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Two-dimensional (2D) nanoreactors with cascade catalytic activity for glucose oxidation and hydrogen peroxide decomposition are prepared via immobilizing glucose oxidase (GOx) on Ti3C2 MXene nanosheets. Amino-rich polypeptide, poly- l -lysine (PLL), is applied to modify the ultra-thin Ti3C2 MXene nanosheets with a compatible surface for GOx immobilization. The PLL-modified Ti3C2 nanosheets possess a positively charged surface and show an excellent GOx loading capacity as high as 50 wt% of the Ti3C2 nanosheets. The physically adsorbed enzymes are then cross-linked with the amine groups in the PLL chains to form a robust GOx-PLL network covered on the MXene nanosheets. The GOx-conjugated Ti3C2-PLL (Ti3C2-PLL-GOx) nanosheets showed superior enzymatic activities than the activities of GOx immobilized on an inert porous silica substrate, largely because that the Ti3C2 nanosheets can catalyze the decomposition of the toxic intermediate H2O2 generated from the glucose oxidation. Given the excellent electrical conductivity of Ti3C2 MXene, the Ti3C2-PLL-GOx nanosheets are further deposited on glassy carbon electrode to construct a high-performance biosensor with a glucose detection limit of 2.6 μM.

We report a facile and versatile method to homogeneously deposit monolith membrane with uniform, high density of metallic nanoparticles via a “ship-in-a-bottle” strategy. Polyamidoamine (PAMAM) dendrimer, an excellent matrix for complexing with metal ions, is pre-infiltrated and applied as the directing agent for in-situ confined-formation of palladium nanoparticles (PdNPs) inside the mesopores. Efficiency of this method is demonstrated to prepare homogeneous PdNPs-deposited hierarchically porous graphitic carbon (HPGC) membrane with uniform metallic particle size (2.0–2.5 nm) and high palladium loading (~34.4 wt%). Taking advantages of fast molecule diffusion rate in hierarchically porous structure and high conductivity of graphitic carbon substance, the PdNPs-dispersed HPGC membranes are applied as monolith electrodes for electrochemical applications. The PdNPs-deposited HPGC membrane electrode exhibits excellent electrocatalytic activity toward the catalytic oxidation of dopamine, uric acid and ascorbic acid, as well as high sensitivity and selectivity in simultaneous determination of these compounds in real serum samples. The limit of detections for dopamine, uric acid and ascorbic acid are 1.3 × 10−8, 2.6 × 10−8 and 3.7 × 10−8 M, respectively, at least one order lower than that achieved on electrochemical sensors reported previously. This work provides a versatile method for efficient preparation and stabilization of monodisperse metallic NPs in diverse porous materials, leading to possible applications in devices, catalysis, and electrochemical sensing.

To attain insights into language repetition during online doctor-patient communication (DPC), understand why doctors and patients use repetition, and improve the current deficiencies in online medical platforms.The study performed a content analysis of 72 sets of textual doctor-patient conversations on the Chinese online medical consultation platform Chunyu Doctor.Repetitions occurred 1412 times in the 72 sets of online DPC. Patient self-repetitions were the most prevalent (30.7 %), while patient repetitions of doctors were the least common (17.1 %). Doctors used repetitions for explanations and affirmations. Patients used repetition for emphasis, verification, and turn-taking. The repetition frequencies of doctors and patients were primarily influenced by personal factors. However, doctor-dimension factors exerted a greater impact on the frequency of patient repetitions.The reasons for repetitions in online DPC differ from those offline. Online DPC increases patient initiative and reduces doctor authority. Nevertheless, it could be affected by gender stereotypes generated during offline consultations. Doctors still dominated the conversations but attended sufficiently to the patient discourse. Online DPC is gradually attempting to fulfill the expectations of a new patient-centered healthcare pattern.The findings yield suggestions for healthcare providers and the designers of online healthcare platforms.

SiO2 nanotubes (NTs), with uniform diameter (∼25 nm) and tailored shell thickness (1–5 nm), and featuring chemically asymmetric surfaces (a silane-functionalized exterior surface and a negatively charged (−Si–O–) interior surface) are prepared by a facile, template-free approach. Owing to their chemically asymmetric properties, positively charged cargoes can be selectively loaded with high content into the SiO2 NTs via electrostatic interaction. Mediated by polyamidoamine dendrimers preassembled in the NTs, different noble metal nanoparticles can be selectively deposited inside the NTs with high density and uniform size. Owing to their high specific surface area and elongated pore structure with lengths up to several micrometers, the SiO2 NTs exhibit a high loading capacity (80 wt %) for positively charged therapeutic agents, which exhibit sustained cargo release properties on the order of several months if the NTs are assembled into a membrane structure.

The efficacy of hydrophobic chemotherapy drugs in cancer treatment is often hampered by their poor solubility in the physiological environment, which causes their low delivery efficiency in the body. This manuscript develops an intelligent nanocarrier (~100 nm) drug delivery system that can highly load a water-insoluble drug, and possesses desirable tumor-targeting properties for cancer therapy. In this system, highly porous silica nanoparticles (pore volume ~ 1.4 cm3 g−1) with a dendritic pore structure (denoted as DMSN) are applied as a matrix for drug loading. A facile, vacuum rotary evaporation-mediated casting method is applied to quantitatively load a high content of a hydrophobic drug (i.e., paclitaxel) in the DMSN matrix. A thiol-modified poly(methacrylic acid) (denoted as PMAsh) shell is then assembled and crosslinked via disulfide bonds on the particle surface to improve the dispersibility of the particles in an aqueous environment. After functionalization of the PMAsh shell with the targeting ligand transferrin (Tf), the nanocarriers exhibit accumulation ability on tumor cells, both in vitro and in vivo. Combining the fascinating properties of high drug-loading, excellent colloidal stability, low cytotoxicity, targeting ability and glutathione-responsive PMAsh shell deconstruction properties, the nanocarriers described here hold great promise for the efficient delivery of hydrophobic drugs and tumor treatment.

The tiny Ag nanoparticles-uniformly decorated Ti3+ self-doped porous black TiO2 pillars (Ag-TPBTPs) are prepared, which show obvious surface plasmon resonance (SPR) and extend the photoresponse to visible light and near-infrared region (∼1500 nm). The Ag-TPBTPs exhibit excellent solar-driven photocatalytic activities by mineralizing of high-toxic 2,4-dichlorophenol (∼99%), which is three times higher than that of the pristine TiO2. The remarkable solar-driven photocatalytic performance can be ascribed to the porous pillars structure offering more surface active sites, the self-doped Ti3+ and SPR effect of Ag nanoparticles improving the utilization of solar light, and enhancing the spatial separation efficiency of photogenerated charge carriers.

The light-bias-dependent behavior of external quantum efficiency (EQE) in kesterite Cu2ZnSnS4 solar cells utilizing different buffers has been reported. Under red light bias, the blue EQE can be enhanced significantly, exceeding unity in magnitude due to photoconductivity of buffers increasing depletion region width and thereby increasing collection efficiency. Under blue light bias, the red EQE increases only in devices with a hybrid buffer. It stays constant with a CdS buffer due to saturated photoconductivity and even decreases with an In2S3 buffer due to optical injection of blue photons through the more transparent In2S3 into the absorber. Under white illumination, the enhancement can be observed only with unsaturated buffers such as In2S3 and the hybrid buffer, while the red EQE reduces due to optical injection. This light-bias-dependent behavior in EQE (including EQE exceeding unity) can be attributed to two key factors: photoconductivity of the buffer layers combined with low minority carrier life...

Kesterite Cu2ZnSnS4 (CZTS) thin-film solar cells have drawn worldwide attention because of outstanding performance and earth-abundant constituents. However, problems such as coexistence of complex secondary phases, the band tailing issue, short minority lifetime, bulk defects, and undesirable band alignment at p–n interfaces need to be addressed for further efficiency improvement. In this regard, Cd alloying shows promise for dealing with some of these problems. In this work, a beyond 11% efficient Cd-alloyed CZTS solar cell is achieved, and the effects of Cd-alloying and mechanism underpinning the performance improvement have been investigated. The introduction of Cd can significantly reduce the band tailing issue, which is confirmed by the reduction in the difference between the photoluminescence peak and optical band gap (Eg) as well as decreased Urbach energy. The microstructure, minority lifetime, and electrical properties of CZTS absorber are greatly improved by Cd alloying. Further XPS analyses sho...

A drawback of nanocrystal-based processing, that leads to the notoriously poor crystallinity of pure-sulfide Cu2ZnSnS4 absorber, was recently reported to be effectively overcome by the annealing of thin films made from the ink of metastable wurtzite Cu2ZnSnS4 nanocrystals in a combined S and SnS atmosphere. However, the formation pathway from nanometer-sized crystals in the wurtzite phase to micrometer-sized grains with the kesterite phase during this process still lacks in-depth study. In this work, the spatial grain growth and composition evolution during the sulfurization of wurtzite nanocrystal coatings are systematically investigated by classifying samples into temperature and time series. In the process of heating up, the reversible migration of Cu and Zn species contributes to a continuous growth of kesterite Cu2ZnSnS4 grains on the surface. At higher temperature, a fast phase-transition growth from wurtzite Cu2ZnSnS4 nanoparticles to kesterite grains is also directly observed in the region away fr...

Low Voc is the major factor limiting the current efficiency of pure sulfide Cu2ZnSnS4 (CZTS) thin film solar cells. In this work, stacking two CZTS layers with different majority doping levels is employed to increase Voc. With this double-layer structure, the obtained highest efficiency is 7.57% with Voc of 734 mV, Jsc of 15.4 mA/cm2 and FF of 67.0%. Compared to the traditional device with single CZTS layer (Efficiency: 7.62%, Voc: 665 mV, Jsc: 20.0 mA/cm2, FF: 57.3%), the average Voc has been increased by 70–80 mV. However the Jsc was decreased due to voids within the CZTS and severe band tailing problem, limiting the further boost of efficiency for double-layer CZTS solar cell.

Pure-sulfide Cu2ZnSnS4 thin film solar cells were fabricated employing a facile and low-cost preparation procedure by depositing wurtzite CZTS nanocrystals, followed by high temperature sulfurization. The exploration of previously reported devices with >4.8% efficiency has demonstrated the potential application of wurtzite nanocrystals in optoelectronic devices. Moreover, TEM-EDS characterization revealed the presence of compositional fluctuations within the fine-grained sublayer that may limit the performance of the final devices. To reduce the fine-grained sublayer and further improve the crystalline quality of the active large-grained layer of our solar cells, the Na doping method and the sulfurization process were both systematically studied in this work. The crystal phase, morphology, elemental composition, and photovoltaic performance were characterized. These results indicate that, for the wurtzite material system, (1) tuning the Na amount is necessary, yet insufficient to ensure the good performan...

The large open circuit voltage (Voc) deficit (Eg/ q -Voc) is the key factor limiting the current efficiency of pure sulfide Cu 2 ZnSnS 4 (CZTS) thin film solar cells. This present work reports CZTS devices with a Voc of over 710 mV by utilizing either In 2 S 3 buffer or In 2 S 3 /CdS hybrid buffer. The improvement in Voc mainly results from (i) an increased carrier concentration in CZTS due to In-doping when the In 2 S 3 buffer is adjacent to the CZTS absorber and (ii) favorable conduction band alignments at the CZTS/buffer interface. However, devices with In 2 S 3 buffers suffer from having a lower Fill Factor (FF) and short circuit current density (Jsc) when compared with those with CdS buffers. In contrast devices with In 2 S 3 /CdS hybrid buffers not only yield an enhancement in Voc, but also give the same level of FF and an even higher Jsc relative to CdS buffers, thereby increasing the efficiency from 5.5% to 6.6%. These hybrid In 2 S 3 /CdS buffers provide a promising way to reduce the Voc deficit and further boost the efficiency of pure sulfide CZTS solar cells.

An innovative approach to overcome the main challenge of solution-based pure-sulfide Cu2ZnSnS4 thin film solar cells by sulfurizing quaternary Cu2ZnSnS4 nanocrystals into nearly micron-sized large grains in a few minutes is presented. We developed an efficient phase-transition-driven grain growth strategy to explore the application of metastable wurtzite Cu2ZnSnS4 nano-materials in the photovoltaic field. The obtained Cu2ZnSnS4 thin film has a typical bilayer microstructure containing large grains on the top and fine grains at the bottom. Clear variations of phase, morphology, and component redistribution of the Cu2ZnSnS4 thin film were identified after the sulfurization process, which is critical to get a dense large-grained Cu2ZnSnS4 layer from quaternary nanocrystals. By tuning the composition of the wurtzite Cu2ZnSnS4 nanocrystals, annealing conditions, and sodium-containing compound, laboratory-scale photovoltaic cells with 4.83% efficiency were demonstrated without anti-reflection coatings. These results suggest the potential application of metastable wurtzite nanocrystals in pure-sulfide Cu2ZnSnS4 solar cells. This unique approach may also open up new opportunities to other optoelectronic devices, such as CuIn(S,Se)2, Cu2(In,Ga)Se4, CdTe, and Cu2ZnGe(S,Se)4 solar cells.

Kesterite Cu2ZnSnS4 (CZTS) thin films were fabricated using a low-cost and environmentally friendly route from a dimethylformamide (DMF) solution of a metal–thiourea complex. Thermal gravimetric analysis (TGA) has been performed to reveal the thermal decomposition behavior of the CZTS precursors for drying and sulfurization process design. A facile solution method of in situ introducing sodium dopant by adding NaOH into the precursor solution is presented. The sodium dopant improves the open circuit voltage (Voc) and fill factor (FF) and thereby enhances the power conversion efficiency from 4.47% to 5.68%. The enhanced performance is related to the increased grain size and increased minority carrier lifetime. A large number of large voids observed in the bulk absorber and at the absorber/back contact interface are considered to be the main reason for the low short circuit current density (Jsc).

We report a reproducible enhancement of the open circuit voltage in Cu2ZnSnS4 solar cells by introduction of a very thin CeO2 interlayer between the Cu2ZnSnS4 absorber and the conventional CdS buffer. CeO2, a non-toxic earth-abundant compound, has a nearly optimal band alignment with Cu2ZnSnS4 and the two materials are lattice-matched within 0.4%. This makes it possible to achieve an epitaxial interface when growing CeO2 by chemical bath deposition at temperatures as low as 50 °C. The open circuit voltage improvement is then attributed to a decrease in the interface recombination rate through formation of a high-quality heterointerface.

Back contact modification plays an important role in improving energy conversion efficiency of Cu2ZnSnS4 (CZTS) thin film solar cells. In this paper, an ultrathin carbon layer is introduced on molybdenum (Mo)-coated soda lime glass (SLG) prior to the deposition of CZTS precursor to improve the back contact and therefore enhance CZTS solar cell efficiency. By introducing this layer, the short circuit current (Jsc) and device conversion efficiency increase for both nonvacuum (sol-gel) and vacuum (sputtering) methods. Specifically, for the sol-gel based process, Jsc increases from 13.60 to 16.96 mA/cm(2) and efficiency from 4.47% to 5.52%, while for the sputtering based process, Jsc increases from 17.50 to 20.50 mA/cm(2) and efficiency from 4.10% to 5.20%. Furthermore, introduction of this layer does not lead to any deterioration of either open circuit voltage (Voc) or fill factor (FF).

Highly efficient, ultrathin (~400 nm) pure sulfide kesterite Cu2ZnSnS4 (CZTS) solar cells have been realized by interface reaction route controlling and self-organized nano-pattern at the back contact. The Al2O3 intermediate layer introduced at the Mo/CZTS interface can effectively inhibit the detrimental interfacial reaction between CZTS and Mo in the initial stage of sulfurization, and then turns into a self-organized nanopattern yielding a nanoscale opening for electrical contact. With this interface modification, the traditional issues of phase segregation (secondary phases) and voids at the back contact region can be well addressed, which greatly improves uniformity and reduces back contact recombination. As a result, this interface modification not only leads to beyond 8% ultrathin CZTS solar cells but also yields two certificated world record efficiencies: 9.26% for 0.237 cm2 small area and 7.61% for 1 cm2 standard kesterite CZTS solar cells (normal thickness). Solar cells made from inexpensive, non-toxic elements can reach record efficiencies with judicious application of aluminium oxide (Al2O3). Ultrathin films of kesterite semiconductors composed of copper–zinc–tin–sulfur (CZTS) atoms achieve high light absorption but suffer from poor power conversion. Researchers at the University of New South Wales, Australia, led by Xiaojing Hao, found that inserting nanometer-thin dielectrics such as aluminium oxide between a CZTS film and a reflective back contact raised conversion efficiency in two ways. The initially continuous insulating film suppressed decomposition reactions, which cause high device resistance and recombination velocity. Then, during the formation of the molybdenum–sulfur back contact layer, the aluminium oxide self-organizes into a nanoporous film. The openings in the dielectric enable direct connection of the CZTS film to the electrical circuit, boosting conversion efficiency by 1–2% over other approaches. Over 8% efficient ultrathin kesterite Cu2ZnSnS4 (CZTS) solar cells have been developed by interface reaction route controlling and self-organized nanopattern at the back contact. An ultrathin dielectric Al2O3 intermediate layer is inserted into the Mo/CZTS interface to inhibit the detrimental interfacial reaction between CZTS and Mo, and then turns into a self-organized nanopatterning with opening for electrical contact. The typical issues of phase segregation and voids at the back contact region therefore can be addressed, which reduces back contact recombination and improves the device performance. A 7.6% efficiency world record for 1 cm2 CZTS solar cells also has been achieved by this interface modification.

Sulfurization with various atmosphere and postheat treatments has been reported for earth abundant kesterite Cu2ZnSnS4 (CZTS) preparation as cost-effective material for next-generation solar cells. A full understanding of the nanoscale microstructure and chemistry of CZTS/CdS interface obtained from these different fabrication routes is currently lacking, yet is critical to developing optimal processing routes for high-performance kesterite solar cells. Here, the first detailed investigation of the interfacial microstructure and chemistry of CdS/Cu2ZnSnS4 heterojunctions is presented. For CZTS obtained from sulfurization in a sulfur-only atmosphere where highly defective surfaces are present, air annealing followed by etching in the initial stage of chemical bath deposition (CBD) process can effectively eliminate interfacial defects and allow the epitaxial growth of CBD-CdS, improving the minority lifetime, open circuit voltage (VOC), and fill factor (FF) of the devices, while blocking Cd diffusion and deteriorating short circuit current (Jsc). For CZTS from sulfurization in a combined sulfur and SnS atmosphere where CBD-CdS can directly epitaxially grow on CZTS and Cd-diffusion is clearly observed, associated devices show the longest lifetime and the highest efficiency of 8.76%. Epitaxial growth of CdS and Cd diffusion into CZTS are found to be two crucial features minimizing interfacial recombination and achieving high-efficiency devices. This will not only enhance the understanding of the device structure and physics of kesterite based solar cells, but also provide an effective way for designing other chalcogenide heterojunction solar cells.