Low-temperature Solution Method Research Articles

In-situ synthesis Al-fumarate on polyurethane foam as a monolithic desiccant for adsorption heat pump systems

Metal-organic framework (MOF) is considered the most promising adsorbent in adsorption heat pump (AHP) systems, owing to its high water-harvesting capacity and rapid adsorption kinetics. However, the practical implementation of powdery MOF usually suffers from poor recovery and easy agglomeration. In this work, a novel Al-fumarate loaded on polyurethane (PU) foam (PU/Al-fumarate) to construct a monolithic desiccant was designed using an in-situ synthetic self-assembly technology. Two synthesis strategies including mixed solvent thermal method (M method) and low-temperature solution method (L method) were implemented and compared. The influences of different synthesis methods on the MOF loading rate, crystal phase, chemical composition, pore structure, microscopic morphology, and the adsorption/desorption performance of monolithic desiccants were systematically discussed. The results showed that the two synthesis methods had no fundamental effects on the composition and crystal phase of PU/Al-fumarate. However, the M-method design strategy possessed a better MOF loading rate (71.76 %), higher specific surface area (722.15 m2·g−1), and more excellent water-adsorption capacity (0.333 g·g−1) as compared with the monolithic adsorbent synthesized by L-method technology. Furthermore, the resulting monolithic desiccant designed by the M-method strategy showed low desorption activation energy and good cyclic stability. Therefore, this novel PU foam-based Al-fumarate synthesized by M-method as monolithic desiccant will provide a potential candidate for AHP system.

Enhance the efficiency of perovskite solar cells using W doped SnO2 electron transporting layer

AbstractFor low temperature (≤180 °C) processed perovskite solar cells (PSCs), SnO2 has been proven to be one of the most effective electron transporting layer. However, problems, such as poor electric conductivity and high defect density, inevitably exist in the SnO2 films which are fabricated using low temperature solution methods. Element doping of SnO2 film is a feasible strategy to alleviate the above problems. Herein, W doping of the SnO2 is realized through addition of ammonium tungstate hydrate into the molecular precursor of SnO2. The W doped SnO2 film exhibits higher conductivity, and can better extract and transport the electrons from the perovskite films. Hence, power conversion efficiency is boosted from 20.60 % for the reference PSCs to 21.83 % for PSCs fabricated on 2.5 mg mL−1 ammonium tungstate hydrate doped SnO2 films.

Myristic acid-tetradecanol-capric acid ternary eutectic/SiO2/MIL-100(Fe) as phase change humidity control material for indoor temperature and humidity control

Building materials with the dual function of temperature and humidity regulation can improve people's living comfort and reduce energy consumption. In this work, a simple and convenient strategy for building a comfortable indoor temperature and humidity environment was proposed. The phase change humidity control material (PCHCM) was prepared by the mixing of form-stable composite phase change material (CPCM) as temperature-control component and hygroscopic MIL-100(Fe) as humidity-control component. In PCHCM, the CPCM was obtained by molten recombination of myristic acid, tetradecanol, and capric acid (MA-TD-CA) as phase change material and hydrophilic fumed silica (SiO2) as porous carrier, and MIL-100(Fe) was synthesized by low-temperature solution method. Thermal analysis indicated that, under the optimized mass ratio of 28.8%MA-61.2%TD-10%CA, the CPCM containing 30 % SiO2 could effectively prevent the leakage of ternary eutectic, with a suitable phase change temperature and enthalpy (21.74 °C, 96.70 J·g−1). The thermal and wet performance evaluation confirmed that the PCHCMs containing 40–50 % CPCM had human body comfortable phase change temperature (26.96–27.26 °C) and high saturation adsorption capacity (0.179–0.205 g/g) at 60 % RH as well as outstanding thermal and wet cycle reliability, indicating the novel MA-TD-CA/SiO2/MIL-100(Fe) PCHCM has broad application potential in room temperature and humidity control and building energy conservation.

Nanomolar detection of essential amino acid in dairy products using a novel electrochemical sensor based on zinc cobaltite nanoflowers embedded porous 3D reduced graphene oxide

L-tryptophan (L-Trp) is a vital amino acid that sways neuronal function, immunity, and gut homeostasis, and its accurate detection in food samples is crucial. The aim of this study is to integrate zinc cobaltite (ZCO) nanoparticles and 3D porous reduced graphene oxide (rGO) on a screen-printed carbon electrode (SPCE) surface for building a novel electrochemical sensor to sensitively detect L-Trp in food products. A low-temperature aqueous solution method was employed in ZCO nanoflower synthesis and a hydrothermal approach was utilized to prepare 3D rGO. SEM, elemental mapping, XRD, Raman spectroscopy, XPS, and EIS characterizations were performed on the prepared nanocomposite, ZCO/3DrGO. Electrochemical experiments conducted with the cyclic and differential pulse voltammetric techniques were used for effectively assessing the catalytic power of ZCO/3DrGO/SPCE. With a low detection limit of 3 nM, high sensitivity of 19.53 μAμM−1cm−2, and a broad linear range of 0.08–5.93; 5.93–87.18 μM, the sensor demonstrated promising electrocatalytic activity towards L-Trp. Further, the reliability of the sensor was proved by analyzing its stability, repeatability, reproducibility, and selectivity towards L-Trp. The successful detection of L-Trp in dairy products (yogurt, milk, and cottage cheese) using the proposed sensor evinced its practical feasibility with high recovery of 98.16%–101.16% and low RSD of 2.8%.

A comparative photocatalytic degradation study of cationic and anionic dyes using ZnIn2S4 photocatalyst

Semiconductor mediated photocatalysis has emerged as a promising solution for dye degradation and environmental remediation. Zinc Indium Sulfide (ZnIn2S4, ZIS) is a benign, eco-friendly, visible-light-responsive photocatalyst, exhibiting excellent optoelectronic properties. In this work, we present a scalable, low temperature and template-free chemical aqueous solution method for the synthesis of ZIS. The obtained powder sample was used for a comparative dye degradation study of cationic (Malachite green) and anionic (Congo red) dye. The higher photocatalytic efficiency of ZIS is due to the higher BET surface area (55.042 m2 g−1) and low band gap (2.3 eV). Under Sunlight, almost 80 percent degradation occurs within 20 min of the experiment for both Malachite green (MG) and anionic Congo red (CR) dye, outperforming previously reported results. Scavenger studies were used to figure out the radicals involved in photocatalytic mechanics and to come up with viable photocatalytic degradation routes. The reusability and stability of ZIS were carried out up to the 5th cycles. Our result revealed that ZIS possesses high stability, reusability, and efficient potential to be an effective dye degradation photocatalyst.

Photoluminescence of wurtzite-type Ce-doped ZnS nanocrystals processed by a low-temperature aqueous solution approach

Undoped and Ce-doped ZnS nanocrystals with hexagonal wurtzite structure were synthesized by a low-temperature aqueous solution method that uses l-cysteine as complexing and capping agent. The morphology analysis revealed the formation of polydisperse nanocrystals with sizes in the range of 2–4 nm, while the energy dispersive X-ray spectroscopy showed that all the samples were sulfur deficient. The presence of Ce3+ species in the Ce-doped samples was confirmed by the X-ray photoelectron spectroscopy technique. UV–vis spectroscopy indicated that all samples had a blue shift of optical bandgap compared to bulk ZnS. According to the room-temperature photoluminescence studies, the spectra of Ce-doped ZnS nanocrystals exhibited a broad band emission consisting of UV and blue components, associated with ZnS defects, and a green component due to the 5d-4f transition of Ce3+.

Impact of Br-doping on the optical and optoelectronic properties of CsPbCl3 crystals

The all-inorganic halide perovskite CsPbX3 (X = I, Br and Cl) with outstanding optoelectronic properties and is expected to be the next generation of optoelectronic detection materials. However, the CsPbCl3 crystal is difficult to grow by low-temperature solution method. Here, we report a series of Br-doped CsPbCl3 crystals by Vertical Bridgman method. Crystal structure, spectra properties and photoelectric performances of CsPbCl3-xBrx single crystals were studied systematically. Photoluminescence (PL), X-ray excited luminescence (XEL) and UV–vis spectra can be tuned by Br-doped in the CsPbCl3 crystals. Furthermore, the basic photoelectric properties were investigated for Br-doped CsPbCl3 crystals and the optimum component of CsPbBr2.64Cl0.36 crysatal displays the highest resistivity of 2.8 × 109 Ω cm, and an on/off ratio of ∼ 25. Our work provides a feasible strategy for optimizing the photoelectric properties of doped halide perovskite crystal.

Cs3Cu2I5/ZnO Heterostructure for Flexible Visible-Blind Ultraviolet Photodetection

Wearable, portable, and biocompatible optoelectronic devices made of all-green and abundant materials and fabricated by low-temperature solution method are the key point in the development of next generation of intelligent optoelectronics. However, this is usually limited by the weaknesses of mono-component materials, such as non-adjustable photoresponse region, high carrier recombination rate, high signal-to-noise ratio, as well as the weak mechanical flexibility of bulk films. In this work, the Cs3Cu2I5/ZnO heterostructure flexible photodetectors were constructed by a low-temperature solution method combined with spin-coating technique. The heterostructure combines the low dark current and strong deep ultraviolet absorption of Cs3Cu2I5 quantum dots with the high carrier mobility of ZnO quantum dots as well as the efficient charge separation of the vertical p-n junction, to improve the photodetection performance. The heterostructure shows enhanced light/dark current ratio and ultraviolet-to-visible rejection ratios. Under an illumination of 280 nm light, an optical detectivity as high as 1.26 × 1011 Jones was obtained; the optical responsivity and response time are much better than those of control devices. After 300 times of 180° bending cycles, the photocurrent had no obvious change. The results demonstrate that the Cs3Cu2I5/ZnO heterostructure has great potential in wearable and portable visible-blind ultraviolet optoelectronic devices.

Highly-efficient perovskite solar cells based on controllable oxygen defects in tin oxide electron transport layers

Defects regulation of metal oxide electron transport layers (ETLs) such as SnO2 is an effective strategy for improving the power conversion efficiency (PCE). However, it is difficult to control the surface defects of SnO2 using low boiling point solvents, thereby limiting the performance of the perovskite solar cells (PSCs). For this, we prepared high-quality SnO2 films by a low-temperature solution method, and found that solvent had an obvious influence on the energy level and oxygen vacancy within SnO2. The SnO2 electron transport layer was prepared by isopropanol (I–SnO2) dimethoxyethanol (D-SnO2), respectively. Comparing with I–SnO2, D-SnO2 shows excellent photoelectric properties. The perovskite cells based on D-SnO2 exhibited the optimal performance, and the efficiency increased to 20.35% from 18.63% of the device based on I–SnO2.

Facile synthesis and lithium storage mechanism study of directly usable tin-based metal organic framework

• Tin-based MOFs have been successfully prepared and directly applied to Li-ion storage without annealing treatment. • The modified Sn-PA anode material has excellent electrochemical properties such as high reversible capacity and long-cycle stability. • The stable structural unit of Sn-PA and the active sites of Sn and O atoms are considered the reason for their excellent electrochemical performance. Tin-based materials have been demonstrated to be promising candidates for LIBs owing to their dramatic lithium storage properties. However, its large volume variation and poor cyclic stability severely impede practical utilization. In the present study, a novel Sn-based metal–organic framework (Sn-PA) has been one-step synthesized by a facile low-temperature aqueous solution method and has been directly used as anode materials, without subsequent annealing treatment. The simulated structure diagram and theoretically calculated revealed that in Sn-PA MOFs, Tin ions combine with four oxygen atoms from three organic ligands to form a stable and unique network structure. With a layered network structure and efficient electron transport channels, the Sn-PA electrode exhibits excellent electrochemical performance, achieves a high reversible capacity of 1530 mAh g −1 after 400 cycles at a current density of 0.5 A g −1 , and provides a highly stable capacity of 777 mAh g −1 at a high current density of 5 A g −1 . Kinetic analyses verified that the reversible synergistic effects between O atoms with high electro-negativity and Sn atoms with high capacity, as the main storage center of lithium ions, contribute to its excellent electrochemical performance.

Double Layer Growth of ZnO Nanorods by a Low Temperature Solution Method: Synthesis and Photoluminescence Properties

In the present work, double layer Zinc Oxide (ZnO) nanorods (NRs) were fabricated hydrothermally and their photoluminescence (PL) properties were investigated. Two different recipes and their combination were used to obtain double layer vertically well-aligned ZnO NRs. These recipes include polyethylenimine (PEI) and citrate as additives in the growth solution resulting long NRs with a broad defect emission and relatively short NRs with a near band-edge ultraviolet (UV) emission, respectively. Double layer growth of long-long (LL), long-short (LS) and short-short (SS) ZnO NRs were considered. Grown samples were annealed in a forming gas atmosphere for a better quality NR structure. LL ZnO NRs (long ZnO NRs grown on a long ZnO NR layer) with a 65 µm thickness showed a broad yellow-orange PL emission and no any near band-edge UV emission was observed. LS ZnO NRs representing short ZnO NRs grown on a long ZnO NR layer (LS1= 36 µm, LS2= 48 µm and LS3= 44 µm) showed an enhanced near band-edge UV emission when compared to that of the long ZnO NRs. The UV intensity was found to decrease with the increase in thickness of the NRs in LS samples. Finally, SS ZnO NR sample, (short ZnO NRs grown on a short ZnO NR layer) which has a thickness of 33 µm, displayed a stronger near band-edge UV emission with a negligible broad emission than that of as-grown SS ZnO NRs (UV peak intensity ratio 59). This study should be important for applications where longer NRs with enhanced PL properties are strictly required.

Progress of defect and defect passivation in perovskite solar cells

Research on perovskite solar cells is prevalent because of their excellent photovoltaic performance. Most of the perovskite films are prepared by polycrystalline perovskite films and low-temperature solution method, thus inevitably creating a high density of defects, including point defects and extended defects. These defects can also be divided into two types: shallow-level defects and deep-level defects. The multiple types of defects are the main cause of nonradiative recombination, which will limit the enhancement of photovoltaic properties and stability of solar cell devices. In this paper, we review the latest advances in defect passivation and describe in detail the mechanisms of different methods to passivate defects at the surface and interface of perovskite films to reduce nonradiative recombination. We also summarize the research results about the defect passivation to reduce the deep energy level traps by Lewis acid and base, anion and cation, and the results about the conversion of defects into wide band gap materials as well. The effects of various strategies to modulate the mechanism of passivation of perovskite surface/interface defects are also elaborated. In addition, we discuss the intrinsic link between crystal defects and device stability, and provide an outlook on the feasibility of defect passivation strategies in future research.

Monolithic Perovskite/Silicon-Heterojunction Tandem Solar Cells with Nanocrystalline Si/SiOx Tunnel Junction

Perovskite/silicon tandem solar cells have strong potential for high efficiency and low cost photovoltaics. In monolithic (two-terminal) configurations, one key element is the interconnection region of the two subcells, which should be designed for optimal light management and prevention of parasitic p/n junctions. We investigated monolithic perovskite/silicon-heterojunction (SHJ) tandem solar cells with a p/n nanocrystalline silicon/silicon-oxide recombination junction for improved infrared light management. This design can additionally provide for resilience to shunts and simplified cell processing. We probed modified SHJ solar cells, made from double-side polished n-type Si wafers, which included the proposed front-side p/n tunnel junction with the p-type film simultaneously functioning as selective charge transport layer for the SHJ bottom cell, trying different thicknesses for the n-type layer. Full tandem devices were then tested, by applying a planar n-i-p mixed-cation mixed-halide perovskite top cell, fabricated via low temperature solution methods to be compatible with the processed Si wafer. We demonstrate the feasibility of this tandem cell configuration over a 1 cm2 area with negligible J-V hysteresis and a VOC ~1.8 V, matching the sum of the VOC-s contributed by the two components.

Surface modified hybrid ZnSnO3 nanocubes for enhanced piezoelectric power generation and wireless sensory application

Piezoelectric Nanogenerators (PENGs), which can convert ambient mechanical stimuli into electrical energy, are held in high regard due to their cost-effectiveness, energy harvesting applications, and potential as self-powered sensors. We report an aluminum-doped zinc stannate (ZnSnO3) PENG that can achieve high electrical outputs with respect to the external force. In order to enrich the piezoelectric mechanics, a low-temperature solution method was adopted in our work to synthesize ZnSnO3 nanocubes with an average side length of only 30 – 55 nm. Furthermore, ZnSnO3 was doped with 1–5 wt% of aluminum nanoparticles. We report that 2 wt% of aluminum doped ZnSnO3 showed the highest electrical output in terms of open circuit voltages and short circuit current. The nanogenerator device achieved an average open-circuit voltage of 80–175 V with a frequency range of 60 BPM (Beats Per Minute) to 240 BPM, an unprecedented electrical output in comparison to current ZnSnO3-based PENGs. With the presented high output-to-size ratio taken into consideration, the device was mounted in a helmet and tested as an energy harvester and wireless human motion sensor, which can generate electric charge as well as detect human movements and transmit the corresponding signals wirelessly. Our work is indicative of a promising smart helmet using organic-inorganic hybrid materials.

Amorphous calcium phosphate nanoparticles using adenosine triphosphate as an organic phosphorus source for promoting tendon\u2013bone healing

BackgroundRotator cuff tear (RCT) is a common problem of the musculoskeletal system. With the advantage of promoting bone formation, calcium phosphate materials have been widely used to augment tendon-bone healing. However, only enhancing bone regeneration may be not enough for improving tendon–bone healing. Angiogenesis is another fundamental factor required for tendon–bone healing. Therefore, it’s necessary to develop a convenient and reliable method to promote osteogenesis and angiogenesis simultaneously, thereby effectively promoting tendon–bone healing.MethodsThe amorphous calcium phosphate (ACP) nanoparticles with dual biological activities of osteogenesis and angiogenesis were prepared by a simple low-temperature aqueous solution method using adenosine triphosphate (ATP) as an organic phosphorus source. The activities of osteogenesis and angiogenesis and the effect on the tendon–bone healing of ACP nanoparticles were tested in vitro and in a rat model of acute RCT.ResultsThe ACP nanoparticles with a diameter of tens of nanometers were rich in bioactive adenosine. In vitro, we confirmed that ACP nanoparticles could enhance osteogenesis and angiogenesis. In vivo, radiological and histological evaluations demonstrated that ACP nanoparticles could enhance bone and blood vessels formation at the tendon–bone junction. Biomechanical testing showed that ACP nanoparticles improved the biomechanical strength of the tendon–bone junction and ultimately promoted tendon–bone healing of rotator cuff.ConclusionsWe successfully confirmed that ACP nanoparticles could promote tendon–bone healing. ACP nanoparticles are a promising biological nanomaterial in augmenting tendon–bone healing.Graphic abstract

Excellent near-infrared response performance in p-CuS/n-Si heterojunction using a low-temperature solution method

The solution method is recognized as the most promising type for the preparation of CuS particles because of the advantages of high yield and easy tuning. In this work, p-type CuS nanoparticles were synthesized by a low-temperature water bath method, and the effects of different copper sources, synthesis temperatures, and different raw material ratios on the preparation of CuS were investigated. The X-ray diffraction XRD results indicate that the prepared CuS is polycrystalline with a hexagonal structure. The optical data show that the bandgap of the prepared CuS is between 2.52-2.69 eV. SEM images show that the difference in copper source significantly affects the morphology of CuS particles. Based on the high optical absorption coefficient, p-CuS/n-Si heterojunction photodetectors were constructed from the synthesized CuS and n-Si wafers with an inverted pyramidal structure to investigate their photoresponse capability. The results show that under the irradiation of 980nm near-infrared light, it has a maximum responsivity of 0.493mA/W at 0V bias, indicating its good self-driven ability. At -5V bias, the maximum responsivity of 1.322 A/W and the switching ratio of 5171 show that p-CuS/n-Si heterojunction photodetectors have great potential to be used in the near-infrared detection field.

Enhanced photodetection of perovskite nanoplatelet devices by vertically stacked PEDOT: PSS/PbS/CsPbCl3 architecture

Vertically stacked PEDOT: PSS/PbS/CsPbCl3 phototransistors were fabricated by a low-temperature solution method, the electrical and optoelectrical properties were investaged. The photodetectors based on PEDOT: PSS/PbS/CsPbCl3 phototransistors exhibited a high responsivity of 147.35 A/W, detectivity of 6.77 × 1012 Jones, and signal-to-noise ratio of 102 under a relatively low external bias. The results indicate vertically stacked PEDOT: PSS/PbS/CsPbCl3 architecture is a promising candidate for high-performance broadband photodetection and portable low-voltage optoelectronic devices.

Colloidal synthesis of NiMn2O4 nanodisks decorated reduced graphene oxide for electrochemical applications

This work describes the preparation of spinel NiMn2O4 nanodisks decorated reduced graphene oxide (rGO) via low-temperature colloidal solution method and analyzes their performances as electro-active electrode for electrochemical sensor and supercapacitors. The morphological analysis revealed the well-decorated spinel NiMn2O4 nanodiks over the rGO surfaces. The crystalline, structure, and composition of spinel NiMn2O4nanodisks decorated rGO was studied and extensively used as electrode materials for electrochemical applications. For sensing measurements, the NiMn2O4/rGO composite modified GCE expressed the high sensitivity of 78.56 mA.mM−1·cm−2 with an excellent linear dynamic range of 1.0 μM–500.0 μM towards the acetylacetone chemical. The electrode prepared by NiMn2O4/rGO composite was applied to fabricate the double layer electrochemical supercapacitors. NiMn2O4/rGO electrode showed a reasonably high specific capacitance of 356 F g−1 at a current density of 0.5 Ag−1 in 1 M Na2SO4 electrolyte. The fabricated supercapacitor exhibited the admirable rate capability by maintaining 86% from initial capacity after 5000 cycles. The prepared NiMn2O4/rGO composite and obtained results are the promising electrode materials for achieving high-performance sensing and supercapacitors.

Perovskite Tandem Solar Cells: From Fundamentals to Commercial Deployment.

Multi-junction (tandem) solar cells (TSCs) consisting of multiple light absorbers with considerably different band gaps show great potential in breaking the Shockley-Queisser (S-Q) efficiency limit of a single junction solar cell by absorbing light in a broader range of wavelengths. Perovskite solar cells (PSCs) are ideal candidates for TSCs due to their tunable band gaps, high PCE up to 25.2%, and easy fabrication. PSCs with high PCEs are typically fabricated via a low temperature solution method, which are easy to combine with many other types of solar cells like silicon (Si), copper indium gallium selenide (CIGS), narrow band gap PSCs, dye-sensitized, organic, and quantum dot solar cells. As a matter of fact, perovskite TSCs have stimulated enormous scientific and industrial interest since their first development in 2014. Significant progress has been made on the development of perovskite TSCs both in the research laboratories and industrial companies. This review will rationalize the recent exciting advancement in perovskite TSCs. We begin with the introduction of the historical development of TSCs in a broader context, followed by the summary of the state-of-the-art development of perovskite TSCs with various types of device architectures. We then discuss the strategies for improving the PCEs of perovskite TSCs, including but not limited to the design considerations on the transparency of perovskite absorbers and metal electrodes, protective layers, and recombination layers (RLs)/tunnel junctions (TJs), with a particular focus on the band gap tuning and thickness adjustment of active layers. We subsequently introduce a range of measurement techniques for the characterization of perovskite TSCs. We also cover other core issues related to the large-scale applications and commercialization. Finally, we offer our perspectives on the future development of emerging photovoltaic technologies as the device performance enhancement and cost reduction are central to almost any type of solar cell applied in the perovskite TSCs.

Fabrication of Ultraviolet Photodetectors Based on Fe-Doped ZnO Nanorod Structures.

In this paper, 100 nm-thick zinc oxide (ZnO) films were deposited as a seed layer on Corning glass substrates via a radio frequency (RF) magnetron sputtering technique, and vertical well-aligned Fe-doped ZnO (FZO) nanorod (NR) arrays were then grown on the seed layer-coated substrates via a low-temperature solution method. FZO NR arrays were annealed at 600 °C and characterized by using field emission scanning microscopy (FE-SEM) and X-ray diffraction spectrum (XRD) analysis. FZO NRs grew along the preferred (002) orientation with good crystal quality and hexagonal wurtzite structure. The main ultraviolet (UV) peak of 378 nm exhibited a red-shifted phenomenon with Fe-doping by photoluminescence (PL) emission. Furthermore, FZO photodetectors (PDs) based on metal–semiconductor–metal (MSM) structure were successfully manufactured through a photolithography procedure for UV detection. Results revealed that compared with pure ZnO NRs, FZO NRs exhibited a remarkable photosensitivity for UV PD applications and a fast rise/decay time. The sensitivities of prepared pure ZnO and FZO PDs were 43.1, and 471.1 for a 3 V applied bias and 380 nm UV illumination, respectively.