Ionic Liquid Modified Polymer Intermediate Layer for Improved Charge Extraction toward Efficient and Stable Perovskite/Silicon Tandem Solar Cells.

Monolithic perovskite/silicon tandem solar cells have been attracted much attention in recent years. Despite their high performances, the stability issue of perovskite-based devices is recognized as one of the key challenges to realize industrial application. When comes to the perovskite top subcell, the interface between perovskite and electron transporting layers (usually C60) significantly affects the device efficiency as well as the stability due to their poor adhesion. Here, different from the conventional interfacial passivation using metal fluorides, a hybrid intermediate layer is proposed-PMMA functionalized with ionic liquid (IL)-is introduced at the perovskite/C60 interface. The application of PMMA essentially improves the interfacial stability due to its strong hydrophobicity, while adding IL relieves the charge accumulation between PMMA and the perovskite. Thus, an optimal wide-bandgap perovskite solar cells achieves power conversion efficiency of 20.62%. These cells are further integrated as top subcells with silicon bottom cells in a monolithic tandem structure, presenting an optimized PCE up to 27.51%. More importantly, such monolithic perovskite/silicon cells exhibit superior stability by maintaining 90% of initial efficiency after 1200 h under continuous illumination.

Effect of Different Selenium Species on Indole-3-Acetic Acid Activity of Selenium Nanoparticles Producing Strain Bacillus altitudinis LH18.

Acting as a growth regulator, Indole-3-acetic acid (IAA) is an important phytohormone that can be produced by several Bacillus species. However, few studies have been published on the comprehensive evaluation of the strains for practical applications and the effects of selenium species on their IAA-producing ability. The present study showed the selenite reduction strain Bacillus altitudinis LH18, which is capable of producing selenium nanoparticles (SeNPs) at a high yield in a cost-effective manner. Bio-SeNPs were systematically characterized by using DLS, zeta potential, SEM, and FTIR. The results showed that these bio-SeNPs were small in particle size, homogeneously dispersed, and highly stable. Significantly, the IAA-producing ability of strain was differently affected under different selenium species. The addition of SeNPs and sodium selenite resulted in IAA contents of 221.7 µg/mL and 91.01 µg/mL, respectively, which were 3.23 and 1.33 times higher than that of the control. This study is the first to examine the influence of various selenium species on the IAA-producing capacity of Bacillus spp., providing a theoretical foundation for the enhancement of the IAA-production potential of microorganisms.

Self-Immolative Hydrogels with Stimulus-Mediated On-Off Degradation.

Hydrogels are of interest for a wide range of applications from sensors to drug delivery and tissue engineering. Self-immolative polymers, which depolymerize from end-to-end following a single backbone or end-cap cleavage, offer advantages such as amplification of the stimulus-mediated cleavage event through a cascade degradation process. It is also possible to change the active stimulus by changing only a single end-cap or linker unit. However, there are very few examples of self-immolative polymer hydrogels, and the reported examples exhibited relatively poor stability in their nontriggered state or slow degradation after triggering. Described here is the preparation of hydrogels composed of self-immolative poly(ethyl glyoxylate) (PEtG) and poly(ethylene glycol) (PEG). Hydrogels formed from 2 kg/mol 4-arm PEG and 1.2 kg/mol PEtG with a light-responsive linker end-cap had high gel content (90%), an equilibrium water content of 89%, and a compressive modulus of 26 kPa. The hydrogel degradation could be turned on and off repeatedly through alternating cycles of irradiation and dark storage. Similar cycles could also be used to control the release of the anti-inflammatory drug celecoxib. These results demonstrate the potential for self-immolative hydrogels to afford a high degree of control over responses to stimuli in the context of smart materials for a variety of applications.

Highly tunable properties in pressure-treated two-dimensional Dion-Jacobson perovskites.

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.

Photonic Nanolaser with Extreme Optical Field Confinement.

We proposed a photonic approach to a lasing mode supported by low-loss oscillation of polarized bound electrons in an active nano-slit-waveguide cavity, which circumvents the confinement-loss trade-off of nanoplasmonics, and offers an optical confinement down to sub-1-nm level with a peak-to-background ratio of ∼30 dB. Experimentally, the extremely confined lasing field is realized as the dominant peak of a TE_{0}-like lasing mode around 720-nm wavelength, in 1-nm-level width slit-waveguide cavities in coupled CdSe nanowire pairs. The measured lasing characteristics agree well with the theoretical calculations. Our results may pave a way towards new regions for nanolasers and light-matter interaction.

Layered 2D Halide Perovskites beyond the Ruddlesden-Popper Phase: Tailored Interlayer Chemistries for High-Performance Solar Cells.

Layered halide perovskites (LHPs) with crystallographically 2D structures have gained increasing interest for photovoltaic applications due to their superior chemical stability and intriguing anisotropic properties, which are in contrast to their conventional 3D perovskite counterparts. The most frequently studied LHPs are Ruddlesden-Popper (RP) phases, which suffer from a carrier-transport bottleneck due to the van der Waals gap associated with their intrinsic organic interlayer structures. To address this issue, Dion-Jacobson (DJ) and alternating-cation-interlayer (ACI) LHPs have rapidly emerged, which exhibit unique structural and (opto)electronic characteristics that may resemble those of the 3D counterparts owing to the eliminated or reduced van der Waals gap. Improved photophysical properties have been achieved in DJ and ACI LHPs, leading towards better photovoltaic performance. Here we provide a comprehensive discussion on the merits and promises of DJ and ACI LHPs from a chemistry perspective. Then, we review recent progress on the synthesis and tailoring of DJ and ACI LHP crystals and thin films, as well as their optoelectronic properties and photovoltaic performance. Finally, we discuss possible pathways to overcome critical challenges to realize the full potential of DJ and ACI LHPs for high-performance solar cells and beyond.

Isothermal pressure-derived metastable states in 2D hybrid perovskites showing enduring bandgap narrowing.

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.

Simultaneous band-gap narrowing and carrier-lifetime prolongation of organic-inorganic trihalide perovskites.

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.

Proposed liquid-cooled nanowire lasers.

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.

Hyperbolic Dispersion Arising from Anisotropic Excitons in Two-Dimensional Perovskites.

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.

Pseudohalide-induced moisture tolerance in perovskite CH3 NH3 Pb(SCN)2 I thin films.

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.

Unveiling Alterations of Epigenetic Modifications and Chromatin Architecture Leading to Lipid Metabolic Reprogramming during the Evolutionary Trastuzumab Adaptation of HER2-Positive Breast Cancer.

Secondary trastuzumab resistance represents an evolutionary adaptation of HER2-positive breast cancer during anti-HER2 treatment. Most current studies have tended to prioritize HER2 and its associated signaling pathways, often overlooking broader but seemingly less relevant cellular processes, along with their associated genetic and epigenetic mechanisms. Here, transcriptome data is not only characterized but also examined epigenomic and 3D genome architecture information in both trastuzumab-sensitive and secondary-resistant breast cancer cells. The findings reveal that the global metabolic reprogramming associated with trastuzumab resistance may stem from genome-wide alterations in both histone modifications and chromatin structure. Specifically, the transcriptional activities of key genes involved in lipid metabolism appear to be regulated by variant promoter H3K27me3 and H3K4me3 modifications, as well as promoter-enhancer interactions. These discoveries offer valuable insights into how cancer cells adapt to anti-tumor drugs and have the potential to impact future diagnostic and treatment strategies.

An Imbalance in Histone Modifiers Induces tRNA-Cys-GCA Overexpression and tRF-27 Accumulation by Attenuating Promoter H3K27me3 in Primary Trastuzumab-Resistant Breast Cancer.

tRNA-derived fragments (tRFs) play crucial roles in cancer progression. Among them, tRF-27 has been identified as a key factor in promoting naïve trastuzumab resistance in HER2-positive breast cancer. However, the origin of tRF-27 remains uncertain. In this study, we propose that the upregulated expression of specific cysteine tRNAs may lead to the increased accumulation of tRF-27 in trastuzumab-resistant JIMT1 cells. Mechanistically, the reduced inhibitory H3K27me3 modification at the promoter regions of tRF-27-related tRNA genes in JIMT1 cells, potentially resulting from decreased EZH2 and increased KDM6A activity, may be a critical factor stimulating the transcriptional activity of these tRNA genes. Our research offers fresh insights into the mechanisms underlying elevated tRF-27 levels in trastuzumab-resistant breast cancer cells and suggests potential strategies to mitigate trastuzumab resistance in clinical treatments.

Highly Efficient Monolithic Perovskite/Perovskite/Silicon Triple-Junction Solar Cells.

Wide-bandgap metal halide perovskites have demonstrated promise in multijunction photovoltaic (PV) cells. However, photoinduced phase segregation and the resultant low open-circuit voltage (Voc) have greatly limited the PV performance of perovskite-based multijunction devices. Here, a alloying strategy is reported to achieve uniform distribution of triple cations and halides in wide-bandgap perovskites by doping Rb+ and Cl- with small ionic radii, which effectively suppresses halide phase segregation while promoting the homogenization of surface potential. Based on this strategy, a Voc of 1.33 V is obtained from single-junction perovskite solar cells, and a VOC approaching 3.0 V and a power conversion efficiency of 25.0% (obtained from reverse scan direction, certified efficiency: 24.19%) on an 1.04 cm2 photoactive area can be achieved in a perovskite/perovskite/c-Si triple-junction tandem cell, where the certification efficiency is by far the greatest performance of perovskite-based triple-junction tandem solar cells. This work overcomes the performance deadlock of perovskite-based triple-junction tandem cells by setting a materials-by-design paradigm.

Dissolving microneedle system containing Ag nanoparticle-decorated silk fibroin microspheres and antibiotics for synergistic therapy of bacterial biofilm infection.

Most cases of delayed wound healing are associated with bacterial biofilm infections due to high antibiotic resistance. To improve patient compliance and recovery rates, it is critical to develop minimally invasive and efficient methods to eliminate bacterial biofilms as an alternative to clinical debridement techniques. Herein, we develop a dissolving microneedle system containing Ag nanoparticles (AgNPs)-decorated silk fibroin microspheres (SFM-AgNPs) and antibiotics for synergistic treatment of bacterial biofilm infection. Silk fibroin microspheres (SFM) are controllably prepared in an incompatible system formed by a mixture of protein and carbohydrate solutions by using a mild all-aqueous phase method and serve as biological templates for the synthesis of AgNPs. The SFM-AgNPs exert dose- and time-dependent broad-spectrum antibacterial effects by inducing bacterial adhesion. The combination of SFM-AgNPs with antibiotics breaks the limitation of the antibacterial spectrum and achieves better efficacy with reduced antibiotic dosage. Using hyaluronic acid (HA) as the soluble matrix, the microneedle system containing SFM-AgNPs and anti-Gram-positive coccus drug (Mupirocin) inserts into the bacterial biofilms with sufficient strength, thereby effectively delivering the antibacterial agents and realizing good antibiofilm effect on Staphylococcus aureus-infected wounds. This work demonstrates the great potential for the development of novel therapeutic systems for eradicating bacterial biofilm infections.

Recent Progress in Interfacial Dipole Engineering for Perovskite Solar Cells.

Design and modification of interfaces have been the main strategies in developing perovskite solar cells (PSCs). Among the interfacial treatments, dipole molecules have emerged as a practical approach to improve the efficiency and stability of PSCs due to their unique and versatile abilities to control the interfacial properties. Despite extensive applications in conventional semiconductors, working principles and design of interfacial dipoles in the performance/stability enhancement of PSCs are lacking an insightful elucidation. In this review, we first discuss the fundamental properties of electric dipoles and the specific roles of interfacial dipoles in PSCs. Then we systematically summarize the recent progress of dipole materials in several key interfaces to achieve efficient and stable PSCs. In addition to such discussions, we also dive into reliable analytical techniques to support the characterization of interfacial dipoles in PSCs. Finally, we highlight future directions and potential avenues for research in the development of dipolar materials through tailored molecular designs. Our review sheds light on the importance of continued efforts in this exciting emerging field, which holds great potential for the development of high-performance and stable PSCs as commercially demanded.

Designing polymers for cartilage uptake: effects of architecture and molar mass.

Osteoarthritis (OA) is a progressive disease, involving the progressive breakdown of cartilage, as well as changes to the synovium and bone. There are currently no disease-modifying treatments available clinically. An increasing understanding of the disease pathophysiology is leading to new potential therapeutics, but improved approaches are needed to deliver these drugs, particularly to cartilage tissue, which is avascular and contains a dense matrix of collagens and negatively charged aggrecan proteoglycans. Cationic delivery vehicles have been shown to effectively penetrate cartilage, but these studies have thus far largely focused on proteins or nanoparticles, and the effects of macromolecular architectures have not yet been explored. Described here is the synthesis of a small library of polycations composed of N-(2-hydroxypropyl)methacrylamide (HPMA) and N-(3-aminopropyl)methacrylamide (APMA) with linear, 4-arm, or 8-arm structures and varying degrees of polymerization (DP) by reversible addition fragmentation chain-transfer (RAFT) polymerization. Uptake and retention of the polycations in bovine articular cartilage was assessed. While all polycations penetrated cartilage, uptake and retention generally increased with DP before decreasing for the highest DP. In addition, uptake and retention were higher for the linear polycations compared to the 4-arm and 8-arm polycations. In general, the polycations were well tolerated by bovine chondrocytes, but the highest DP polycations imparted greater cytotoxicity. Overall, this study reveals that linear polymer architectures may be more favorable for binding to the cartilage matrix and that the DP can be tuned to maximize uptake while minimizing cytotoxicity.

Variation of Charge Carrier Dynamics for Polycrystalline Perovskite Films by One-Step Solution and Vapor-Deposition Methods.

To date, solution-processing and vapor-deposition fabrication methods have achieved huge successes in high-efficiency perovskite solar cells (PSCs) and satisfy special demanding requirements for diverse application purposes, respectively. Although people realize that the fabrication procedure is crucial in device performance, insightful studies of charge carrier dynamics in perovskite films by different methods still lack. In this work, we compare the carrier behaviors in one-step spin-coated and dual-source coevaporated MAPbI3 perovskite films by combining time-resolved photoluminescence spectroscopy and carrier dynamics simulation. We suggest that strains, lattice orientations, and defects at buried side of perovskite films, which are associated with different preparation processes, lead to variations in carrier behaviors. Hence fabrication of perovskite layers should be elaborately designed in order to satisfy the needs of different carrier behaviors in specified device configurations of PSCs such as smooth planar or textured monolithic tandem structures.

Chromatin accessibility dynamics insight into crosstalk between regulatory landscapes in poplar responses to multiple treatments.

Perennial trees develop and coordinate endogenous response signaling pathways, including their crosstalk and convergence, to cope with various environmental stresses which occur simultaneously in most cases. These processes are involved in gene transcriptional regulations that depend on dynamic interactions between regulatory proteins and corresponding chromatin regions, but the mechanisms remain poorly understood in trees. In this study, we detected chromatin regulatory landscapes of poplar under abscisic acid, methyl jasmonate, salicylic acid and sodium chloride (NaCl) treatment, through integrating ATAC-seq and RNA-seq data. Our results showed that the degree of chromatin accessibility for a given gene is closely related to its expression level. However, unlike the gene expression that shows treatment-specific response patterns, changes in chromatin accessibility exhibit high similarities under these treatments. We further proposed and experimentally validated that a homologous gene copy of RESPONSIVE TO DESICCATION 26 mediates the crosstalk between jasmonic acid and NaCl signaling pathways by directly regulating the stress-responsive genes and that circadian clock-related transcription factors like REVEILLE8 play a central role in response of poplar to these treatments. Overall, our study provides a chromatin insight into the molecular mechanism of transcription regulatory networks in response to different environmental stresses and raises the key roles of the circadian clock of poplar to adapt to adverse environments.

Novel thermo and ion-responsive copolymers based on metallo-base pair directed host-guest complexation for highly selective recognition of Hg2+ in aqueous solution.

The development of materials with highly selective recognition towards Hg2+ is of great significance in environmental monitoring. Herein, a novel thermo-responsive copolymer with Hg2+ recognition property is prepared via thermally-initiated copolymerization of 5'-O-Acryloyl 5-methyl-uridine (APU) and N-isopropylacrylamide (NIPAM). The chemical structure and stimuli-sensitive properties of poly(N-isopropylacrylamide-co-5-methyl-uridine) (P(NIPAM-co-APU)) linear polymers and hydrogel are thoroughly investigated. At the supramolecular level, P(NIPAM-co-APU) linear polymers could respond to both temperature and Hg2+ stimuli with highly selective recognition towards Hg2+ over other 18 metal ion species (at least 5 fold difference) and common anions. Upon capturing Hg2+ by APU units as host metal receptors, the lower critical solution temperature (LCST) of P(NIPAM-co-APU, PNU-7 and PNU-11) linear polymers are significantly shifted more than 10 °C due to the formation of stable APU-Hg2+-APU directed host-guest complexes. Accordingly, at the macroscopic level, P(NIPAM-co-APU) hydrogel display selective and robust recognition of Hg2+ under optimum conditions, and its maximum Hg2+ uptake capacity was 33.1 mg g-1. This work provides a new option for Hg2+ recognition with high selectivity, which could be facilely integrated with other smart systems to achieve satisfactory detection of environmental Hg2+.