Abnormal In-Plane Thermomechanical Behavior of Two-Dimensional Hybrid Organic–Inorganic Perovskites

The implementation of two-dimensional (2D) hybrid organic–inorganic perovskites (HOIPs) in semiconductor device applications will have to accommodate the co-existence of strain and temperature stressors and requires a thorough understanding of the thermomechanical behavior of 2D HOIPs. This will mitigate thermomechanical stability issues and improve the durability of the devices, especially when one considers the high susceptibility of 2D HOIPs to temperature due to their soft nature. Here, we employ atomic force microscopy (AFM) stretching of suspended membranes to measure the temperature dependence of the in-plane Young’s modulus (E∥) of model Ruddlesden–Popper 2D HOIPs with a general formula of (CH3(CH2)3NH3)2(CH3NH3)n−1PbnI3n+1 (here, n = 1, 3, or 5). We find that E∥ values of these 2D HOIPs exhibit a prominent non-monotonic dependence on temperature, particularly an abnormal thermal stiffening behavior (nearly 40% change in E∥) starting around the order–disorder transition temperature of the butylammonium spacer molecules, which is significantly different from the thermomechanical behavior expected from their 3D counterpart (CH3NH3PbI3) or other low-dimensional material systems. Further raising the temperature eventually reverses the trend to thermal softening. The magnitude of the thermally induced change in E∥ is also much higher in 2D HOIPs than in their 3D analogs. Our results can shed light on the structural origin of the thermomechanical behavior and provide needed guidance to design 2D HOIPs with desired thermomechanical properties to meet the application needs

Precise Control of Quantum Confinement in Cesium Lead Halide Perovskite Quantum Dots via Thermodynamic Equilibrium

Cesium lead halide (CsPbX₃) nanocrystals have emerged as a new family of materials that can outperform the existing semiconductor nanocrystals due to their superb optical and charge-transport properties. However, the lack of a robust method for producing quantum dots with controlled size and high ensemble uniformity has been one of the major obstacles in exploring the useful properties of excitons in zero-dimensional nanostructures of CsPbX₃. Here, we report a new synthesis approach that enables the precise control of the size based on the equilibrium rather than kinetics, producing CsPbX₃ quantum dots nearly free of heterogeneous broadening in their exciton luminescence. The high level of size control and ensemble uniformity achieved here will open the door to harnessing the benefits of excitons in CsPbX₃ quantum dots for photonic and energy-harvesting applications

Fluorinated Covalent Organic Polymers for High Performance Sulfur Cathodes in Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries by far offer higher theoretical energy density than that of the commercial lithium-ion battery counterparts, but suffer predominantly from an irreversible shuttling process involving lithium polysulfides. Here, we report a fluorinated covalent organic polymer (F-COP) as a template for high performance sulfur cathodes in Li–S batteries. The fluorination allowed facile covalent attachment of sulfur to a porous polymer framework via nucleophilic aromatic substitution reaction (SNAr), leading to high sulfur content, e.g., over 70 wt %. The F-COP framework was microporous with 72% of pores within three well-defined pore sizes, viz. 0.58, 1.19, and 1.68 nm, which effectively suppressed polysulfide dissolution via steric and electrostatic hindrance. As a result of the structural features of the F-COP, the resulting sulfur electrode exhibited high electrochemical performance of 1287.7 mAh g–1 at 0.05C, 96.4% initial Columbic efficiency, 70.3% capacity retention after 1000 cycles at 0.5C, and robust operation for a sulfur loading of up to 4.1 mgsulfur cm–2. Our findings suggest the F-COP family with the adaptability of SNAr chemistry and well-defined microporous structures as useful frameworks for highly sustainable sulfur electrodes in Li–S batteries

Controlling Anisotropy of Quantum-Confined CsPbBr₃ Nanocrystals by Combined Use of Equilibrium and Kinetic Anisotropy

Anisotropic semiconductor nanocrystals with controlled quantum confinement are important in many applications for the directionality of the flow of photons and charge carriers combined with the properties of confined exciton. Here, we report the strategy that introduces controlled morphological anisotropy with one- and two-dimensional confinements in CsPbBr3 nanocrystals via the simultaneous use of thermodynamic equilibrium and kinetic anisotropy. In this approach, the halide equilibrium recently shown to control the size of zero-dimensional perovskite quantum dots under hot-injection condition is combined with the anisotropic growth kinetics that becomes more prominent at a lower temperature. Nanoribbons, nanowires, and nanoplatelets exhibiting well-defined confined exciton transition and high-emission polarization anisotropy were obtained at room temperature. While two seemingly incompatible modes of size control (equilibrium and kinetics) are combined, each mode controls the size in a different direction of the anisotropic perovskite nanocrystals, enabling the simultaneous control of confinement and morphological anisotropy

Mechanical Properties of 2D LiInP₂Se₆: Implication for Semiconductor Applications

Metal phosphorus trichalcogenides (MPTCs) are emerging 2D semiconductor materials with unique functional properties that set them apart from other 2D systems. Despite the importance of their mechanical properties for improving the semiconductor device’s durability and performance, as well as for utilizing strain effects to customize material properties and create new functionality, our current understanding of MPTCs’ mechanical behavior is lacking and lags behind our knowledge of their other properties. Here, we use LiInP2Se6 as a model example of MPTCs and report the first experimental measurements of the elastic and plastic (fracture) properties along both in-plane and out-of-plane directions by atomic force microscopy and nanoindentation. Being a 2D material that is entirely inorganic, LiInP2Se6 surprisingly exhibits mechanical properties that resemble those of hybrid organic–inorganic materials rather than pure inorganic 2D materials. It has a soft crystal structure with low elastic moduli, a low difference in in-plane vs out-of-plane mechanical properties, and a combination of elastic and plastic characteristics of hybrid organic–inorganic materials. Our work provides the mechanical information critically needed to mitigate and/or harness the strain effects in LiInP2Se6-based semiconductor devices and sheds light on the mechanical behaviors of MPTCs with indispensable insights

Additional file 1 of Spatiotemporally controlled drug delivery via photothermally driven conformational change of self-integrated plasmonic hybrid nanogels

Additional file 1: Text S1. Calculation of the photothermal conversion efficiency. Table S1. Name and the molecular weight of the used linker molecules and nomenclatures of the PHNs synthesized with the linker molecules. Fig S1. Optimization of photoinitiator concentration for obtaining homogenous size distribution of GNPs. Fig S2. Hydrodynamic diameter distribution of the M-PHNs according to the reaction time between 1 and 15 min. Fig S3. Hydrodynamic diameters of PNIPAM nanogels without GNPs according to the reaction time. Fig S4. Absorbance spectra of colloidal GNPs and M-PHNs. Insets display the colors of the colloidal solutions. Fig S5. Monitoring of the thermal stability of M-PHNs and PHNs during 10 cycles of the heating/cooling procedure. Fig S6. Narrow scans of the XPS spectra focused on the selected elements of C, N, O, and Au. Fig S7. TEM images of the PHNs with different linker molecules (i.e., MBA (M-PHN), tryptophan (T-PHN), sucrose (S-PHN), PEG-da (P-PHN), alginate (A-PHN), and gelatin (G-PHN)). Fig S8. Optical properties and colloidal stabilities of the PHNs synthesized with different linker molecules. Fig S9. Molecular weights of alginate, PNIPAM, PNIPAM-alg, and A-PHN measured by SLS analysis. Fig S10. Solubility tests using the lyophilized A-PHN with various concentrations in water. Fig S11. Confirmation of the alginate incorporation in the A-PHN via calcium ion-mediated gelation method by adding 100 mM CaCl2. Fig S12. Energy-dispersive X-ray spectroscopy of A-PHN from Fig. 2g. Fig S13. Schematic image of the GNP structures used in the computation at different diameters of PHN. Fig S14. Linear relationship of -ln(θ) versus time obtained from the cooling period of the thermal curve in Fig. 3g. Fig S15. Light-responsive heat generation of dehydrated PHNs under light illumination. Fig S16. Monitoring of the solution temperature under a commercial LED. Fig S17. In situ Raman spectra of A-PHN gels under 785 nm laser illumination. Fig S18. Temperature-dependent 1H-NMR study of A-PHN dispersed in D2O. Fig S19. Standard curve of doxorubicin by absorbance at 480 nm. Fig S20. Drug release kinetics by different power densities of the LED. Fig S21. Monitoring the mean diameters of A-PHN by changing the buffer pH conditions. Fig S22. Monitoring the Raman spectra of released dox under temporally controlled light modulation. Fig S23. Colloidal stability of A-PHNs under different biological media. Fig S24. Biocompatibility tests using MTT assay to A375P. Fig S25. Images of Pearson’s colocalization coefficient (k) plots for dox versus Hoechst from Fig. 5e (i). Fig S26. Cellular internalization of A-PHNs into A375P cell. Fig S27. Computational simulation results of heat generation from vesicles including A-PHN. Fig S28. Observation of the damage to the cytoskeleton by A-PHNs under exposure to 532 nm laser at 3.5 W/cm2. Fig S29. Confocal fluorescent images of endocytic vesicles before and after laser illumination. Fig S30. Observation of nuclear fragments in A375P cells after treatment with ptx, A-PHN, and ptx@A-PHN (with light exposure), respectively

Data_Sheet_1_The Nature of Noradrenergic Volume Transmission From Locus Coeruleus to Brainstem Mesencephalic Trigeminal Sensory Neurons.DOCX

Noradrenergic neurons in the locus coeruleus (LC) release noradrenaline (NA) that acts via volume transmission to activate extrasynaptic G-protein coupled receptors (GPCRs) in target cells throughout the brain. As the closest projection, the dorsal LC laterally adjoins the mesencephalic trigeminal nucleus (MTN), in which proprioceptive primary sensory neurons innervating muscle spindles of jaw-closing muscles are exceptionally located. MTN neurons express α2-adrenergic receptors (α2-ARs) and display hyperpolarization-activated cyclic nucleotide-gated (HCN) currents (Ihs), which is downregulated by α2-AR activation. To quantify the activity-dependent outcome of volume transmission of NA from LC to MTN, we investigated how direct LC activation inhibits Ih in MTN neurons by performing dual whole-cell recordings from LC and MTN neurons. Repetition of 20 Hz spike-train evoked with 1-s current-pulse in LC neurons every 30 s resulted in a gradual decrease in Ih evoked every 30 s, revealing a Hill-type relationship between the number of spike-trains in LC neurons and the degree of Ih inhibition in MTN neurons. On the other hand, when microstimulation was applied in LC every 30 s, an LC neuron repeatedly displayed a transient higher-frequency firing followed by a tonic firing at 5–10 Hz for 30 s. This subsequently caused a similar Hill-type inhibition of Ih in the simultaneously recorded MTN neuron, but with a smaller Hill coefficient, suggesting a lower signal transduction efficacy. In contrast, 20 Hz activity induced by a 1-s pulse applied every 5–10 s caused only a transient facilitation of Ih inhibition followed by a forced termination of Ih inhibition. Thus, the three modes of LC activities modulated the volume transmission to activate α2-adrenergic GPCR to differentially inhibit Ih in MTN neurons.</p

Photothermally Modulated Intracellular Delivery of Therapeutic Proteins Using Gold-Collagen Hybrid Nanoparticles

Stimuli-responsive nanoparticles have attracted considerable attention as nanocarriers for the intact intracellular delivery of active biotherapeutics with high stability and controllability. In this study, we developed light- and heat-responsive gold-collagen hydrogel nanoparticles (Au-CHPs) for the intracellular delivery of therapeutic proteins. Au-CHPs composed of collagen, thermosensitive polymers, and gold nanoparticles were fabricated by the simultaneous reduction of gold ions during radical polymerization. Under resonant light, Au-CHPs induce proximate environmental changes by immediately increasing the local temperature. Three proteins, fibroblast growth factor, superoxide dismutase, and epidermal growth factor, with different cellular functions were electrostatically incorporated into the Au-CHPs with a high loading efficiency of over 57%. Photothermal triggering through Au-CHPs boosted wound healing, reactive oxygen species scavenging, and cellular spheroid growth, owing to the on-demand release and rapid diffusion of proteins. We envision that stimuli-responsive hybrid materials for carrying bioactive proteins will help with the development of controlled delivery systems for biomedical and cosmeceutical applications

Synthesis and Optical Properties of One Year Air-Stable Chiral Sb(III) Halide Semiconductors

Chiral hybrid metal-halide semiconductors (MHS) pose as ideal candidates for spintronic applications owing to their strong spin–orbit coupling (SOC), and long spin relaxation times. Shedding light on the underlying structure–property relationships is of paramount importance for the targeted synthesis of materials with an optimum performance. Herein, we report the synthesis and optical properties of 1D chiral (R-/S-THBTD)SbBr5 (THBTD = 4,5,6,7-tetrahydro-benzothiazole-2,6-diamine) semiconductors using a multifunctional ligand as a countercation and a structure directing agent. (R-/S-THBTD)SbBr5 feature direct and indirect band gap characteristics, exhibiting photoluminescence (PL) light emission at RT that is accompanied by a lifetime of a few ns. Circular dichroism (CD), second harmonic generation (SHG), and piezoresponse force microscopy (PFM) studies validate the chiral nature of the synthesized materials. Density functional theory (DFT) calculations revealed a Rashba/Dresselhaus (R/D) spin splitting, supported by an energy splitting (ER) of 23 and 25 meV, and a Rashba parameter (αR) of 0.23 and 0.32 eV·Å for the R and S analogs, respectively. These values are comparable to those of the 3D and 2D perovskite materials. Notably, (S-THBTD)SbBr5 has been air-stable for a year, a record performance among chiral lead-free MHS. This work demonstrates that low-dimensional, lead-free, chiral semiconductors with exceptional air stability can be acquired, without compromising spin splitting and manipulation performance

Additional file 1: of Combination therapy of vitamin C and thiamine for septic shock in a multicentre, double-blind, randomized, controlled study (ATESS): study protocol for a randomized controlled trial

SPIRIT 2013 checklist: recommended items to address in a clinical trial protocol and related documents. (DOC 125 kb