispersed by Au nanoparticles (NPs) were prepared by a sol–gel spin-coating approach. The crystal structure, optical and photocatalytic properties of the films were investigated with a special emphasis on the influences of x. The approximately spherical Au NPs with 20–45 nm in diameter are embedded uniformly in the amorphous BaTiO3 matrix. The absorption peaks appeared at the wavelength from 580 to 620 nm are due to the surface plasmon resonance (SPR) effect of Au NPs, and the SPR peaks generally manifest a red-shift with increasing x from 5 to 45. The Aux/BaTiO3 composite film with the optimal SPR effect (x = 35) exhibits the highest photocatalytic activity for the degradation of Rhodamine B (RhB) aqueous solution among all films under whole spectrum sunlight irradiation.

Preparation of Ag/SiO2 near-infrared absorbers using the combination of sputtering and spin-coating depositions

This study presents the design and fabrication of near-infrared (NIR) absorbers constructed in multilayer structures using Ag and SiO2 materials. The absorbers, consisting of Ag and SiO2 films, were fabricated using sputtering and spin-coating approaches, respectively. The fabricated absorbing devices were evaluated using ultraviolet–visible-NIR spectra. Results revealed that the structure of the Ag/SiO2/Ag films exhibited an NIR absorbing effect. The absorbing properties were substantially influenced by the fabrication parameters and the thickness of the multilayer films. Furthermore, the NIR absorbing performance improved significantly when the SiO2 layer was annealed at 300°C before the deposition of the top Ag film. Additionally, the absorptance of the absorbers was affected by the thickness of the top Ag layer. The long-term stability of the multilayer absorber was tested and verified based on absorptance data analysis. The NIR absorbing performance can be further improved using the optimal device design of the film thickness and by fabricating additional Ag/SiO2 layers.

Improving the Production of Self-Assembled ZnS:Mn Nanocrystals through the Modification of Sol Gel – Spin Coating Approaches

It is difficult to produce a good film consisted of nanocrystals with good alignment. So far, a lot of methods and especially expensive vacuum-based methods have been used to produce such films. In this paper, sol gel and spin coating method were introduced. The combination of these simple and cheaper methods was used because of the high potential of those methods to produce good quality nanocrystals. First, nanocrystals were produced by sol gel method and later spin coating was done to control the thickness of the nanocrystals film. During the spin coating process, a metal tape was used to avoid solution from splashing out from the glass substrate. Subsequently, nanocrystals film was heated up from room temperature to 400 °C. To study the alignment of nanocrystals, Field Emission Scanning Electron Microscopy (FE-SEM) was used. Through this analysis, we found that the nanocrystals was in spherical pattern and the alignment of this film was well arrayed. Here, the combination of the two cheaper and simpler methods can be used to produce good quality of nanocrystals thin film and at the same time can save our research cost.

Solvent-controlled spin-coating method for large-scale area deposition of two-dimensional silica nanosphere assembled layers.

In this article, we show that introducing a N,N-dimethyl-formamide (DMF) solvent for silica nanosphere (SNS) monolayer spin-coating can offer a low-cost and simple spin-coating approach for SNS monolayer deposition even on large-area silicon surfaces. From our method, more than 95% monolayer coverage for a 2 in round Si surface was achieved, which is one of the highest reported coverage by a spin-coating method. We prove that DMF offers highly enhanced wettability and slow solvent evaporation rate compared to a conventional solvent, water, in addition to excellent SNS dispersibility in solution preventing SNS cluster deposition on the surface and consequently produces a close-packed SNS monolayer with good uniformity over the surface. In addition, the benefits of DMF are retained as the deposition area increases indicating its high tolerance to spin-coating area. Better than 90% SNS monolayer coverage on a 4 in Si substrate was achieved with the DMF spin-coating method. Moreover, DMF has the advantage that SNS spin-coating can be done under common ambient laboratory conditions with 100% pure DMF unlike previous approaches which require humidity and temperature controls or additional surfactant additions to the solution.