High-Throughput Growth of Armored Perovskite Single Crystal Fibers for Pixelated Arrays.

The poor machinability of halide perovskite crystals severely hampered their practical applications. Here a high-throughput growth method is reported for armored perovskite single-crystal fibers (SCFs). The mold-embedded melt growth (MEG) method provides each SCF with a capillary quartz shell, thus guaranteeing their integrality when cutting and polishing. Hundreds of perovskite SCFs, exemplified by CsPbBr3, CsPbCl3, and CsPbBr2.5I0.5, with customized dimensions (inner diameters of 150-1000 µm and length of several centimeters), are grown in one batch, with all the SCFs bearing homogeneity in shape, orientation, and optical/electronic properties. Versatile assembly protocols are proposed to directly integrate the SCFs into arrays. The assembled array detectors demonstrated low-level dark currents (< 1 nA) with negligible drift, low detection limit (< 44.84 nGy s-1), and high sensitivity (61147 µC Gy-1 cm-2). Moreover, the SCFs as isolated pixels are free of signal crosstalk while showing uniform X-ray photocurrents, which is in favor of high spatial resolution X-ray imaging. As both MEG and the assembly of SCFs involve none sophisticated processes limiting the scalable fabrication, the strategy is considered to meet the preconditions of high-throughput productions.

Efficient Screening of Pharmaceutical Cocrystals by Microspacing In-Air Sublimation.

Cocrystal screening and single-crystal growth remain the primary obstacles in the development of pharmaceutical cocrystals. Here, we present a new approach for cocrystal screening, microspacing in-air sublimation (MAS), to obtain new cocrystals and grow high-quality single crystals of cocrystals within tens of minutes. The method possesses the advantages of strong designable ability of devices, user-friendly control, and compatibility with materials, especially for the thermolabile molecules. A novel drug-drug cocrystal of favipiravir (FPV) with salicylamide (SAA) was first discovered by this method, which shows improved physiochemical properties. Furthermore, this method proved effective in cultivating single crystals of FPV-isonicotinamide (FPV-INIA), FPV-urea, FPV-nicotinamide (FPV-NIA), and FPV-tromethamine (FPV-Tro) cocrystals, and the structures of these cocrystals were determined for the first time. By adjusting the growth temperature and growth distance precisely, we also achieved single crystals of 10 different paracetamol (PCA) cocrystals and piracetam (PIR) cocrystals, which underscores the versatility and efficiency of this method in pharmaceutical cocrystal screening.

High Sensitivity and Ultra-Broad-Range NH3 Sensor Arrays by Precise Control of Step Defects on The Surface of Cl2-Ndi Single Crystals.

Vapor sensors with both high sensitivity and broad detection range are technically challenging yet highly desirable for widespread chemical sensing applications in diverse environments. Generally, an increased surface-to-volume ratio can effectively enhance the sensitivity to low concentrations, but often with the trade-off of a constrained sensing range. Here, an approach is demonstrated for NH3 sensor arrays with an unprecedentedly broad sensing range by introducing controllable steps on the surface of an n-type single crystal. Step edges, serving as adsorption sites with electron-deficient properties, are well-defined, discrete, and electronically active. NH3 molecules selectively adsorb at the step edges and nearly eliminate known trap-like character, which is demonstrated by surface potential imaging. Consequently, the strategy can significantly boost the sensitivity of two-terminal NH3 resistance sensors on thin crystals with a few steps while simultaneously enhancing the tolerance on thick crystals with dense steps. Incorporation of these crystals into parallel sensor arrays results in ppb-to-% level detection range and a convenient linear relation between sheet conductance and semi-log NH3 concentration, allowing for the precise localization of vapor leakage. In general, the results suggest new opportunities for defect engineering of organic semiconductor crystal surfaces for purposeful vapor or chemical sensing.

High-Quality Acousto-Optic Modulators with High Diffraction Efficiency, Polarization Extinction Ratio, and Small Insertion Loss Based on a Novel BaO-TeO2 -WO3 Glass.

The Q-switched material and device have attracted extensive attention due to their irreplaceable role in pulsed lasers. In this paper, BaO-TeO2 -WO3 glass (BTW glass) with sound velocity and sound attenuation coefficient of 3422 m-1 s and 0.653 dB cm-1 is successfully selected and fabricated as acousto-optic material. Both free-spaced and fiber-coupled acousto-optic modulation devices based on BTW glass are designed and fabricated. The primary parameters such as diffraction efficiency, polarization extinction ratio, and insertion loss are comparable to or even surpassed that of commercial devices. A 1064 nm pulsed laser is successfully realized with a BTW glass free-spaced acousto-optic modulator. The maximum optical conversion efficiency, the narrowest pulse width, and the maximum single pulse energy of the 1064 nm pulsed laser are 32%, 54 ns, and 242.6 µJ, respectively. Both the device and laser performance indicate that the BTW glass is a remarkable acousto-optic material.

Dimensional and Optoelectronic Tuning of Lead-free Perovskite Cs3 Bi2 I9-n Brn Single Crystals for Enhanced Hard X-ray Detection.

Inorganic Bi-based perovskites have shown great potential in X-ray detection for their large absorption to X-rays, diverse low-dimensional structures, and eco-friendliness without toxic metals. However, they suffer from poor carrier transport properties compared to Pb-based perovskites. Here, we propose a mixed-halogen strategy to tune the structural dimensions and optoelectronic properties of Cs3 Bi2 I9-n Brn (0≤n≤9). Ten centimeter-sized single crystals are successfully grown by the Bridgman technique. Upon doping bromine to zero-dimensional Cs3 Bi2 I9 , the crystal transforms into a two-dimensional structure as the bromine content reaches Cs3 Bi2 I8 Br. Correspondingly, the optoelectronic properties are adjusted. Among these crystals, Cs3 Bi2 I8 Br exhibits negligible ion migration, moderate resistivity, and the best carrier transport capability. The sensitivities in 100 keV hard X-ray detection are 1.33×104 and 1.74×104  µC Gyair -1 cm-2 at room temperature and 75 °C, respectively, which are the highest among all reported bismuth perovskites. Moreover, the lowest detection limit of 28.6 nGyair s-1 and ultralow dark current drift of 9.12×10-9  nA cm-1 s-1 V-1 are obtained owing to the high ionic activation energy. Our work demonstrates that Br incorporation is an effective strategy to enhance the X-ray detection performance by tuning the dimensional and optoelectronic properties.

Different Dissolution Molecular Pathways of Azilsartan Crystals with Different Forms Revealed by In Situ Atomic Force Microscopy.

Here, using in situ atomic force microscopy (AFM), the dissolution behaviors and dissolution molecular pathways of two azilsartan crystals, the isopropanol solvate (AZ-IPA), and form I (AZ-I), in pure water and 6-30% poly(ethylene glycol) (PEG) aqueous solutions are revealed. The dissolution behaviors of step retreat and etch pit formation are observed on the (100) faces of the two crystals, with a single step corresponding to one molecular monolayer in crystal structures. Etching rates of pits increase with PEG concentration. Furthermore, our results show that AZ-IPA dissolves by the direct detachment of molecules from the step front to solution. Such a mechanism remains even when the PEG concentration changes. However, AZ-I dissolves primarily by the surface diffusion mechanism involving molecular detachment from the step front at first and then diffusion over the terraces before desorption into solution. PEG promotes the dissolution of AZ-I crystals by favoring the molecular detachment from the step front.

Achieving a Record Scintillation Performance by Micro-Doping a Heterovalent Magnetic Ion in Cs3 Cu2 I5 Single-Crystal.

An ultrabright, ultrafast, and low-cost ideal scintillator has been critically absent and is sorely desired in scintillation detection, but has hitherto not been found. Here, a high-quality bulk Cs3 Cu2 I5 :Mn single-crystal scintillator with ultrahigh light yield (≈95 772 photons per MeV, 137 Cs γ-rays), excellent energy resolution (3.79%, 662 keV), and ultrafast scintillation decay time (3 ns, 81.5%) is reported. In mechanism, it is found that micro-doping of a heterovalent magnetic ion (at the ppm level) can effectively modulate the luminescence kinetics of self-trapped excitons in the scintillator. Compared with previous reports, the introduction of trace amounts of magnetic Mn2+ (≈18.6 ppm) in Cs3 Cu2 I5 single-crystal shortens the scintillation decay time by several hundred times, transforming the slow decay into an ultrafast decay. Simultaneously, the light yield is also increased about three times to the highest value so far. From the comprehensive performance of the micro-doped Cs3 Cu2 I5 :Mn single-crystal, these excellent scintillation properties, physical characteristics suitable for practical applications, and low-cost advantages render this single-crystal an ideal scintillator with great potential for commercialization.

Efficient Suppression of Persistent Photoconductivity in ß-Ga2O3-Based Photodetectors with Square Nanopore Arrays.

In this work, square nanopore arrays were developed on the surface of ß-Ga2O3 microflakes using focused ion beam (FIB) etching, and solar-blind photodetectors (PDs) were fabricated based on the ß-Ga2O3 microflakes with square nanopore arrays. The ß-Ga2O3 microflake-based device was transformed from a gate voltage depletion mode to an oxygen depletion mode by FIB etching. The developed device exhibited excellent solar-blind PD performance with extremely high responsivity (1.8 × 105 at 10 V), detectivity (3.4 × 1018 Jones at 10 V), and light-to-dark ratio (9.3 × 108 at 5 V) as well as good repeatability and excellent stability. The intrinsic mechanism responsible for this performance was then systematically discussed. This work opens up a new avenue for the fabrication of high-performance ß-Ga2O3-based low-dimensional PDs with high reproducibility by employing the FIB etching process.

Crystal growth and negative thermal expansion properties of a Y2Mo4O15 single crystal.

A bulk-size single crystal of Y2Mo4O15 with 20 × 11 × 8 mm3 was successfully grown by the top-seed solution growth (TSSG) method. The full-width at half maximum of (100) and (010) crystal faces is 37 and 27 arcsec, respectively. The thermal conductivity coefficients κ 11, κ 22, κ 33, and κ 13 are determined to be 1.519, 2.097, 0.445, and 0.997 W m-1 K-1, respectively. It is worth noting that the Y2Mo4O15 crystal shows significant anisotropy thermal expansion properties, which exhibits a negative thermal expansion along the b-axis (α 22 = -5.11 × 10-6 K-1). The crystal structure analysis shows that the shrinking of Mo-O bond lengths along the b-axis with the increasing temperature would be the main origin of the negative thermal expansion properties for Y2Mo4O15 crystal, which does not comply with the current mechanism.

The effect of triethylamine on dye-sensitized upconversion luminescence and its application in nanoprobes and photostability.

Triethylamine (TEA) is an effective medium for inhibiting dye aggregation and improving the luminescence of dye-sensitized lanthanide-doped upconversion nanoparticles (UCNPs). However, excessive TEA will cause quenching of upconversion luminescence. In this paper, the possible mechanism of TEA affecting upconversion luminescence is discussed. It is found that TEA can enhance the nucleophilicity of the solvent, leading to dye shedding from the nanoparticles. Reducing the dielectric constant of the solvent can make TEA play a more positive role in upconversion luminescence and photostability of dye-sensitized UCNPs. When heptanol is selected as the solvent for CyBSO-sensitized ß-NaYF4:20%Yb3+,2%Er3+ (UNs), TEA can increase the upconversion luminescence by 6.0 times relative to that in methanol. More importantly, the optimal content of TEA in heptanol is 3700 times more than that in methanol. Under the action of large amounts of TEA in heptanol, a novel upconversion nanoprobe for detecting ascorbic acid is developed with a limit of detection of 0.103 µM and high selectivity over potential interfering species. Meanwhile, the high concentration of TEA in heptanol can improve the photostability of CyBSO-sensitized UNs by 10.4 times, which is of paramount importance for the practical application of dye-sensitized UCNPs.

2D SiP2/h-BN for a Gate-Controlled Phototransistor with Ultrahigh Sensitivity.

Two-dimensional (2D) materials are extremely attractive for the construction of highly sensitive photodetectors due to their unique electronic and optical properties. However, developing 2D photodetectors with ultrahigh sensitivity for extremely low-light-level detection is still a challenge owing to the limitation of high dark current and low detectivity. Herein, a gate-controlled phototransistor based on 2D SiP2/hexagonal boron nitride (h-BN) was rationally designed and demonstrated ultrahigh sensitivity for the first time. With a back-gate device geometry, the SiP2/h-BN phototransistor exhibits an ultrahigh detectivity of 3.4 × 1013 Jones, which is one of the highest values among 2D material-based photodetectors. In addition, the phototransistor also shows a gate tunable responsivity of ≤43.5 A/W at a gate voltage of 30 V due to the photogating effect. The ultrahigh sensitivity of the SiP2-based phototransistor is attributed to the extremely low dark current suppressed by the phototransistor configuration and the improved photocurrent by using h-BN as a substrate to reduce charge scattering. This work provides a facile strategy for improving the detectivity of photodetectors and validates the great potential of 2D SiP2 phototransistors for ultrasensitive optoelectronic applications.

High-Performance and Self-Powered X-Ray Detectors Made of Smooth Perovskite Microcrystalline Films with 100†µm Grains.

Perovskite single crystals and polycrystalline films have complementary merits and deficiencies in X-ray detection and imaging. Herein, we report preparation of dense and smooth perovskite microcrystalline films with both merits of single crystals and polycrystalline films through polycrystal-induced growth and hot-pressing treatment (HPT). Utilizing polycrystalline films as seeds, multi-inch-sized microcrystalline films can be in situ grown on diverse substrates with maximum grain size reaching 100 µm, which endows the microcrystalline films with comparable carrier mobility-lifetime (µτ) product as single crystals. As a result, self-powered X-ray detectors with impressive sensitivity of 6.1×104  µC Gyair -1 cm-2 and low detection limit of 1.5 nGyair s-1 are achieved, leading to high-contrast X-ray imaging at an ultra-low dose rate of 67 nGyair s-1 . Combining with the fast response speed (186 µs), this work may contribute to the development of perovskite-based low-dose X-ray imaging.

Morphology dependent light-induced photoluminescence enhancement of CsPbBr3 microcrystals.

Herein, we report a facile method for growing CsPbBr3 cube and prism microcrystals by microspacing in-air sublimation. Morphology-dependent photoluminescence behavior investigation reveals that the CsPbBr3 cubes show higher photoluminescence quantum yield and longer PL lifetime than the prisms. In contrast, CsPbBr3 prisms exhibit more considerable light-induced photoluminescence enhancement.

Homogeneously Oriented Organic Single-Crystalline Patterns Grown by Microspacing In-Air Sublimation.

Fabrication of single-crystalline organic semiconductor patterns is of key importance to enable practical applications. However due to the poor controllability on nucleation locations and the intrinsic anisotropic nature of single-crystals, growth of single-crystal patterns with homogeneous orientation is a big challenge especially by the vapor method. Herein a vapor growth protocol to achieve patterned organic semiconductor single-crystals with high crystallinity and uniform crystallographic orientation is presented. The protocol relies on the recently invented microspacing in-air sublimation assisted with surface wettability treatment to precisely pin the organic molecules at desired locations, and inter-connecting pattern motifs to induce homogeneous crystallographic orientation. Single-crystalline patterns with different shapes and sizes, and uniform orientation are demonstrated exemplarily by using 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT). Field-effect transistor arrays fabricate on the patterned C8-BTBT single-crystal patterns show uniform electrical performance: a 100% yield with an average mobility of 6.28 cm2  V-1  s-1 and in a 5 × 8 array. The developed protocols overcome the uncontrollability of the isolated crystal patterns in vapor growth on non-epitaxial substrates, making it possible to align the anisotropic electronic nature of single-crystal patterns in large-scale devices integration.

Polymer-Assisted Compressed Flux Growth: A Universal and High-Yield Method for Dimension-Controlled Single Crystals.

Single crystals possess the most perfect and stable morphology and represent the intrinsic and upper limits of performance when integrated into various application scenarios. However, for a large portion of the newly emerging low-dimensional and molecular materials, the mass production of crystals with a desirable shape is still challenging. Here, a universal and high-yield method to grow functional single crystals with controlled dimensions is provided that can be directly integrated into a device. By utilizing a polymeric flux in combination with a compressed growth space, numerous materials can be grown into size-controllable single crystalline flakes, with millions produced in one batch. This scalable growth method shows promise for the large-scale integration of micro-single-crystals as functional components, as exemplified by the construction of a 5 in. field-effect transistor array.

A processable, scalable, and stable full-color ultralong afterglow system based on heteroatom-free hydrocarbon doped polymers.

Although room-temperature phosphorescence (RTP) organic materials are a widely-studied topic especially popular in recent decades, long-lived RTP able to fulfil broad time-resolved application requirements reliably, are still rare. Polymeric materials doped with phosphorescent chromophores generally feature high productivity and diverse applications, compared with their crystalline counterparts. This study proves that pure polycyclic aromatic hydrocarbons (PAHs) may even outperform chromophores containing hetero- or heavy-atoms. Full-color (blue, green, orange and red) polymer-PAHs with lifetimes >5000 ms under ambient conditions are constructed, which provide impressive values compared to the widely reported polymer-based RTP materials in the respective color regions. The polymer-PAHs could be fabricated on a large-scale using various methods (solution, melt and in situ polymerization), be processed into diverse forms (writing ink, fibers, films, and complex 3D architectures), and be used in a range of applications (anti-counterfeiting, information storage, and oxygen sensors). Plus their environmental (aqueous) stability makes the polymer-PAHs a promising option to expand the portfolio of organic RTPs.

Ammonia Electrosynthesis with a Stable Metal-Free 2D Silicon Phosphide Catalyst.

Metal-free 2D phosphorus-based materials are emerging catalysts for ammonia (NH3 ) production through a sustainable electrochemical nitrogen reduction reaction route under ambient conditions. However, their efficiency and stability remain challenging due to the surface oxidization. Herein, a stable phosphorus-based electrocatalyst, silicon phosphide (SiP), is explored. Density functional theory calculations certify that the N2 activation can be realized on the zigzag Si sites with a dimeric end-on coordinated mode. Such sites also allow the subsequent protonation process via the alternating associative mechanism. As the proof-of-concept demonstration, both the crystalline and amorphous SiP nanosheets (denoted as C-SiP NSs and A-SiP NSs, respectively) are obtained through ultrasonic exfoliation processes, but only the crystalline one enables effective and stable electrocatalytic nitrogen reduction reaction, in terms of an NH3 yield rate of 16.12 µg h-1  mgcat. -1 and a Faradaic efficiency of 22.48% at -0.3 V versus reversible hydrogen electrode. The resistance to oxidization plays the decisive role in guaranteeing the NH3 electrosynthesis activity for C-SiP NSs. This surface stability endows C-SiP NSs with the capability to serve as appealing electrocatalysts for nitrogen reduction reactions and other promising applications.

Passively Q-switched single crystal fiber pulsed laser at 1.05†µm with T3C2Tx as the saturable absorber.

In this paper, Ti3C2Tx MXene prepared by LiF/HCl etching method was spin-coated on glass substrate and sapphire substrate as the saturable absorber (SA), and the MXene SA is combined with Yb: LuAG single crystal fiber (SCF) for the first time to achieve a 1.05 µm passively Q-switched pulsed laser output with the average power, pulse width, and repetition frequency of 1.989 W, 149.6 ns, and 365.44 kHz, respectively, which is the highest average power ever reported for passively Q-switched SCF pulsed lasers. This work enriches the research on SCF pulsed lasers and provides a feasible approach for achieving high-power all-solid-state pulsed lasers.

Highly tumoricidal efficiency of non-oxidized MXene-Ti3C2Tx quantum dots on human uveal melanoma.

Uveal melanoma (UM) is a highly malignant intraocular tumor with poor prognosis. Current topical ophthalmic therapies purpose to conserve the eye and useful vision. Due to the risks and limited clinical benefits, the topical treatments of UM remain challenging and complex. In this study, newly developed non-oxidized MXene-Ti3C2Tx quantum dots (NMQDs-Ti3C2Tx) are proposed for UM treatment. Surprisingly, NMQDs-Ti3C2Tx shows significant tumor-killing effects on UM cells in a dose-dependent manner and causes severe necrosis near the injection site on the xenograft UM tumor model. Moreover, NMQDs-Ti3C2Tx exhibits excellent biocompatibility with normal retina pigment epithelium (RPE) cells and does not cause any damage in C57BL/6 mice eyes. Mechanistically, NMQDs-Ti3C2Tx inhibits the proliferation, invasion, and migration of UM cells via its desirable reactive oxygen species (ROS) generation ability, which causes lipid peroxidation and mitophagy, triggering cell ferroptosis. Furthermore, NMQDs-Ti3C2Tx is detected accumulating in autolysosomes which exacerbates cell death. This work provides new light on the topical treatment of UM.

Spontaneous Raman spectra analysis and efficient nanosecond pulse Raman laser of a BaTeW2O9 crystal.

In this Letter, the spontaneous Raman spectra of a novel, to the best of our knowledge, crystal α-BaTeW2O9 (α-BTW) are characterized and analyzed. The relative Raman gain coefficient of the α-BTW crystal is calculated to be 0.84 times that of YVO4. With a 35-mm-long crystal, the first-order Raman laser of α-BTW operating at 1178 nm is realized. The simple external resonator setup is employed in the first-order Raman laser of α-BTW. The pump source is a lamp-pumped electric-optical Q switched Nd:YAG laser amplifier system operating at 1064 nm with a pulse width of 10 ns. The Raman laser exhibits a threshold of 14.7 MW/cm2. In our experiments, a maximum pulse energy of 21.5 mJ is obtained with an optical-to-optical conversion efficiency and slope efficiency of 43.6%, 57.9%, respectively. Due to its high laser damage threshold, relative high Raman gain coefficient, and excellent thermal properties, the α-BTW crystal is a potential Raman material.