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1.
Angew Chem Int Ed Engl ; : e202411499, 2024 Aug 21.
Artículo en Inglés | MEDLINE | ID: mdl-39166900

RESUMEN

Crystal structural rearrangements unavoidably introduce defects into materials, where even these small changes in local lattice structure could arouse a prominent impact on the overall nature of crystals. Contrary to the traditional notion that defects obstruct carrier transport, herein, we report a promoted transport mechanism of nonluminescent carriers in single-crystalline CH3NH3PbI3 nanowires (1345.2 cm2 V-1 s-1, about a 14-fold improvement), enabled by the phase transition induced defects (PTIDs). Carriers captured by PTIDs evade both the radiative and non-radiative recombinations during the incomplete tetragonal-to-orthorhombic phase transition at low temperatures, forming a specific nonluminescent state that exhibits an efficient long-distance transport and thereby realize a prominent enhancement of photocurrent responsivity for photodetector applications. The findings provide broader insights into the carrier transport mechanism in perovskite semiconductors and have significant implications for their rational design for photoelectronic applications at varied operating temperatures.

2.
Artículo en Inglés | MEDLINE | ID: mdl-39052932

RESUMEN

Native mass spectrometry (MS), ion mobility (IM), and collision-induced unfolding (CIU) have all been widely used to study the binding of small molecules to proteins and their complexes. Despite many successes in detecting subtle gas-phase stability differences in smaller systems dominated by single-domain subunits, studies targeting complexes comprised of large, multidomain subunits still face many challenges. For example, polyketide synthases (PKSs) are multiprotein enzymes that use their modular architecture to produce polyketide natural products and form the basis for nearly one-third of pharmaceuticals. Here, we describe the development of CIU methods capable of extracting information from these multiprotein complexes and demonstrate the current limits of quantitative CIU technology by probing the stabilities ∼280 kDa PKS dimer protein complexes. Our approach detects the evidence of the stability shifts associated with substrate binding that accounts for <0.1% of the mass for the intact assembly.

3.
Artículo en Inglés | MEDLINE | ID: mdl-39038158

RESUMEN

The type 1 polyketide synthase (PKS) assembly line uses its modular structure to produce polyketide natural products that form the basis of many pharmaceuticals. Currently, several cryoelectron microscopy (cryo-EM) structures of a multidomain PKS module have been constructed, but much remains to be learned. Here we utilize ion-mobility mass spectrometry (IM-MS) to record size and shape information and detect different conformational states of a 207 kDa didomain dimer comprised of ketosynthase (KS) and acyl transferase (AT), excised from full-length module. Furthermore, gas-phase stability differences between these different conformations are captured by collision induced unfolding (CIU) technology. Additionally, through tracking these forms as a function of time, we elucidate a detailed disassembly pathway for KS-AT dimers for the first time.

4.
ACS Appl Mater Interfaces ; 16(30): 39506-39516, 2024 Jul 31.
Artículo en Inglés | MEDLINE | ID: mdl-39013107

RESUMEN

Based on their excellent stability, high carrier mobility, and wide photoresponse range, composites formed by embedding perovskite quantum dots (PQDs) into metal-organic frameworks (PQDs@MOF) show great development potential in the field of photocatalysis, including the toxic hexavalent chromium (Cr6+) degradation, CO2 reduction, H2 production, etc. However, the rapid recombination of photogenerated carriers is still a major obstacle to the improvement of photocatalytic performance, and the internal mechanism of photocatalysis is still unclear. In this work, we construct a novel double heterojunction photocatalyst by encapsulating CsPbBr3 PQDs in Zr-based metal-organic frameworks (UiO-67) and loading additional hole-acceptor pentylenetetrazol (PTZ). Spontaneous photoinduced charge-transfer and separation between interfaces are confirmed by time-resolved photoluminescence and transient absorption spectroscopy. Furthermore, compared with pure UiO-67, the photoactivity of CsPbBr3 PQDs@UiO-67@PTZ increased 3-fold due to the long-lived charge-separated state. Our findings provide a new guideline for the design of PQDs@MOF-based photocatalysts with long-lived photogenerated carriers and outstanding photocatalytic activity.

5.
Front Cell Infect Microbiol ; 14: 1395267, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38817449

RESUMEN

Background: Traditional Chinese medicine (TCM) comprising herbal formulas has been used for millennia to treat various diseases, such as insomnia, based on distinct syndrome types. Although TCM has been proposed to be effective in insomnia through gut microbiota modulation in animal models, human studies remain limited. Therefore, this study employs machine learning and integrative network techniques to elucidate the role of the gut microbiome in the efficacies of two TCM formulas - center-supplementing and qi-boosting decoction (CSQBD) and spleen-tonifying and yin heat-clearing decoction (STYHCD) - in treating insomnia patients diagnosed with spleen qi deficiency and spleen qi deficiency with stomach heat. Methods: Sixty-three insomnia patients with these two specific TCM syndromes were enrolled and treated with CSQBD or STYHCD for 4 weeks. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI) and Insomnia Severity Index (ISI) every 2 weeks. In addition, variations in gut microbiota were evaluated through 16S rRNA gene sequencing. Stress and inflammatory markers were measured pre- and post-treatment. Results: At baseline, patients exhibiting only spleen qi deficiency showed slightly lesser severe insomnia, lower IFN-α levels, and higher cortisol levels than those with spleen qi deficiency with stomach heat. Both TCM syndromes displayed distinct gut microbiome profiles despite baseline adjustment of PSQI, ISI, and IFN-α scores. The nested stratified 10-fold cross-validated random forest classifier showed that patients with spleen qi deficiency had a higher abundance of Bifidobacterium longum than those with spleen qi deficiency with stomach heat, negatively associated with plasma IFN-α concentration. Both CSQBD and STYHCD treatments significantly improved sleep quality within 2 weeks, which lasted throughout the study. Moreover, the gut microbiome and inflammatory markers were significantly altered post-treatment. The longitudinal integrative network analysis revealed interconnections between sleep quality, gut microbes, such as Phascolarctobacterium and Ruminococcaceae, and inflammatory markers. Conclusion: This study reveals distinct microbiome profiles associated with different TCM syndrome types and underscores the link between the gut microbiome and efficacies of Chinese herbal formulas in improving insomnia. These findings deepen our understanding of the gut-brain axis in relation to insomnia and pave the way for precision treatment approaches leveraging TCM herbal remedies.


Asunto(s)
Medicamentos Herbarios Chinos , Microbioma Gastrointestinal , Medicina Tradicional China , Trastornos del Inicio y del Mantenimiento del Sueño , Humanos , Microbioma Gastrointestinal/efectos de los fármacos , Trastornos del Inicio y del Mantenimiento del Sueño/tratamiento farmacológico , Medicamentos Herbarios Chinos/farmacología , Medicamentos Herbarios Chinos/uso terapéutico , Masculino , Femenino , Persona de Mediana Edad , Adulto , ARN Ribosómico 16S/genética , Bazo/microbiología , Síndrome , Qi
6.
Small ; 20(26): e2310414, 2024 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-38294968

RESUMEN

As opposed to natural photosynthesis, a significant challenge in a semiconductor-based photocatalyst is the limited hole extraction efficiency, which adversely affects solar-to-fuel efficiency. Recent studies have demonstrated that photocatalysts featuring spatially isolated dual catalytic oxidation/reduction sites can yield enhanced hole extraction efficiencies. However, the decay dynamics of excited states in such photocatalysts have not been explored. Here a ternary barbell-shaped CdS/MoS2/Cu2S heterostructure is prepared, comprising CdS nanorods (NRs) interfaced with MoS2 nanosheets at both ends and Cu2S nanoparticles on the sidewall. By using transient absorption (TA) spectra, highly efficient charge separation within the CdS/MoS2/Cu2S heterostructure are identified. This is achieved through directed electron transfer to the MoS2 tips at a rate constant of >8.3 × 109 s-1 and rapid hole transfer to the Cu2S nanoparticles on the sidewall at a rate of >6.1 × 1010 s-1, leading to an exceptional overall charge transfer constant of 2.3 × 1011 s-1 in CdS/MoS2/Cu2S. The enhanced hole transfer efficiency results in a remarkably prolonged charge-separated state, facilitating efficient electron accumulation within the MoS2 tips. Consequently, the ternary CdS/MoS2/Cu2S heterostructure demonstrates a 22-fold enhancement in visible-light-driven H2 generation compare to pure CdS nanorods. This work highlights the significance of efficient hole extraction in enhancing the solar-to-H2 performance of semiconductor-based heterostructure.

7.
J Gastrointest Oncol ; 13(5): 2197-2218, 2022 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-36388689

RESUMEN

Background: Cancer-associated fibroblasts (CAFs) are vital components of gastric cancer (GC) microenvironments, which impact the aggressive characteristics of GC cells. The objective of this study is to evaluate the influence of High Mobility Group Box (HMGB) on CAF-related GC. Methods: The tissues of 10 GC patients who underwent surgery the Sanya Central Hospital of Hainan Province from July 2018 to July 2019 were collected for the clinical study. Moreover, the GC cell lines, including MGC-803, AGS, and SGC-7901, were used in vitro experiment. We investigated the molecular mechanism of the miR-200b/HMGB3 axis in affecting the chemoresistance and epithelial-mesenchymal transition (EMT) of GC cells induced by CAFs. Cell transfection, Cell Counting Kit-8 (CCK-8), Transwell assay, western blot, enzyme-linked immunosorbent assay (ELISA), and other experiments were employed. Results: We found that miR-200b was down-regulated, yet HMGB3 was up-regulated in CAF-related GC. The CAFs markedly promoted cisplatin (CDDP) resistance, proliferation, invasion, migration, and EMT of GC cells. Gain-assay of miR-200b demonstrated that miR-200b inhibited the HMGB3 release from CAFs. In-vivo experiments confirmed that the growth and EMT of GC cells co-cultured with CAF-miR-200b were significantly reduced. Furthermore, CAFs enhanced the activation of ERK, JNK, and the Wnt/ß-catenin pathways, and those pathways, as well as the malignant behaviors of GC cells, were obviously attenuated by miR-200b or HMGB3 silencing. Conclusions: Collectively, HMGB3 derived from CAFs is negatively regulated by miR-200b and promotes the malignant behaviors of GC cells.

8.
Dis Markers ; 2022: 8928282, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-36438902

RESUMEN

Long noncoding RNAs (lncRNAs) are revealed to be involved in the tumorigenesis and progression of human malignancies mediated by microRNA (miRNA) via the competing endogenous RNA (ceRNA) mechanism, a newly proposed "RNA language." However, the lncRNA-associated competing triplet (lncACT) network among ceRNA transcripts in clear cell renal cell carcinoma (ccRCC) is currently lacking. We carried out differential expression analysis to identify aberrantly expressed lncRNAs, miRNAs, and mRNAs by analyzing the RNA-seq data of 420 ccRCC tissues and 71 noncancerous kidney tissues obtained from The Cancer Genome Atlas (TCGA). Then, a ccRCC-specific ceRNA network was built using computational algorithms, including miRcode, TargetScan, miRanda, and miRTarBase. In total, 1491 dysregulated lncRNAs were found between normal renal tissues and ccRCC (fold change > 4 and false discovery rate < 0.01). A ceRNA network that comprised of 46 DElncRNAs, 11 DEmiRNAs, and 55 DEmRNAs was established by integrating the lncRNA/miRNA and miRNA/mRNA interactions into lncACTs. Several lncRNAs were identified to be significantly associated with clinical features of ccRCC patients. Notably, four key lncRNAs (TCL6, HOTTIP, HULC, and PCGEM1) were tightly correlated with both patients' clinical characteristics and overall survival (log-rank P < 0.05), indicating their potential important roles in ccRCC. HOTTIP may be a potential prognostic and therapeutic molecular marker for ccRCC patients. Collectively, our results provide a comprehensive view of the lncRNA-associated ceRNA regulatory network for a better understanding of the mechanisms and prognosis biomarkers for ccRCC.


Asunto(s)
Carcinoma de Células Renales , Neoplasias Renales , MicroARNs , ARN Largo no Codificante , Humanos , Carcinoma de Células Renales/genética , Carcinoma de Células Renales/metabolismo , Regulación Neoplásica de la Expresión Génica , Redes Reguladoras de Genes , Neoplasias Renales/genética , Neoplasias Renales/metabolismo , MicroARNs/genética , MicroARNs/metabolismo , ARN Largo no Codificante/genética , ARN Largo no Codificante/metabolismo , ARN Mensajero/genética
9.
Sci Rep ; 12(1): 19222, 2022 11 10.
Artículo en Inglés | MEDLINE | ID: mdl-36357426

RESUMEN

This paper proposes an optimal reactive power control method to maximize wind farm revenue and minimize the total electrical losses of a doubly-fed induction generator (DFIG)-based wind farm. Specifically, the split Bregman method is used to solve the optimal control problem in a distributed manner. That is, the optimization problem is decomposed into sub-problems by the optimal distributed control strategy, and each sub-problem is solved independently in each local controller through the parallel method, which reduces the calculating burden and improves the information privacy. Thus, when a fault occurs, the proposed distributed control strategy can overcome the system fault and improve the reliability and security of the system. Furthermore, an economic financial model of annual revenue is contributed to examine the income impact with or without certified emission reduction (CER) by the clean development mechanism (CDM). Compared with the dual ascent (DA) method, sequential quadratic programming (SQP) method and the proportional dispatch method (PDM), the annual revenue (AR) of the wind farm using the proposed split Bregman method is the highest. Simulation results demonstrate that this method has promising performance in both optimization quality and computational efficiency.


Asunto(s)
Reproducibilidad de los Resultados , Simulación por Computador
10.
ACS Omega ; 7(12): 10365-10371, 2022 Mar 29.
Artículo en Inglés | MEDLINE | ID: mdl-35382338

RESUMEN

Two-dimensional (2D) and quasi-2D Ruddlesden-Popper (RP) phase organolead halide perovskites are promising materials for both photovoltaic and optoelectronic devices. Although they are known to be more stable when exposed to moisture than their 3D counterpart, chemical degradation of these materials under moisture, which not only leads to a significant drop in device performance but also leads to lead leakage, yet remains one of the most serious hurdles for their practical applications. To gain insight into the degradation mechanism of 2D/quasi-2D perovskites under moisture conditions, the degradation pathway of 2D/quasi-2D (PEA)2(MA) n-1PbnI3n+1 (PEA = C6H5C2H4NH3 +, MA = CH3NH3 +, and n is the number of perovskite layers between adjacent organic spacer layers) perovskite single crystals (SCs) and thin film are explored. We observe the degradation process by mapping the photoluminescence of the 2D perovskites and demonstrate that the larger-n phases all directly degrade into the relative stable n = 1 phase and MAI and PbI2, which is a mechanism different from that in previous reports and further confirmed in the 2D perovskite thin film. This degradation process is also found to be independent of the boundary and morphology of the SCs. This discovery provides a new perspective for understanding the chemical degradation of the 2D perovskite materials and may inspire new solutions for improving their moisture stability.

11.
Eur J Orthod ; 44(4): 420-426, 2022 08 16.
Artículo en Inglés | MEDLINE | ID: mdl-35290462

RESUMEN

BACKGROUND AND OBJECTIVES: Cementoblasts can communicate with osteoclasts by synthesis and secretion of cytokines, such as RANKL, OPG, and M-CSF. Previously, we reported that irisin promotes the differentiation of cementoblasts, while the effect of irisin on cementoblast-mediated osteoclastogenesis remains inconclusive. This study aimed to explore the effect of irisin on the expression of osteoclastogenesis-related cytokines in cementoblasts. MATERIAL AND METHODS: An immortalized murine cementoblast cell line OCCM-30 was used. Immunofluorescence and Western Blot were performed to identify the expression of irisin receptor integrin alphaV and the activation of its downstream signals in OCCM-30 cells. Cells were treated with irisin (100 ng/ml) for various time lengths ranging from 0 to 72 hours, and then qRT-PCR was used to detect the expression of osteoclastogenesis-related genes, including RANKL, IL-6, M-CSF, OPG, Wnt5A, Sema3A. Cells were also incubated with irisin in a series of concentrations (0-200 ng/ml) for 24 hours, and then qRT-PCR and ELISA were performed to examine the above osteoclastogenesis-related cytokines. RESULTS: Irisin receptor integrin alphaV was expressed in OCCM-30 cells and its downstream signaling pathways were markedly activated by irisin. Both qRT-PCR and ELISA results revealed that RANKL and IL-6 were up-regulated by irisin while M-CSF, OPG, Wnt5A, Sema3A remained unaffected. CONCLUSIONS: OCCM-30 cells were responsive to the stimulation of irisin. The expression of RANKL and IL-6 was significantly enhanced by irisin, suggesting a possible promotive effect on cementoblast-mediated osteoclastogenesis.


Asunto(s)
Cemento Dental , Osteoclastos , Animales , Proteínas Portadoras/metabolismo , Proteínas Portadoras/farmacología , Diferenciación Celular , Fibronectinas/metabolismo , Fibronectinas/farmacología , Integrina alfaV/metabolismo , Integrina alfaV/farmacología , Interleucina-6/metabolismo , Interleucina-6/farmacología , Factor Estimulante de Colonias de Macrófagos/metabolismo , Factor Estimulante de Colonias de Macrófagos/farmacología , Ratones , Osteoprotegerina/metabolismo , Ligando RANK/metabolismo , Semaforina-3A/metabolismo , Semaforina-3A/farmacología
12.
J Am Chem Soc ; 143(45): 19128-19136, 2021 Nov 17.
Artículo en Inglés | MEDLINE | ID: mdl-34730344

RESUMEN

Layered two-dimensional (2D) lead halide perovskites are a class of quantum well (QW) materials, holding dramatic potentials for optical and optoelectronic applications. However, the thermally activated exciton dissociation into free carriers in 2D perovskites, a key property that determines their optoelectronic performance, was predicted to be weak due to large exciton binding energy (Eb, about 100-400 meV). Herein, in contrast to the theoretical prediction, we discover an ultrafast (<1.4 ps) and highly efficient (>80%) internal exciton dissociation in (PEA)2(MA)n-1PbnI3n+1 (PEA = C6H5C2H4NH3+, MA = CH3NH3+, n = 2-4) 2D perovskites despite the large Eb. We demonstrate that the exciton dissociation activity in 2D perovskites is significantly promoted because of the formation of exciton-polarons with considerably reduced exciton binding energy (down to a few tens of millielectronvolts) by the polaronic screening effect. This ultrafast and high-yield exciton dissociation limits the photoluminescence of 2D perovskites but on the other hand well explains their exceptional performance in photovoltaic devices. The finding should represent a common exciton property in the 2D hybrid perovskite family and provide a guideline for their rational applications in light emitting and photovoltaics.

13.
J Phys Chem Lett ; 12(5): 1475-1480, 2021 Feb 11.
Artículo en Inglés | MEDLINE | ID: mdl-33530690

RESUMEN

Doping with a transition metal is an effective way to tune the optical properties of semiconductor nanocrystals (NCs). The excitation of transition-metal dopants in NCs is through an internal energy transfer from a host exciton, by which the short-lived exciton energy can be "stored" at the dopant for a significantly longer lifetime. Herein, using Mn-doped CsPbCl3 perovskite NCs as an example, we report that the long-lived excited state at Mn dopants can be efficiently extracted from the NCs through an external energy transfer (EET) to rhodamine B (RhB) molecules adsorbed on the NC surface. The EET process leads to a delayed RhB emission. The EET rate is found to increase from 0.16 to 1.42 ms-1 as the number of RhB molecules adsorbed per NC increases from 1 to 8.9, leading to energy extraction efficiency up to 71%. This work suggests the potential of Mn-doped perovskite NCs for applications in photon energy conversion and biological imaging.

14.
ACS Omega ; 6(51): 35427-35432, 2021 Dec 28.
Artículo en Inglés | MEDLINE | ID: mdl-34984274

RESUMEN

The temperature-induced phase transition in two-dimensional (2D) layered perovskites was recently found to be incomplete even if the temperature dropped to tens of kelvin. However, its intrinsic cause still remains unclear, and the information on the phase transition in individual single crystals (SCs) is also limited. Herein, we study the phase transition process in individual (n-C4H9NH3)2PbI4 SCs using a home-built photoluminescence (PL)-scanned image microscope. At 83 K, the phase transition is indeed incomplete, leading to the coexistence and inhomogeneous distributions of room-temperature and low-temperature phases. We map the distribution of phase transition degree on individual SCs at 83 K, which exhibits a strong positive (negative) correlation with the distribution of local defects (PL lifetimes) at 293 K, indicating that the phase transition is enhanced by initial defects. Our findings might provide new insight into the phase transition of (n-C4H9NH3)2PbI4 crystals, which is of potential value for applications based on 2D layered perovskites.

15.
Biochemistry ; 60(2): 125-134, 2021 01 19.
Artículo en Inglés | MEDLINE | ID: mdl-33342208

RESUMEN

Ferulic acid decarboxylase catalyzes the decarboxylation of various substituted phenylacrylic acids to their corresponding styrene derivatives and CO2 using the recently discovered cofactor prenylated FMN (prFMN). The mechanism involves an unusual 1,3-dipolar cycloaddition reaction between prFMN and the substrate to generate a cycloadduct capable of undergoing decarboxylation. Using native mass spectrometry, we show the enzyme forms a stable prFMN-styrene cycloadduct that accumulates on the enzyme during turnover. Pre-steady state kinetic analysis of the reaction using ultraviolet-visible stopped-flow spectroscopy reveals a complex pattern of kinetic behavior, best described by a half-of-sites model involving negative cooperativity between the two subunits of the dimeric enzyme. For the reactive site, the cycloadduct of prFMN with phenylacylic acid is formed with a kapp of 131 s-1. This intermediate converts to the prFMN-styrene cycloadduct with a kapp of 75 s-1. Cycloelimination of the prFMN-styrene cycloadduct to generate styrene and free enzyme appears to determine kcat for the overall reaction, which is 11.3 s-1.


Asunto(s)
Carboxiliasas/química , Carboxiliasas/metabolismo , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/metabolismo , Escherichia coli/enzimología , Flavinas/metabolismo , Neopreno/metabolismo , Sitios de Unión , Catálisis , Dominio Catalítico , Cinética , Prenilación
16.
J Phys Chem Lett ; 11(21): 9045-9050, 2020 Nov 05.
Artículo en Inglés | MEDLINE | ID: mdl-33044078

RESUMEN

The encapsulation of perovskite quantum dots (PQDs) in metal organic frameworks (MOFs) is a promising strategy for fabricating stable and functional perovskite solid composites (denoted as PQDs@MOF), which have exhibited great potential for optoelectronics, catalysis, and luminesce applications. However, the exciton diffusion distance, one of the key factors determining the performance of PQDs@MOF in these applications, remains unknown. Herein, by using time-resolved and photoluminescence-scanned imaging microscopy, we report the observation of long-distance exciton transport (278 ± 12.6 nm) and high diffusion coefficient (0.0428 ± 0.0039 cm2/s) in MAPbBr3 PQDs@MOF microcrystals. We show that the long exciton diffusion length, which is seven times longer than that in colloid MAPbBr3 PQD solid films, can be attributed to the strong dipole-dipole coupling between adjacent PQDs embedded in the MOF matrix and their long carrier lifetimes. These findings demonstrate the great potential of PQDs@MOF crystals for optoelectronic applications.

17.
J Am Chem Soc ; 142(35): 15091-15097, 2020 Sep 02.
Artículo en Inglés | MEDLINE | ID: mdl-32786774

RESUMEN

Layered two-dimensional (2D) hybrid perovskites are naturally formed multiple quantum well (QW) materials with promising applications in quantum and optoelectronic devices. In principle, the transport of excitons in 2D perovskites is limited by their short lifetime and small mobility to a distance within a few hundred nanometers. Herein, we report an observation of long-distance carrier transport over 2 to 5 µm in 2D perovskites with various well thicknesses. Such a long transport distance is enabled by trap-induced exciton dissociation into long-lived and nonluminescent electron-hole separated state, followed by a trap-mediated charge transport process. This unique property makes 2D perovskites comparable with 3D perovskites and other traditional semiconductor QWs in terms of a carrier transport property and highlights their potential application as an efficient energy/charge-delivery material.

18.
J Am Chem Soc ; 141(51): 20089-20096, 2019 Dec 26.
Artículo en Inglés | MEDLINE | ID: mdl-31791123

RESUMEN

Divalent manganese cation (Mn2+) doped perovskite materials are of great interest for their unique optical, magnetic, and electric properties. Herein, we report an excitation-dependent emission color tuning from an individual Mn-doped CsPbCl3 microcrystal (MC) with a wide color tuning range, reversible and continuous color change, and high photostability. We demonstrate that the Mn-doped CsPbCl3 MCs exhibit dual-color emission from both host excitons (blue) and Mn-dopants (orange) through an internal energy transfer (IET) process. By simple change of the laser excitation repetition rate or pulse intensity, the relative emission intensity between exciton (Iexciton) and Mn-dopant (IMn) can be continuously and reversibly tuned from IMn/Itotal (Itotal = IMn + Iexciton) = 0.9-0.8 to 0.1-0.2, corresponding to a color change from orange to blue. Such emission color tuning is enabled by the saturation of Mn-dopant emission at high excitation intensity and a linear dependence of exciton emission with excitation intensity. Transient spectroscopy and temperature-dependent photoluminescence (PL) measurements confirm that the exciton-to-dopant IET in Mn-doped CsPbCl3 MCs is mediated by some shallow trap states, rather than through a direct transfer pathway. Therefore, the saturation of Mn-dopant emission is caused by a bottlenecked energy transfer effect by saturating the mediating trap states at high excitation intensities. The Mn-doped MCs also exhibit a high photostability on the reversible switch of emission color between orange and blue for more than 300 cycles within a continuous operation time of 14 h. In view of the stable and color-switchable emission properties, Mn-doped perovskite MCs may find application in nanophotonic devices using a single MC.

19.
J Phys Chem Lett ; 10(14): 3950-3954, 2019 Jul 18.
Artículo en Inglés | MEDLINE | ID: mdl-31244166

RESUMEN

Two-dimensional (2D) hybrid perovskites have emerged as promising materials for optoelectronic devices owing to their improved stability. The crystal edges of layered 2D perovskites were found to play an important role in device performance by providing a pathway to dissociate bound excitons into long-lived free charge carriers. However, their formation mechanism and whether they are controllable remain unclear. Herein, we report a photoluminescence (PL) imaging study on layered (BA)2(MA)n-1PbnI3n+1 (BA = CH3(CH2)3NH3+, MA = CH3NH3+) perovskite single crystals before and after treatment with butylammonium iodide (BAI) and methylammonium iodide (MAI) solutions. We find that the crystal edges with exciton dissociation ability are induced by the loss of BA ligands and can be removed by adding additional BA cations and regenerated by BA-to-MA cation exchange. This work presents a simple yet efficient method to develop and control the properties of crystal edges for better applications in 2D perovskite devices.

20.
J Phys Chem Lett ; 10(10): 2357-2362, 2019 May 16.
Artículo en Inglés | MEDLINE | ID: mdl-31006244

RESUMEN

Metal-halide perovskites are promising optical gain materials because of their excellent photophysical properties. Recently, large perovskite single crystals with phase purity, less defects, and over millimeter dimensions have been successfully synthesized. However, the optical gain effect from these large-size single crystals has not yet been realized. Herein, we for the first time report efficient two-photon pumped amplified spontaneous emission (ASE) from millimeter-sized CsPbBr3 single crystals (SCs) with a low threshold of 0.65 mJ cm-2 and an optical gain of 38 cm-1. Furthermore, the CsPbBr3 SCs also exhibit ultrastable ASE under continuous laser irradiation for more than 40 h (corresponds to 1.5 × 108 laser shots) at ambient condition. This work suggests the potential application of large-size perovskite single crystals in practical nonlinear optical devices.

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