Dual Peaks Research Articles

Characterization of global fire activity and its spatiotemporal patterns for different land cover types from 2001 to 2020

Fire is a widespread phenomenon that plays an important role in Earth's ecosystems. This study investigated the global spatiotemporal patterns of burned areas, daytime and nighttime fire counts, and fire radiative power (FRP) from 2001 to 2020. The month with the largest burned area, daytime fire count, and FRP presented a bimodal distribution worldwide, with dual peaks in early spring (April) and summer (July and August), while the month with the largest nighttime fire count and FRP showed a unimodal distribution, with a peak in July. Although the burned area showed decline at the global scale, a significant increase occurred in temperate and boreal forest regions, where nighttime fire occurrence and intensity have consistently increased in recent years. The relationships among burned area, fire count, and FRP were further quantified in 12 typical fire-prone regions. The burned area and fire count exhibited a humped relationship with FRP in most tropical regions, whereas the burned area and fire count constantly increased when the FRP was below approximately 220 MW in temperate and boreal forest regions. Meanwhile, the burned area and FRP generally increased with the fire count in most fire-prone regions, indicating an increased risk of more intense and larger fires as the fire count increased. The spatiotemporal dynamics of burned areas for different land cover types were also explored in this study. The results suggest that the burned areas in forest, grassland, and cropland showed dual peaks in April and from July to September while the burned areas in shrubland, bareland, and wetlands usually peaked in July or August. Significant increases in forest burned area were observed in temperate and boreal forest regions, especially in the western U.S. and Siberia, whereas significant increases in cropland burned area were found in India and northeastern China.

Non-Enzymatically Colorimetric Bilirubin Sensing Based on the Catalytic Structure Disruption of Gold Nanocages.

As an essential indicator of liver function, bilirubin is of great significance for clinical diagnosis. A non-enzymatic sensor has been established for sensitive bilirubin detection based on the bilirubin oxidation catalyzed by unlabeled gold nanocages (GNCs). GNCs with dual-localized surface plasmon resonance (LSPR) peaks were prepared by a one-pot method. One peak around 500 nm was ascribed to gold nanoparticles (AuNPs), and the other located in the near-infrared region was the typical peak of GNCs. The catalytic oxidation of bilirubin by GNCs was accompanied by the disruption of cage structure, releasing free AuNPs from the nanocage. This transformation changed the dual peak intensities in opposite trend, and made it possible to realize the colorimetric sensing of bilirubin in a ratiometric mode. The absorbance ratios showed good linearity to bilirubin concentrations in the range of 0.20~3.60 μmol/L with a detection limit of 39.35 nM (3σ, n = 3). The sensor exhibited excellent selectivity for bilirubin over other coexisting substances. Bilirubin in real human serum samples was detected with recoveries ranging from 94.5 to 102.6%. The method for bilirubin assay is simple, sensitive and without complex biolabeling.

Numerical study of turbulent non-premixed cool flames at high and supercritical pressures: Real gas effects and dual peak structure

Numerical study of turbulent non-premixed cool flames at high and supercritical pressures: Real gas effects and dual peak structure

Disentangling Dual Emission Dynamics in Lead Bromide Perovskite

AbstractMetal halide perovskites exhibit intriguing properties for optoelectronic and electronic applications. Understanding their intrinsic photoexcitation and band‐tail dynamics is essential for exploring novel functionality and improving device performance. This report addresses the band‐tail luminescence of lead bromide perovskite (APbBr3) single crystals, where A is methylammonium, formamidinium, and cesium. Using time‐resolved photoluminescence (PL) spectroscopy, the dynamics of well‐defined dual emission peaks are unambiguously resolved from the picosecond to the microsecond scale. Whereas the long‐lived states exhibit similar recombination dynamics at high temperatures, a clear, fast transition occurs between the high and low energy states at low temperatures, indicating direct communication between these two states. These time‐resolved PL spectra shed light on the intrinsic optical properties of metal halide perovskites.

Antiferroelectric orthorhombic P-to-R phase transition induced exotic electrocaloric effect in NaNbO3-based lead-free ceramics

Phase transition is expected in designing high-performance electrocaloric effect (ECE). However, hidden antiferroelectricity in NaNbO3-based ceramics complicates ECE evolution as compared to conventional ferroic materials. Therefore, a NaNbO3−xBi0.5Li0.5TiO3 (x = 0.08, 0.10, and 0.12) system is introduced to explore ECE performance in P (Pbma), Q (P21ma), and R (Pnma) phases since a Bi0.5Li0.5TiO3 dopant plays a Janus role in stabilizing ferroelectric Q (x = 0.08 and 0.10) and inducing the antiferroelectric (AFE) relaxor R phase (x = 0.12). Rietveld refinement reveals a phase structure change from the P/Q to R state. Bi0.5Li0.5TiO3 addition makes a downshift of P-to-R transition temperature accompanied by an increase in relaxation property, as certified by dielectric analysis/piezoelectric force images, in situ XRD/Raman spectra, and ferroelectric tests. Additionally, a square P–E loop evolves into less-sharp and finally changes into a slant one with increasing Bi0.5Li0.5TiO3 content. ECE is directly measured, and its peak value increases from 0.15 K for x = 0.08 and 0.21 K for x = 0.10 and finally to 0.11 K for x = 0.12 composition. Interestingly, dual ECE peaks appear in x = 0.10, and it is probably contributed by R relaxor polar nanodomains. This work not only clarifies actual ECE behavior in AFE orthorhombic (P/R) NaNbO3-based ceramics but also fulfills understandings of AFE P-to-R transitions in modulating ECE.

Generalization of the Ratiometric Method to Extend pH Range Measurements of the BCECF Probe

There is a variety of fluorescent probes for pH measurements and which are mainly used for biological systems. In general, they can be classified into two groups. The first group includes fluorescent pH probes which exhibit a single fluorescence emission peak. For these probes, the fluorescence excitation profile is pH-dependent and the shape of the emission spectra remains almost constant. Hence, the ratiometric pH measurement-which makes pH determination independent of the probe concentration-is implemented when the excitation is performed at two excitation wavelengths and the fluorescence emission is measured at one wavelength. The second group exhibits a dual fluorescence emission peak. Here, each protonated or deprotonated form exhibits characteristics emission and/or absorption spectra. Shifts between spectra obtained for protonated and deprotonated species can be exploited in order to perform a ratiometric measurement. In this study we present a methodology that evaluates the precision of the ratiometric measurements based on multiple wavelengths excitation to determine the optimum wavelengths combination for pH determination in biological samples. This methodology using the BCECF probe is applied to measure the pH drift in cell culture medium. It exhibits a high precision and significantly extends the range of validity for pH measurements spanning from very acidic to basic.

Ratio fluorescence sensor based on CD/Cu-MOFs for detection of Hg2.

Trace detection of toxic heavy metals is a very important and difficult problem in several areas: convenience, sensitivity, and reliability. Herein, we develop an innovative fluorescence resonance energy transfer (FRET)-based ratio fluorescence sensor for the detection of heavy metal mercury ion (H g 2+). The sensing platform is composed of coumarin derivatives (CDs) and a copper metal-organic framework (Cu-MOF) named CD/Cu-MOF. The constructed CD/Cu-MOFs ratio fluorescence sensor exhibits dual emission peaks at 430 and 505nm under the single excitation wavelength of 330nm. With the addition of H g 2+, the fluorescence intensity of the system at 430nm gradually increased, and the fluorescence intensity at 505nm remained stable, resulting in a change in the fluorescence ratio. There is a good logarithmic relationship between the H g 2+ concentration in the range from 2×10-8 to 0.001nM and the ratio of the fluorescence emission intensity of the system (F 430/F 505) (R 2=0.9901), and its calculated detection limit is 3.76×10-9 n M. In addition, the CD/Cu-MOFs ratio fluorescence sensor has achieved a good recovery rate of standard addition in the actual food sample recovery experiment, which provides an effective method for the detection of H g 2+ in food samples.

Activated cascade effect for dual-mode ratiometric and smartphone-assisted visual detection of curcumin and F− based on nitrogen-doped carbon dots

The growing persistence of harmful ion or drug molecular residues has always been considered as a matter of concern due to its importance in biological and environmental processes, which requires taking measures to maintain environmental health sustainably and effectively. Inspired by the multi-system and visual quantitative detection of nitrogen-doped carbon dots (N-CDs), we develop a novel cascade nano-system based on dual emission carbon dots for on-site visual quantitative detection of curcumin and fluoride ion (F−). Herein, tris (hydroxymethyl) aminomethane (Tris) and m-dihydroxybenzene (m-DHB) are elected as reaction precursors to synthesize dual-emission N-CDs by a one-step hydrothermal method. The obtained N-CDs exhibit dual emission peaks at 426 nm (blue) and 528 nm (green) with quantum yields of 53 % and 71 %, respectively. Then, trace curcumin and F− intelligent off-on-off sensing probe is formed by taking advantage of the activated cascade effect. As for the occurrence of inner filter effect (IFE) and fluorescence resonance energy transfer (FRET), the green fluorescence of N-CDs quenches remarkably, called as OFF initial state. Then the curcumin-F− complex leads to the hypochromatic shift of the absorption band from 532 to 430 nm, which activates the green fluorescence of N-CDs, named as ON state. Meanwhile, the blue fluorescence of N-CDs is quenched due to the FRET, called as OFF terminal state. This system shows good linear relationships from 0 to 35 μM and 0 to 40 μM with low detection limits of 29 nM and 42 nM for curcumin and F− ratiometric detection, respectively. Moreover, a smartphone-assisted analyzer is developed for on-site quantitative detection. Furthermore, we design a logic gate for logistics information storage, which proves the possibility of a logic gate based on N-CDs in practical application. Thus, our work will provide an effective strategy for environmental quantitative monitoring and information storage encryption.

Heat transfer characteristics of jet impingement on a surface mounted with ribs using LES

The present study investigates flow and heat transfer features of jet impingement on a surface fitted with detached ribs at Re = 20,000 using OpenFOAM 4.1 based large eddy simulation (LES). The WALE SGS model is applied. A wall resolved simulation is performed to understand the flow behaviour and heat transfer enhancement in the impingement regions and ribs. The WALE model is observed to be suitable for accurate calculations of complex application-based flow configurations. A comprehensive discussion on flow physics is carried out to understand heat transfer in the rib regions and the effects of flow and turbulence parameters. The investigation reveals that augmentations in the velocity and turbulence are directly linked to the local heat transfer enhancement in the clearance between the ribs and heated plate. A dual peak exists for turbulence kinetic energy profiles. The local heat transfer is observed to be maximum in the clearance region between the second rib and plate. The region of maximum local heat transfer was observed to be related to the peak velocity and turbulence kinetic energy in the same region. The present computation is capable of capturing small-scale dynamics and turbulence structures. The present results may be utilized in testing RANS-based turbulence models and the findings are useful for researchers and engineers working on EV, HPC and related cooling industries where high localized cooling is required.

Effects of swirl number and bluff body on swirling flow dynamics

Bluff-body swirling flows have been widely employed in gas-turbine combustors to achieve flame stabilization. Meanwhile, considerable efforts have been made to understand swirling flow dynamics, the effects of swirl number and bluff body on flow structure and dynamics are still not well understood. To this end, a series of direct numerical simulations of isothermal swirling flows have been conducted in this work in order to investigate the impact of swirl numbers and bluff-body diameters on the flow structure, Reynolds stresses, and turbulent kinetic energy (TKE) transport. It is found that a change in the swirl number can affect the inner recirculation zone (IRZ) and hence momentum transport. Specifically, as the swirl number increases, the vortex core formed at downstream locations can merge with the IRZ. Moreover, including the bluff body not only contributes to the formation of the IRZ but also serves as a disturbance source for the flow, which is favorable for the formation of large-scale vortex structures. Then, the impact of swirl number and bluff body on Reynolds shear stresses and anisotropy invariants is investigated to identify the locations of the inter shear layer (ISL), the outer shear layer (OSL), and the main swirling zone (MSZ). The results show that as the swirl number increases, both the ISL and MSZ shift to the wall, indicating a large IRZ. Furthermore, the analysis of TKE indicates that for cases with a bluff body, TKE mainly occurs in the ISL and OSL, featuring a dual peak distribution. However, for cases without a bluff body, the distribution of TKE is primarily concentrated in the ISL. These results suggest that both increasing the swirl number and/or including the bluff body could help with TKE transport, which can lead to a wide range of TKE distribution.

Scalable On‐Chip Microdisk Resonator Spectrometer

AbstractOn‐chip micro‐spectrometers are sought after with great effort owing to extensive potential applications in mobile optical sensing and imaging. By multiplexing more physical channels, the reconstructive spectrometers based on the spectral‐to‐spatial mapping technique can improve the spectral range. However, this method is challenging to implement and sustain due to the increase in system complexity and the decrease of dynamic range or spectral resolution. Here, a micro‐spectrometer utilizing a single tunable microdisk resonator (MDR) is demonstrated. Such a single MDR spectrometer has only one physical channel to receive all spectral components with a compact size, overcoming the trade‐off among spectral resolution, spectral range, and dynamic range. Leveraging the wavelength and temperature‐dependent response matrix, unknown spectra are reconstructed from their corresponding output light intensity vector. The fabricated device illustrates a high resolution of 0.01 nm for a dual peak and a medium resolution of 0.2 nm in the 20 nm spectral range. A wide variety of complex input spectra, including narrowband and broadband spectral signals, can be well recovered, exhibiting the robustness of the spectral reconstruction approach. Moreover, this proposed spectrometer exhibits ease of scalability and flexible configuration to a spectrometer array covering a set of desired and even discrete spectral ranges.

Ultralong Near Infrared Room Temperature Phosphorescence in Cu(I) Metal‐Organic Framework Based‐on D–π–A–π–D Linkers

AbstractMaterials taking abundant advantage of triplet states luminescence have risen lots of attention in decades. In this work, a Cu(I) metal‐organic framework (MOF) with synchronous metal‐to‐ligand charge transfer (MLCT) state and triplet emission of the ligand is synthesized from a D–π–A–π–D ligand with suitable energy gap. The Cu(I) MOF possessed MLCT emission in the range of 450–505 nm with microsecond lifetimes (1.07 to 5.38 µs) and a triplet state emission in near infrared (NIR) region ≈705 nm with lifetimes of 1.85 ms at 300 K and 25.16 ms at 77 K, much longer than those of reported Cu(I) MOFs. Moreover, a white light is obtained through adjusting the relative intensity of dual peaks. More importantly, NIR long persistent luminescence of Cu‐MOF is observed by naked eyes under cryogenic condition. Multiple factors such as the delicate design of the D–π–A–π–D structure of ligand, the enhanced spin‐orbital coupling by Cu(I) networks, and the tight packing mode of the framework promote the generation of MLCT emission and ultralong NIR room temperature phosphorescence. The combination of calculation and experiment to analyse the luminescence mechanism of Cu(I) MOFs provides ideas for the development of Cu(I)‐based intelligently responsive materials with RTP properties.

Epidemiology of Respiratory Syncytial Virus-Associated Acute Lower Respiratory Tract Infection among Hospitalized Under-5s in Northwestern Nigeria

Abstract Objective Globally, 33 million cases of respiratory syncytial virus (RSV) infections occur annually among under-fives (5s). Ninety-nine percent of deaths from RSV occur in low- and middle-income countries. Under-five pneumonia mortality in Nigeria was estimated at 140,520 in 2017, but RSV epidemiological data are scant due to poor awareness and limited testing. Vaccines for RSV are currently under development and RSV mortality data from this high mortality, low resource setting are essential to maximizing the potential benefit of vaccination as well as promoting vaccine uptake. This study aimed to describe the epidemiology of RSV-associated acute lower respiratory tract infection (ALRTI) in children younger than 5 years in Zaria, Northwestern Nigeria. Methods A prospective cohort study was conducted among children aged 1 month to 5 years who were hospitalized with ALRTI in the Emergency Pediatric Unit of a tertiary hospital in Zaria from November 2018 to October 2019. Naso-pharyngeal swabs were obtained for RSV testing using a point-of-care immunoassay technique. Results Thirty-three percent (35/106) of the children had RSV-related ALRTI. The median age of RSV-positive cases was 8 months (IQR 3–14). Two-thirds of children (68.6%, 24/35) were below 12 months. The RSV mortality rate was 5.7% (2/35). RSV occurred in 10 months of the year with peaks in March and July. Conclusion A third of admitted children with ALRTI were positive for RSV. Therefore RSV significantly contributes to childhood pneumonia and the dual seasonal peak observed in our study may have implications for vaccine implementation.

Dual emissive carbon dots: Synthesis strategies, properties and its ratiometric sensing applications

Carbon dots (CDs) have received much attention in the field of sensing as fluorescent nanomaterials. They possess simple preparation, excellent optical properties, low toxicity, and brilliant biocompatibility. Photoluminescence in CDs is caused by chemical features, such as graphitic conjugated cores, molecular fluorophores and surface defect states. The emission wavelength of fabricated CDs primarily accumulates single bands in the blue, green or red region. Meanwhile, the structure of CDs and the relationship between their structure and optical properties are still being debated. Apart from that, the existence of single emission bands reduces the efficiency of CDs for sensing multiple analytes in a single process. To overcome this issue, dual conjugated emitters have been designed using carbon dots, quantum dots and metal–organic frameworks. Their fabrication is time-consuming, requires purification and has unequal photostability. It is critical to design and produce nanoprobes with no labeling and intrinsic dual emission. Thus, this review demonstrates the fundamentals to enlighten the PL mechanism for the multi-emissive response in CDs through ultrafast time-resolved and DFT techniques. An attempt is made to provide an in-depth understanding of diversified paths, such as modulation in their interparticle distance, integration of rare-earth metals and metallic to elucidate the duality in their emission spectra. We have provided insights into implementing intrinsic dual emissive CDs in different ratiometric models. Current states, portable challenges, the significance of fabricating CDs with dual emission peaks and their applications are rationally discussed. The main focus of the review is to discuss various methods and parameters to induce different emissions in CDs with single or dual bands rather than the sensing mechanisms. The goal of this review is to describe the theoretical justification for the sensing response of CDs by varying different parameters, such as pH, precursor, etc.

Experimental and Theoretical Study for Proton Transfer of Aggregated‐Induced Emission Active Fluorescent Schiff Bases

AbstractIn this paper, we studied the effect of increasing the conjugation in compound 3 on the proton transfer and aggregation‐induced emission properties. Compound 3 exhibited the dual absorption peak at 420 nm and 320 nm, which was redshifted by 50 nm compared to compound 2 (previous report). Compound 3 emits exhibited a peak at 530 nm with a Stokes’ shift of 110 nm after photoexcitation at 420 nm. In a high polarity medium, the absorption and emission spectra of compound 3 showed redshifts of 50 nm and 20 nm, respectively. Further, compound 3 displayed the aggregation‐induced emission enhancement in THF/H2O (60 % v/v). Additionally, the proton transfer process in compounds 2 and 3 was evaluated through theoretical calculations via determining the relative free energies of possible tautomeric forms. It was determined that the small energy barriers for compound 2 in the S1 state suggested the presence of the proton transfer process; however, high energy barriers and high stabilization and Boltzmann population of 3.KK tautomeric form at S0 and S1 state for compound 3 discommoded the proton transfer process. Further, the aggregated form of compound 3 (20 μM; CH3OH/HEPES buffer (4 : 1; v/v) pH=7.04) was utilized to recognize Cu2+ ions with the lowest detection limit of 1.5 nM and Stern‐Volmer binding constant of 2.8×105 M−1. A noted decrease in the hydrodynamic size of compound 3 from 400 nm to 40 nm in the presence of Cu2+ ions confirmed the disaggregation with a decrease in emission intensity. Compound 3 was also employed as a Cu2+ ions recognizer in different collected samples with good percentage recovery.

Dual seasonal pattern for hemorrhagic fever with renal syndrome and its potential determinants in China

Hemorrhagic fever with renal syndrome (HFRS) continued to affect human health across Eurasia, which complicated by climate change has posed a challenge for the disease prevention measures. Nation-wide surveillance data of HFRS cases were collected during 2008–2020.The seasonality and epidemiological features were presented by combining the HFRS incidence and the endemic types data. Factors potentially involved in affecting incidence and shaping disease seasonality were investigated by generalized additive mixed model, distributed lag nonlinear model and multivariate meta-analysis. A total of 76 cities that reported totally 111,054 cases were analyzed. Three endemic types were determined, among them the Type I cities (Hantaan virus-dominant) were related to higher incidence level, showing one spike every year in Autumn-Winter season; Type II (Seoul virus-dominant) cities were related to lower incidence, showing one spike in Spring, while Type III (Hantaan/Seoul-mixed type) showed dual peaks with incidence lying between. Persistently heavy rainfall had significantly negative influence on HFRS incidence in Hantaan virus-dominant endemic area, while a significantly opposite effect was identified when continuously heavy rainfall induced floods, where temperature and relative humidity affected HFRS incidence via an approximately parabolic or linear manner, however few or no such effects was shown in Seoul virus-dominant endemic areas, which was more vulnerable to temperature variation. Dual seasonal pattern of HFRS was depended on the dominant genotypes of hantavirus, and impact of climate on HFRS was greater in Hantaan virus-dominant endemic areas, than in Seoul virus-dominant areas.

Shock Boundary Layer Interaction and Aero-Optical Effects in a Transonic Flow over Hemisphere-on-Cylinder Turrets

Hemisphere-on-cylinder turrets are the main airborne optical platform structure. However, an unsteady shock boundary layer interaction (SBLI) would act on flow separation and turbulent wake, which causes serious aero-optical effects with high spatial and temporal frequency characteristics. In this paper, the SBLI phenomenon of a hemisphere-on-cylinder turret is recorded in a wind tunnel at Ma = 0.7 using shadowing and Mach-Zehnder interferometer measurements. Its wavefront distortion is measured using the Shack-Hartmann measurement. The detached eddy simulation (DES) based on SST k - ω turbulence model and ray-tracing methods are used to reproduce the transonic flow and optical aberration. Experiments and simulations suggest that the SBLI causes the flow to separate earlier relative to a subsonic flow over the turret. The time-averaged root-mean-square of optical path difference (OPD) over the beam aperture is 0.56 λ∼0.59 λ with λ as the wavelength, while the root-mean-square of the time-averaged OPD is about 0.45 λ. The local shock and wavefront distortion have dual peak frequencies at S t D = f D / U ∞ = 0.24 and 0.34, different from the single-peak-frequency phenomenon of a subsonic flow over turrets. Fast model decomposition of wavefront can be performed by proper orthogonal decomposition (POD) of its Zernike coefficients. The first two modes contain the shock’s reciprocating motion.

Luminescence mechanism of InGaAs self-fit well-cluster composite structure with super-wide spectra

This paper reports an InGaAs/GaAs well-cluster composite(WCC) quantum structure, which has shown great advantages in the development of new types of lasers with super-wide spectra. The spectral bandwidth is broadened to 6-fold broader than that of a classic InGaAs quantum well under the same carrier density. However, the luminescence mechanism of InGaAs/GaAs WCC structure is still unclear because of the self-fit distribution of indium contents and hybrid strain types in InxGa1-xAs material. In this paper, the gain spectra and energy band structure containing both compressive and tensile strain states are obtained to reveal the super-wide spectra with dual peaks in transverse electric (TE) and transverse magnetic (TM) polarization modes. The super-wide spectrum with a bimodal feature is attributed to all emissions from normal In0.17Ga0.83As region and indium-deficient InxGa1-xAs regions caused by the self-fit migration of indium atoms. The band offsets of heavy holes and light holes in normal and indium-deficient InxGa1-xAs regions are determined by calculating the peak space of TE and TM spectra. In addition, the thickness fluctuation and hybrid strain distribution in the asymmetrical WCC structure are also obtained by comparing the intensity of dual peaks. The significance of this result is that it not only reveals the energy band characteristics and luminescence mechanism but also determines the critical thickness of indium atom self-fit migration. The result is significant to greatly enhance the performance of InGaAs-based WCC tunable lasers in extending spectral tuning range.

Single silica-coated Mn-doped CsPbCl3 perovskite quantum dots with enhanced stability and excellent optical properties

Halide perovskite quantum dots (QDs) have been considered to be a potential emitting materials for illumination and display applications. Unfortunately, the toxicity and poor stability can greatly limit their practical application. Herein, the Mn2+-doped CsPbCl3 and SiO2-coated Cs(Pb,Mn)Cl3 perovskite QDs have been developed to solve the tricky problem without affecting their optical properties. Firstly, the mono-dispersed pure CsPbCl3 perovskite QDs with cubic morphologies are prepared by using a modified hot-injection method, as a control group. Next, the low-Pb content Cs(Pb,Mn)Cl3 perovskite QDs with distinctive dual emission peaks has been successfully obtained, including the CsPbCl3 host emission and the Mn2+ emission. Based on this, a new strategy for synthesizing single Cs(Pb,Mn)Cl3@SiO2 core-shell QDs with their initial cubic morphology and optical properties has been developed, which using the Cs(Pb,Mn)Cl3 nanoparticles as a precursor and choosing the APTES as the surface ligand. Photo-stability tests indicate that the Cs(Pb,Mn)Cl3 and Cs(Pb,Mn)Cl3@SiO2 perovskite QDs are markedly more stable than the pure CsPbCl3 QDs, indicating that the crystal engineering and host packaging are all effective way to improve the stability. Meanwhile, the PL intensity of Cs(Pb,Mn)Cl3@SiO2 dispersed in a mixed solution of toluene and water can retained 63% of the initial value even after 14 h, which are much higher than Cs(Pb,Mn)Cl3 (31%). Therefore, the Cs(Pb,Mn)Cl3 after SiO2 coating is the more effective way to improve stability than that of the Mn2+ doping. This work not only provides a simple and reliable synthesis way to synthesize the single core-shell particles, which can be suitable for other perovskite systems, but also compares the two methods of the crystal engineering and the host packaging to improve the stability of perovskite QDs for practical application.

Chiral Luminescent Sensor Eu-BTB@d-Carnitine Applied in the Highly Effective Ratiometric Sensing of Curing Drugs and Biomarkers for Diabetes and Hypertension.

Chiral drugs are of great significance in drug development and life science because one pair of enantiomers has a different combination mode with target biological active sites, leading to a vast difference in physical activity. Metal-organic framework (MOF)-based chiral hybrid materials with specific chiral sites have excellent applications in the highly effective sensing of drug enantiomers. Sitagliptin and clonidine are effective curing drugs for controlling diabetes and hypertension, while insulin and norepinephrine are the biomarkers of these two diseases. Excessive use of sitagliptin and clonidine can cause side effects such as stomach pain, nausea, and headaches. Herein, through post-synthetic strategy, MOF-based chiral hybrid material Eu-BTB@d-carnitine (H3BTB = 1,3,5-benzenetrisbenzoic acid) was synthesized. Eu-BTB@d-carnitine has dual emission peaks at 417 and 616 nm when excited at 330 nm. Eu-BTB@d-carnitine can be applied in luminescent recognition toward sitagliptin and clonidine with high sensitivity and low detection limit (for sitagliptin detection, Ksv is 7.43 × 106 [M-1]; for clonidine detection, Ksv is 9.09 × 106 [M-1]; limit of detection (LOD) for sitagliptin is 10.21 nM, and LOD of clonidine is 8.34 nM). In addition, Eu-BTB@d-carnitine can further realize highly sensitive detection of insulin in human fluids with a high Ksv (2.08 × 106 [M-1]) and a low LOD (15.48 nM). On the other hand, norepinephrine also can be successfully discriminated by the hybrid luminescent platform of Eu-BTB@d-carnitine and clonidine with a high Ksv value of 4.79 × 106 [M-1] and a low LOD of 8.37 nM. As a result, the chiral hybrid material Eu-BTB@d-carnitine can be successfully applied in the highly effective ratiometric sensing of curing drugs and biomarkers for diabetes and hypertension.