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All‐inorganic perovskite quantum dots (QDs) with high photoluminescence quantum yield, narrow spectral bandwidth, and broad spectral tunability have broad applications. However, perovskite QDs suffer from poor stability and the fast anion‐exchange reaction between different halide ions. Herein, we embedded green‐light‐emitting CsPbBr3 QDs and red‐light‐emitting CsPb(Br/I)3 QDs into carboxyl‐containing polymethyl methacrylate (PMMA) by the hot‐injection method. As a result, the as‐prepared perovskite@PMMA composites not only retain high luminescence but also exhibit good water resistance. Moreover, this treatment prevents anion exchange between different halide QD particles in the solid state. The applications in light‐emitting diodes and cellular labeling agents are also carried out to demonstrate their good stability. Waterproof particles: CsPbBr3 particles were successfully encapsulated into carboxyl‐containing PMMA and exhibited good stability in water. The water resistance of 500 nm CsPbBr3@PMMA composites was tested (figure shows photographs of the composites water solution under daylight and UV light). The relative PL emission intensity decreased very slowly over time, retaining 90% of its original value after 12 h exposure to water. [ABSTRACT FROM AUTHOR]

Near-infrared-downconversion-near-infrared (NIR-DC-NIR) bioimaging based on lanthanide doped upconversion nanoparticles (UCNPs) has received much attention due to its deeper penetration, and higher contrast imaging and signal-to-noise ratio in biological tissues. The size of UCNPs determines the mechanism and rate of cell uptake of the nanoparticles and their ability to permeate through biological tissues. Herein, we experimentally and theoretically demonstrate downconversion-near-infrared (DC-NIR) emission behavior in different sized UCNPs ranging from 5–150 nm. Interestingly, 15–40 nm UCNPs have more effective DC-NIR emissions than 150 nm UCNPs and an extremely high excitation threshold, which is entirely different from the size-dependent upconversion-visible (UC-VIS) emissions usually observed in UCNPs. We also observed that the intensity ratio of the DC-NIR emission to the UC-VIS emission decreases with the increase of the particle size and the excitation power, attributed to the more efficient upconversion (UC) process. Finally, we further confirmed that the competition process between the UC population and non-radiative relaxation to the DC-NIR level plays a key role in size-independent DC-NIR emissions. Our discovery would provide guidance for optimizing and designing NIR-DC-NIR NPs for bioimaging applications. [ABSTRACT FROM AUTHOR]

Localized electric filed enhancement by surface plasmon resonance (SPR) of noble metal nanoparticles is an effective method to amplify the upconversion luminescence (UCL) strength of upconversion nanoparticles (UCNPs), whereas the highly effective UCL enhancement of UCNPs in colloids has not been realized until now. Here, we designed and fabricated the colloidal Au-Ag nanocage@NaYF4@NaYF4:Yb,Er core-shell hybrid with different intermediate thickness (NaYF4) and tunable SPR peaks from visible wavelength region to NIR region. After the optimization of the intermediate spacer thickness (~7.5 nm) of NaYF4 NPs and the SPR peak (~950 nm) of noble metal nanoparticles, an optimum enhancement as high as ~25 folds was obtained. Systematic investigation indicates that UCL enhancement mainly originates from the influence of the intermediate spacer and the coupling of Au-Ag nanocages with the excitation electromagnetic field of the UCNPs. Our findings may provide a new thinking on designing highly effective metal@UCNPs core-shell hybrid in colloids. [ABSTRACT FROM AUTHOR]

The present study involved preparing five novel Fe-Cr-Al alloy steels with varying Al content based on commercially available 3Cr steel. The effect of Al content on the mechanical properties and corrosion performance in a CO 2 -O 2 coexistence environment was investigated in novel Fe-3Cr-(0–2.5)Al alloy steels, and the microhardness, impact, and tensile properties were measured and compared. The corrosion rate, corrosion product film, and corrosion mechanism were studied using a weight-loss method, microscopic characterization, and electrochemical tests. The results showed that the tensile and impact properties of Fe-Cr-Al alloy steels exhibited a decreasing trend with increasing Al content. No localized corrosion was observed at an Al content of 2 wt%, attributed to the formation of a dense amorphous corrosion product film on the material surface and pre-passivation. Among the alloy steels examined in this study, the 3Cr2Al alloy steel exhibited the most optimal balance between mechanical properties and corrosion resistance. • Five novel Fe-Cr-Al alloy steels were successfully prepared. • The optimal Al content for balancing mechanical and corrosion properties was given. • Enhancement mechanism of CO 2 -O 2 corrosion resistance in Fe-Cr-Al alloy steel through the addition of Al. [ABSTRACT FROM AUTHOR]

The meter reading with machine vision greatly improves the efficiency of industrial monitoring. However, the pointer and scales of the meter can be occluded by rain or dirt, which greatly reduces the accuracy of the meter reading recognition. To solve this problem, we propose a generative adversarial network (PMS-GAN) with pointer generation and main scale detection for occluded meter reading. Specifically, dilated convolution block is designed to correlate separated pointer features. Then multi-scale feature fusion mechanism is proposed to guarantee the precision of pointer generation and main scale detection with guidance of semantic information. Moreover, feature enhancement mechanism is proposed to construct the long-range relationship for generating pointer under high occlusion. Finally, the reading is accomplished by calculating local angle with generated pointer and detected main scales. Experiments show that PMS-GAN can generate more intact pointer and detect main scales to guarantee the success and accuracy of occluded meter reading. • PMS-GAN is proposed to read meter with occluded pointer and scales. • DC block is designed to correlate the separated features for pointer generation. • The MFFM and FEM are proposed to enhance the generation ability of PMS-GAN. • The proposed reading calculation guarantees the accuracy of reading occluded meter. • The proposed PMS-GAN improves success rate and accuracy for reading occluded meter. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lead-free 0D K 3 SbCl 6 perovskite nanocrystals are firstly synthesized. • Mn2+ ions doped 0D K 3 SbCl 6 perovskite nanocrystals are successfully synthesized. • The white emission is realized in Mn2+-K 3 SbCl 6 perovskite nanocrystals. • The WLED based on Mn2+- K 3 SbCl 6 perovskite NCs with different CCT are realized. In recent years, the lead-free zero-dimensional (0D) perovskite nanocrystals (NCs) with isolated octahedral structure have attracted wide attentions due to their unique photoelectric properties, such as the excellent absorption cross-sections, large exciton binding energy and low carrier mobility. However, the emitting wavelength of the lead-free 0D perovskite NCs can only be modulated in the green and blue spectral region. Until now, how to realize the red and white emission in the lead-free 0D perovskite NCs is still a challenge. In this work, the lead-free 0D K 3 SbCl 6 perovskite NCs were firstly developed by the hot injection synthesis method. Through controlling the synthetic temperature, the as-prepared NCs exhibit the blue emission centered at 440 nm with the highest photoluminescence quantum yield (PLQY) of 22.3%. Furthermore, the Mn2+ ions were further doped into 0D lead-free K 3 SbCl 6 perovskite NCs, leading to the additional red light emission attributed to the intrinsic transition (4T 1 −6A 1) of Mn2+ ions. By controlling the Mn2+ ion doping concentration, the white light emission with PLQY of 37.2% was realized. Finally, the white light emitting devices (WLEDs) with the Commission Internationale de L'Eclairage 1931(CIE) of (0.29, 0.28), (0.32, 0.30) and (0.35, 0.30) were fabricated by combining the as-prepared Mn2+-K 3 SbCl 6 perovskite NCs with commercial 365 nm UV light chips. The white-light performances of the as-fabricated WLEDs were modulated with tunable correlated color temperature (CCT) from 8173 to 4779 K, which exhibit the high color-rendering index (CRI) more than 80. These results provide the opportunity for the future applications of 0D lead-free perovskite NCs in the lighting and lasing field of LEDs. [ABSTRACT FROM AUTHOR]

Abstract Due to the ultrathin structure, functional groups and excellent physical-chemical properties, Two-dimensional (2D) MXenes shows great potential for biomedical applications. Here, we prepared TiO 2 inverse opal photonic crystals (IOPCs)/Ti 3 C 2 quantum dots (QDs) composite film through the self-assembly method. Because of the widen absorption band of Ti 3 C 2 QDs, TiO 2 IOPCs/Ti 3 C 2 composite film could have photocurrent effect from 280 to 900 nm, and the internal power conversion efficiency could reach to 26% at 350 nm. Owing to favourable energy levels, Ti 3 C 2 QDs were formed the Type-II Heterojunction with TiO 2 , thus enabling directional transport charge for efficient charge separation. The Type-II Heterojunction photoelectrochemical (PEC) sensor consisting of TiO 2 /Ti 3 C 2 /Nafion electrode exhibited high stability, sensitivity, and selectivity for the detection of glutathione in buffered solution and cell extracts. Thus, the TiO 2 /Ti 3 C 2 /Nafion composite film provides a promising green electrode for sensitive PEC detection, which could realize some potential applications for disease early precaution and diagnose. [ABSTRACT FROM AUTHOR]

The ultraviolet (UV)-blue radiation of sunlights usually induce the photodegradation of organic photovoltaic materials, leading to the lifetime degeneration of solar cells. A luminescent converter layer for UV-blue to visible photoconversion is a promising way to harvest UV-blue sunlights and transforms them into visible lights that can be directly absorbed by active materials of solar cells. In this work, highly transparent Ag/YVO 4 :Eu 3+ /PMMA film were fabricated, which could not only filter out the harmful UV light as well as absorb multiband wavelengths ranging of 400–540 nm, but also could convert them into red lights which match well with band gap of photovoltaic materials. Then, we experimentally and theoretically investigated the luminescence enhancements with various Ag nanoparticles (NPs) size, concentration and excitation wavelengths. The luminescent enhancements were realized under the multiband wavelength excitation ranging of 280–538 nm. The maximum luminescence enhancement is 23-fold for Ag/YVO 4 :Eu 3+ /PMMA film under the excitation wavelength of 468 nm matching well with the localized surface plasmonic resonance (LSPR) of Ag NPs. Furthermore, we provide evidence that such enhancement is resulted from excitation field enhancement instead of Purcell effect. Our findings provide us a thinking on designing highly effective and transparent plasmon/luminescent converter, which may be utilized to improve the photostability and efficiency of solar cells. [ABSTRACT FROM AUTHOR]

Room temperature phosphorescence (RTP) materials are highly attractive in many fields, but it is still a great challenge to obtain RTP materials with color tunability. Herein, we report a new type of multicolor phosphorescence carbon dots (CDs) through confining CDs into rigid crystal network through the introduction of ionic bonds. The RTP color can rationally vary from green (553 nm) to orange-red (640 nm) under different excitation wavelengths. More importantly, the obtained CDs can also maintain their RTP emission in ethanol solution. The excitation-dependent property was owing to the existence of polychromatic emission centers on the surface of CDs, and the generation of RTP can be attributed to the ionic bond in CDs system to suppress non-radiative transition of triplet states. Based on this unique multicolor RTP phenomenon, the CDs were successfully applied in anticounterfeiting and light-emitting diodes. This finding not only provides a new strategy for the preparation of multicolor RTP materials but also reveals a great potential of CDs in developing novel optical materials. [Display omitted] • We report a new type of color-tunable phosphorescence carbon dots (CDs) under ambient conditions. • The RTP color can rationally vary from 553 to 640 nm. • The CDs ethanol solution also maintained a bright RTP (625 nm). • Based on this unique color-tunability RTP phenomenon, the CDs were successfully applied in anticounterfeiting and light-emitting diodes (LEDs). [ABSTRACT FROM AUTHOR]

Color-tunable phosphorescence has received extensive attention in recent years. Herein, a facile approach for the synthesis of carbon dots (CDs) in urea crystals (referred to as uCDs) is reported. Excitation dependence under ambient conditions and multicolor room temperature phosphorescence (RTP), changing from yellow–green (570 nm) to orange (610 nm) at excitation wavelengths of 365 and 460 nm, is observed in the synthesized uCDs. The multicolor emission can be attributed to the existence of multiple emitting centers in the uCDs and it is determined that hydrogen bonding plays a critical role in achieving RTP. High intensity phosphorescence was achieved by external heating of the prepared uCDs@150, which forms a tighter rigid urea matrix and results in an attained lifetime of 281 ms. Based on these unique color-tunable properties, the synthesized uCDs@150 have potential applications in anticounterfeiting and light-emitting diode technologies. This study not only proposes a strategy to prepare photo-stimulated multicolor RTP materials, but also reveals the potential of CDs in exploiting novel optical materials with unique properties. • Carbon dots with emission wavelength above 600 nm were successfully prepared. • Multiple emission centers exist for carbon dots. • By reheating, the luminescence intensity of carbon dots was increased by about 2 times. • The carbon dot afterglow lifetime was increased by about three times by reheating. [ABSTRACT FROM AUTHOR]

Upconversion (UC) nanomaterials with the ability to convert incident infrared photons to visible or ultraviolet emissions have attracted remarkable interest and hold great promising applications ranging from bioimaging to display devices. However, their low UCL efficiency does not satisfy the requirement of various practical applications. In this work, we successfully prepared Dy 2 O 3 /Au and Sm 2 O 3 /Au nanocomposites by a simple co-precipitation method. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy were used to characterize the samples. The UC broadband enhancements illuminating with various power density of 980 nm are systemically investigated. The maximum UCL enhancement is 35-fold and 48-fold for Dy 2 O 3 /Au and Sm 2 O 3 /Au nanocomposites under 980 nm excitation. The UC population processes and enhancement mechanism are carefully studied. The luminescence enhancement in the composites is mainly attributed to the enhanced thermal effect. [ABSTRACT FROM AUTHOR]

• Al3+-Cs 2 AgBiCl 6 NCs are successfully synthesized. • Al3+-Cs 2 AgBiCl 6 NCs show bright STE emission with PLQY ∼17.2%. • Al3+-Cs 2 AgBiCl 6 NCs exhibit ultrahigh air stability. • A WLED based on lead-free perovskite NCs is realized. Lead-free halide perovskite nanocrystals (NCs) have caused widespread concerns for solving the toxicity and instability problems of lead perovskites. Here, we synthesized Al3+-Cs 2 AgBiCl 6. Through controlling the doping content of Al3+ ions, the Al3+-Cs 2 AgBiCl 6 exhibit bright self-trapped exciton (STE) red emission. The photoluminescence quantum efficiency (PLQY) increases significantly from 0.98% to 17.2%, which is higher than the record value (16%) of the currently reported red-emitting lead-free double perovskite. The enhancement of PL of NCs is accomplished by indirect to direct bandgap transition assisted by doping of Al3+ ions, as supported by density functional theory (DFT) calculations. Moreover, the Al3+-Cs 2 AgBiCl 6 exhibit ultrahigh stability and can maintain their original structure for more than 7 months, which demonstrates the best stability comparing with the reported double perovskite nanocrystals. Finally, the white light emitting diode (WLED) was fabricated. These results provide opportunities for the future application of lead-free double perovskite in the field of optoelectronics. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Lanthanide acetate promoted CsPbCl 3 NWs were firstly synthesized. • Effect of lanthanide and AcO− ions in the formation of CsPbCl 3 NWs was demonstrated. • CsPbCl 3 NWs with low trap density and high carries separation efficiency were realized. • Self-powered UV photodetector of CsPbCl 3 NWs was fabricated for the first time. Recently, photodetectors based on perovskite nanomaterials have attracted considerable attention in the visible spectral region owing to their large absorption coefficients, long diffusion lengths and high optical gains. However, the fabrication of self-powered visible-blind ultraviolet (UV) photodetectors is still challenging for the perovskite nanomaterials. This work developed the self-powered UV photodetector based on the Eu(AcO) 3 promoted CsPbCl 3 nanowires (NWs), enabled by the great separation efficiency of electron-hole pairs and high electron mobility of the one-dimentional (1D) morphology of perovskite materials. The perovskite CsPbCl 3 NWs were synthesized by a modified hot-injection method with assistant of Eu(AcO) 3 additive. As supported by the experimental investigations and DFT calculations, the adsorption of Eu3+ and AcO− ions to the surface of perovskite not only promotes the anisotropic growth of perovskite in (2 0 0) orientation, but also efficently passivates the halide defect of the perovskite nanomaterials. Moreover, the self-powered UV photodetector based on the Eu(AcO) 3 promoted CsPbCl 3 NWs displays a high responsivity of 398 mA W−1, detectivity up to 3.3 × 1011 Jones and fast response speed (24 ms) at 360 nm without external bias. The responsivity and detectivity of the device based on CsPbCl 3 NWs are improved 8 and 205 times, comparing with the device based on bare CsPbCl 3 NCs without passivation, respectively. In addition, the detectivity is comparable to some previous reports about perovskite NC-based UV photodetectors with additional bias. Our findings demonstrate the promising potential of 1D perovskite NWs for developing the next-generation self-powered UV photodetectors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Au NRs in situ chemically anchored onto the Ti 3 C 2 QDs-interspersed Ti 3 C 2 nanosheet. • Plasmon-induced hot electrons could efficiently transfer from Au NRs to TDTS. • Au NRs/TDTS composite was employed to the full-spectrum PEC water splitting. • Au NRs/TDTS composite displayed a stable and remarkable gas production rate. Efficient utilization of solar energy for economical photoelectrochemical (PEC) water splitting requires highly active and stable photoelectrodes with the abilities of harvesting broadband light from ultraviolet to infrared. Herein, we report on the synthesis and characterization of plasmonic gold nanorods (NRs) in situ decorated onto the Ti 3 C 2 MXene quantum dots-interspersed Ti 3 C 2 nanosheet (TDTS) as well as their implementation as photoanodes for full-spectrum solar-light-activated PEC water splitting. The TDTS is prepared by a hydrothermal method, followed the plasmonic Au NRs chemically anchored on the surface of TDTS via a seed growth method. Under the illumination of simulated solar light (100 mW cm−2), the optimized Au NRs/TDTS hybrid composite displays a stable and remarkable gas production rate that is about 3.4 times higher than that of pristine TDTS, and broadened spectral response range of 300–1100 nm. Such high performance arises from the generating strong plasmon-induced hot electrons of Au NRs that inject into TDTS with efficient charge separation and transfer at the interface. X-ray photoelectron spectroscopy and femtosecond time-resolved transient absorption measurements provide direct evidences that the plasmon-induced interfacial hot electrons could efficient transfer from Au to TDTS with the quantum efficiency of 16 ± 5%. This strategy provides an avenue for designing plasmon-mediated composite systems to effectively harvest full-spectrum solar light conversion into chemical energy. [ABSTRACT FROM AUTHOR]

A large area TiO 2 film supported by vertically ordered Au nanorod superlattice array (O-AuNRs/TiO 2) is fabricated on a glass substrate. Compared to both pristine TiO 2 film and the TiO 2 film supported by randomly-oriented AuNRs (R-AuNRs/TiO 2), the O-AuNRs/TiO 2 delivers highly enhanced photocatalytic hydrogen evolution rate, benefiting from the significant localized surface plasmon resonance (LSPR) enhancement by O-AuNRs. [Display omitted] • TiO 2 film supported by Au nanorod superlattice array (O-AuNRs/TiO 2) was fabricated on a glass. • Well-ordered and closely-packed AuNR superlattice dramatically boosts the local electromagnetic field. • O-AuNRs architecture plays a key role in enhancing the photocatalytic activity of TiO 2 film. • O-AuNRs/TiO 2 exhibits a highly enhanced photocatalytic hydrogen evolution rate, 58 times of unsupported TiO 2 film. Photocatalytic hydrogen generation from water as a renewable non-polluting technique for converting solar energy to chemical energy has recently attracted worldwide attention. However, low hydrogen production efficiency of traditional photocatalysis still remains as a challenge. Here, we report a large area TiO 2 film supported by vertically ordered Au nanorods superlattice array (O-AuNRs/TiO 2), which demonstrates excellent photocatalytic performances of hydrogen evolution from water under solar and visible light irradiation. The O-AuNRs/TiO 2 architecture enables the significant localized surface plasmon resonance (LSPR) enhancement, including both local electromagnetic field effect and hot electron transfer effect, which promotes the photocatalytic hydrogen evolution rate of the TiO 2 film by 58 times. The photocatalytic efficiency of O-AuNRs/TiO 2 exceeds that of the TiO 2 film supported by randomly oriented AuNRs by over five times. Finite difference time domain (FDTD) modeling results support that the strong coupling of O-AuNRs enhances the electromagnetic field intensity along the longitudinal axis in the gaps between adjacent AuNRs and the average electric field enhancement factors at the interface between the AuNRs and TiO 2 of O-AuNRs/TiO 2. This work demonstrates the substantial performance boost of conventional photocatalyst by LSPR enhancement, thus provides a promising tactic to devise highly efficient photocatalytic system for solar energy conversion. [ABSTRACT FROM AUTHOR]