Low-temperature Solution Approach Research Articles

Dispersed SnO2 colloids using sodium dodecyl benzene sulfonate for high-performance planar perovskite solar cells

Recently, SnO2-based perovskite solar cells (PSCs) have become more promising than traditional-material-based PSCs because of their simple low-temperature solution approach and low cost; meanwhile, the high-temperature process of mesoporous TiO2-based PSCs still offers a higher power conversion efficiency (PCE). In planar-based PSCs, nonradiative recombination of electron-hole pairs at the SnO2/perovskite interface leads to a loss of potential and a reduced PCE. Here, the SnO2-SDBS electron transport layer (ETL) is employed in PSCs to depress the defects of the SnO2 layer and the grain boundaries of the perovskite film. The surfactant SDBS was used as a wetting agent for SnO2 nanoparticles, to improve dispersibility. In addition, the benzene sulfonic acid group of SDBS attached to the SnO2-SDBS film can control the process of perovskite crystallization, producing a vertically aligned growth and large-grain perovskite layer. Finally, the open-circuit voltage was improved from 1.038 to 1.077 V and the PCE increased from 18.01% to 19.25% in the devices using the SnO2-SDBS ETL. The incorporation of SnO2-SDBS as an ETL paves the way to further performance enhancements of SnO2-based planar PSCs.

Tin fluoride assisted growth of air stable perovskite derivative Cs2SnI6 thin film as a hole transport layer

Dye sensitized solar cells are promising low-cost and environmentally friendly alternatives to conventional semiconductor solar cells. However, the use of liquid electrolytes containing the iodide/tri-iodide redox couple causes long-term problems such as electrode corrosion and electrolyte leakage. Here we report the facile low-temperature solution approach to fabricate the perovskite derivative Cs2SnI6 thin film as an alternative hole conductor for solid state dye sensitized solar cells under ambient air condition. Impact of the addition of tin fluoride (SnF2) on the crystalline structure, morphology and optoelectronic properties of cesium-tin-iodide thin films was investigated. The absorbance spectrum exhibited a band gap value of 1.27 eV of semiconducting Cs2SnI6 perovskite derivative. Hall Effect measurement showed the improved mobility of SnF2 treated Cs2SnI6 thin films. The 10% SnF2 treated Cs2SnI6 thin films achieved the highest mobility with the value of 468.1 cm2.V−1.s−1. These findings demonstrated the suitability of perovskite derivative Cs2SnI6 thin film as a hole transport layer as well as a promising light harvesting layer for solar cell applications.

Band Structure Engineering of Interfacial Semiconductors Based on Atomically Thin Lead Iodide Crystals.

To explore new constituents in two-dimensional (2D) materials and to combine their best in van der Waals heterostructures is in great demand as being a unique platform to discover new physical phenomena and to design novel functionalities in interface-based devices. Herein, PbI2 crystals as thin as a few layers are synthesized, particularly through a facile low-temperature solution approach with crystals of large size, regular shape, different thicknesses, and high yields. As a prototypical demonstration of band engineering of PbI2 -based interfacial semiconductors, PbI2 crystals are assembled with several transition metal dichalcogenide monolayers. The photoluminescence of MoS2 is enhanced in MoS2 /PbI2 stacks, while a dramatic photoluminescence quenching of WS2 and WSe2 is revealed in WS2 /PbI2 and WSe2 /PbI2 stacks. This is attributed to the effective heterojunction formation between PbI2 and these monolayers; type I band alignment in MoS2 /PbI2 stacks, where fast-transferred charge carriers accumulate in MoS2 with high emission efficiency, results in photoluminescence enhancement, and type II in WS2 /PbI2 and WSe2 /PbI2 stacks, with separated electrons and holes suitable for light harvesting, results in photoluminescence quenching. The results demonstrate that MoS2 , WS2 , and WSe2 monolayers with similar electronic structures show completely distinct light-matter interactions when interfacing with PbI2 , providing unprecedented capabilities to engineer the device performance of 2D heterostructures.

Self-assembly of Pt nanocrystals into three-dimensional superlattices results in enhanced electrocatalytic performance for methanol oxidation

A simple low-temperature solution approach was developed to directly realize a series of three-dimensional Pt nanocrystal superlattices composed of well-defined interior Pt nanocrystals for enhanced electrocatalytic performance for methanol oxidation.

Achieving copper sulfide leaf like nanostructure electrode for high performance supercapacitor and quantum-dot sensitized solar cells

Copper sulfide is an important multifunctional semiconductor that has attracted considerable attention owing to its outstanding properties and multiple applications, such as energy storage and electrochemical energy conversion. This paper describes a cost-effective and simple low-temperature solution approach to the preparation of copper sulfide for supercapacitors (SCs) and quantum-dot sensitized solar cells (QDSSCs). X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy confirmed that the nickel foam with a coriander leaf like nanostructure had been coated successfully with copper sulfide. As an electrode material for SCs, the CC-3 h showed excellent specific capacitance (5029.28 at 4 A g−1), energy density (169.73 W h kg−1), and superior cycling durability with 107% retention after 2000 cycles. Interestingly, the QDSSCs equipped with CC-2 h and CC-3 h counter electrodes (CEs) exhibited a maximum power conversion efficiency of 2.52% and 3.48%, respectively. The improved performance of the CC-3 h electrode was attributed mainly to the large surface area (which could contribute sufficient electroactive species), good conductivity, and high electrocatalytic activity. Overall, this work delivers novel insights into the use of copper sulfide and offers an important guidelines for the fabrication of next level energy storage and conversion devices.

Synthesis of folding flake-like CuO sub-microstructure and its application on mercury (II) sensor

Folding flake-like CuO sub-microstructure was successfully prepared on a large scale using a facile 1, 6-hexanediamin assisted low-temperature solution approach. The growth mechanism of the sample was discussed based on the time-resolved experiments. The experimental results demonstrated that the microstructures of CuO strongly depended on the concentration of the 1, 6-hexanediamin. The as-prepared CuO sub-microstructures were dispersed in Chitosan solution to fabricate composite film on glass carbon electrode. The electrochemical study has shown that the folding flake-like CuO sub-microstructure exhibits highest catalytic effect on Hg2+ than other CuO sub-microstructures. The amperometric response exhibited that the folding flake-like CuO sub-microstructure modified glassy carbon electrode has a good response for Hg2+ with a linear range of 1–200 μM in pH 6.0 phosphate buffered solutions.

Facile Preparation of Self-Assembled Hydrogel-like GdPO4·H2O Nanorods

Of the methods employed in the preparation of one-dimensional lanthanide phosphate (LnPO(4)) nanorods/nanowires, such as GdPO(4), the hydrothermal method has been mainly used as a synthetic route. In this study, we report a facile low-temperature solution approach to prepare GdPO 4*H(2)O nanorods by simply refluxing GdCl(3) and KH(2)PO(4) for only 15 min at 88 degrees C, an approach that can easily be scaled up by increasing the reagent amounts. We observed a highly viscous macroscopic hydrogel-like material when we mixed as-prepared GdPO(4)*H(2)O nanomaterials with H(2)O. Hydrogels are an important class of biomaterials. Their building blocks, normally formed from protein-, peptide-, polymer-, and lipid-based materials, offer three-dimensional scaffolds for drug delivery, tissue engineering, and biosensors. Our preliminary results showed that GdPO(4)*H(2)O hydrogels could be used for encapsulation and drug release, and that they were biocompatible, acting as scaffolds to foster cell proliferation. These findings suggested that they might have biomedical uses. Our findings may lead to the creation of other inorganic nanomaterial-based hydrogels apart from the organic and biomolecular protein-, peptide-, polymer-, and lipid-based building blocks.

Self-assembly synthesis of cactuslike Cu 2O 3D nanoarchitectures via a low-temperature solution approach

Cu 2O nanocactuses were synthesized via a simple, low-temperature, and no time-consuming wet chemical route. The synthesized products were systematically studied by X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. The results showed that the formation of Cu 2O nanocactuses was strongly depended on the addition of CTAB and NaOH. The structural evolution of the cactuslike Cu 2O was found to follow dissolution and recrystallization processes. It is noteworthy that the stepwise synthetic procedure was crucial to the growth of the final nanoarchitectures. UV–vis spectrum was also used to estimate the absorption and photodegradation ability of the nanocactuses.

Porous Iron Oxide Based Nanorods Developed as Delivery Nanocapsules

A low-temperature solution approach (90-95 degrees C) using FeCl(3) and urea was carried out to synthesize beta-FeOOH nanorods in aqueous solution. The as-synthesized beta-FeOOH nanorods were further calcined at 300 degrees C to form porous nanorods with compositions including both beta-FeOOH and alpha-Fe(2)O(3). The derived porous nanorods were engineered to assemble with four layers of polyelectrolytes (polyacrylic acid (PAA)/polyethylenimine(PEI)/PAA/PEI) on their surfaces as polyelectrolyte multilayer nanocapsules. Fluorescein isothiocyanate (FITC) molecules were loaded into the polyelectrolyte multilayer nanocapsules in order to investigate drug release and intracellular delivery in Hela cells. The as-prepared nanocapsules showed ionic strength-dependent control of the permeability of the polyelectrolyte shells. The release behavior of the entrapped FITC from the FITC-loaded nanocapsules exhibited either controlled- or sustained-release trends, depending on the compactness of the polyelectrolyte shells on the nanorod surfaces. Cytotoxicity measurements demonstrate that the native nanorods and the polymer-coated nanorods have excellent biocompatibility in all dosages between 0.1 ng mL(-1) and 100 microgm L(-1). The time dependence of uptake of FITC-loaded nanocapsules by Hela cancer cells observed by laser confocal microscopy indicates that the nanocapsules can readily be taken up by cancer cells in 15 min, a relatively short period of time, while the slow release of the FITC from the initial perimembrane space into the cytoplasm was followed by release into the nucleus after 24 h.

Nanocrystalline ZnO particles: Low-temperature solution approach from a single molecular precursor

ZnO nanoparticles were synthesized in a simple solution route without assistance of base, surfactant, template etc., at relatively very low temperature, by a single-step process. The growth rate was greatly controlled by the presence of water-immiscible non-polar solvent, which led to formation of almost pure ZnO nanoparticles with near UV emission. On the other hand, water-miscible polar solvent generates fully defected deep-level emissive ZnO nanoparticles, which agglomerate on standing due to the solvent homogeneity in the reaction mixture. The growth mechanism of ZnO nanoparticles is discussed based on the effect of solvent polarity and water miscibility with respect to particle growth rate. The structural information provided by XRD, Raman scattering, FE-SEM, TEM, and PL spectra confirms the validity of proposed growth mechanism for the ZnO nanoparticles. The experimental results reveal that the ZnO crystal growths are more sensitive to the mixture of solvents, which depends on the miscibility, polarity, and homogeneity of precursor in the reaction medium.

Iron Oxide Nanopropellers Prepared by a Low-Temperature Solution Approach

The alpha-Fe(2)O(3) (hematite) nanopropellers were synthesized via a low-temperature solution-based method using FeCl(2) as a precursor in the presence of urea and glycine hydrochloride. The formation of alpha-Fe(2)O(3) nanopropellers is strongly depended on the addition of glycine hydrochloride, which serves as a pH modulator and affects the oxidation rate of Fe(2+). The structural evolution of the propeller-structured hematite was found to follow dissolution and recrystallization processes. For the structural conformation, each nanopropeller presents a hexagonal central column closed by six equivalent surfaces of {(-)1100} and the six arrays of the nanopropeller structure are a result of growth along +/- [(-)1100], +/- [(-)1010], and +/-[0(-)110]. Preliminary results show that the magnetic maghemite (gamma-Fe(2)O(3)) nanopropellers could also be prepared by a reduction and reoxidation process from the alpha-Fe(2)O(3) (hematite) nanopropeller precursors.

Manipulation of ZnO Nanowire by Low-Temperature Solution Approach

ABSTRACTA catalyst free, structure-induced heterogeneous nucleation and direct growth of ZnO nanowires on organic and inorganic substrates was prepared by low-temperature solution approach process. The experimental results showed that ZnO nanowires could be directly synthesized upon the concave of substrate without any pre-seeding. In this work ZnO nanowires were grown on both polystyrene bead layer and physical-grinded wafer substrate. ZnO nanowires with a broad aspect ratio of 10−2 ∼ 102 was controlled mainly by adjusting of reactant concentration and pH state of solution. A needle-like ZnO nanotip were also prepared by a two-step limited growth condition as a result that tip diameter is several nanometers only, which may be highly in favor of the field emission. Structure-induced heterogeneous nucleation and growth facilitates the fabrication of ZnO nanowires as the potential photoeletronic units in field-emission displays.

Low-temperature solution approach toward highly aligned ZnO nanotip arrays

Highly aligned and free-standing ZnO nanotip arrays grown on the ZnO films by soft chemical method are proposed. X-ray diffraction analysis shows that the ZnO nanotips are hexagonal wurtzite structure, and the c-axes of nanotips are perfectly along the substrate surface normal. HRTEM demonstrates the ZnO nanotip to be a single crystal. Room temperature photoluminescence of the ZnO nanotips has a strong UV emission band at 378 nm. The field emission of ZnO nanotip arrays shows a turn-on field of about 10.8 V/μm at a current density of 0.1 μA/cm and emission current density up to about 1 mA/cm 2 at a bias field of 19.5 V/μm. The mild technique for fabricating ZnO nanotip arrays is believed to open novel possibilities for nanoscale optoelectronic device applications.