Sharp Emission Research Articles

Effect of annealing temperatures on the structural and photoluminescence properties of Tb3+ ions doped BiPO4 nanophosphors

ABSTRACT In this paper the synthesis of BiPO4:Tb3+ phosphor by co-precipitation method and effects of annealing temperature on its structural, crystallinity and photoluminescence properties have been investigated. The crystallinity of the phosphor was found to increase up to 800°C of annealed temperature for 2 h without changing its phase. However, a change from low temperature monoclinic phase to high temperature monoclinic phase was observed when annealed at 1000°C for 2 h. Photoluminescence spectra showed strong and sharp emission peaks of Tb3+ upon excitation at 351 nm and the peaks intensities were found to increase with increase of annealing temperature up to 800°C. However intensities were found decreasing drastically for 1000°C annealed sample, which may be due to the change of phase upon annealing. Emission of cyan colour was observed from CIE study. These observations indicate that the prepared phosphors may have potential applications in solid-state lighting systems.

Photoluminescence and scintillation properties of Eu-doped Ga2O3 single crystals grown by the floating zone method

We developed undoped, Eu 1%-, 3%-, and 10%-doped Ga2O3 samples by the floating zone method to evaluate their photoluminescence and scintillation properties. The photoluminescence of the undoped, Eu 1%-, and 3%-doped samples showed intense host emission in the UV–vis range, while the Eu 10%-doped sample exhibited strong emission at 700–800 nm. In the scintillation spectra obtained upon X-ray excitation, host emission was observed in all the samples, and the Eu-doped ones exhibited some sharp emission lines due to the 4f–4f transitions of Eu3+. Among the samples investigated, the Eu 1%-doped sample showed the highest emission intensity for both scintillation and thermally stimulated luminescence.

Scintillation characteristics of Nd3+-doped BaO–Al2O3–TeO2 glasses

Photoluminescence and scintillation characteristics of Nd3+-doped TeO2 glasses [(15–x)BaO–5Al2O3–80TeO2–xNd2O3 (x = 0.1–1.0)] were evaluated. The Nd3+-doped TeO2 glasses exhibited sharp emission peaks originating from the 4f–4f transition of Nd3+ in photoluminescence. The 0.1% Nd3+-doped TeO2 glass showed the highest quantum yield (about 33%). In addition, 0.1%–1.0% Nd3+-doped TeO2 glasses showed photoluminescence decay time constants in the time range of 128–194 μs originating from the 4F3/2 → 4I9/2 transition of Nd3+. In scintillation, the 0.1%–1.0% Nd3+-doped TeO2 glasses exhibited sharp scintillation peaks at around 905, 1060, and 1335 nm ascribed to the 4f–4f transitions of Nd3+. The 0.5% and 1.0% Nd3+-doped TeO2 glasses exhibited high intensities. The decay times of the Nd3+-doped TeO2 glasses under X-ray were in the time range of 123–174 μs. Moreover, the Nd3+-doped TeO2 glasses exhibited afterglow levels of about 618–829 ppm.

Importance of BODIPY-based Chemosensors for Cations and Anions in Bio-imaging Applications

Background:Chemosensor compounds are useful for sensitive selective detection of cations and anions with fluorophore groups in an attempt to develop the effective selectivity of the sensors. Although familiar fluorescent sensors utilizing inter-molecular interactions with the cations and anions, an extraordinary endeavor was executed the preparation of fluorescent-based sensor compounds. 4,4-difluoro-4- bora-3a,4a-diaza-s-indacene (Bodipy) and its derivatives were firstly used as an agent in the imaging of biomolecules due to their interesting structures, complexation, and fluorogenic properties. Among the fluorescent chemosensors used for cations and anions, Bodipy-based probes stand out owing to the excellent properties such as sharp emission profile, high stability, etc. In this review, we emphasize the Bodipy-based chemosensor compounds, which have been used to image cations and anions in living cells, because of as well as the biocompatibility and spectroscopic properties.Methods:Research and online content related to chemosensor online activity is reviewed. The advances, sensing mechanisms and design strategies of the fluorophore exploiting selective detection of some cation and anions with Bodipy-based chemosensors are explained. It could be claimed that the using of Bodipy-based chemosensors is very important for cations and anions in bio-imaging applications.Results:Molecular sensors or chemosensors are molecules that show a change can be detected when affected by the analyte. They are capable of producing a measurable signal when they are selective for a particular molecule. Molecular and ion recognition that it is important in biological systems such as enzymes, genes, environment, and chemical fields. Due to the toxic properties of many heavy metal ions, it is of great importance to identify these metals due to their harmful effects on living metabolism and the pollution they create in the environment. This process can be performed with analytical methods based on atomic absorption and emission. The fluorescence methods among chemosensor systems have many advantages such as sensitivity, selectivity, low price, simplicity of using the instrument and direct determination in solutions. The fluorescence studies can be applied at nanomolar concentrations.Conclusion:During a few decades, a lot of Bodipy-based chemosensors for the detection of cations & anions have been investigated in bio-imaging applications. For the Bodipy-based fluorescent chemosensors, the Bodipy derivatives were prepared by different ligand groups for the illumination of the photophysical and photochemical properties. The synthesized Bodipy-based chemosensors have remarkable photophysical properties, such as a high quantum yield, strong molar absorption coefficient etc. Moreover, these chemosensors were successfully implemented on living organisms for the detection of analytes.

Low-temperature large-scale hydrothermal synthesis of optically active PEG-200 capped single domain MnFe2O4 nanoparticles

Herein, we report an intrinsic fluorescence in polyethylene glycol (PEG) coated manganese ferrite (MnFe2O4) magnetic nano particles (MNPs). Generally, nano ferrites (NFs) do not show fluorescence characteristics, however, imparting fluorescence in these materials can be valuable for many applications as the stipulation of external control over the properties by external field provides an opportunity to develop active-controlled devices. In the present work, PEG-200 coated MnFe2O4 MNPs have been synthesized by a large-scale, facile one-pot hydrothermal method. The optical properties of MnFe2O4 MNPs have been by photoluminescence (PL) spectroscopy suggest that the prepared sample is showing sharp emission spectra at 422 nm, corresponding to the violet band, and second at 458 nm corresponding to the blue band. The presence of oxygen vacancy created at both tetrahedral and octahedral sites and shallow hole defects are responsible for the PL behavior in the PEG-coated MnFe2O4. The time-resolved PL (TRPL) results suggest that the MnFe2O4 MNPs have two decay times τ1=1.29ns and τ2=6.85ns which are non-correlated and correspond to different defect states. The electronic bandgap of the MNPs is 3 eV obtained from the Tauc plot using UV absorption spectra. Moreover, the structural analysis has been carried out using X-ray diffraction and various optical and magnetic properties have been correlated to structural parameters and cation distribution. The ferromagnetic resonance (FMR) spectra of the MnFe2O4 MNPs sample show a broad single peak which confirms the ferromagnetic characteristics of the sample and the g-value obtained for the sample is 1.98 which suggests that the super exchange interactions (SEI) dominates over the dipolar interaction. The M-H loop confirms the single domain nature of the sample and the saturation magnetization (SM) is 68 emu/g. The obtained value of SM is higher than the previously reported literature due to an increase in the occupancy of Fe3+ and Mn2+ ions at octahedral sites (Neel’s model). Further, the FTIR spectra confirm the spinel phase formation, and the size distribution and average size are obtained using electron microscopy analysis. The intrinsic fluorescent PEG-coated MnFe2O4 are highly suitable for a diverse range of biomedical (bio-imaging, sensing, magnetic resonance imaging (MRI) contrast agent), optoelectronics, and optical applications.

Hybrid device of hexagonal boron nitride nanoflakes with defect centres and a nano-fibre Bragg cavity

Solid-state quantum emitters coupled with a single mode fibre are of interest for photonic and quantum applications. In this context, nanofibre Bragg cavities (NFBCs), which are microcavities fabricated in an optical nanofibre, are promising devices because they can efficiently couple photons emitted from the quantum emitters to the single mode fibre. Recently, we have realized a hybrid device of an NFBC and a single colloidal CdSe/ZnS quantum dot. However, colloidal quantum dots exhibit inherent photo-bleaching. Thus, it is desired to couple an NFBC with hexagonal boron nitride (hBN) as stable quantum emitters. In this work, we realize a hybrid system of an NFBC and ensemble defect centres in hBN nanoflakes. In this experiment, we fabricate NFBCs with a quality factor of 807 and a resonant wavelength at around 573 nm, which matches well with the fluorescent wavelength of the hBN, using helium-focused ion beam (FIB) system. We also develop a manipulation system to place hBN nanoflakes on a cavity region of the NFBCs and realize a hybrid device with an NFBC. By exciting the nanoflakes via an objective lens and collecting the fluorescence through the NFBC, we observe a sharp emission peak at the resonant wavelength of the NFBC.

The role of CNT in surface defect passivation and UV emission intensification of ZnO nanoparticles

We report on the controlled enhancement of the UV emission from ZnO nanoparticles synthesized via hydrothermal sol-gel routes. Various characterization techniques were used in this study to determine the crystal structure, defect formation, morphology and size of the ZnO nanoparticles. Firstly, the crystallinity of the ZnO nanoparticles was assessed by X-ray diffraction. The role of the precursor quantities on their morphology and bandgap states was investigated via transmission electron microscopy and photoluminescence spectroscopy, respectively. Subsequently, the impurity content and related bonds were evaluated by Fourier-transform infrared spectroscopy. In this work, the ZnO nanoparticles manifest a sharp UV emission along with a subdued green emission in the visible region. Conjoining ZnO with carbon nanotubes (CNT) suppressed the visible emission, as well as blueshifted and intensified the UV emission by ∼5-fold. These results suggest that CNT are effective in passivating the surface states of ZnO nanoparticles.

Synthesis and optical spectroscopy of Na3Y(VO4)2:Eu3+ phosphors for thermometry and display applications.

A new Na3Y(VO4)2:Eu3+ (NYVO:Eu3+) phosphor was prepared using the sol–gel method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to evaluate phase purity and particle size, respectively. The optical properties were investigated by UV-visible absorption, PL, and PLE spectroscopies. The absorption measurements show the formation of the vanadate host by the presence of its characteristic band in the visible region related to VO43− groups. The experimental results show that the NYVO:Eu3+ phosphors exhibit high-brightness and thermally stable emission. Under near-ultraviolet (UV) excitation, both the broadband emission from VO43− groups and the sharp peak emissions from Eu3+ ions are observed. The highest luminescence intensity was achieved for an optimal europium concentration of 15 mol%. The study of the chromaticity parameters of these compounds gives a thermally stable hot emission in the red domain, with a color purity of about 85%, which qualifies the NYVO:Eu3+ compound as a potential phosphor for light-emitting diode (LED) applications. Thermal sensing using NYVO:Eu3+ phosphors are based on monitoring the luminescence intensity ratio between the NYVO host emission and Eu3+ luminescence lines. Notably, the optical thermometry of NYVO:Eu3+ was characterized based on the fluorescence intensity ratio of VO43− and Eu3+ emissions in the 298–440 K range, with maximum absolute and relative sensitivities of 3.4% K−1 and 0.0032 K−1 respectively and a temperature uncertainty of 0.01. NYVO:Eu3+ can then be considered as a potential red phosphor for application in ultraviolet-pumped white light-emitting diodes and as a potential optical thermometer. It provides new possibilities for the design of multifunctional materials for red light-emitting diodes and for non-contact thermometry.

NEURAL NETWORK PREDICTION OF LEAKAGE CURRENT BASED ON THE THEORY OF TIME SERIES FORECASTING

Means of measuring and controlling the value of the leakage current have proven themselves as an effective technical method of monitoring the state of the insulation of the electric motor. The use of devices that allow not only to fix, but also to predict the achievement of dangerous values of the leakage current, which makes it possible to inform the service personnel in advance about the possible danger, and thus reduce the time for simple electrical equipment and use the technological pause for maintenance, repair or replacement of electric motors without waiting their complete rejection. Neural networks used to predict the reliability of electric motors have proven to be effective in predicting these complex processes. On the basis of the obtained experimental data, neural networks were synthesized, both on the basis of technological parameters and on the basis of the theory of time series. A comparison of the operating features of a neural network based on technological parameters and a neural network based on the theory of time series indicates that: the first type of neural network works more efficiently with sharp emissions of the predicted leakage current; the second type of neural networks more accurately models the value of the predicted value near its relatively averaged readings. The peculiarities of the prediction of these neural networks proved the need to create a selection criterion responsible for choosing the most effective of the synthesized neural networks at a certain point in time.

Reinforced Optical Properties of Sm3+ Complexes with β-Hydroxyketone Ligand by Using Methylated Auxiliary Ligands

Solution precipitation method was used to synthesize two avant-grade ternary complexes of Sm3+ ion with 2-hydroxy-4,6-dimethoxy-acetophenone (HDMA) as prime ligand and 5,6-dimethyl-1,10-phenathroline (dmphen) as auxillary ligand. Characterization of these complexes was accomplished by means of elemental analysis, 1H NMR, FT-IR and photoluminescence spectroscopy. Emission spectra recorded at ambient temperature, displayed sharp emission bands at 564, 600 and 646 nm attributed to 4G5/2→6Hj (j = 5/2, 7/2, 9/2) f-f transitions of metal ion. The decent decay time of luminescence and superior colour purity reported in complexes. The correlated colour temperature of these complexes established them as warm light source. The quantum yield was also evaluated for both complexes. HDMA alone could sensitize Sm3+ ion proficiently but the inclusion of auxillary ligands neocuproine (neo) or 5,6-dimethyl-1,10-phenathroline (dmphen) resulted in reinforced optical properties. The results of emission spectra illustrated that these ternary complexes can be one of the most promising substances for fabrication of display devices.

(La,Dy)2W2O9 tungstates: Selected synthesis, enhanced luminescence through Gd3+ co-doping, and favorable quantum efficiency

In this study, a series of well dispersed (La1-xDyx)2W2O9 and (La0.98-yGdyDy0.02)2W2O9 phosphors were selected synthesized by co-precipitation and subsequent calcination, where the effects of RE3+:WO42- molar ratio and solution pH were investigated. The triclinic (La1-xDyx)2W2O9 exhibited a series of sharp emission peaks assigned to 4F9/2→6H15/2, 6H13/2, 6H11/2, 6H9/2 transitions of Dy3+, with the 575 nm (4F9/2→6H13/2) emission being the strongest under the excitation of 350 nm. The optimal Dy3+ concentration was determined to be 2 at%. Gd3+ co-doping apparently affect the phase and luminescence of the final product. The product undergoes a phase transformation from triclinic to monoclinic when Gd3+ doping level is over 25 at%. The emission intensity, quantum yield, color purity, and thermal stability of the (La0.98Dy0.02)2W2O9 phosphor were comprehensively enhanced by Gd3+ co-doping and favorable quantum efficiency of 51.23% was obtained.

Local charge regulation by doping Li+ in BaGa2O4:Bi3+ to generate multimode luminescence for advanced optical Morse code

In the field of advanced anti-counterfeiting research, it is a hot issue to develop a multimodal anti-counterfeiting material with adjustable luminescence characteristics. Here, persistent luminescent materials of BaGa2O4:xBi3+ (x = 0-0.02) and BaGa2O4:0.005Bi3+,yLi+ (y = 0.001–0.02) were synthesized by a solid state reaction at high temperature. BaGa2O4: Bi3+ exhibited a broad blue emission at ∼470 nm (transition from [GaO4]) and a sharp NIR emission at ∼710 nm (3P1→1S0 transition of Bi3+), upon UV excitation at 250 nm. Incorporation of Li+ in BGO: 0.005Bi3+ induced the emission color shifting from blue to green. After stoppage of UV excitation, the BGO:0.005Bi3+ exhibited white afterglow with emission peaks at the range of 500–700 nm. However, incorporation of Li+ leaded to a stronger green afterglow and a weaker NIR afterglow. When the afterglow disappeared, the sample outputted afterglow again after heating processing. The prepared samples exhibited time- and temperature-dependent multimode luminescence, so they were used as components, combined with Morse code to realize multi-modal dynamic anti-counterfeiting. The outcomes in this work indicate that the prepared luminescent materials have broad prospects in advanced anti-counterfeit applications.

Enhanced luminescence performance in double perovskite Na4/5Gd16/15-xMgWO6: xEu3+ red-emitting phosphors for white LEDs through cation modification

Red-emitting phosphors with efficient emission and outstanding thermal stability play a vital role in enhancing the luminescence performance and lighting quality of the phosphor-converted white light-emitting diodes. However, eliminating the concentration quenching and thermal quenching of the red-emitting phosphors is still a significant challenge for the development of efficient light source. Here, a series of red-emitting Na4/5Gd16/15-xMgWO6: xEu3+ phosphors with enhanced luminescence performance were designed and prepared by sol-gel method. Crystal structure, luminescence properties, and decay results were investigated and discussed in detail. It is found that these red-emitting phosphors are monoclinic crystals with C2/m space group. Under near-ultraviolet and blue light excitation, Na4/5Gd16/15-xMgWO6: xEu3+ phosphors exhibit sharp red emission of Eu3+. A delayed concentration quenching of luminescence is demonstrated at a high Eu3+-doping concentration of x = 0.6, which result in alleviated nonradiative relaxation and thus increased decay time of Eu3+. Besides, the phosphor can achieve a superior thermal stability and maintain the luminescence intensity of 82.5% even up to 150 °C by changing the local environment based on cation vacancy engineering and cation disorder effect. The Na4/5Gd16/15-xMgWO6: xEu3+ phosphors are demonstrated to have great application prospects in the solid state lighting.

NIR-II emissive AIEgen photosensitizers enable ultrasensitive imaging-guided surgery and phototherapy to fully inhibit orthotopic hepatic tumors

Accurate diagnosis and effective treatment of primary liver tumors are of great significance, and optical imaging has been widely employed in clinical imaging-guided surgery for liver tumors. The second near-infrared window (NIR-II) emissive AIEgen photosensitizers have attracted a lot of attention with higher-resolution bioimaging and deeper penetration. NIR-II aggregation-induced emission-based luminogen (AIEgen) photosensitizers have better phototherapeutic effects and accuracy of the image-guided surgery/phototherapy. Herein, an NIR-II AIEgen phototheranostic dot was proposed for NIR-II imaging-guided resection surgery and phototherapy for orthotopic hepatic tumors. Compared with indocyanine green (ICG), the AIEgen dots showed bright and sharp NIR-II emission at 1250 nm, which extended to 1600 nm with high photostability. Moreover, the AIEgen dots efficiently generated reactive oxygen species (ROS) for photodynamic therapy. Investigations of orthotopic liver tumors in vitro and in vivo demonstrated that AIEgen dots could be employed both for imaging-guided tumor surgery of early-stage tumors and for ‘downstaging’ intention to reduce the size. Moreover, the therapeutic strategy induced complete inhibition of orthotopic tumors without recurrence and with few side effects.Graphical

Dual-mode optical thermometry based on Bi3+/Sm3+ co-activated BaGd2O4 phosphor with tunable sensitivity

A series of the BaGd2O4:Bi3+, Sm3+ phosphors with dual emission centers were prepared by high-temperature solid-phase method. X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, fluorescence spectroscopy, lifetime decay curve, and variable temperature emission spectroscopy were used to systematically study the structure, luminescence performance, and temperature characteristics of the samples. At ultraviolet stimulation, BaGd2O4:Bi3+, Sm3+ phosphors exhibit broad band blue emission, corresponding to the transition of Bi3+ from 3P1 level to 1S0 level, and sharp red characteristic emission, corresponding to the Sm3+ ions’ energy level transition from 4G5/2 to 6Hm/2(m = 5,7,9). In addition, the Bi3+ and Sm3+ ions’ emission positions in BaGd2O4 host are ideally separated. Based on the property, FIR can be employed to test the difference of temperature in response to performances between Bi3+ blue light emission and Sm3+ red light emission. For the Bi3+/Sm3+ co-doped system, it is found that their relative sensitivity gradually decreases with the increase of the Sm3+ ion concentration, the value of maximum can reach 1.105%K−1, which makes it possible to synthesize temperature sensing materials with adjustable sensitivity. The relative sensitivity can also be calculated by experiments related to the decay lifetime, and the value of maximum obtained was 1.662%K−1. Thus, BaGd2O4:Bi3+, Sm3+ systems are superior non-contact optical pyrometer materials with ultrahigh temperature sensitivity and superhigh signal discriminability.

Role of localized phonon vibration in luminescence performance of Pr doped Ba(Mg0.28Zr0.16Ta0.56)O3 transparent ceramics

Oxygen-assisted high temperature solid-state reaction approach was employed for the fabrication of Pr activated Ba(Mg0.28Zr0.16Ta0.56)O3 transparent ceramic phosphor. Retiveld refinement of X-ray diffraction pattern was carried out to reveal the lattice parameters and crystal structural information. Under the blue-light excitation of λex = 473 nm, the phosphor exhibits a sharp intense red emission centered at 645 nm, accompanied by several other weak peaks. PL evolution with temperature shows a significant luminescence quenching behavior, and the underlying multi-phonon interaction with optical center is revealed by proposing an unprecedent theoretical calculation work. Such a phonon effect is further confirmed from the red-shift of peak position with temperature, and the involved phonon energy of 50.7 meV is determined from Raman scattering measurement. More interestingly, the fitted results of transient-state PL spectra show a fluctuation of luminescence lifetime at various temperatures, further indicating a significant effect of phonon vibration in the system.

Highly efficient and thermally stable Eu3+ activated phosphate based phosphors for wLEDs: An experimental and DFT study

Europium ions-activated alkali- alkaline phosphate phosphors with sharp red-light emission were designed via compositional ternary phase diagram for the first time. A number of polyphosphate phosphors including Eu3+ activated NaCa(PO3)3 were prepared via solid state reaction route. The synthesized phosphors exhibited narrow red light emissions around 612 nm initiating from Eu3+ f-f transitions. Corresponding excitation spectra of Eu3+ ions in the present host displayed characteristics f-f transition along with a charge transfer (CT) band. Origin of CT band was clarified utilizing band structure and density of states (DOS) analysis via Density functional theory (DFT). Experimentally calculated band gap was obtained as 5.59 eV and verified through band structure analysis. The concentration quenching mechanism was explored by varying the Eu3+ concentration, revealing 4 mol% as the optimum concentration and the quenching was controlled via dipole–dipole interaction. High thermal stability (~90.17%) was correlated with structural rigidity related to bond length distortion index evaluated using DFT. The Internal quantum yield (IQY) of prepared phosphors was obtained as ~86%. Additionally, Judd-Ofelt (JO) theory was utilized to assess local surrounding environment nearby europium ion in NaCa(PO3)3 host. In addition, near ultraviolet (NUV) chip was coated with the NaCa0.96Eu0.04(PO3)3 and commercial blue and green-light-emitting phosphors to fabricate the white light emitting diode (wLED). The fabricated LED showed high color-rendering-index (CRI) of 85.1 and suitable correlated-color-temperature (CCT) of 5661 K. The results suggested that the Eu3+ activated NaCa(PO3)3 phosphors were suitable for white LEDs.

Hydrogen-Bonding-Mediated Molecular Vibrational Suppression for Enhancing the Fluorescence Quantum Yield Applicable for Visual Phenol Detection.

It is generally accepted that while efficient suppression of molecular vibration is inevitable for purely organic phosphors due to their long emission lifetime in the regime of 1 ms or longer, fluorophores having a lifetime in the nanoseconds regime are not sensitive to collisional quenching. Here, however, we demonstrate that a fluorophore, 2,5-bis(hexyloxy)terephthaldehyde (BHTA), capable of having hydrogen bonding (H bonding) via its two aldehyde groups can have a largely enhanced (450%) fluorescence quantum yield (QY) in amorphous poly(acrylic acid) (PAA) matrix compared to its crystalline powder. We ascribe this enhanced QY to the efficient suppression of molecular vibrations via intermolecular H bonding. We confirm this feasibility by conducting temperature-dependent fluorescence emission intensity measurement. As gaseous phenol can intervene with the H bonding between BHTA and PAA, interestingly, BHTA embedded in PAA can selectively detect gaseous phenol by a sharp fluorescence emission intensity drop that is visibly recognizable by the naked eye. The results provide an insightful molecular design strategy for a fluorophore and fluorometric sensory system design for enhanced photoluminescence QY and convenient detection of various volatile organic compounds.

Impacts of emission changes in China from 2010 to 2017 on domestic and intercontinental air quality and health effect

Abstract. China has experienced dramatic changes in emissions since 2010, which accelerated following the implementation of the Clean Air Action program in 2013. These changes have resulted in significant air quality improvements that are reflected in observations from both surface networks and satellite observations. Air pollutants, such as PM2.5, surface ozone, and their precursors, have long enough lifetimes in the troposphere to be easily transported downwind. Emission changes in China will thus not only change the domestic air quality but will also affect the air quality in other regions. In this study, we use a global chemistry transport model (CAM-chem) to simulate the influence of Chinese emission changes from 2010 to 2017 on both domestic and foreign air quality. We then quantify the changes in air-pollution-associated (including both PM2.5 and O3) premature mortality burdens at regional and global scales. Within our simulation period, the population-weighted annual PM2.5 concentration in China peaks in 2011 (94.1 µg m−3) and decreases to 69.8 µg m−3 by 2017. These estimated national PM2.5 concentration changes in China are comparable with previous studies using fine-resolution regional models, though our model tends to overestimate PM2.5 from 2013 to 2017 when evaluated with surface observations. Relative to 2010, emission changes in China increased the global PM2.5-associated premature mortality burdens through 2013, among which a majority of the changes (∼ 93 %) occurred in China. The sharp emission decreases after 2013 generated significant benefits for human health. By 2017, emission changes in China reduced premature deaths associated with PM2.5 by 108 800 (92 800–124 800) deaths per year globally, relative to 2010, among which 92 % were realized in China. In contrast, the population-weighted, annually averaged maximum daily 8 h ozone concentration peaked in 2014 and did not reach 2010 levels by 2017. As such, O3 generated nearly 8500 (6500–9900) more premature deaths per year in 2017 compared to 2010. Downwind regions, such as South Korea, Japan, and the United States, generally experienced O3 improvements following 2013 due to the decreased export of ozone and its precursors. Overall, we conclude that the sharp emission reductions in China over the past decade have generated substantial benefits for air quality that have reduced premature deaths associated with air pollution at a global scale.

Biosynthesis of triangular-shape ZnO nanoparticles using Tecoma stans and its antimicrobial activity

The present work reports the first green synthesis of zinc oxide nanoparticles (ZnO-NPs) using Tecoma stans leaf extract. The TEM images show triangular shape ZnO-NPs with sizes ranging from 15 to 20 nm. The XPS spectrum revealed the presence of Zn and O in the sample. Photoluminescence studies of ZnO-NPs displayed a sharp emission of blue band at 447 nm, attributed to the defect structures in ZnO crystal. The synthesized ZnO-NPs showed excellent antimicrobial activity against 5 bacterial and 4 fungal strains with the highest zone of inhibition (ZOI) of 24 mm and 30 mm being shown against Achromobacter spanius and Penicillium citirinum strain using 1 mM ZnO nanoparticles solution, respectively. Furthermore, the current study reveals that ZnO NPs have prospective uses in various medical and industrial domains, making the study extremely relevant and beneficial to the scientific community.