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1.
Artigo em Inglês | MEDLINE | ID: mdl-32601216

RESUMO

The application of pressure can achieve novel structures and exotic phenomena in condensed matters. However, such pressure-induced transformations are generally reversible and useless for engineering materials for ambient-environment applications. Here, we report comprehensive high-pressure investigations on a series of Dion-Jacobson (D-J) perovskites A'A n-1Pb n I3n+1 [A' = 3-(aminomethyl) piperidinium (3AMP), A = methylammonium (MA), n = 1, 2, 4]. Our study demonstrates their irreversible behavior, which suggests pressure/strain engineering could viably improve light-absorber material not only in situ but also ex situ, thus potentially fostering the development of optoelectronic and electroluminescent materials. We discovered that the photoluminescence (PL) intensities are remarkably enhanced by one order of magnitude at mild pressures. Also, higher pressure significantly changes the lattices, boundary conditions of electronic wave functions, and possibly leads to semiconductor-metal transitions. For (3AMP)(MA)3Pb4I13, permanent recrystallization from 2D to three-dimensional (3D) structure occurs upon decompression, with dramatic changes in optical properties.

2.
Nat Commun ; 11(1): 151, 2020 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-31919343

RESUMO

State-of-the-art halide perovskite solar cells have bandgaps larger than 1.45 eV, which restricts their potential for realizing the Shockley-Queisser limit. Previous search for low-bandgap (1.2 to 1.4 eV) halide perovskites has resulted in several candidates, but all are hybrid organic-inorganic compositions, raising potential concern regarding device stability. Here we show the promise of an inorganic low-bandgap (1.38 eV) CsPb0.6Sn0.4I3 perovskite stabilized via interface functionalization. Device efficiency up to 13.37% is demonstrated. The device shows high operational stability under one-sun-intensity illumination, with T80 and T70 lifetimes of 653 h and 1045 h, respectively (T80 and T70 represent efficiency decays to 80% and 70% of the initial value, respectively), and long-term shelf stability under nitrogen atmosphere. Controlled exposure of the device to ambient atmosphere during a long-term (1000 h) test does not degrade the efficiency. These findings point to a promising direction for achieving low-bandgap perovskite solar cells with high stability.

3.
Chin Med J (Engl) ; 132(22): 2716-2723, 2019 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-31725448

RESUMO

BACKGROUND: Endostatin, a biologically active fragment of collagen XVIII, has been observed in patients with ischemic heart disease. The aim of the present study was to investigate whether endostatin overexpression could attenuate cardiac hypertrophy by inhibiting the cyclic adenosine monophosphate-protein kinase A (cAMP-PKA) signaling pathway. METHODS: This study was examined in vivo in rats and in vitro in primary neonatal rat cardiomyocytes treated with angiotensin (Ang) II to model cardiac hypertrophy. Twenty-four male Sprague-Dawley rats were randomized into adenovirus (Ad)-green fluorescent protein, Ang II, Ad-endostatin, and Ang II + Ad-endostatin groups (n = 6 in each group). Four weeks later, all the rats were weighed and sacrificed after transthoracic echocardiography. Cardiac function was evaluated by transthoracic echocardiography, cardiomyocyte size was evaluated by hematoxylin-eosin staining. Levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were evaluated by quantitative reverse-transcription polymerase chain reaction or Western blotting, PKA level was evaluated by Western blotting, and cAMP level was evaluated by enzyme-linked immunosorbent assay. Statistical significance among multiple groups was evaluated by one-way analysis of variance. RESULTS: Endostatin overexpression reduced the increases in left ventricle (LV) mass (P = 0.0063), LV mass/body weight (BW) (P = 0.0013), interventricular septal thickness (IVS) in diastole (P = 0.0013), IVS in systole (P = 0.0056), left ventricular posterior wall thickness (LVPW) in diastole (P = 0.0291), LVPW in systole (P = 0.0080), heart weight (HW) (P = 0.0138), HW/BW (P = 0.0001), and HW/tibial length (P = 0.0372) in Ang II-treated rats. In addition, endostatin overexpression reduced cardiomyocyte cross-sectional area expansion, and reduced the levels of ANP and BNP in Ang II-treated rats (P = 0.0251 and 0.0477 for messenger RNA [mRNA]), and primary neonatal rat cardiomyocytes (P = 0.0188 and P = 0.0024 for mRNA; P = 0.0023 and 0.0013 for protein, respectively). Additionally, endostatin overexpression reduced the increase of cAMP (P = 0.0054) and PKA (P = 0.0328) levels in cardiomyocytes treated with Ang II. Treatment with cAMP reversed the effects of endostatin overexpression on ANP (P = 0.0263) and BNP (P = 0.0322) levels in cardiomyocytes induced by Ang II. CONCLUSION: Endostatin overexpression could alleviate cardiac hypertrophy by inhibiting the cAMP-PKA signaling pathway.


Assuntos
Angiotensina II/farmacologia , Cardiomegalia/induzido quimicamente , Cardiomegalia/metabolismo , Endostatinas/metabolismo , Animais , Western Blotting , AMP Cíclico/metabolismo , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Ecocardiografia , Imunofluorescência , Masculino , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Ratos , Ratos Sprague-Dawley , Transdução de Sinais/efeitos dos fármacos
4.
PLoS One ; 14(9): e0222665, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31539408

RESUMO

BACKGROUND AND AIM: Depression is often accompanied by thoughts of self-harm, which are a strong predictor of subsequent suicide attempt and suicide death. Few empirical data are available regarding the temporal correlation between depression symptoms and suicidal ideation. We investigated the anecdotal concern that suicidal ideation may increase during a period of depression improvement. DATA: Longitudinal Patient Health Questionnaire (PHQ)-9 is a questionnaire of 9 multiple-choice questions to assess the frequency of depressive symptoms within the previous two weeks. We analyzed a chronic depression treatment population's electronic health record (EHR) data, containing 610 patients' longitudinal PHQ-9 scores (62% age 45 and older; 68% female) within 40 weeks. METHODS: The irregular and sparse EHR data were transformed into continuous trajectories using Gaussian process regression. We first estimated the correlations between the symptoms (total score of the first 8 questions; PHQ-8) and suicide ideation (9th question score; Item 9) using the cross-correlation function. We then used an artificial neural network (ANN) to discover subtypes of depression patterns from the fitted depression trajectories. In addition, we conducted a separate analysis using the unfitted raw PHQ scores to examine PHQ-8's and Item 9's pattern changes. RESULTS: Results showed that the majority of patients' PHQ-8 and Item 9 scores displayed strong temporal correlations. We found five patterns in the PHQ-8 and the Item 9 trajectories. We also found 8% - 13% of the patients have experienced an increase in suicidal ideation during the improvement of their PHQ-8. Using a trajectory-based method for subtype pattern detection in depression progression, we provided a better understanding of temporal correlations between depression symptoms over time.


Assuntos
Depressão/epidemiologia , Aprendizado de Máquina , Ideação Suicida , Adulto , Feminino , Humanos , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Distribuição Normal , Escalas de Graduação Psiquiátrica , Indução de Remissão , Inquéritos e Questionários , Fatores de Tempo
5.
Nat Commun ; 10(1): 482, 2019 01 29.
Artigo em Inglês | MEDLINE | ID: mdl-30696817

RESUMO

Organic-inorganic hybrid perovskites such as methylammonium lead iodide (CH3NH3PbI3) are game-changing semiconductors for solar cells and light-emitting devices owing to their defect tolerance and exceptionally long carrier lifetimes and diffusion lengths. Determining whether the dynamically disordered organic cations with large dipole moment benefit the optoelectronic properties of CH3NH3PbI3 has been an outstanding challenge. Herein, via transient absorption measurements employing an infrared pump pulse tuned to a methylammonium vibration, we observe slow, nanosecond-long thermal dissipation from the selectively excited organic mode to the inorganic sublattice. The resulting transient electronic signatures, during the period of thermal-nonequilibrium when the induced thermal motions are mostly concentrated on the organic sublattice, reveal that the induced atomic motions of the organic cations do not alter the absorption or the photoluminescence response of CH3NH3PbI3, beyond thermal effects. Our results suggest that the attractive optoelectronic properties of CH3NH3PbI3 mainly derive from the inorganic lead-halide framework.

6.
Phys Rev Lett ; 121(12): 127401, 2018 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-30296165

RESUMO

Excitations of free electrons and optical phonons are known to permit access to the negative real part of relative permittivities (ϵ^{'}<0) that yield strong light-matter interactions. However, negative ϵ^{'} arising from excitons has been much less explored. Via development of a dielectric-coating based technique described herein, we report fundamental optical properties of two-dimensional hybrid perovskites (2DHPs), composed of alternating layers of inorganic and organic sublattices. Low members of 2DHPs (N=1 and N=2) exhibit negative ϵ^{'} stemming from the large exciton binding energy and sizable oscillator strength. Furthermore, hyperbolic dispersion (i.e., ϵ^{'} changes sign with directions) occurs in the visible range, which has been previously achieved only with artificial metamaterials. Such naturally occurring, exotic dispersion stems from the extremely anisotropic excitonic behaviors of 2DHPs, and can intrinsically support a large photonic density of states. We suggest that several other van der Waals solids may exhibit similar behaviors arising from excitonic response.

7.
Proc Natl Acad Sci U S A ; 115(32): 8076-8081, 2018 08 07.
Artigo em Inglês | MEDLINE | ID: mdl-30038004

RESUMO

Materials in metastable states, such as amorphous ice and supercooled condensed matter, often exhibit exotic phenomena. To date, achieving metastability is usually accomplished by rapid quenching through a thermodynamic path function, namely, heating-cooling cycles. However, heat can be detrimental to organic-containing materials because it can induce degradation. Alternatively, the application of pressure can be used to achieve metastable states that are inaccessible via heating-cooling cycles. Here we report metastable states of 2D organic-inorganic hybrid perovskites reached through structural amorphization under compression followed by recrystallization via decompression. Remarkably, such pressure-derived metastable states in 2D hybrid perovskites exhibit enduring bandgap narrowing by as much as 8.2% with stability under ambient conditions. The achieved metastable states in 2D hybrid perovskites via compression-decompression cycles offer an alternative pathway toward manipulating the properties of these "soft" materials.

8.
Nat Commun ; 9(1): 2792, 2018 07 18.
Artigo em Inglês | MEDLINE | ID: mdl-30022022

RESUMO

Hybrid organic-inorganic perovskites are emerging semiconductors for cheap and efficient photovoltaics and light-emitting devices. Different from conventional inorganic semiconductors, hybrid perovskites consist of coexisting organic and inorganic sub-lattices, which present disparate atomic masses and bond strengths. The nanoscopic interpenetration of these disparate components, which lack strong electronic and vibrational coupling, presents fundamental challenges to the understanding of charge and heat dissipation. Here we study phonon population and equilibration processes in methylammonium lead iodide (MAPbI3) by transiently probing the vibrational modes of the organic sub-lattice following above-bandgap optical excitation. We observe inter-sub-lattice thermal equilibration on timescales ranging from hundreds of picoseconds to a couple of nanoseconds. As supported by a two-temperature model based on first-principles calculations, the slow thermal equilibration is attributable to the sequential phonon populations of the inorganic and organic sub-lattices, respectively. The observed long-lasting thermal non-equilibrium offers insights into thermal transport and heat management of the emergent hybrid material class.

9.
Adv Mater ; : e1800973, 2018 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-29984441

RESUMO

The chemical stabilities of hybrid perovskite materials demand further improvement toward long-term and large-scale photovoltaic applications. Herein, the enhanced chemical stability of CH3 NH3 PbI3 is reported by doping the divalent anion Se2- in the form of PbSe in precursor solutions to enhance the hydrogen-bonding-like interactions between the organic cations and the inorganic framework. As a result, in 100% humidity at 40 °C, the 10% w/w PbSe-doped CH3 NH3 PbI3 films exhibited >140-fold stability improvement over pristine CH3 NH3 PbI3 films. As the PbSe-doped CH3 NH3 PbI3 films maintained the perovskite structure, a top efficiency of 10.4% with 70% retention after 700 h aging in ambient air is achieved with an unencapsulated 10% w/w PbSe:MAPbI3 -based cell. As a bonus, the incorporated Se2- also effectively suppresses iodine diffusion, leading to enhanced chemical stability of the silver electrodes.

10.
Opt Express ; 26(4): 4665-4673, 2018 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-29475314

RESUMO

While the nanowire (NW) lasers have attracted much attentions as nanoscale coherent sources in recent years, the heat accumulation and temperature-rise-induced breakdown remain challenges to improving the lasers for practical applications. Here we propose a microscale liquid-cooled approach to address the issue. Calculated results show that, compared with conventional air-cooled lasing systems, liquid-cooled NW lasers can allow much higher thermal power. By keeping the NW temperature below 373 K, the allowed thermal power in water is about 21 times that in air (850 µW in water versus 40 µW in air). Transient temperature evolution reveals a much faster heat dissipation of the NW in water (30 ns) than in air (7 µs), indicating a much higher allowable repetition rate in water than in air (e.g., 10 MHz versus 100 kHz). Our results suggest a possible route to compact NW lasers with higher power, new materials and new operation modes.

11.
Proc Natl Acad Sci U S A ; 113(32): 8910-5, 2016 08 09.
Artigo em Inglês | MEDLINE | ID: mdl-27444014

RESUMO

The organic-inorganic hybrid lead trihalide perovskites have been emerging as the most attractive photovoltaic materials. As regulated by Shockley-Queisser theory, a formidable materials science challenge for improvement to the next level requires further band-gap narrowing for broader absorption in solar spectrum, while retaining or even synergistically prolonging the carrier lifetime, a critical factor responsible for attaining the near-band-gap photovoltage. Herein, by applying controllable hydrostatic pressure, we have achieved unprecedented simultaneous enhancement in both band-gap narrowing and carrier-lifetime prolongation (up to 70% to ∼100% increase) under mild pressures at ∼0.3 GPa. The pressure-induced modulation on pure hybrid perovskites without introducing any adverse chemical or thermal effect clearly demonstrates the importance of band edges on the photon-electron interaction and maps a pioneering route toward a further increase in their photovoltaic performance.

12.
J Phys Chem Lett ; 7(15): 2879-87, 2016 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-27396858

RESUMO

We report on the carrier-rotor coupling effect in perovskite organic-inorganic hybrid lead iodide (CH3NH3PbI3) compounds discovered by isotope effects. Deuterated organic-inorganic perovskite compounds including CH3ND3PbI3, CD3NH3PbI3, and CD3ND3PbI3 were synthesized. Devices made from regular CH3NH3PbI3 and deuterated CH3ND3PbI3 exhibit comparable performance in band gap, current-voltage, carrier mobility, and power conversion efficiency. However, a time-resolved photoluminescence (TRPL) study reveals that CH3NH3PbI3 exhibits notably longer carrier lifetime than that of CH3ND3PbI3, in both thin-film and single-crystal formats. Furthermore, the comparison in carrier lifetime between CD3NH3PbI3 and CH3ND3PbI3 single crystals suggests that vibrational modes in methylammonium (MA(+)) have little impact on carrier lifetime. In contrast, the fully deuterated compound CD3ND3PbI3 reconfirmed the trend of decreasing carrier lifetime upon the increasing moment of inertia of cationic MA(+). Polaron model elucidates the electron-rotor interaction.

13.
Mol Med Rep ; 12(5): 7116-22, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26397056

RESUMO

Sympathetic activity is enhanced in heart failure and hypertensive rats. The aims of the current study were: i) To investigate the association between renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP) in response to intravenous injection of the ganglionic blocker hexamethonium; and ii) to determine whether normal Wistar rats and spontaneously hypertensive rats (SHRs) differ in their response to hexamethonium. RSNA and MAP were recorded in anaesthetized rats. Intravenous injection of four doses of hexamethonium significantly reduced the RSNA, MAP and heart rate (HR) in the Wistar rats and SHRs. There were no significant differences in the RSNA, MAP or HR between Wistar rats and SHRs at the two lowest doses of hexamethonium. However, the two highest doses of hexamethonium resulted in a greater reduction in the RSNA and MAP in SHRs compared with Wistar rats. There was a significant positive correlation between the alterations in RSNA and MAP in response to the intravenous injection of hexamethonium in the Wistar rats and SHRs. There were no significant differences in the timing of the maximal effects on RSNA, MAP or HR or in recovery following hexamethonium treatment. These results suggest that there is an association between the RSNA and MAP response to intravenous injection of hexamethonium and that the alterations in MAP in response to hexamethonium may be used to evaluate basal sympathetic nerve activity.


Assuntos
Anti-Hipertensivos/farmacologia , Pressão Sanguínea/efeitos dos fármacos , Hexametônio/farmacologia , Animais , Frequência Cardíaca/efeitos dos fármacos , Masculino , Ratos , Ratos Endogâmicos SHR , Ratos Wistar , Sistema Nervoso Simpático/efeitos dos fármacos , Sistema Nervoso Simpático/metabolismo
15.
Angew Chem Int Ed Engl ; 54(26): 7617-20, 2015 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-25968343

RESUMO

Two pseudohalide thiocyanate ions (SCN(-) ) have been used to replace two iodides in CH3 NH3 PbI3 , and the resulting perovskite material was used as the active material in solar cells. In accelerated stability tests, the CH3 NH3 Pb(SCN)2 I perovskite films were shown to be superior to the conventional CH3 NH3 PbI3 films as no significant degradation was observed after the film had been exposed to air with a relative humidity of 95 % for over four hours, whereas CH3 NH3 PbI3 films degraded in less than 1.5 hours. Solar cells based on CH3 NH3 Pb(SCN)2 I thin films exhibited an efficiency of 8.3 %, which is comparable to that of CH3 NH3 PbI3 based cells fabricated in the same way.

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