Controlled synthesis of sulfhydryl-dendritic mesoporous silica nanospheres for ultrafast extraction and sensitive analysis of organochlorine herbicides containing amide groups.

The distinctive morphology of dendritic mesoporous silica nanoparticles (DMSN) has recently attracted considerable attention in scientific community. However, synthesis of DMSN with well-defined structure and uniform size for ultrafast extraction of trace herbicide residues from environmental and food samples remains to be a compelling challenge. In this study, sulfhydryl functionalized dendritic mesoporous silica (SH-DMSN) was synthesized and the SH-DMSN showcases monodisperse microspheres with flower shape and precisely tailored and controllable pore sizes. This distinctive structural configuration accelerates mass transfer within the silica layer, resulting in heightened adsorption efficiencies. Furthermore, the particle sizes (455, 765, and 808) of the adsorbent can be meticulously fine-tuned by introducing distinct templates. Specifically, when the particle size is 765 nm, the optimized SH-DMSN exhibits a substantial specific surface area (691.32 m²/g), outstanding adsorption efficiencies (>90 %), remarkably swift adsorption and desorption kinetics (2 min and 3 min, respectively), and exceptional stability. The superior adsorption capabilities of this novel adsorbent, ranging from 481.65 to 1021.7 µg/g for organochlorine herbicides containing amide groups, can be attributed to the interplay of S-π interactions, halogen bonding, and electrostatic attraction interaction. These interactions involve the lone pair electrons of sulfhydryl and silanol groups with the π-electrons, halogen atoms and amide groups in herbicide molecules. This study not only offers a new perspective on advancing the practical utilization of dendritic mesoporous silica but also provides a pragmatic strategy for the separation and analysis of herbicides in diverse sample matrices.

Photoluminescence Enhancement in Silica-Confined Ligand-Free Perovskite Nanocrystals by Suppression of Silanol-Induced Traps and Phase Impurities.

The detriments of intrinsic silanol groups in mesoporous silica to the photoluminescence (PL) of lead halide perovskite nanocrystals (LHP NCs) confined in the template have never been determined and clearly elucidated. Here, we disclose that silanol-induced Cs+ and Br- deficiencies prompt the generation of traps and CsPb2Br5 impurities. The temperature-dependent PL spectra verify the higher energetic barrier of trap states in CsPbBr3 NCs confined in silanol-rich mesoporous silica. Femtosecond transient absorption spectra reveal the trapped state mediates a broadband photoinduced absorption and long-lived decay pathway of CsPbBr3 NCs in silanol-rich templates. A remarkable improvement (up to 160-fold) in PL quantum yields is realized by simple silanol elimination. This work demonstrates the detrimental effects of silanol sites on the PL properties of LHP NCs impregnated in mesoporous silica and provides a new perspective for the ligand-free synthesis of high-quality LHP NCs in mesoporous templates by facile impregnation for practical applications.

Controllable synthesis of uniform flower-shaped covalent organic framework microspheres as absorbent for solid-phase extraction of trace 2,4-dichlorophenol.

Controllable synthesis of micro-flower covalent organic frameworks (MFCOFs) with controllable size, monodisperse, spherical, and beautiful flower shape was realized by using 2,5-diformylfuran (DFF) and p-phenylenediamine (p-PDA) as building blocks at room temperature. High-quality MFCOFs (5 - 7 µm) were synthesized by controlling the kind of solvent, amounts of monomers, catalyst content, and reaction time. The synthesized MFCOFs possessed uniform mesopores deriving from the intrinsic pores of frameworks and wide-distributed pores belonging to the gap between the petals. The MFCOFs-packed solid-phase extraction (SPE) column shows adsorption capacity of about 8.85 mg g-1 for 2,4-dichlorophenol (2,4-DCP). The MFCOF-based SPE combined with the HPLC method was established for the determination of 2,4-DCP in environmental water. The linear range of this method is 20-1000 ng mL-1 (R2 > 0.9994), and limit of detection (S/N = 3) is 10.9 ng mL-1. Spiked recoveries were 94.3-98.5% with relative standard deviations lower than 2.3%.

Magnetic porous carbon material derived from imine-linked covalent organic frameworks for magnetic solid phase extraction of trace chlorine-containing herbicides in soil.

Here, imine-linked covalent organic frameworks coated Fe3O4 microspheres were fabricated and employed as the self-template to prepare magnetic porous carbon material. The magnetic solid phase extraction (MSPE) performance of such magnetic covalent organic frameworks derived porous carbons (CMCOFs) were studied for the first time, and the improved MSPE performance was verified. The variations of chemical and material properties in the carbonization processes were studied, and it was found that the CMCOFs carbonated at 400°C exhibited highest adsorption efficiencies for chlorine-containing herbicides due to the formation of nitrile components at this stage. The CMCOFs retained high adsorption efficiencies (above 90 %) to chlorine-containing herbicides at wide pH range (3-12) and high salt concentration. The CMCOFs-based MSPE coupled with HPLC technique was in good potential for analysis of trace chlorine-containing herbicides in soil samples. Under the optimized conditions, this approach displayed short extraction and elution time (5 and 8 min) and low limits of detection (0.35-5.5 ng/mL) for chlorine-containing herbicides. The recoveries of spiked analytes and the relative standard deviations in real soil samples were 81.86 %-110.9 % and less than 5.92 %, respectively. This study provides an efficient method for the analysis of trace chlorine-containing herbicides in complex samples, as well as give some inspiration on material modulation by controlled carbonization to achieve improved sorption performances.

Deep learning and targeted metabolomics-based monitoring of chewing insects in tea plants and screening defense compounds.

Tea is an important cash crop that is often consumed by chewing pests, resulting in reduced yields and economic losses. It is important to establish a method to quickly identify the degree of damage to tea plants caused by leaf-eating insects and screen green control compounds. This study was performed through the combination of deep learning and targeted metabolomics, in vitro feeding experiment, enzymic analysis and transient genetic transformation. A small target damage detection model based on YOLOv5 with Transformer Prediction Head (TPH-YOLOv5) algorithm for the tea canopy level was established. Orthogonal partial least squares (OPLS) was used to analyze the correlation between the degree of damage and the phenolic metabolites. A potential defensive compound, (-)-epicatechin-3-O-caffeoate (EC-CA), was screened. In vitro feeding experiments showed that compared with EC and epicatechin gallate, Ectropis grisescens exhibited more significant antifeeding against EC-CA. In vitro enzymatic experiments showed that the hydroxycinnamoyl transferase (CsHCTs) recombinant protein has substrate promiscuity and can catalyze the synthesis of EC-CA. Transient overexpression of CsHCTs in tea leaves effectively reduced the degree of damage to tea leaves. This study provides important reference values and application prospects for the effective monitoring of pests in tea gardens and screening of green chemical control substances.

The impact of digital economy on green total factor productivity considering the labor-technology-pollution factors.

The digital economy provides new impetus for the high-quality development of manufacturing industry. Through the DEA-Malmquist model and panel regression model, this paper confirmed that there is a positive and significant relationship between the development of digital economy and the green total factor productivity (GTFP) of manufacturing industry. The research result is as follows: (1) the development of digital economy can enhance the overall GTFP of manufacturing industry. (2) The green technology progress brought by the development of digital economy is the main path to promote the GTFP of manufacturing industry. (3) The heterogeneity analysis shows that the impact of digital economy on GTFP of high pollution manufacturing industry is significantly positive, the impact of labor-intensive manufacturing industry is significantly negative, and the impact of technology intensive manufacturing industry is not obvious. The contributions of this study are as follow. In terms of theory, this study theoretically continues Solow's classical theory, demonstrating the scientific nature of digital technology progress in promoting GTFP growth. In empirical analysis, this study build a new digital economy development level evaluation index system based on the perspective of manufacturing industry. In addition, this study also add a labor-technology-pollution perspective for the development of relevant policies.

Functional diversity of subgroup 5 R2R3-MYBs promoting proanthocyanidin biosynthesis and their key residues and motifs in tea plant.

The tea plant (Camellia sinensis) is rich in polyphenolic compounds. Particularly, flavan-3-ols and proanthocyanidins (PAs) are essential for the flavor and disease-resistance property of tea leaves. The fifth subgroup of R2R3-MYB transcription factors comprises the primary activators of PA biosynthesis. This study showed that subgroup 5 R2R3-MYBs in tea plants contained at least nine genes belonging to the TT2, MYB5, and MYBPA types. Tannin-rich plants showed an expansion in the number of subgroup 5 R2R3-MYB genes compared with other dicotyledonous and monocot plants. The MYBPA-type genes of tea plant were slightly expanded. qRT-PCR analysis and GUS staining analysis of promoter activity under a series of treatments revealed the differential responses of CsMYB5s to biotic and abiotic stresses. In particular, CsMYB5a, CsMYB5b, and CsMYB5e responded to high-intensity light, high temperature, MeJA, and mechanical wounding, whereas CsMYB5f and CsMYB5g were only induced by wounding. Three genetic transformation systems (C. sinensis, Nicotiana tabacum, and Arabidopsis thaliana) were used to verify the biological function of CsMYB5s. The results show that CsMYB5a, CsMYB5b, and CsMYB5e could promote the gene expression of CsLAR and CsANR. However, CsMYB5f and CsMYB5g could only upregulate the gene expression of CsLAR but not CsANR. A series of site-directed mutation and domain-swapping experiments were used to verify functional domains and key amino acids of CsMYB5s responsible for the regulation of PA biosynthesis. This study aimed to provide insight into the induced expression and functional diversity model of PA biosynthesis regulation in tea plants.

Amphiphilic polymers facilitated solid-phase extraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry for direct extraction and analysis of zearalenone and zearalanone in corn juice samples.

In this work, amphiphilic polymers synthesized from carboxylated carbon nanotubes stabilized high internal phase emulsions are demonstrated to be capable of direct extracting zearalenone and zearalanone in samples consisting of an oil-water emulsion system. Under optimal conditions, the maximum adsorption capacities for zearalenone and zearalanone are 17.27 and 13.26 mg/g. The adsorption is mainly attributed to π-π interaction, hydrophobic interaction, and hydrogen-bonding interaction for zearalenone and zearalanone. The adsorption isotherms reveal that the adsorption of zearalenone and zearalanone on amphiphilic polymers synthesized from carboxylated carbon nanotubes stabilized high internal phase emulsions follows Freundlich model with multilayer and heterogeneous adsorption due to the presence of multiple kinds of adsorption sites. The relative recoveries of the spiked zearalenone and zearalanone in corn juice samples range from 85% to 93% with relative standard deviations lower than 3.52%. The results manifest the high efficiency of amphiphilic polymers synthesized from carboxylated carbon nanotubes stabilized high internal phase emulsions for the adsorption and separation of analytes in the oil-water emulsion system. This study provides a new perspective on adsorbent engineering for the adsorption application in heterogeneous media.

Molecular characterization of a novel non-segmented double-stranded RNA mycovirus isolated from Penicillium citrinum strain RCEF7060.

Penicillium citrinum is a commonly occurring filamentous fungus with a worldwide distribution. However, no sequence data for viruses in P. citrinum have been reported. Here, we characterized a novel dsRNA virus from the hospital indoor air fungal strain P. citrinum RCEF 7060, which we have named "Penicillium citrinum non-segmented dsRNA virus 1" (PcNRV1). The genome of PcNRV1 dsRNA is 2,895 bp in length and contains two open reading frames encoding a protein with an unknown function in ORF1 and a putative RNA-dependent RNA polymerase (RdRp) in ORF2. Sequence comparisons and phylogenetic analysis showed that PcNRV formed a well-supported independent clade together with members of the proposed genus "Unirnavirus" and was most closely related to Penicillium miczynskii RNA virus 1 (PmRV1), with 76.45% amino acid sequence identity in the RdRp. Thus, PcNRV1 is a novel non-segmented dsRNA mycovirus belonging to the proposed genus "Unirnavirus" and is the first characterized viral sequence from P. citrinum.

Porous capillary monolithic column coupled with ultrahigh performance liquid chromatography-tandem mass spectrometry for fast and effective separation and determination of estrogens.

In this work, a porous capillary monolithic column was simply prepared by in situ thiol-alkyne click polymerization of dipentaerythritol hexakis (3-mercaptopropionate) and dimethyl dipropargylmalonate in fused-silica capillary. The capillary monolithic column shows excellent permeability, high porosity, and thoiether-rich groups, thereby, a high-efficient capacity for trace estrogens from complex samples are obtained via electron-donor-acceptor π-π interaction and hydrophobic interaction. The highest adsorption efficiency for estrogens is achieved at pH = 7.0 with a flow rate of 0.200 mL min-1. The superior adsorption capacities of the as-prepared capillary column for eight estrogens range from 0.092 mg m-1 to 0.31 mg m-1. A simple, reliable, and sensitive method for the determination of eight estrogens in biological and environmental samples is developed using the monolithic polymer as in-tube solid-phase microextraction coupled with ultrahigh performance liquid chromatography-tandem mass spectrometry (SPME-UPLC-MS/MS), and the total instrumental analysis time for the SPME-UPLC-MS/MS procedures was about 60 min per sample. The developed method shows a wide linear range (0.0500-5.00 µg L-1), and low limits of detection (5.34-9.63 ng L-1) for estrogens. The concentrations of estrogens in serum, urine, and pond water samples are found to be no more than 3.69, 0.741, and 1.04 µg L-1, respectively, and the satisfying recoveries for the eight estrogens range from 80.3% to 113% with relative standard deviations (n = 5) of 1.5-9.4%. The established method is highly potential for extraction and analysis of ultratrace target estrogens in complex matrices, such as biological and environmental samples.

Long noncoding RNA GAS5 alleviates the inflammatory response of human periodontal ligament stem cells by regulating the NF-κB signalling pathway.

OBJECTIVES: This study investigated the role of lncRNA growth arrest-specific transcript 5 (GAS5) in the inflammatory response of periodontal ligament stem cells (PDLSCs) during periodontitis with attempts to its possible mechanisms. MATERIALS AND METHODS: Gingiva samples were collected from healthy people and patients with periodontitis. The ligature-induced periodontitis model was established in mice. Cell transfection was utilized to knock down and overexpress GAS5 in PDLSCs. Quantitative real-time polymerase chain reaction (qRT-PCR) and fluorescence in situ hybridization were performed to detect the GAS5 expression. In combination with high-throughput sequencing technology, qRT-PCR, Western blotting, and immunofluorescence were performed to detect the effects of GAS5 on cytokines and proteins in the NF-κB pathway. RESULTS: GAS5 expression decreased in PDLSCs subjected to compressive force. GAS5 expression was downregulated in the gingiva tissues from patients with periodontitis. Consistent with the results of clinical samples, GAS5 expression decreased in the mouse ligature-induced periodontitis model. GAS5 expression was downregulated in PDLSCs under tumour necrosis factor (TNF)-α stimulation. Knockdown and overexpression of GAS5 increased and decreased the expression of cytokines induced by TNF-α in PDLSCs, respectively. The sequencing results showed that overexpressing GAS5 was related to genes in the NF-κB pathway. Overexpressing GAS5 alleviated p65 phosphorylation and inhibited the entry of p65 into the nucleus in the TNF-α activated NF-κB pathway, whereas GAS5 knockdown resulted in contrasting results. CONCLUSIONS: GAS5 alleviated the expression of cytokines in PDLSCs by inhibiting activation of the TNF-α-mediated NF-κB pathway. These findings provide new insight into the regulation of the PDLSCs inflammation response.

Magnetic phenolic resin core-shell structure derived carbon microspheres for ultrafast magnetic solid-phase extraction of triazine herbicides.

In this study, monodisperse magnetic carbon microspheres were successfully synthesized through the carbonization of phenolic resin encapsulated Fe3 O4 core-shell structures. The magnetic carbon microspheres showed high performance in ultrafast extraction and separation of trace triazine herbicides from environmental water samples. Under optimized conditions, both the adsorption and desorption processes could be achieved in 2 min, and the maximum adsorption capacity for simazine and prometryn were 387.6 and 448.5 µg/g. Coupled with high-performance liquid chromatography-ultraviolet detection technology, the detection limit of triazine herbicides was in the range of 0.30-0.41 ng/mL. The mean recoveries ranged from 81.44 to 91.03% with relative standard deviations lower than 7.47%. The excellent magnetic solid-phase extraction performance indicates that magnetic carbon microspheres are promising candidate adsorbents for the fast analysis of environmental contaminants.

Wettability tunable metal organic framework functionalized high internal phase emulsion porous monoliths for fast solid-phase extraction and sensitive analysis of hydrophilic heterocyclic amines.

Surface wettability greatly influences the adsorptive, catalytic, and diffuse performances of a porous material. To realize the improved adsorption performance to hydrophilic heterocyclic amines (HAs), polymeric high internal phase emulsions (polyHIPEs) that can be tuned from hydrophobic to hydrophilic is synthesized by facilely regulating the amount of metal organic frameworks (MOFs). The water contact angle of the MOFs and polyHIPEs hybrids (MOFs@polyHIPEs) decreases from 133° to 0° as the amount of amide-modified MOFs increases from 0% to 10%. The hydrophilization of divinybenzene (DVB) based polyHIPEs by MOFs hybridization significantly enhances their adsorption performance and enables them to be suitable for the solid phase extraction (SPE) of hydrophilic HAs. Under the optimized conditions, the MOFs@polyHIPEs achieve adsorption capacities ranging from 42.89 to 86.71 µg/g for HAs through the π-π interaction and hydrogen bonding. The adsorption follows the pseudo-second-order kinetic model, and the nitrogen atoms in/on the imidazole ring are identified as the active adsorption sites for hydrogen bonding. This SPE method, along with HPLC-MS detection, provides detection limits of HAs as low as 0.00020-0.00040 ng/mL. This work offers a feasible strategy in tuning the surface wettability of polyHIPEs without post-modification to achieve high-efficiency enrichment and analysis of HAs.

Interaction between laccase and diethylstilbestrol based on multispectral and chromatography analyses.

Diethylstilbestrol (DES) is a synthetic form of oestrogen that does not easily degrade in the environment and can be harmful to human health. Herein, the mechanism of the interaction between laccase and DES was investigated by various spectroscopic means and high-performance liquid chromatography (HPLC). The results of fluorescence experiments showed that the quenching of intrinsic fluorescence of laccase by DES was due to a static quenching, forming a binding site. According to the Förster non-radiative energy transfer theory (FRET), the action distance R0 between DES and laccase was 4.708 nm, r was 5.81 nm, and the energy transfer efficiency E was 22.08%, respectively. Both UV-Vis absorption spectra and FT-IR spectra indicated changes in the conformation and surroundings of the enzyme and changed in the secondary structure of laccase. Multispectral synthesis showed that the interaction of laccase with DES caused a change in the secondary structure of laccase. The degradation experiments showed that laccase could degrade DES, and the DES content decreased with time. This study provides a new theoretical basis and experimental method for further research on the reaction mechanism of the laccase degradation of DES. It may also provide a reference basis for human biological and environmental safety evaluations.

Aptamer functionalized and reduced graphene oxide hybridized porous polymers SPE coupled with LC-MS for adsorption and detection of human α-thrombin.

In this study, reduced graphene oxide (rGO) hybridized high internal phase emulsions were developed and polymerized as porous carriers for aptamer (5'/5AmMC6/-AGT CCG TGG TAG GGC AGG TTG GGG TGA CT-3') modification to enrich human α-thrombin from serum. The structure and properties of the materials were confirmed by scanning electron microscope (SEM), Fourier transform infrared spectroscope (FT-IR), and X-ray photoelectron spectra (XPS). The adsorption ability and selectivity were studied and the thrombin was detected with liquid chromatography-mass spectrometry (LC-MS). The adsorption of thrombin onto the sorbent was achieved within 30 min and the desorption was realized using 5.0 mL of acetonitrile/water (80/20, v/v). The thrombin was quantified by LC-MS according to its characteristic peptide sequence of ELLESYIDGR.

Ultrasensitive Temperature Sensing Based on Ligand-Free Alloyed CsPbClx Br3-x Perovskite Nanocrystals Confined in Hollow Mesoporous Silica with High Density of Halide Vacancies.

Temperature sensing based on fluorescent semiconductor nanocrystals has recently received immense attention. Enhancing the trap-facilitated thermal quenching of the fluorescence should be an effective approach to achieve high sensitivity for temperature sensing. Compared with conventional semiconductor nanocrystals, the defect-tolerant feature of lead halide perovskite nanocrystals (LHP NCs) endows them with high density of defects. Here, hollow mesoporous silica (h-SiO2 ) template-assisted ligand-free synthesis and halogen manipulation (chloride-importing) are proposed to fabricate highly defective yet fluorescent CsPbCl1.2 Br1.8 NCs confined in h-SiO2 (CsPbCl1.2 Br1.8 NCs@h-SiO2 ) for ultrasensitive temperature sensing. The trap barrier heights, exciton-phonon scattering, and trap state filling process in the CsPbCl1.2 Br1.8 NCs@h-SiO2 and CsPbBr3 NCs@h-SiO2 are studied to illustrate the higher temperature sensitivity of CsPbCl1.2 Br1.8 NCs@h-SiO2 at physiological temperature range. By integrating the thermal-sensitive CsPbCl1.2 Br1.8 NCs@h-SiO2 and thermal-insensitive K2 SiF6 :Mn4+ phosphor into the flexible ethylene-vinyl acetate polymer matrix, ratiometric temperature sensing from 30.0 °C to 45.0 °C is demonstrated with a relative temperature sensitivity up to 13.44% °C-1 at 37.0 °C. The composite film shows high potential as a thermometer for monitoring the body temperature. This work demonstrates the unparalleled temperature sensing performance of LHP NCs and provides new inspiration on switching the defects into advantages in sensing applications.

Plasma proteomic screening and validation of novel biomarkers in Takayasu's arteritis.

OBJECTIVES: To screen and validate differential proteins as novel biomarkers in active Takayasu's arteritis (TAK). METHODS: Plasma samples from 40 active, 40 inactive patients, and 40 healthy controls were collected. Protein profiles of plasma were mapped by two-dimensional gel electrophoresis. Differential protein spots were detected and identified by image analysis and mass spectrometry. Plasma concentrations of proteins were measured to validate candidate biomarkers. The area under the receiver operating characteristic (ROC) curve (AUC) of circulating plasma concentrations of candidate biomarkers were calculated to assess diagnostic value. RESULTS: With a total of 1507 matched gel spots, there were 170 differential expression spots between active and inactive TAK, including 139 up-regulated and 31 downregulated. Only 11 proteins could be identified by mass spectrometry. Serum amyloid A(SAA), fibrinogen, complement C4a, complement C3c, complement C4b binding protein(C4bp), recombination acting gene protein 1(RAG1), alpha-1-acid glycoprotein, alpha-1-microglobulin, complement C7, complement factor H related protein-1 were up-regulated in active patients, while serum amyloid P was down-regulated. Active patients had higher circulating levels of RAG1(P<0.001), C4bp (p=0.012) and SAA (p<0.001), compared to inactive patients, while inactive patients had higher levels than controls (RAG1, p=0.011; C4bp, p=0.012; SAA, p=0.005). The composite AUC with SAA, RAG1, and C4bp was 0.94 (95%CI 0.86-0.98) for discriminating activity, larger than 0.71(95% CI 0.60-0.80) for ESR (p=0.0004) or 0.75(95%CI 0.64-0.84) for CRP (p=0.0014), respectively. ONCLUSIONS: Some acute-phase and immunology-related proteins may serve as novel biomarkers of TAK. Further study of these proteins may be helpful to elucidate the pathologic mechanism.

Colorimetric sensing of chloride in sweat based on fluorescence wavelength shift via halide exchange of CsPbBr3 perovskite nanocrystals.

Considering the high importance of the rapid detection of chloride ion (Cl-) in sweat for the diagnosis of fibrotic cysts, we have investigated the heterogeneous halide exchange between CsPbBr3 perovskite nanocrystals (PNCs) in n-hexane and Cl- in aqueous solution. The results show that CsPbBr3 PNCs could achieve fast halide exchange with Cl- in the aqueous phase under magnetic stirring at pH = 1, accompanied by a significant wavelength blue shift and vivid fluorescence color changes from green to blue. Therefore, a fluorescence wavelength shift-based colorimetric sensing of Cl- based on the halide exchange of CsPbBr3 PNCs has been developed to realize the rapid detection of Cl- in sweat. Compared with the conventional fluorescence intensity-based method, this method is of high convenience since the whole procedure could be achieved within 5 min without any sample pretreatment (even no dilution), demonstrating promising application prospects. Graphical Abstract Fluorescence wavelength-shift based colorimetric sensing of chloride in sweat via halide exchange of CsPbBr3 perovskite nanocrystals.

Dual-Mode of Fluorescence Turn-On and Wavelength-Shift for Methylamine Gas Sensing Based on Space-Confined Growth of Methylammonium Lead Tribromide Perovskite Nanocrystals.

The defect-tolerant nature of lead halide perovskites renders outstanding luminescence by simple space-confined growth in nanopores. The fluorescence turn-on and wavelength-shift phenomena could be found in the formation of methylammonium lead tribromide (MAPbBr3) nanocrystals in hollow SiO2 nanospheres triggered by the reaction between methylamine (MA) gas and HPbBr3/PbBr2@SiO2 nanospheres. The enhanced fluorescence intensity is linear with the MA concentration in the range of 1.0-95 ppm with a limit of detection (LOD) of 70 ppb (S/N = 3). In addition, the maximum emission wavelength is consistently red-shifted from 478.7 to 510.6 nm as the MA concentration increases from 1.0 to 95 ppm, imparting the potential for colorimetric sensing. By combining the fluorescence turn-on and colorimetric sensing modes, the flexible method meets the demands for visual discrimination and point-of-care determination with portable devices.