High‐κ Solid‐Gate Transistor Configured Graphene Biosensor with Fully Integrated Structure and Enhanced Sensitivity

A fully integrated graphene field‐effect transistor (GFET) nanosensor utilizing a novel high‐κ solid‐gating geometry for a practical biosensor with enhanced sensitivity is presented. Herein, an “in plane” gate supplying electrical field through a 30 nm HfO₂ dielectric layer is employed to eliminate the cumbrous external wire electrode in conventional liquid‐gate GFET nanosensors that undesirably limits the device potential in on‐site sensing applications. In addition to the advantage in the device integration degree, the transconductance level is found to be increased by about 50% over liquid‐gate GFET devices in aqueous‐media, thereby improves the sensitivity performance in sensor applications. As the first demonstration of biosensing applications, a small‐molecule antibiotic, kanamycin A, is detected by means of an aptameric competitive affinity principle. It is experimentally shown that the label‐free and specific quantification of kanamycin A with a concentration resolution at 11.5 × 10^?9 m is achievable through a single direct observation of the 200 s fast bioassay without any further noise canceling. These results demonstrate the utility and practicability of the new devices in label‐free biosensing as a novel analytical tool, and potentially hold great promise in other significant biomedical applications.     

A Universal,Label‐Free,and Sensitive Optical Enzyme‐Sensing System for Nuclease and Methyltransferase Activity Based on Light Scattering of Carbon Nanotubes

A label‐free, enzyme‐responsive nanosystem that uses a DNA/single‐walled carbon nanotube (SWNT) assembly as the substrate is demonstrated for the sensitive, universal detection of restriction and nonrestriction endonucleases as well as methyltransferases in a homogeneous solution on the basis of light scattering (LS) of carbon nanotubes. This protocol is based on the different binding affinities of SWNTs to single‐ and double‐stranded DNA. This difference can lead to different LS signals that can be used for the detection of nuclease cleavage activity. The assay only requires a label‐free oligonucleotide probe, significantly reducing the typical cost. The LS technique and the use of a nuclease‐specific oligonucleotide probe impart extraordinarily high sensitivity and selectivity. This light scattering assay is universal and label‐free with a detection limit of 5 × 10^?6 U μL^?1 for S1 nuclease, 1 × 10^?4 U μL^?1 for EcoRI endonuclease, and 1 × 10^?2 U μL^?1 for EcoRI methylase. In principle, this assay can be used to detect any kind of nuclease by simply changing the DNA sequences of the specific probe.     

Photoluminescence Detection of Biomolecules by Antibody‐Functionalized Diatom Biosilica

Diatoms are single‐celled algae that make microscale silica shells called “frustules”, which possess intricate nanoscale features imbedded within periodic two‐dimensional pore arrays. In this study, antibody‐functionalized diatom biosilica frustules serve as a microscale biosensor platform for selective and label‐free photoluminescence (PL)‐based detection of immunocomplex formation. The model antibody rabbit immunoglobulin G (IgG) is covalently attached to the frustule biosilica of the disk‐shaped, 10‐µm diatom Cyclotella sp. by silanol amination and crosslinking steps to a surface site density of 3948 ± 499 IgG molecules µm^?2. Functionalization of the diatom biosilica with the nucleophilic IgG antibody amplifies the intrinsic blue PL of diatom biosilica by a factor of six. Furthermore, immunocomplex formation with the complimentary antigen anti‐rabbit IgG further increases the peak PL intensity by at least a factor of three, whereas a non‐complimentary antigen (goat anti‐human IgG) does not. The nucleophilic immunocomplex increases the PL intensity by donating electrons to non‐radiative defect sites on the photoluminescent diatom biosilica, thereby decreasing non‐radiative electron decay and increasing radiative emission. This unique enhancement in PL emission is correlated to the antigen (goat anti‐rabbit IgG) concentration, where immunocomplex binding follows a Langmuir isotherm with binding constant of 2.8 ± 0.7 × 10^?7 M .     

Extreme Two‐Phase Cooling from Laser‐Etched Diamond and Conformal,Template‐Fabricated Microporous Copper

This paper reports the first integration of laser‐etched polycrystalline diamond microchannels with template‐fabricated microporous copper for extreme convective boiling in a composite heat sink for power electronics and energy conversion. Diamond offers the highest thermal conductivity near room temperature, and enables aggressive heat spreading along triangular channel walls with 1:1 aspect ratio. Conformally coated porous copper with thickness 25 µm and 5 µm pore size optimizes fluid and heat transport for convective boiling within the diamond channels. Data reported here include 1280 W cm^?2 of heat removal from 0.7 cm² surface area with temperature rise beyond fluid saturation less than 21 K, corresponding to 6.3 × 10⁵ W m^?2 K^?1. This heat sink has the potential to dissipate much larger localized heat loads with small temperature nonuniformity (5 kW cm^?2 over 200 µm × 200 µm with <3 K temperature difference). A microfluidic manifold assures uniform distribution of liquid over the heat sink surface with negligible pumping power requirements (e.g., <1.4 × 10^?4 of the thermal power dissipated). This breakthrough integration of functional materials and the resulting experimental data set a very high bar for microfluidic heat removal.     

Quantum‐Dot‐Functionalized Poly(styrene‐co‐acrylic acid) Microbeads: Step‐Wise Self‐Assembly,Characterization, and Applications for Sub‐femtomolar Electrochemical Detection of DNA Hybridization

A novel nanoparticle label capable of amplifying the electrochemical signal of DNA hybridization is fabricated by functionalizing poly(styrene‐co‐acrylic acid) microbeads with CdTe quantum dots. CdTe‐tagged polybeads are prepared by a layer‐by‐layer self‐assembly of the CdTe quantum dots (diameter = 3.07 nm) and polyelectrolyte on the polybeads (diameter = 323 nm). The self‐assembly procedure is characterized using scanning and transmission electron microscopy, and X‐ray photoelectron, infrared and photoluminescence spectroscopy. The mean quantum‐dot coverage is (9.54 ± 1.2) × 10³ per polybead. The enormous coverage and the unique properties of the quantum dots make the polybeads an effective candidate as a functionalized amplification platform for labelling of DNA or protein. Herein, as an example, the CdTe‐tagged polybeads are attached to DNA probes specific to breast cancer by streptavidin–biotin binding to construct a DNA biosensor. The detection of the DNA hybridization process is achieved by the square‐wave voltammetry of Cd²⁺ after the dissolution of the CdTe tags with HNO₃. The efficient carrier‐bead amplification platform, coupled with the highly sensitive stripping voltammetric measurement, gives rise to a detection limit of 0.52 fmol L^?1 and a dynamic range spanning 5 orders of magnitude. This proposed nanoparticle label is promising, exhibits an efficient amplification performance, and opens new opportunities for ultrasensitive detection of other biorecognition events.     

Plasmonic Heterostructure TiO2‐MCs/WO3−x‐NWs with Continuous Photoelectron Injection Boosting Hot Electron for Methane Generation

Nonmetallic plasmonic heterostructure TiO₂‐mesocrystals/WO_3?x‐nanowires (TiO₂‐MCs/WO_3?x‐NWs) are constructed by coupling mesoporous crystal TiO₂ and plasmonic WO_3?x through a solvothermal procedure. The continuous photoelectron injection from TiO₂ stabilizes the free carrier density and leads to strong surface plasmon resonance (SPR) of WO_3?x, resulting in strong light absorption in the visible and near‐infrared region. Photocatalytic hydrogen generation of TiO₂‐MCs/WO_3?x‐NWs is attributed to plasmonic hot electrons excited on WO_3?x‐NWs under visible light irradiation. However, utilization of injected photoelectrons on WO_3?x‐NWs has low efficiency for hydrogen generation and a co‐catalyst (Pt) is necessary. TiO₂‐MCs/WO_3?x‐NWs are used as co‐catalyst free plasmonic photocatalysts for CO₂ reduction, which exhibit much higher activity (16.3 µmol g^?1 h^?1) and selectivity (83%) than TiO₂‐MCs (3.5 µmol g^?1 h^?1, 42%) and WO_3?x‐NWs (8.0 µmol g^?1 h^?1, 64%) for methane generation under UV–vis light irradiation. A photoluminescence study demonstrates the photoelectron injection from TiO₂ to WO_3?x, and the nonmetallic SPR of WO_3?x plays a great role in the highly selective methane generation during CO₂ photoreduction.     

Virus‐Tethered Magnetic Gold Microspheres with Biomimetic Architectures for Enhanced Immunoassays

In immunoassays, non‐specific bindings to biosensing surfaces can be effectively prevented by formation of biocompatible and hydrophilic self‐assembled monolayer (SAM) on the surfaces. A thin gold (Au) layer on magnetic microspheres, 15 μm in diameter, enables facile SAM formation and thereby accepts second layer of filamentous virus scaffolds for the immobilization of functional proteins. The merger of the virus and SAM‐Au protected microspheres not only provides exceptionlly dense antibody loading, but also resembles biological cellular structures that enhance ligand‐receptor interactions. Site‐specific biotinylation of filamenous viruses allows formation of free‐standing virus threads (>1.0 × 10¹⁰) on streptavidin‐modified SAM‐Au microspheres. The augmented yield of antibody loading, due to the increased surface to volume ratio, on virus‐modified Au microspheres is confirmed by measuring fluorescence intensities. The bead‐based immunoassays for the detection of cardiac marker proteins exhibit increased sensitivity of virus‐Au microspheres, as low as 20 pg mL^?1 of cardiac troponin I in serum, and extremely low non‐specific adsorption when compared with bare polymer beads. This increased sensitivity due to filamentous morphology and SAM‐Au layer demonstrates the feasibility of merging viruses with non‐biological materials to yield biomimetic tools for the enhanced bead‐based immunoassays.     

Rationally Engineered Electrodes for a High‐Performance Solid‐State Cable‐Type Supercapacitor

Wire‐shaped electrodes for solid‐state cable‐type supercapacitors (SSCTS) with high device capacitance and ultrahigh rate capability are prepared by depositing poly(3,4‐ethylenedioxythiophene) onto self‐doped TiO₂ nanotubes (D‐TiO₂) aligned on Ti wire via a well‐controlled electrochemical process. The large surface area, short ion diffusion path, and high electrical conductivity of these rationally engineered electrodes all contribute to the energy storage performance of SSCTS. The cyclic voltammetric studies show the good energy storage ability of the SSCTS even at an ultrahigh scan rate of 1000 V s^?1, which reveals the excellent instantaneous power characteristics of the device. The capacitance of 1.1 V SSCTS obtained from the charge–discharge measurements is 208.36 µF cm^?1 at a discharge current of 100 µA cm^?1 and 152.36 µF cm^?1 at a discharge current of 2000 µA cm^?1, respectively, indicating the ultrahigh rate capability. Furthermore, the SSCTS shows superior cyclic stability during long‐term (20 000 cycles) cycling, and also maintains excellent performance when it is subjected to bending and succeeding straightening process.     

One‐Pot Preparation of Polymer–Enzyme–Metallic Nanoparticle Composite Films for High‐Performance Biosensing of Glucose and Galactose

New polymer–enzyme–metallic nanoparticle composite films with a high‐load and a high‐activity of immobilized enzymes and obvious electrocatalysis/nano‐enhancement effects for biosensing of glucose and galactose are designed and prepared by a one‐pot chemical pre‐synthesis/electropolymerization (CPSE) protocol. Dopamine (DA) as a reductant and a monomer, glucose oxidase (GOx) or galactose oxidase (GaOx) as the enzyme, and HAuCl₄ or H₂PtCl₆ as an oxidant to trigger DA polymerization and the source of metallic nanoparticles, are mixed to yield polymeric bionanocomposites (PBNCs), which are then anchored on the electrode by electropolymerization of the remaining DA monomer. The prepared PBNC material has good biocompatibility, a highly uniform dispersion of the nanoparticles with a narrow size distribution, and high load/activity of the immobilized enzymes, as verified by transmission/scanning electron microscopy and electrochemical quartz crystal microbalance. The thus‐prepared enzyme electrodes show a largely improved amperometric biosensing performance, e.g., a very high detection sensitivity (99 or 129 µA cm^?2 mM ^?1 for glucose for Pt PBNCs on bare or platinized Au), a sub‐micromolar limit of detection for glucose, and an excellent durability, in comparison with those based on conventional procedures. Also, the PBNC‐based enzyme electrodes work well in the second‐generation biosensing mode. The proposed one‐pot CPSE protocol may be extended to the preparation of many other functionalized PBNCs for wide applications.     

Self‐Assembly of Nanoparticle‐Spiked Pillar Arrays for Plasmonic Biosensing

Plasmonic biosensors have demonstrated superior performance in detecting various biomolecules with high sensitivity through simple assays. Scaled‐up, reproducible chip production with a high density of hotspots in a large area has been technically challenging, limiting the commercialization and clinical translation of these biosensors. A new fabrication method for 3D plasmonic nanostructures with a high density, large volume of hotspots and therefore inherently improved detection capabilities is developed. Specifically, Au nanoparticle‐spiked Au nanopillar arrays are prepared by utilizing enhanced surface diffusion of adsorbed Au atoms on a slippery Au nanopillar arrays through a simple vacuum process. This process enables the direct formation of a high density of spherical Au nanoparticles on the 1 nm‐thick dielectric coated Au nanopillar arrays without high‐temperature annealing, which results in multiple plasmonic coupling, and thereby large effective volume of hotspots in 3D spaces. The plasmonic nanostructures show signal enhancements over 8.3 × 10⁸‐fold for surface‐enhanced Raman spectroscopy and over 2.7 × 10²‐fold for plasmon‐enhanced fluorescence. The 3D plasmonic chip is used to detect avian influenza‐associated antibodies at 100 times higher sensitivity compared with unstructured Au substrates for plasmon‐enhanced fluorescence detection. Such a simple and scalable fabrication of highly sensitive 3D plasmonic nanostructures provides new opportunities to broaden plasmon‐enhanced sensing applications.     

A Protein‐Nanocellulose Paper for Sensing Copper Ions at the Nano‐ to Micromolar Level

Tracing heavy metals is a crucial issue in both environmental and medical samples. In this work, a sensing biomolecule, the cyanobacterial C‐phycocyanin (CPC), is integrated into a nanocellulose matrix, and with this, a biosensor for copper ions is developed. The assembly of CPC‐functionalized nanocellulose into a red‐fluorescent, copper‐sensitive hybrid film “CySense”, enhances protein stability and facilitates the reuse and the regeneration of the sensor for several cycles over 7 days. CySense is suitable for the analysis of complex medical samples such as human serum filtrate. The reported biosensor reliably detects copper ion contents with a lower detection limit of 200 × 10^?9m and an IC50 of 4.9 × 10^?6m as changes in fluorescence emission intensity that can be measured with a fluorimeter or a microarray laser scanner.     

Poly[oligo(ethylene glycol) methacrylate‐co‐glycidyl methacrylate] Brush Substrate for Sensitive Surface Plasmon Resonance Imaging Protein Arrays

Surface plasmon resonance imaging (SPRi) is a unique microarray method for label‐free and multiplexed bio‐assays. However, it currently cannot be used to detect human serum samples due to its low sensitivity and poor specificity. A poly[oligo(ethylene glycol) methacrylate‐co‐glycidyl methacrylate] (POEGMA‐co‐GMA) brush was synthesized by surface‐initiated atom transfer radical polymerization (SI‐ATRP) and used as a unique supporting matrix for SPRi arrays to efficiently load probe proteins for high sensitivity while reducing nonspecific adsorptions for good selectivity. Results indicate that the polymer brush has a high protein loading capacity (1.8 protein monolayers), low non‐specific protein adsorption (below the SPR detection limit), and high immobilization stability. Three model biomarkers, α‐fetoprotein, carcinoembryonic antigen, and hepatitis B surface antigen were simultaneously detected in human serum samples by a SPRi chip for the first time, showing detection limits of 50, 20, and 100 ng mL^?1, respectively. This work demonstrates great potential for a SPRi biochip as a powerful label‐free and high‐throughput detection tool in clinical diagnosis and biological research. Since the SPR detection is limited by the sensing film thickness, this approach particularly offers a unique way to significantly improve the sensitivity in the SPR detecting thickness range.     

Labeling of Adipose‐Derived Stem Cells by Oleic‐Acid‐Modified Magnetic Nanoparticles

The in vivo tracking of adipose derived stem cells (ASCs) is of essential concern when they are used as seed cells in tissue engineering. This study explores the feasibility of using magnetic nanoparticles (MNs), a type of contrast agents in magnetic resonance imaging (MRI), to label ASCs such that the labeled ASCs could be tracked in vivo by MRI non‐invasively and repeatedly. To do this, MNs of <10 nm surface‐coated with oleic acid are synthesized via a high‐temperature solution‐phase reaction. Cytotoxicity of the as‐synthesized MNs at concentrations up to 0.1 mg mL^?1 on 10⁴ cells mL^?1 ASCs is evaluated by LDH release. Since only minor cytotoxicity is detected, the effects of the labeling technique on cellular behaviors and uptake by labeled cells are investigated. Cell proliferation and differentiation with and without MNs are compared. The results show that proliferation of ASCs (10⁴ cells mL^?1) labeled by MNs (0.05 mg mL^?1) is significantly enhanced and dependent on the labeling time. The MNs are located in the vesicles within cytoplasm of ASCs. The cellular uptake reaches as high as ～180 pg/cell. Nevertheless, the labeled ASCs still maintained adipogenic and osteogenic differentiation. Hence, the feasibility of labeling ASCs by oleic acid coated MNs is ascertained and it was better to label the cells during their quiescent stage. The labeled ASCs can also be in vivo detected by MRI in a subcutaneous model in vivo. Further MRI tracking of the labeled ASCs in long‐term follow‐up would thus follow this current study.     

Gold Nanoparticle–Colloidal Carbon Nanosphere Hybrid Material: Preparation,Characterization, and Application for an Amplified Electrochemical Immunoassay

A rapid microwave‐hydrothermal method has been developed to prepare monodisperse colloidal carbon nanospheres from glucose solution, and gold nanoparticles (AuNPs) are successfully assembled on the surface of the colloidal carbon nanospheres by a self‐assembly approach. The resulting AuNP/colloidal carbon nanosphere hybrid material (AuNP/C) has been characterized and is expected to offer a promising template for biomolecule immobilization and biosensor fabrication because of its satisfactory chemical stability and the good biocompatibility of AuNPs. Herein, as an example, it is demonstrated that the as‐prepared AuNP/C hybrid material can be conjugated with horseradish peroxidase‐labeled antibody (HRP‐Ab₂) to fabricate HRP‐Ab₂‐AuNP/C bioconjugates, which can then be used as a label for the sensitive detection of protein. The amperometric immunosensor fabricated on a carbon nanotube‐modified glass carbon electrode was very effective for antibody immobilization. The approach provided a linear response range between 0.01 and 250 ng mL^?1 with a detection limit of 5.6 pg mL^?1. The developed assay method was versatile, offered enhanced performances, and could be easily extended to other protein detection as well as DNA analysis.     

Nanoporous PtRu Alloy Enhanced Nonenzymatic Immunosensor for Ultrasensitive Detection of Microcystin‐LR

A novel nonenzymatic immunosensor for sensitive detection of Microcystin‐LR (MC‐LR) is constructed using a graphene platform combined with mesoporous PtRu alloy as a label for signal amplification. Primary antibody‐Microcystin‐LR (Ab₁) is immobilized onto the surface of a graphene sheet (GS) through an amidation reaction between the carboxylic acid groups attached to the GS and the available amine groups of Ab₁. Mesoporous PtRu alloy, prepared by corrosion PtRuAl alloys, is employed as a label to immobilize secondary antibody (Ab₂). The resulting nanoparticles, PtRu‐Ab₂, are used as labels for the immunosensor to detect MC‐LR. Under optimal conditions, the immunosensor exhibits a wide linear response to MC‐LR that ranges from 0.01 to 28 ng·mL^?1, with a low detection limit of 9.63 pg·mL^?1 MC‐LR. The proposed immunsensor shows good reproducibility, selectivity, and stability. The assayed results of polluted water with the sandwich‐type sensor are acceptable. Importantly, this methodology may provide a promising ultrasensitive assay strategy for other environmental pollutants.     

Ionic‐Liquid‐Doped Polyaniline Inverse Opals: Preparation,Characterization, and Application for the Electrochemical Impedance Immunoassay of Hepatitis B Surface Antigen

A 3D ordered macroporous (3DOM) ionic‐liquid‐doped polyaniline (IL‐PANI) inverse opaline film is fabricated with an electropolymerization method and gold nanoparticles (AuNPs) are assembled on the film by electrostatic adsorption, which offers a promising basis for biomolecular immobilization due to its satisfactory chemical stability, good electronic conductivity, and excellent biocompatibility. The AuNP/IL‐PANI inverse opaline film could be used to fabricate an electrochemical impedance spectroscopy (EIS) immunosensor for the determination of Hepatitis B surface antigen (HBsAg). The concentration of HBsAg is measured using the EIS technique by monitoring the corresponding specific binding between HBsAg and HBsAb (surface antibody). The increased electron transfer resistance (R_et) values are proportional to the logarithmic value of the concentration of HBsAg. This novel immunoassay displays a linear response range between 0.032 pg mL^?1 and 31.6 pg mL^?1 with a detection limit of 0.001 pg mL^?1. The detection of HBsAg levels in several sera showed satisfactory agreement with those using a commercial turbidimetric method.     

Transparent and Robust Silica Coatings with Dual Range Porosity for Enzyme‐Based Optical Biosensing

Hierarchically porous transparent silica coatings combine large specific surface area with enhanced pore accessibility for optical biosensing. This paper describes a versatile approach to fabricate optically transparent silica coatings with multiscale porosity. Thin films (around 1 μm in thickness) of an aqueous suspension of primary silica aggregates form a mesoporous, interconnected matrix, and sacrificial polymer particles template well‐defined, discrete macropores with high structural integrity. The total surface area achieved is around 200 m² g^?1 with mesopore sizes of 20–40 nm and macropores of 250 nm, with a total porosity of 84%. The macro/meso dual range of porosity allows enhanced biocatalyst loadings of l ‐lactate dehydrogenase for detection of lactate. The functionalized films showed a linear response within the range of interest of 1–20 × 10^?3m of lactate. These biosensing coatings therefore strongly enhance sensitivity, speed and reliability of optically based lactate detection as compared to classical thin films with monomodal mesopore structure. Particle‐based simulations and experiments reveal that both the location and connectivity of the macropores control the biosensing performance. The coatings and procedure presented here are versatile, scalable, inexpensive, and are therefore compatible with a wide range of deposition techniques suitable for industrial and health care applications.     

Degenerately Hydrogen Doped Molybdenum Oxide Nanodisks for Ultrasensitive Plasmonic Biosensing

Plasmonic biosensors based on noble metals generally suffer from low sensitivities if the perturbation of refractive‐index in the ambient is not significant. By contrast, the features of degenerately doped semiconductors offer new dimensions for plasmonic biosensing, by allowing charge‐based detection. Here, this concept is demonstrated in plasmonic hydrogen doped molybdenum oxides (H_xMoO₃), with the morphology of 2D nanodisks, using a representative enzymatic glucose sensing model. Based on the ultrahigh capacity of the molybdenum oxide nanodisks for accommodating H⁺, the plasmon resonance wavelengths of H_xMoO₃ are shifted into visible‐near‐infrared wavelengths. These plasmonic features alter significantly as a function of the intercalated H⁺ concentration. The facile H⁺ deintercalation out of H_xMoO₃ provides an exceptional sensitivity and fast kinetics to charge perturbations during enzymatic oxidation. The optimum sensing response is found at H_1.55MoO₃, achieving a detection limit of 2 × 10^?9m at 410 nm, even when the biosensing platform is adapted into a light‐emitting diode‐photodetector setup. The performance is superior in comparison to all previously reported plasmonic enzymatic glucose sensors, providing a great opportunity in developing high performance biosensors.     

Long Minority‐Carrier Diffusion Length and Low Surface‐Recombination Velocity in Inorganic Lead‐Free CsSnI3 Perovskite Crystal for Solar Cells

Sn‐based perovskites are promising Pb‐free photovoltaic materials with an ideal 1.3 eV bandgap. However, to date, Sn‐based thin film perovskite solar cells have yielded relatively low power conversion efficiencies (PCEs). This is traced to their poor photophysical properties (i.e., short diffusion lengths (<30 nm) and two orders of magnitude higher defect densities) than Pb‐based systems. Herein, it is revealed that melt‐synthesized cesium tin iodide (CsSnI₃) ingots containing high‐quality large single crystal (SC) grains transcend these fundamental limitations. Through detailed optical spectroscopy, their inherently superior properties are uncovered, with bulk carrier lifetimes reaching 6.6 ns, doping concentrations of around 4.5 × 10¹⁷ cm^?3, and minority‐carrier diffusion lengths approaching 1 µm, as compared to their polycrystalline counterparts having ≈54 ps, ≈9.2 × 10¹⁸ cm^?3, and ≈16 nm, respectively. CsSnI₃ SCs also exhibit very low surface recombination velocity of ≈2 × 10³ cm s^?1, similar to Pb‐based perovskites. Importantly, these key parameters are comparable to high‐performance p‐type photovoltaic materials (e.g., InP crystals). The findings predict a PCE of ≈23% for optimized CsSnI₃ SCs solar cells, highlighting their great potential.     

Fabrication of Large‐Scale Single‐Crystalline PrB6 Nanorods and Their Temperature‐Dependent Electron Field Emission

A simple catalysis‐free approach that utilises a gas–solid reaction for the synthesis of large‐scale single‐crystalline PrB₆ nanorods using Pr and BCl₃ as starting materials is demonstrated. The nanorods exhibit a low turn‐on electric field (2.80 V µ‐b;m^?1 at 10 µ‐b;A cm^?2), a low threshold electric field (6.99 V µ‐b;m^?1 at 1 mA cm^?2), and a high current density (1.2 mA cm^?2 at 7.35 V µ‐b;m^?1) at room temperature (RT). The turn‐on and threshold electric field are found to decrease clearly from 2.80 to 0.95 and 6.99 to 3.55 V µ‐b;m^?1, respectively, while the emission current density increases significantly from 1.2 to 13.8 mA cm^?2 (at 7.35 V µ‐b;m^?1) with an increase in the ambient temperature from RT to 623 K. The field enhancement factor, emission current density, and the dependence of the effective work function with temperature are investigated. The possible mechanism of the temperature‐dependent emission from PrB₆ nanorods is discussed.