Association Between Sleep Efficiency Variability and Cognition Among Older Adults: Cross-Sectional Accelerometer Study.

Background: Sleep efficiency is often used as a measure of sleep quality. Getting sufficiently high-quality sleep has been associated with better cognitive function among older adults; however, the relationship between day-to-day sleep quality variability and cognition has not been well-established. Objective: We aimed to determine the relationship between day-to-day sleep efficiency variability and cognitive function among older adults, using accelerometer data and 3 cognitive tests. Methods: We included older adults aged >65 years with at least 5 days of accelerometer wear time from the National Health and Nutrition Examination Survey (NHANES) who completed the Digit Symbol Substitution Test (DSST), the Consortium to Establish a Registry for Alzheimer's Disease Word-Learning subtest (CERAD-WL), and the Animal Fluency Test (AFT). Sleep efficiency was derived using a data-driven machine learning algorithm. We examined associations between sleep efficiency variability and scores on each cognitive test adjusted for age, sex, education, household income, marital status, depressive symptoms, diabetes, smoking habits, alcohol consumption, arthritis, heart disease, prior heart attack, prior stroke, activities of daily living, and instrumental activities of daily living. Associations between average sleep efficiency and each cognitive test score were further examined for comparison purposes. Results: A total of 1074 older adults from the NHANES were included in this study. Older adults with low average sleep efficiency exhibited higher levels of sleep efficiency variability (Pearson r=-0.63). After adjusting for confounding factors, greater average sleep efficiency was associated with higher scores on the DSST (per 10% increase, ß=2.25, 95% CI 0.61 to 3.90) and AFT (per 10% increase, ß=.91, 95% CI 0.27 to 1.56). Greater sleep efficiency variability was univariably associated with worse cognitive function based on the DSST (per 10% increase, ß=-3.34, 95% CI -5.33 to -1.34), CERAD-WL (per 10% increase, ß=-1.00, 95% CI -1.79 to -0.21), and AFT (per 10% increase, ß=-1.02, 95% CI -1.68 to -0.36). In fully adjusted models, greater sleep efficiency variability remained associated with lower DSST (per 10% increase, ß=-2.01, 95% CI -3.62 to -0.40) and AFT (per 10% increase, ß=-.84, 95% CI -1.47 to -0.21) scores but not CERAD-WL (per 10% increase, ß=-.65, 95% CI -1.39 to 0.08) scores. Conclusions: Targeting consistency in sleep quality may be useful for interventions seeking to preserve cognitive function among older adults.

Identifying Predictive Risk Factors for Future Cognitive Impairment Among Chinese Older Adults: Longitudinal Prediction Study.

Background: The societal burden of cognitive impairment in China has prompted researchers to develop clinical prediction models aimed at making risk assessments that enable preventative interventions. However, it is unclear what types of risk factors best predict future cognitive impairment, if known risk factors make equally accurate predictions across different socioeconomic groups, and if existing prediction models are equally accurate across different subpopulations. Objective: This paper aimed to identify which domain of health information best predicts future cognitive impairment among Chinese older adults and to examine if discrepancies exist in predictive ability across different population subsets. Methods: Using data from the Chinese Longitudinal Healthy Longevity Survey, we quantified the ability of demographics, instrumental activities of daily living, activities of daily living, cognitive tests, social factors and hobbies, psychological factors, diet, exercise and sleep, chronic diseases, and 3 recently published logistic regression-based prediction models to predict 3-year risk of cognitive impairment in the general Chinese population and among male, female, rural-dwelling, urban-dwelling, educated, and not formally educated older adults. Predictive ability was quantified using the area under the receiver operating characteristic curve (AUC) and sensitivity-specificity curves through 20 repeats of 10-fold cross-validation. Results: A total of 4047 participants were included in the study, of which 337 (8.3%) developed cognitive impairment 3 years after baseline data collection. The risk factor groups with the best predictive ability in the general population were demographics (AUC 0.78, 95% CI 0.77-0.78), cognitive tests (AUC 0.72, 95% CI 0.72-0.73), and instrumental activities of daily living (AUC 0.71, 95% CI 0.70-0.71). Demographics, cognitive tests, instrumental activities of daily living, and all 3 recreated prediction models had significantly higher AUCs when making predictions among female older adults compared to male older adults and among older adults with no formal education compared to those with some education. Conclusions: This study suggests that demographics, cognitive tests, and instrumental activities of daily living are the most useful risk factors for predicting future cognitive impairment among Chinese older adults. However, the most predictive risk factors and existing models have lower predictive power among male, urban-dwelling, and educated older adults. More efforts are needed to ensure that equally accurate risk assessments can be conducted across different socioeconomic groups in China.

CYX-5, a G-protein biassed MOP receptor agonist, DOP receptor antagonist and KOP receptor agonist, evokes constipation but not respiratory depression relative to morphine in rats.

BACKGROUND: Strong opioid analgesics such as morphine alleviate moderate to severe acute nociceptive pain (e.g. post-surgical or post-trauma pain) as well as chronic cancer pain. However, they evoke many adverse effects and so there is an unmet need for opioid analgesics with improved tolerability. Recently, a prominent hypothesis has been that opioid-related adverse effects are mediated by ß-arrestin2 recruitment at the µ-opioid (MOP) receptor and this stimulated research on discovery of G-protein biassed opioid analgesics. In other efforts, opioids with MOP agonist and δ-opioid (DOP) receptor antagonist profiles are promising for reducing side effects c.f. morphine. Herein, we report on the in vivo pharmacology of a novel opioid peptide (CYX-5) that is a G-protein biassed MOP receptor agonist, DOP receptor antagonist and kappa opioid (KOP) receptor agonist. METHODS: Male Sprague-Dawley received intracerebroventricular bolus doses of CYX-5 (3, 10, 20 nmol), morphine (100 nmol) or vehicle, and antinociception (tail flick) was assessed relative to constipation (charcoal meal and castor oil-induced diarrhoea tests) and respiratory depression (whole body plethysmography). RESULTS: CYX-5 evoked naloxone-sensitive, moderate antinociception, at the highest dose tested. Although CYX-5 did not inhibit gastrointestinal motility, it reduced stool output markedly in the castor oil-induced diarrhoea test. In contrast to morphine that evoked respiratory depression, CYX-5 increased tidal volume, thereby stimulating respiration. CONCLUSION: Despite its lack of recruitment of ß-arrestin2 at MOP, DOP and KOP receptors, CYX-5 evoked constipation, implicating a mechanism other than ß-arrestin2 recruitment at MOP, DOP and KOP receptors, mediating constipation evoked by CYX-5 and potentially other opioid ligands.

Design of fast-onset antidepressant by dissociating SERT from nNOS in the DRN.

Major depressive disorder (MDD) is one of the most common mental disorders. We designed a fast-onset antidepressant that works by disrupting the interaction between the serotonin transporter (SERT) and neuronal nitric oxide synthase (nNOS) in the dorsal raphe nucleus (DRN). Chronic unpredictable mild stress (CMS) selectively increased the SERT-nNOS complex in the DRN in mice. Augmentation of SERT-nNOS interactions in the DRN caused a depression-like phenotype and accounted for the CMS-induced depressive behaviors. Disrupting the SERT-nNOS interaction produced a fast-onset antidepressant effect by enhancing serotonin signaling in forebrain circuits. We discovered a small-molecule compound, ZZL-7, that elicited an antidepressant effect 2 hours after treatment without undesirable side effects. This compound, or analogous reagents, may serve as a new, rapidly acting treatment for MDD.

Prevention of the return of extinguished fear by disrupting the interaction of neuronal nitric oxide synthase with its carboxy-terminal PDZ ligand.

Exposure therapy based on the extinction of fear memory is first-line treatment for post-traumatic stress disorder (PTSD). However, fear extinction is relatively easy to learn but difficult to remember, extinguished fear often relapses under a number of circumstances. Here, we report that extinction learning-induced association of neuronal nitric oxide synthase (nNOS) with its carboxy-terminal PDZ ligand (CAPON) in the infralimbic (IL) subregion of medial prefrontal cortex negatively regulates extinction memory and dissociating nNOS-CAPON can prevent the return of extinguished fear in mice. Extinction training significantly increases nNOS-CAPON association in the IL. Disruptors of nNOS-CAPON increase extracellular signal-regulated kinase (ERK) phosphorylation and facilitate the retention of extinction memory in an ERK2-dependent manner. More importantly, dissociating nNOS-CAPON after extinction training enhances long-term potentiation and excitatory synaptic transmission, increases spine density in the IL, and prevents spontaneous recovery, renewal and reinstatement of remote fear of mice. Moreover, nNOS-CAPON disruptors do not affect other types of learning. Thus, nNOS-CAPON can serve as a new target for treating PTSD.

Nitric oxide-donating and reactive oxygen species-responsive prochelators based on 8-hydroxyquinoline as anticancer agents.

Metal ion chelators based on 8-hydroxyquinoline (8-HQ) have been widely explored for the treatment of many diseases. When aimed at being developed into potent anticancer agent, a largely unmet issue is how to avoid nonspecific chelation of metal ions by 8-HQ in normal cells or tissues. In the current work, a two-step strategy was employed to both enhance the anticancer activity of 8-HQ and improve its cancer cell specificity. Considering the well-known anticancer activity of nitric oxide (NO), NO donor furoxan was first connected to 8-HQ to construct HQ-NO conjugates. These conjugates were screened for their cytotoxicity, metal-binding ability, and NO-releasing efficiency. Selected conjugates were further modified with a ROS-responsive moiety to afford prochelators. Among all the target compounds, prodrug HQ-NO-11 was found to potently inhibit the proliferation of many cancer cells but not normal cells. The abilities of metal chelation and NO generation by HQ-NO-11 were confirmed by various methods and were demonstrated to be essential for the anticancer activity of HQ-NO-11. In vivo studies revealed that HQ-NO-11 inhibited the growth of SW1990 xenograft to a larger extent than 8-HQ. Our results showcase a general method for designing novel 8-HQ derivatives and shed light on obtaining more controllable metal chelators.

Neuroprotective Effect of N-Cyclohexylethyl-[A/G]-[D/E]-X-V Peptides on Ischemic Stroke by Blocking nNOS-CAPON Interaction.

The protein-protein interaction between neuronal nitric oxide syntheses (nNOS) and the carboxy-terminal PDZ ligand of nNOS (CAPON) is a potential target for the treatment of ischemic stroke. Our previous study had identified ZLc-002 as a promising lead compound for inhibiting nNOS-CAPON coupling. To find better neuroprotective agents disrupting the ischemia-induced nNOS-CAPON interaction, a series of N-cyclohexylethyl-[A/G]-[D/E]-X-V peptides based on the carboxy-terminal tetrapeptide of CAPON was designed, synthesized, and evaluated in this study. Herein, we reported an affinity-based fluorescence polarization (FP) method using 5-carboxyfluorescein (5-FAM) labeled CAPON (496-506) peptide as the probe for high-throughput screening of the small-molecule inhibitors of the PDZ domain of nNOS. N-Cyclohexylethyl-ADAV displayed the most potent affinity for the nNOS PDZ domain in the FP and isothermal titration calorimetry (ITC) (ΔH = -1670 ± 151.0 cal/mol) assays. To improve bioavailability, lipophilicity, and membrane permeability, the Asp methylation was employed to get N-cyclohexylethyl-AD(OMe)AV, which possesses good blood-brain barrier (BBB) permeability in vitro parallel artificial membrane permeability assay (PAMPA)-BBB (Pe = 6.07 cm/s) and in vivo assays. In addition, N-cyclohexylethyl-AD(OMe)AV (10 mg/kg body weight, i.v., immediately after reperfusion) substantially reduced infarct size in rats, which was measured 24 h after reperfusion and subjected to 120 min of middle cerebral artery occlusion (MCAO).

Highly UV Resistant Inch-Scale Hybrid Perovskite Quantum Dot Papers.

Halide perovskite quantum dots (PQDs) are promising materials for diverse applications including displays, light-emitting diodes, and solar cells due to their intriguing properties such as tunable bandgap, high photoluminescence quantum yield, high absorbance, and narrow emission peaks. Despite the prosperous achievements over the past several years, PQDs face severe challenges in terms of stability under different circumstances. Currently, researchers have overcome part of the stability problem, making PQDs sustainable in water, oxygen, and polar solvents for long-term use. However, halide PQDs are easily degraded under continuous irradiation, which significantly limits their potential for conventional applications. In this study, an oleic acid/oleylamine (traditional surface ligands)-free method to fabricate perovskite quantum dot papers (PQDP) is developed by adding cellulose nanocrystals as long-chain binding ligands that stabilize the PQD structure. As a result, the relative photoluminescence intensity of PQDP remains over ≈90% under continuous ultraviolet (UV, 16 W) irradiation for 2 months, showing negligible photodegradation. This proposed method paves the way for the fabrication of ultrastable PQDs and the future development of related applications.

Novel µ opioid antagonists derived from the µ opioid agonists endomorphin and [Dmt1 ]DALDA (H-Dmt-D-Arg-Phe-Lys-NH2 ).

Hybrid analogues of the µ opioid agonists endomorphin and [Dmt1 ]DALDA (H-Dmt-D-Arg-Phe-Lys-NH2 , Dmt = 2',6'-dimethyltyrosine) containing cis-4-amino-Pro, trans-4-amino-Pro, cis-4-aminoethyl-Pro or cis-4-guanidinylethyl-Pro in the 2 position of the peptide sequence were synthesized. None of the compounds retained high µ opioid agonist activity and, unexpectedly, substitution of cis-4-amino-Pro resulted in a novel class of potent µ opioid antagonists. In particular, the compound H-Dmt-cis-4-amino-Pro-Trp-Lys-NH2 (CZ-1) turned out to be a highly selective µ opioid antagonist with ~1 nM µ receptor binding affinity.

High-stability inorganic perovskite quantum dot-cellulose nanocrystal hybrid films.

Inorganic perovskite quantum dots (IPQDs) such as cesium lead halide (CsPbX3, X = Cl, Br and I) quantum dots have attracted much attention for developing cadmium-free quantum light-emitting displays (QLEDs) based on outstanding light emission properties including narrow full width at half maximum (FWHM), tunable bandgap and ultrahigh (>90%) photoluminescence quantum yield (PLQY). Nevertheless, their poor stability under ambient conditions, at high temperature or under continuous light irradiation is the main problem for practical applications. In this study, a new method is proposed to effectively stabilize CsPbBr3 IPQDs by synthesizing them with sulfate-functionalized cellulose nanocrystals (CNCs) at room temperature without using traditional quantum dot stabilizers such as oleylamine (OLA) and oleic acid (OA). The as-prepared CsPbBr3 IPQD/CNC hybrid paper-like films are highly stable and the relative photoluminescence (PL) intensity can be maintained at 92% under continuous UV light (306 nm, 15 W) illumination for 130 h, >99% at high temperature (100 °C) for 130 h, and >99% in ambient conditions for 15 d. Additionally, the PLQY and FWHM of IPQD/CNC are 45.69% and 22 nm, respectively. The ultrahigh stability and narrow FWHM characteristics proposed here for IPQD/CNC hybrid films can provide new possibilities for practical applications in the future development of IPQD-related devices.

Intracerebroventricular administration of CYX-6, a potent µ-opioid receptor agonist, a δ- and κ-opioid receptor antagonist and a biased ligand at µ, δ & κ-opioid receptors, evokes antinociception with minimal constipation and respiratory depression in rats in contrast to morphine.

Mu opioid receptor (MOPr) agonists are thought to produce analgesia via modulation of G-protein-coupled intracellular signalling pathways whereas the ß-arrestin2 pathway is proposed to mediate opioid-related adverse effects. Here, we report the antinociception, constipation and respiratory depressant profile of CYX-6, a potent MOPr agonist that is also a delta and a kappa opioid receptor (DOPr/KOPr) antagonist and that lacks ß-arrestin2 recruitment at each of the MOPr, DOPr and the KOPr. In anaesthetised male Sprague Dawley rats, an intracerebroventricular (i.c.v.) guide cannula was stereotaxically implanted. After 5-7 days post-surgical recovery, rats received a single i.c.v. bolus dose of CYX-6 (3-30 nmol), morphine (100 nmol) or vehicle. Antinociception was assessed using the warm water tail flick test (52.5 ± 0.5 °C). Constipation was assessed using the charcoal meal gut motility test and the castor oil-induced diarrhoea test. Respiratory depression was measured by whole-body plethysmography in awake, freely moving animals, upon exposure to a hypercapnic gas mixture (8% CO2, 21% O2 and 71% N2). The intrinsic pharmacology of CYX-6 given by the i.c.v. route in rats showed that it produced dose-dependent antinociception. It also produced respiratory stimulation rather than depression and it had a minimal effect on intestinal motility in contrast to the positive control, morphine. CYX-6 is an endomorphin-2 analogue that dissociates antinociception from constipation and respiratory depression in rats. Our findings provide useful insight to inform the discovery and development of novel opioid analgesics with a superior tolerability profile compared with morphine.

Fast-Response, Highly Air-Stable, and Water-Resistant Organic Photodetectors Based on a Single-Crystal Pt Complex.

Organic semiconductors demonstrate several advantages over conventional inorganic materials for novel electronic and optoelectronic applications, including molecularly tunable properties, flexibility, low-cost, and facile device integration. However, before organic semiconductors can be used for the next-generation devices, such as ultrafast photodetectors (PDs), it is necessary to develop new materials that feature both high mobility and ambient stability. Toward this goal, a highly stable PD based on the organic single crystal [PtBr2 (5,5'-bis(CF3 CH2 OCH2 )-2,2'-bpy)] (or "Pt complex (1o)") is demonstrated as the active semiconductor channel-a material that features a lamellar molecular structure and high-quality, intraligand charge transfer. Benefitting from its unique crystal structure, the Pt-complex (1o) device exhibits a field-effect mobility of ≈0.45 cm2 V-1 s-1 without loss of significant performance under ambient conditions even after 40 days without encapsulation, as well as immersion in distilled water for a period of 24 h. Furthermore, the device features a maximum photoresponsivity of 1 × 103 A W-1 , a detectivity of 1.1 × 1012 cm Hz1/2 W-1 , and a record fast response/recovery time of 80/90 µs, which has never been previously achieved in other organic PDs. These findings strongly support and promote the use of the single-crystal Pt complex (1o) in next-generation organic optoelectronic devices.

Highly Efficient and Stable White Light-Emitting Diodes Using Perovskite Quantum Dot Paper.

Perovskite quantum dots (PQDs) are a competitive candidate for next-generation display technologies as a result of their superior photoluminescence, narrow emission, high quantum yield, and color tunability. However, due to poor thermal resistance and instability under high energy radiation, most PQD-based white light-emitting diodes (LEDs) show only modest luminous efficiency of ≈50 lm W-1 and a short lifetime of <100 h. In this study, by incorporating cellulose nanocrystals, a new type of QD film is fabricated: CH3NH3PbBr3 PQD paper that features 91% optical absorption, intense green light emission (518 nm), and excellent stability attributed to the complexation effect between the nanocellulose and PQDs. The PQD paper is combined with red K2SiF6:Mn4+ phosphor and blue GaN LED chips to fabricate a high-performance white LED demonstrating ultrahigh luminous efficiency (124 lm W-1), wide color gamut (123% of National Television System Committee), and long operation lifetime (240 h), which paves the way for advanced lighting technology.

Dissociating nNOS (Neuronal NO Synthase)-CAPON (Carboxy-Terminal Postsynaptic Density-95/Discs Large/Zona Occludens-1 Ligand of nNOS) Interaction Promotes Functional Recovery After Stroke via Enhanced Structural Neuroplasticity.

Background and Purpose- Stroke is a major public health concern worldwide. Although clinical treatments have improved in the acute period after stroke, long-term therapeutics remain limited to physical rehabilitation in the delayed phase. This study is aimed to determine whether nNOS (neuronal NO synthase)-CAPON (carboxy-terminal postsynaptic density-95/discs large/zona occludens-1 ligand of nNOS) interaction may serve as a new therapeutic target in the delayed phase for stroke recovery. Methods- Photothrombotic stroke and transient middle cerebral artery occlusion were induced in mice. Adeno-associated virus (AAV)-cytomegalovirus (CMV)-CAPON-125C-GFP (green fluorescent protein)-3Flag and the other 2 drugs (Tat-CAPON-12C and ZLc-002) were microinjected into the peri-infarct cortex immediately and 4 to 10 days after photothrombotic stroke, respectively. ZLc-002 was also systemically injected 4 to 10 days after transient middle cerebral artery occlusion. Grid-walking task and cylinder task were conducted to assess motor function. Western blotting, immunohistochemistry, Golgi staining, and electrophysiology recordings were performed to uncover the mechanisms. Results- Stroke increased nNOS-CAPON association in the peri-infarct cortex in the delayed period. Inhibiting the ischemia-induced nNOS-CAPON association substantially decreased the number of foot faults in the grid-walking task and forelimb asymmetry in the cylinder task, suggesting the promotion of functional recovery from stroke. Moreover, dissociating nNOS-CAPON significantly facilitated dendritic remodeling and synaptic transmission, indicated by increased dendritic spine density, dendritic branching, and length and miniature excitatory postsynaptic current frequency but did not affect stroke-elicited neuronal loss, infarct size, or cerebral edema, suggesting that nNOS-CAPON interaction may function via regulating structural neuroplasticity, rather than neuroprotection. Furthermore, ZLc-002 reversed the transient middle cerebral artery occlusion-induced impairment of motor function. Conclusions- Our results reveal that nNOS-CAPON coupling can serve as a novel pharmacological target for functional restoration after stroke.

Synthesis and Biological Evaluation of Fentanyl Analogues Modified at Phenyl Groups with Alkyls.

A series of fentanyl analogues modified at the phenyl group of the phenethyl with alkyl and/or hydroxyl and alkoxy, and the phenyl group in the anilido moiety replaced with benzyl or substituted benzyl, were synthesized. The in vitro opioid receptor functional activity of these compounds was evaluated by assessment of their ability to modulate forskolin-stimulated cAMP accumulation and by their ability to induce ß-arrestin2 recruitment. Compound 12 is a potent µ-opioid (MOP) receptor agonist, a potent κ-opioid (KOP) receptor antagonist with weak ß-arrestin2 recruitment activity. Compounds 10 and 11 are potent MOP receptor agonists with weak δ-opioid (DOP) receptor antagonist activity and moderate KOP receptor antagonist activity as well as weak ß-arrestin2 recruitment activity at the MOP receptor. These compounds are promising leads for discovery of potent opioid analgesics with reduced side effects relative to clinically available strong opioid analgesics.

Orthogonal Lithography for Halide Perovskite Optoelectronic Nanodevices.

3D organic-inorganic hybrid halide perovskites have attracted great interest due to their impressive optoelectronic properties. Recently, the emergence of 2D layered hybrid perovskites, with their excellent and tunable optoelectronic behavior, has encouraged researchers to develop the next generation of optoelectronics based on these 2D materials. However, device fabrication methods of scalable patterning on both types of hybrid perovskites are still lacking as these materials are readily damaged by the organic solvents in standard lithographic processes. We conceived the orthogonal processing and patterning method: Chlorobenzene and hexane, which are orthogonal to hybrid perovskites, are utilized in modified electron beam lithography (EBL) processes to fabricate perovskite-based devices without compromising their electronic or optical characteristics. As a proof-of-concept, we used the orthogonal EBL technique to fabricate a 2D layered single-crystal (C6H5C2H4NH3)2PbI4 photodetector featuring nanoscale patterned electrodes and superior photodetection ability with responsivity of 5.4 mA/W and detectivity of 1.07 × 1013 cm Hz1/2/W. Such orthogonal processing and patterning methods are believed to fully enable the high-resolution, high-throughput fabrication of complex perovskite-based electronics in the near future.

Layer-edge device of two-dimensional hybrid perovskites.

Two dimensional layered organic-inorganic hybrid perovskites (2D perovskites) are potential candidates for next generation photovoltaic device. Especially, the out-of-plane surface perpendicular to the superlattice plane of 2D perovskites (layer-edge surface) has presented several exotic behaviors, such as layer-edge states which are found to be crucial for improving the efficiency of 2D perovskite solar cells. However, fundamental research on transport properties of layer-edge surface is still absent. In this report, we observe the electronic and opto-electronic behavior in layer-edge device of 2D perovskites. The dark and photo currents are demonstrated to strongly depend on the crystallographic orientation in layer-edge device, and such anisotropic properties, together with photo response, are related to the thickness of inorganic layers. Finally, due to the abundant hydroxyl groups, water molecules are easy to condense on the layer-edge surface, and the conductance is extremely sensitive to the humidity environment, indicating a potential application of humidity sensor.

Surface Effect on 2D Hybrid Perovskite Crystals: Perovskites Using an Ethanolamine Organic Layer as an Example.

Despite the remarkable progress of optoelectronic devices based on hybrid perovskites, there are significant drawbacks, which have largely hindered their development as an alternative of silicon. For instance, hybrid perovskites are well-known to suffer from moisture instability which leads to surface degradation. Nonetheless, the dependence of the surface effect on the moisture stability and optoelectronic properties of hybrid perovskites has not been fully investigated. In this work, the influence of the surface effect of 2D layered perovskites before and after mechanical exfoliation, representing rough and smooth surfaces of perovskite crystals, are studied. It is found that the smooth 2D perovskite is less sensitive to ambient moisture and exhibits a considerably low dark current, which outperforms the rough perovskites by 23.6 times in terms of photodetectivity. The superior moisture stability of the smooth perovskites over the rough perovskites is demonstrated. Additionally, ethanolamine is employed as an organic linker of the 2D layered perovskite, which further improves the moisture stability. This work reveals the strong dependence of the surface conditions of 2D hybrid perovskite crystals on their moisture stability and optoelectronic properties, which are of utmost importance to the design of practical optoelectronic devices based on hybrid perovskite crystals.

Photostriction of CH3 NH3 PbBr3 Perovskite Crystals.

Organic-inorganic hybrid perovskite materials exhibit a variety of physical properties. Pronounced coupling between phonon, organic cations, and the inorganic framework suggest that these materials exhibit strong light-matter interactions. The photoinduced strain of CH3 NH3 PbBr3 is investigated using high-resolution and contactless in situ Raman spectroscopy. Under illumination, the material exhibits large blue shifts in its Raman spectra that indicate significant structural deformations (i.e., photostriction). From these shifts, the photostrictive coefficient of CH3 NH3 PbBr3 is calculated as 2.08 × 10-8 m2 W-1 at room temperature under visible light illumination. The significant photostriction of CH3 NH3 PbBr3 is attributed to a combination of the photovoltaic effect and translational symmetry loss of the molecular configuration via strong translation-rotation coupling. Unlike CH3 NH3 PbI3 , it is noted that the photostriction of CH3 NH3 PbBr3 is extremely stable, demonstrating no signs of optical decay for at least 30 d. These results suggest the potential of CH3 NH3 PbBr3 for applications in next-generation optical micro-electromechanical devices.