Phosphonium Iodide Featuring Blue Thermally Activated Delayed Fluorescence for Highly Efficient X-ray Scintillator.

Organic scintillators are praised for their abundant element reserves, facile preparation procedures, and rich structures. Herein, a new family of highly efficient organic phosphonium halide salts with thermally activated delayed fluorescence (TADF) are designed by innovatively adopting quaternary phosphonium as the electron acceptor, while dimethylamine group and halide anions (I-) serve as the electron donor. The prepared butyl(2-[2-(dimethylamino)phenyl]phenyl)diphenylphosphonium iodide (C4-I) exhibits bright blue emission and an ultra-high photoluminescence quantum yield (PLQY) of 100%. Efficient charge transfer is realized through the unique n-π and anion-π stacking in solid-state C4-I. Photophysical studies of C4-I suggest that the incorporation of I accounts for high intersystem crossing rate (kISC) and reverse intersystem crossing rate (kRISC), suppressing the intrinsic prompt fluorescence and enabling near-pure TADF emission at room temperature. Benefitting from the large Stokes shift, high PLQY, efficient exciton utilization, and remarkable X-ray attenuation ability endowed by I, C4-I delivers an outstanding light yield of 80721 photons/MeV and a low limit of detection (LoD) of 22.79 nGy·s-1. This work would provide a rational design concept and open up an appealing road for developing efficient organic scintillators with tunable emission, strong X-ray attenuation ability, and excellent scintillator performance.

A Melt-Quenched Luminescent Glass of an Organic-Inorganic Manganese Halide as a Large-Area Scintillator for Radiation Detection.

Glass is a group of materials with appealing qualities, including simplicity in fabrication, durability, and high transparency, and they play a crucial role in the optics field. In this paper, a new organic-inorganic metal halide luminescent glass exhibiting >78 % transmittance at 506-800 nm range together with a high photoluminescence quantum yield (PLQY) of 28.5 % is reported through a low-temperature melt-quenching approach of pre-synthesized (HTPP)2 MnBr4 (HTPP=hexyltriphenylphosphonium) single crystal. Temperature-dependent X-ray diffraction, polarizing microscopy, and molecular dynamics simulations were combined to investigate the glass-crystal interconversion process, revealing the disordered nature of the glassy state. Benefiting from the transparent nature, (HTPP)2 MnBr4 glass yields an outstanding spatial resolution of 10 lp mm-1 for X-ray imaging. The superb optical properties and facility of large-scale fabrication distinguish the organic-inorganic metal halide glass as a highly promising class of materials for optical devices.

Large-Area Laminar TEA2MnI4 Single-Crystal Scintillator for X-ray Imaging with Impressive High Resolution.

Current X-ray imaging scintillators are dominated by inorganic scintillators grown through a high-temperature process. Exploring new types of scintillators with mild growth conditions, high light yields, and eco-friendly chemical compositions is essential and challenging. Herein, the zero-dimensional large-area laminar organic-inorganic hybrid metal halide TEA2MnI4 (TEA = tetraethylammonium) single crystal with dimensions of 50 mm × 60 mm × 0.82 mm is grown via a local-heating solvent evaporation method. Compared with its Cl- and Br-based counterparts, the incorporation of the iodine component enhances the X-ray attenuation ability and significantly accelerates the decay of the photoluminescence of TEA2MnI4. Interestingly, the prepared TEA2MnI4 exhibits a high transmittance of >90% over the range of 515-765 nm and exhibits a high light yield of 26288 photons/MeV, which provides the prerequisite for high-resolution X-ray imaging. The TEA2MnI4 single-crystal scintillator displays an astonishing spatial resolution exceeding 25 line pairs per millimeter, which provides a design concept for a Mn-I-based single crystal for high-performance scintillator applications.

Multidentate Chelation Heals Structural Imperfections for Minimized Recombination Loss in Lead-Free Perovskite Solar Cells.

Tin-based perovskite solar cells (Sn-PSCs) have emerged as promising environmentally viable photovoltaic technologies, but still suffer from severe non-radiative recombination loss due to the presence of abundant deep-level defects in the perovskite film and under-optimized carrier dynamics throughout the device. Herein, we healed the structural imperfections of Sn perovskites in an "inside-out" manner by incorporating a new class of biocompatible chelating agent with multidentate claws, namely, 2-Guanidinoacetic acid (GAA), which passivated a variety of deep-level Sn-related and I-related defects, cooperatively reinforced the passivation efficacy, released the lattice strain, improved the structural toughness, and promoted the carrier transport of Sn perovskites. Encouragingly, an efficiency of 13.7 % with a small voltage deficit of ≈0.47 V has been achieved for the GAA-modified Sn-PSCs. GAA modification also extended the lifespan of Sn-PSCs over 1200 hours.

Zero-Dimensional Zn-Based Halides with Ultra-Long Room-Temperature Phosphorescence for Time-Resolved Anti-Counterfeiting.

Though fluorescence-tag-based anti-counterfeiting technology has distinguished itself with cost-effective features and huge information loading capacity, the clonable decryption process of spatial-resolved anti-counterfeiting cannot meet the requirements for high-security-level anti-counterfeiting. Herein, we demonstrate a spatial-time-dual-resolved anti-counterfeiting system based on new organic-inorganic hybrid halides BAPPZn2 (Cly Br1-y )8 (BAPP=1,4-bis(3-ammoniopropyl)piperazinium, y=0-1) with ultra-long room-temperature phosphorescence (RTP). Remarkably, the afterglow lifetime can be facilely tuned by regulating the halide-induced heavy-atom effect and can be identified by the naked eyes or with the help of a simple machine vision system. Therefore, the short-lived unicolor fluorescence and lasting-time-tunable RTP provide the prerequisites for unicolor-time-resolved anti-counterfeiting, which lowers the decryption-device requirements and further provides the design strategy of advanced portable anti-counterfeiting technology.

Water-Molecule-Induced Emission Transformation of Zero-Dimension Antimony-Based Metal Halide.

Low-dimensional organic-inorganic metal halides have recently emerged as a class of promising luminescent materials. However, the intrinsic toxicity of lead would strongly hamper future application. Herein, we synthesized a new type of lead-free zero-dimensional (0D) antimony-based organic-inorganic metal halide single crystals, (PPZ)2SbCl7·5H2O (PPZ = 1-phenylpiperazine), which features a broadband emission at 720 nm. Ultrafast transient absorption and temperature-dependent photoluminescence (PL) spectra are combined to investigate the PL mechanism, revealing that self-trapped exciton recombination was involved. Furthermore, it is interesting that (PPZ)2SbCl7·5H2O material shows reversible PL emission transformation between red light (720 nm) and yellow light (590 nm) as water molecules are inserted or removed from the lattice. Such reversible emission transformation phenomenon renders the (PPZ)2SbCl7·5H2O as a potential low-cost water sensing material.

Indium-antimony-halide single crystals for high-efficiency white-light emission and anti-counterfeiting.

Although single-source white emissive perovskite has emerged as a class of encouraging light-emitting material, the synthesis of lead-free halide perovskite materials with high luminous efficiency is still challenging. Here, we report a series of zero-dimensional indium-antimony (In/Sb) alloyed halide single crystals, BAPPIn2-2x Sb2x Cl10 (BAPP = C10H28N4, x = 0 to 1), with tunable emission. In BAPPIn1.996Sb0.004Cl10, bright yellow emission with near 100% photoluminescence quantum yield (PLQY) is yielded when it was excited at 320 nm, which turns into bright white-light emission with a PLQY of 44.0% when excited at 365 nm. Combined spectroscopy and theoretical studies reveal that the BAPP4+-associated blue emission and inorganic polyhedron-afforded orange emission function as a perfect pair of complementary colors affording white light in BAPPIn1.996Sb0.004Cl10 Moreover, the interesting afterglow behavior, together with excitation-dependent emission property, makes BAPPIn2-2x Sb2x Cl10 as high-performance anti-counterfeiting/information storage materials.

Superlubricity between a silicon tip and graphite enabled by the nanolithography-assisted nanoflakes tribo-transfer.

Superlubricity between a cone-shaped (sharp) silicon tip and graphite remains a challenge in the nanotribology field. In this paper, an efficient method of achieving superlubricity between a cone-shaped silicon tip and graphite was proposed. Graphite nanoflakes were transferred onto the silicon tip by repeatedly rubbing against the scratches produced by nanolithography on a graphite surface. The superlubricity between the graphite nanoflakes-wrapped tip and highly oriented pyrolytic graphite (HOPG) was attained, and the friction coefficient was reduced to 0.0007. At low normal loads, the frictional force was small and showed a strong correlation with the sliding angle, but as the normal load increased, this dependence gradually decreased. It was firstly found that the transferred graphite nanoflakes on the contact zone of the silicon tip could be transformed into amorphous carbon layers induced by the shear force and high pressure during the superlubricity test process.

Electrical friction modulation on MoS2 using electron beam radiation without electrostatic interactions.

Nanoscale friction under different electronic states and the corresponding friction controlling methods are both scientifically interesting and technologically important. However, friction measurements under electrical modulation are severely hampered by electrostatic forces induced by the charge-trapping effect. Therefore, in this study, we developed a new modulation method free from the charge-trapping effect through electron beam radiation; this method successfully modulated the friction between few-layer MoS2 and the silicon tip on atomic force microscopy. Friction on monolayer MoS2 increased under electron beam radiation. Strong correlations between the accelerating voltage, beam current, and friction force were found, and constant adhesion force demonstrate that the influence of static electricity was eliminated in this method. Excited electron states caused by electron injection could be possible mechanisms for friction modulation. However, the electron beam radiation had a negligible influence on the friction of bilayer MoS2. This study is the first of its kind, revealing the effect of electron beam radiation and electronic states on friction, which is important for the development of tribological theories and nanoelectromechanical systems, and offers a new electrical modulation method for friction tuning.

Structural Health Monitoring System Based on FBG Sensing Technique for Chinese Ancient Timber Buildings.

Due to the long-term service, Chinese ancient timber buildings show varying degrees of wear. Thus, structural health monitoring (SHM) for these cultural and historical treasures is desperately needed to evaluate the service status. Although there are some FBG sensing-based SHM systems, they are not suitable for Chinese ancient timber buildings due to the differences in architectural types, structural loads, materials, and environment. Besides, a technical gap in Fiber Bragg grating (FBG) sensing-based column inclination monitoring exists. To overcome these weaknesses, this paper develops an FBG sensing-based structural health monitoring system for Chinese ancient Chuan-dou-type timber buildings that aims at monitoring structural deformation, i.e., beam deflection and column inclination, temperature, humidity, and fire around the building. An in-situ test and simulation analyses were conducted to verify the effectiveness of the developed SHM system. To validate the long-term-operation of the developed SHM system, monitoring data within 15 months were analyzed. The results show good agreement between the developed SHM system in this paper and other methods. In addition, the SHM system operated well in the first year after its deployment. This implies that the developed SHM system is applicable and effective in the health state monitoring of Chinese ancient Chuan-dou-type timber buildings, laying a foundation for damage prognosis of such types of timber buildings.

Stepwise dual pH and redox-responsive cross-linked polypeptide nanoparticles for enhanced cellular uptake and effective cancer therapy.

The systemic toxicity, reduced cellular internalization, and uncontrollable intracellular drug release of smart nanoparticles (NPs) still need to be overcome for effective cancer therapy. Herein, a series of stepwise dual pH and redox responsive cross-linked polypeptides based on poly(l-lysine-co-N,N-bis(acryloyl)cystamine-co-γ-glutamic acid) (PLBG), were prepared for enhanced cellular uptake and effective cancer therapy. The prepared cross-linked PLBG nanoparticles (PLBG-NPs) exhibit negatively charged surfaces under physiological conditions, and the surface charge of the PLBG-NPs was observed to switch from negative to positive in a slightly acidic tumor extracellular environment at a pH level of ∼6.5. Finally, the endosome escape of the PLBG-NPs was facilitated via a "proton-sponge" effect via protonation of the polymer chain in the endo/lysosome environment of the tumor cell at a pH level of ∼5.0. Moreover, rapid drug release was triggered by a high concentration of reducing glutathione (GSH) in tumor cells via destruction of the disulfide linkages in the PLBG-NPs. Cytotoxicity assays demonstrated that no noticeable cytotoxicity was observed for the PLBG-NPs. However, DOX-loaded PLBG-NPs (PLBG-NPs-DOX) demonstrated remarkable tumor cell killing effects. In HeLa tumor-bearing mice, PLBG-NPs-DOX showed sustained tumor accumulation and enhanced inhibitory effects on tumor growth and angiogenesis. In conclusion, it is suggested that the as-designed novel charge-conversion PLBG-NPs with stepwise pH-responsivity and biodegradability could be used as a potential drug carrier for effective cancer therapy with less systemic toxicity.

Reduction/temperature/pH multi-stimuli responsive core cross-linked polypeptide hybrid micelles for triggered and intracellular drug release.

The high toxicity, poor stability, premature drug release, and lack of intracellular stimuli responsibility of current polymeric micelles still hinder them for potential clinical applications. To address these challenges, a novel type of multi-stimuli responsive, core cross-linked polypeptide hybrid micelles (CCMs) was developed for triggered anticancer drug delivery in tumor microenvironment. The CCMs was prepared via free radical copolymerization by using N,N'-methylene-bis-acylamide (BACy) as the cross-linking agent, 2,2-azobisisobutyronitrile (AIBN) as the initiator, where poly (γ-benzyl-L-glutamate) (PBLG) and N-isopropylacrylamide (NIPPAM) as comonomers. The doxorubicin (DOX) was then introduced into the CCMs by hydrazone bond to prepare the drug-incorporated core cross-linked micelles (CCMs-DOX). By the experimental results, the CCMs showed reduction responsibility due to the degradable disulfide bond in the polymer network. The hydrazone bond can be broken under acidic condition causing a controllable drug release for CCMs-DOX. Compared to only 7.7% DOX release under pH 7.4 at 37°C, a much higher DOX release rate up to 85.3% was observed under 10 mM GSH (pH 5.0, 42°C). In vitro cell assays showed that the blank CCMs showed almost no toxicity against HUVEC cells while the CCMS-DOX exhibited significant cancer cell killing effect. These experimental results suggested that the prepared multi-stimuli responsive polymeric micelles could serve as a smart and promising drug delivery candidate for anti-cancer therapy.

Microstructure Evolution and Flow Stress Model of a 20Mn5 Hollow Steel Ingot during Hot Compression.

20Mn5 steel is widely used in the manufacture of heavy hydro-generator shaft due to its good performance of strength, toughness and wear resistance. However, the hot deformation and recrystallization behaviors of 20Mn5 steel compressed under high temperature were not studied. In this study, the hot compression experiments under temperatures of 850-1200 °C and strain rates of 0.01/s-1/s are conducted using Gleeble thermal and mechanical simulation machine. And the flow stress curves and microstructure after hot compression are obtained. Effects of temperature and strain rate on microstructure are analyzed. Based on the classical stress-dislocation relation and the kinetics of dynamic recrystallization, a two-stage constitutive model is developed to predict the flow stress of 20Mn5 steel. Comparisons between experimental flow stress and predicted flow stress show that the predicted flow stress values are in good agreement with the experimental flow stress values, which indicates that the proposed constitutive model is reliable and can be used for numerical simulation of hot forging of 20Mn5 hollow steel ingot.

Hot Deformation Behavior and a Two-Stage Constitutive Model of 20Mn5 Solid Steel Ingot during Hot Compression.

20Mn5 steel is widely used in the manufacture of heavy hydro-generator shaft forging due to its strength, toughness, and wear resistance. However, the hot deformation and recrystallization behaviors of 20Mn5 steel compressed under a high temperature were not studied. For this article, hot compression experiments under temperatures of 850-1200 °C and strain rates of 0.01 s-1-1 s-1 were conducted using a Gleeble-1500D thermo-mechanical simulator. Flow stress-strain curves and microstructure after hot compression were obtained. Effects of temperature and strain rate on microstructure are analyzed. Based on the classical stress-dislocation relationship and the kinetics of dynamic recrystallization, a two-stage constitutive model is developed to predict the flow stress of 20Mn5 steel. Comparisons between experimental flow stress and predicted flow stress show that the predicted flow stress values are in good agreement with the experimental flow stress values, which indicates that the proposed constitutive model is reliable and can be used for numerical simulation of hot forging of 20Mn5 solid steel ingot.

Surface design and preparation of multi-functional magnetic nanoparticles for cancer cell targeting, therapy, and imaging.

Recently, theranostic candidates based on superparamagnetic iron oxide nanoparticles (SPIONs) providing the combination of therapy and diagnosis have become one of the most promising system in cancer research. However, poor stability, premature drug release, lack of specific tumor cell targeting, and complicated multi-step synthesis processes still hinder them for potential clinical applications. In this research, the multi-functional magnetic nanoparticles (MNPs-DOX) were prepared via a simple assembly process for targeted delivery of doxorubicin (DOX) and enhanced magnetic resonance (MR) imaging detection. Firstly, the multi-functional copolymer coating, polyamidoamine (PAMAM), was designed and synthesized by Michael addition reaction, where N,N-bis(acryloyl)cystamine served as backbone linker, and DOX, dopamine (DA), and polyethylene glycol (PEG) acted as comonomers. The PAMAM was then directly assembled to the surface of SPIONs by the ligand exchange reaction with SPIONs forming the MNPs-DOX. The hydrophilic PEG moieties provide the nanoparticles with colloidal stability and good-dispersity in aqueous solution. Comparing with the quick release of free DOX, the drug release behavior of MNPs-DOX exhibited a sustained drug release. Because the chemical cleavage of disulfide in the polymer backbone, a high cumulative drug release up to 60% in GSH within 48 h was observed, rather than only 26% in PBS (pH 7.4) without GSH. The MR imaging detection experiment showed that the MNPs-DOX had an enhanced T 2 relaxivity of 126 mM-1 S-1 for MR imaging. The results of the cytotoxicity assays showed a remarkable killing effect of cancer cells by MNPs-DOX due to the FA tumor-targeting ligand, comparing with non-targeted drug molecules. All the results showed that the as prepared multi-functional magnetic nanoparticles may serve as a promising theranostic candidate for targeted anticancer drug delivery and efficient detection through MR imaging in medical application.

Thickness dependent friction on few-layer MoS2, WS2, and WSe2.

Nanoscale friction on two-dimensional (2D) materials is closely associated with their mechanical, electronic and photonic properties, which can be modulated through changing thickness. Here, we investigated the thickness dependent friction on few-layer MoS2, WS2, and WSe2 using atomic force microscope at ambient condition and found two different behavior. When a sharp tip was used, the regular behavior of decreasing friction with increasing thickness was reproduced. However, when a pre-worn and flat-ended tip was used, we observed an abnormal trend: on WS2 and WSe2, friction increased monotonically with thickness, while for MoS2, friction decreased from monolayer to bilayer and then subsequently increased with thickness. As suggested by the density functional theory calculation, we hypothesize that the overall frictional behavior is a competition between the puckering effect and the intrinsic energy corrugation within the compressive region. By varying the relative strength of the puckering effect via changing the tip shape, the dependence of friction on sample thickness can be tuned. Our results also suggest a potential means to measure intrinsic frictional properties of 2D materials with minimum impact from puckering.

Assessment of the associations between three VEGF polymorphisms and risk of prostate cancer.

Vascular endothelial growth factor (VEGF) plays a crucial role in the regulation of angiogenesis and is involved in the development and metastasis of common cancers. There were several case-controls studies published to assess the associations of VEGF polymorphisms with risk of prostate cancer, but the findings were inconsistent. We performed a meta-analysis to provide a comprehensive assessment of the associations of three VEGF polymorphisms with risk of prostate cancer. The pooled odds ratio (OR) with 95% confidence interval (95% CI) was calculated to assess the associations. Eleven individual case-control studies with a total of 5,209 cases of prostate cancer and 5,233 controls were finally included into our meta-analysis. Overall, VEGF rs833061 polymorphism was not associated with risk of prostate cancer (T versus C, OR = 1.14, 95% CI 0.91-1.44, P = 0.26; TT versus CC, OR = 1.09, 95% CI 0.67-1.76, P = 0.74; TT versus CC/CT: OR = 1.46, 95% CI 0.67-3.18, P = 0.34; TT/CT versus CC, OR = 1.08, 95% CI 0.82-1.43, P = 0.59). VEGF rs3025039 polymorphism was also not associated with risk of prostate cancer (T versus C, OR = 1.03, 95% CI 0.91-1.16, P = 0.66; TT versus CC, OR = 1.82 95% CI 0.16-20.53, P = 0.63; TT versus CC/CT, OR = 2.00, 95% CI 0.18-22.41, P = 0.57; TT/CT versus CC, OR = 0.72, 95% CI 0.38-1.36, P = 0.31). VEGF rs2010963 polymorphism was not associated with risk of prostate cancer under three models (C versus G, OR = 1.17, 95% CI 0.92-1.48, P = 0.20; CC versus GG, OR = 2.28, 95% CI 0.90-5.75, P = 0.08; CC versus GG/GC, OR = 1.57, 95% CI 0.67-3.68, P = 0.30). In conclusison, current data suggest that those three VEGF polymorphisms are not obviously associated with risk of prostate cancer.

Laparoscopic extraperitoneal repair of symptomatic hydrocele in children: a single-center experience with 73 surgeries.

PURPOSE: To introduce a novel, two-port laparoscopic technique for treatment of hydrocele in children, which allows completely extraperitoneal closure of the patent processus vaginalis (PPV) and does not necessitate laparoscopic suturing skills. PATIENTS AND METHODS: We describe a consecutive series of 56 boys with a median age of 36 months (range 12-144 mos) who presented with a presumably communicating hydrocele. Laparoscopic repair of these hydroceles was performed between July 2009 and June 2010. During surgery, a 5-mm laparoscope and a 3-mm grasping forceps were inserted through an identical umbilical incision (10 mm). The hydrocele sac orifice was closed extraperitoneally by circuit suturing around the internal inguinal ring. RESULTS: All cases were preoperatively diagnosed to be unilaterally based on physical examination and ultrasonography. During surgery, 17 of the 56 (30%) patients presented a contralateral PPV. A total of 73 laparoscopic procedures were achieved, with a success rate of 100%. The mean operative time was 25±6 and 36±5 minutes for unilateral and bilateral operations, respectively. During a median follow-up period of 6 months (range 1-12 mos), neither recurrence nor other postoperative complication was encountered. CONCLUSIONS: Our limited experiences suggest that the two-port, totally extraperitoneal laparoscopic technique could be a safe, effective, and reliable alternative for management of pediatric hydrocele.