3D-Printed Hydrogel-Based Flexible Electrochromic Device for Wearable Displays.

Flexible electrochromic devices (FECDs) are widely explored for diverse applications including wearable electronics, camouflage, and smart windows. However, the manufacturing process of patterned FECDs remains complex, costly, and non-customizable. To address this challenge, a strategy is proposed to prepare integrated FECDs via multi-material direct writing 3D printing. By designing novel viologen/polyvinyl alcohol (PVA) hydrogel inks and systematically evaluating the printability of various inks, seamless interface integration can be achieved, enabling streamlined manufacturing of patterned FECDs with continuous production capabilities. The resultant 3D-printed FECDs exhibit excellent electrochromic and mechanical properties, including high optical contrast (up to 54% at 360 nm), nice cycling stability (less than 5% electroactivity reduction after 10 000 s), and mechanical stability (less than 19% optimal contrast decrease after 5000 cycles of bending). The potential applications of these 3D-printed hydrogel-based FECDs are further demonstrated in wearable electronics, camouflage, and smart windows.

Molecular templating of layered halide perovskite nanowires.

Layered metal-halide perovskites, or two-dimensional perovskites, can be synthesized in solution, and their optical and electronic properties can be tuned by changing their composition. We report a molecular templating method that restricted crystal growth along all crystallographic directions except for [110] and promoted one-dimensional growth. Our approach is widely applicable to synthesize a range of high-quality layered perovskite nanowires with large aspect ratios and tunable organic-inorganic chemical compositions. These nanowires form exceptionally well-defined and flexible cavities that exhibited a wide range of unusual optical properties beyond those of conventional perovskite nanowires. We observed anisotropic emission polarization, low-loss waveguiding (below 3 decibels per millimeter), and efficient low-threshold light amplification (below 20 microjoules per square centimeter).

3D Printing of Robust High-Performance Conducting Polymer Hydrogel-Based Electrical Bioadhesive Interface for Soft Bioelectronics.

Electrical bioadhesive interface (EBI), especially conducting polymer hydrogel (CPH)-based EBI, exhibits promising potential applications in various fields, including biomedical devices, neural interfaces, and wearable devices. However, current fabrication techniques of CPH-based EBI mostly focus on conventional methods such as direct casting, injection, and molding, which remains a lingering challenge for further pushing them toward customized practical bioelectronic applications and commercialization. Herein, 3D printable high-performance CPH-based EBI precursor inks are developed through composite engineering of PEDOT:PSS and adhesive ionic macromolecular dopants within tough hydrogel matrices (PVA). Such inks allow the facile fabrication of high-resolution and programmable patterned EBI through 3D printing. Upon successive freeze-thawing, the as-printed PEDOT:PSS-based EBI simultaneously exhibits high conductivity of 1.2 S m-1 , low interfacial impedance of 20 Ω, high stretchability of 349%, superior toughness of 109 kJ m-3 , and satisfactory adhesion to various materials. Enabled by these advantageous properties and excellent printability, the facile and continuous manufacturing of EBI-based skin electrodes is further demonstrated via 3D printing, and the fabricated electrodes display excellent ECG and EMG signal recording capability superior to commercial products. This work may provide a new avenue for rational design and fabrication of next-generation EBI for soft bioelectronics, further advancing seamless human-machine integration.

Dimensionality Engineering of Lead Organic Chalcogenide Semiconductors.

Two-dimensional (2D) metal organic chalcogenides (MOCs) such as silver phenylselenolate (AgSePh) have emerged as a new class of 2D materials due to their unique optical properties. However, these materials typically exhibit large band gaps, and their elemental and structural versatility remain significantly limited. In this work, we synthesize a new family of 2D lead organic chalcogenide (LOC) materials with excellent structural and dimensionality tunability by designing the bonding ability of the organic molecules and the stereochemical activity of the Pb lone pair. The introduction of electron-donating substituents on the benzenethiol ligands results in a series of LOCs that transition from 1D to 2D, featuring reduced band gaps (down to 1.7 eV), broadband emission, and strong electron-phonon coupling. We demonstrated a prototypical single crystal photodetector with 2D LOC that showed the dimensionality engineering on the transport property of LOC semiconductors. This study paves the way for further development of the synthesis and optical properties of novel organic-inorganic hybrid 2D materials.

Two-Dimensional Halide Pb-Perovskite-Double Perovskite Epitaxial Heterostructures.

Epitaxial heterostructures of two-dimensional (2D) halide perovskites offer a new platform for studying intriguing structural, optical, and electronic properties. However, difficulties with the stability of Pb- and Sn-based heterostructures have repeatedly slowed the progress. Recently, Pb-free halide double perovskites are gaining a lot of attention due to their superior stability and greater chemical diversity, but they have not been successfully incorporated into epitaxial heterostructures for further investigation. Here, we report epitaxial core-shell heterostructures via growing Pb-free double perovskites (involving combinations of Ag(I)-Bi(III), Ag-Sb, Ag-In, Na-Bi, Na-Sb, and Na-In) around Pb perovskite 2D crystals. Distinct from Pb-Pb and Pb-Sn perovskite heterostructures, growths of the Pb-free shell at 45° on the (100) surface of the lead perovskite core are observed in all Pb-free cases. The in-depth structural analysis carried out with electron diffraction unequivocally demonstrates the growth of the Pb-free shell along the [110] direction of the Pb perovskite, which is likely due to the relatively lower surface energy of the (110) surface. Furthermore, an investigation of anionic interdiffusion across heterostructure interfaces under the influence of heat was carried out. Interestingly, halide anion diffusion in the Pb-free 2D perovskites is found to be significantly suppressed as compared to Pb-based 2D perovskites. The great structural tunability and excellent stability of Pb-free perovskite heterostructures may find uses in electronic and optoelectronic devices in the near future.

One-Step Solution Patterning for Two-Dimensional Perovskite Nanoplate Arrays.

Two-dimensional perovskite crystals have attracted significant attention for their diverse optoelectronic characteristics, owing to their superior semiconducting properties. However, the majority of studies to date have focused on single crystals, which pose challenges for integration into device arrays due to their incompatibility with selective growth or conventional lithography techniques. Here, a facile one-step solution process for synthesizing 2D perovskite crystal arrays is proposed through meniscus-guided coating on patterned substrates. We further utilized this method for the synthesis of lateral heterostructure nanoplate arrays. Six different 2D perovskite nanoplate arrays, including epitaxial heterostructures, are successfully realized. Optical and crystallographic characterizations show the high optical performance and crystallinity of the nanoplates. Moreover, this method is further employed to prepare high-performance 2D perovskite nanoplate photosensor arrays. This strategy can be utilized as a guideline for the fundamental investigation of optical properties and the development of high-performance optoelectronics of perovskite materials including photosensors and displays.

Holistic energy landscape management in 2D/3D heterojunction via molecular engineering for efficient perovskite solar cells.

Constructing two-dimensional (2D) perovskite atop of 3D with energy landscape management is still a challenge in perovskite photovoltaics. Here, we report a strategy through designing a series of π-conjugated organic cations to construct stable 2D perovskites and to realize delicate energy level tunability at 2D/3D heterojunctions. As a result, the hole transfer energy barriers can be reduced both at heterojunctions and within 2D structures, and the preferable work function shift reduces charge accumulation at interface. Leveraging these insights and also benefitted from the superior interface contact between conjugated cations and poly(triarylamine) (PTAA) hole transporting layer, a solar cell with power conversion efficiency of 24.6% has been achieved, which is the highest among PTAA-based n-i-p devices to the best of our knowledge. The devices exhibit greatly enhanced stability and reproducibility. This approach is generic to several hole transporting materials, offering opportunities to realize high efficiency without using the unstable Spiro-OMeTAD.

Flexible Supercapacitors Based on Stretchable Conducting Polymer Electrodes.

Supercapacitors are widely used in various fields due to their high power density, fast charging and discharging speeds, and long service life. However, with the increasing demand for flexible electronics, integrated supercapacitors in devices are also facing more challenges, such as extensibility, bending stability, and operability. Despite many reports on stretchable supercapacitors, challenges still exist in their preparation process, which involves multiple steps. Therefore, we prepared stretchable conducting polymer electrodes by depositing thiophene and 3-methylthiophene on patterned 304 stainless steel (SS 304) through electropolymerization. The cycling stability of the prepared stretchable electrodes could be further improved by protecting them with poly(vinyl alcohol)/sulfuric acid (PVA/H2SO4) gel electrolyte. Specifically, the mechanical stability of the polythiophene (PTh) electrode was improved by 2.5%, and the stability of the poly(3-methylthiophene (P3MeT) electrode was improved by 7.0%. As a result, the assembled flexible supercapacitors maintained 93% of their stability even after 10,000 cycles of strain at 100%, which indicates potential applications in flexible electronics.

Two-Dimensional Cs2 AgInx Bi1- x Cl6 Alloyed Double Perovskite Nanoplatelets for Solution-Processed Light-Emitting Diodes.

Lead-free double perovskites have emerged as a promising class of materials with potential to be integrated into a wide range of optical and optoelectronic applications. Herein, the first synthesis of 2D Cs2 AgInx Bi1- x Cl6 (0 ≤ x ≤ 1) alloyed double perovskite nanoplatelets (NPLs) with well controlled morphology and composition is demonstrated. The obtained NPLs show unique optical properties with the highest photoluminescence quantum yield of 40.1%. Both temperature dependent spectroscopic studies and density functional theory calculation results reveal that the morphological dimension reduction and In-Bi alloying effect together boost the radiative pathway of the self-trapped excitons of the alloyed double perovskite NPLs. Moreover, the NPLs exhibit good stability under ambient conditions and against polar solvents, which is ideal for all solution-processing of the materials in low-cost device manufacturing. The first solution-processed light-emitting diodes is demonstrated using the Cs2 AgIn0.9 Bi0.1 Cl6 alloyed double perovskite NPLs as the sole emitting component, showing luminance maximum of 58 cd m-2 and peak current efficiency of 0.013 cd A-1 . This study sheds light on morphological control and composition-property relationships of double perovskite nanocrystals, paving the way toward ultimate utilizations of lead-free perovskite materials in diverse sets of real-life applications.

Design of adhesive conducting PEDOT-MeOH:PSS/PDA neural interface via electropolymerization for ultrasmall implantable neural microelectrodes.

Conducting polymers are emerging as promising neural interfaces towards diverse applications such as deep brain stimulation due to their superior biocompatibility, electrical, and mechanical properties. However, existing conducting polymer-based neural interfaces still suffer from several challenges and limitations such as complex preparation procedures, weak interfacial adhesion, poor long-term fidelity and stability, and expensive microfabrication, significantly hindering their broad practical applications and marketization. Herein, we develop an adhesive and long-term stable conducting polymer neural interface by a simple two-step electropolymerization methodology, namely, the pre-polymerization of polydopamine (PDA) as an adhesive thin layer followed by electropolymerization of hydroxymethylated 3,4-ethylenedioxythiophene (EDOT-MeOH) with polystyrene sulfonate (PSS) to form stable interpenetrating PEDOT-MeOH:PSS/PDA networks. As-prepared PEDOT-MeOH:PSS/PDA interface exhibits remarkably improved interfacial adhesion against metallic electrodes, showing 93% area retention against vigorous sonication for 20 min, which is one of the best tenacious conducting polymer interfaces so far. Enabled by the simple methodology, we can facilely fabricate the PEDOT-MeOH:PSS/PDA interface onto ultrasmall Pt-Ir wire microelectrodes (diameter: 10 µm). The modified microelectrodes display two orders of magnitude lower impedance than commercial products, and also superior long-term stability to previous reports with high charge injection capacity retention up to 99.5% upon 10,000,000 biphasic input pulse cycles. With these findings, such a simple methodology, together with the fabricated high-performance and stable neural interface, can potentially provide a powerful tool for both advanced neuroscience researches and cutting-edge clinical applications like brain-controlled intelligence.

Effects of Lactiplantibacillus plantarum and Lactiplantibacillus brevis on fermentation, aerobic stability, and the bacterial community of paper mulberry silage.

The present study investigated the dynamic profiles of fermentation quality, aerobic stability, and the bacterial community of paper mulberry silage inoculants without (Control) or with Lactiplantibacillus plantarum (LP), Lactiplantibacillus brevis (LB), or their combination (LPLB), which was screened from naturally fermented paper mulberry. The results showed that the inoculated treatments had significantly reduced neutral detergent fiber, water-soluble carbohydrates, and ammoniacal nitrogen contents compared with the control after 60 days of ensiling (the decreased proportion of LP, LB, and LPLB treatments ranged from 7.33%-11.23%, 9.60%-21.44%, and 21.53%-29.23%, respectively, p < 0.05). The pH value of the LP and LB treatments was significantly lower than that of the control after 60 days of ensiling (4.42 and 4.56 vs. 4.71, p < 0.05). The LP treatment promoted lactic acid accumulation and LAB number compared with the control (66.59% vs. 54.12% and 8.71 log10 CFU/g vs. 8.52 log10 CFU/g, respectively, p < 0.05), and the LB and LPLB treatments inhibited the growth of yeast and mold after 14 days of fermentation. After 5 days of aerobic exposure, both the LB and LPLB treatments increased the aerobic stability time and acetic acid content (from 29 to 75 h and 16.14%-48.72%, respectively, p < 0.05), inhibited the growth of yeast and mold, and did not detect butyric acid. Additionally, the bacteria community of each treatment was dominated by Aerococcus on day 3 of ensilage (accounting for 54.36%-69.31%), while the inoculated treatments reduced the abundance of Aerococcus on day 60 (from 59.73% to 85.16%, p < 0.05), and Lactobacillus became the dominant genus (accounting for 54.57%-70.89%). Inoculation of L. plantarum effectively maintained the acidic environment at the end of the fermentation system by maintaining the abundance of Lactobacillus, maximizing the preservation of dry matter and protein, and reducing protein corruption. Inoculation of L. brevis alone or in combination with L. plantarum significantly inhibited the growth of mold and improved the aerobic stability of paper mulberry silage.

Synthesis of double perovskite and quadruple perovskite nanocrystals through post-synthetic transformation reactions.

Lead-free halide perovskite nanocrystals (NCs) represent a group of emerging materials which hold promise for various optical and optoelectronic applications. Exploring facile synthetic methods for such materials has been of great interest to not only fundamental research but also technological implementations. Herein, we report a fundamentally new method to access lead-free Bi-based double perovskite (DP) and quadruple perovskite (or layered double perovskite, LDP) NCs based on a post-synthetic transformation reaction of Cs3BiX6 (X = Cl, Br) zero-dimensional (0D) perovskite NCs under mild conditions. The produced NCs show good particle uniformity, high crystallinity, and comparable optical properties to the directly synthesized NCs. The relatively slow kinetics and stop-on-demand feature of the transformation reaction allow real-time composition-structure-property investigations of the reaction, thus elucidating a cation-alloyed intermediate-assisted transformation mechanism. Our study presented here demonstrates for the first time that post-synthetic transformation of 0D perovskite NCs can serve as a new route towards the synthesis of high-quality lead-free perovskite NCs, and provides valuable insights into the crystal structures, excitonic properties and their relationships of perovskite NCs.

Improved highly efficient Dion-Jacobson type perovskite light-emitting diodes by effective surface polarization architecture.

Quasi-two-dimensional (quasi-2D) perovskites are emerging as promising materials for highly stable light-emitting diodes (LEDs). However, their lower charge transport mobilities and higher defect densities may constrain their light-emitting efficiency. Here, we combine an excessive-salt-assisted (ESA) process with antisolvent treatments to inhibit the defects in Dion-Jacobson-type perovskite LEDs. Such a method could improve the film quality and recombination efficiency. By further investigation, we found that artificially building a bulk junction interface and enhancing surface polarization could play a more important role in promoting the ability of charge carrier injection and recombination for high-performance LED devices. Accordingly, the DJ-type quasi-2D perovskite LED can achieve a high external quantum efficiency (EQE) of 7.1%.

Recent Advances in Ligand Design and Engineering in Lead Halide Perovskite Nanocrystals.

Lead halide perovskite (LHP) nanocrystals (NCs) have recently garnered enhanced development efforts from research disciplines owing to their superior optical and optoelectronic properties. These materials, however, are unlike conventional quantum dots, because they possess strong ionic character, labile ligand coverage, and overall stability issues. As a result, the system as a whole is highly dynamic and can be affected by slight changes of particle surface environment. Specifically, the surface ligand shell of LHP NCs has proven to play imperative roles throughout the lifetime of a LHP NC. Recent advances in engineering and understanding the roles of surface ligand shells from initial synthesis, through postsynthetic processing and device integration, finally to application performances of colloidal LHP NCs are covered here.

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To understand the decomposition of cattle dung in Seriphidium-dominated desert, the changes of dung physical and chemical properties were determined by setting different stacking times (0, 7, 29, 48, 58 h) in May (spring) and September (autumn), respectively. Mesh cage with different openings (no mesh cage, opening up and down, opening up, totally enclosed) were set up to explore the effects of different ecological functional groups of dung beetles on decomposition. The results showed that species richness of dung beetles in spring was significantly higher than that in autumn, and that the abundance of dung beetles in autumn was significantly higher than that in spring. The losses of moisture, total carbon, total nitrogen and total phosphorus in dung were mainly concentrated during 0-29 h in spring, being decreased by 39.4%, 13.9%, 32.1% and 26.7% at 29 h, respectively. Neutral detergent fiber and acid detergent fiber of the dung stacked for 58 h decreased significantly by 8.0% and 16.0% respectively. In autumn, moisture, neutral detergent fiber and acid detergent fiber decreased most rapidly during 0-7 h, being decreased by 85.6%, 10.2% and 20.2% at 7 h, respectively. The concentrations of neutral detergent fiber and acid detergent fiber increased during 7-58 h by 20.0% and 13.7%, respectively. The decomposition of total carbon, total nitrogen and total phosphorus mainly concentrated during 0-29 h, being reduced by17.5%, 55.0% and 64.8%, respectively. The mesh cage with different openings effectively prevented the entering of dung beetles from the corresponding ecological functional groups. With the increases of functional groups of dung beetles, the decomposition rate accelerated, with cattle dung of no mesh cage being significantly higher than other treatments. The species richness and abundance of dung beetles and the stacking time of dung significantly affected the decomposition of cattle dung.

Synthesis of Lead-Free Cs2AgBiX6 (X = Cl, Br, I) Double Perovskite Nanoplatelets and Their Application in CO2 Photocatalytic Reduction.

Morphology control represents an important strategy for the development of functional nanomaterials and has yet to be achieved in the case of promising lead-free double perovskite materials so far. In this work, high-quality Cs2AgBiX6 (X = Cl, Br, I) two-dimensional nanoplatelets were synthesized through a newly developed synthetic procedure. By analyzing the optical, morphological, and structural evolutions of the samples during synthesis, we elucidated that the growth mechanism of lead-free double perovskite nanoplatelets followed a lateral growth process from mono-octahedral-layer (half-unit-cell in thickness) cluster-based nanosheets to multilayer (three to four unit cells in thickness) nanoplatelets. Furthermore, we demonstrated that Cs2AgBiBr6 nanoplatelets possess a better performance in photocatalytic CO2 reduction compared with their nanocube counterpart. Our work demonstrates the first example with two-dimensional morphology of this important class of lead-free perovskite materials, shedding light on the synthetic manipulation and the application integration of such promising materials.

Synthesis of lead-free Cs4(Cd1-xMnx)Bi2Cl12 (0 ≤ x ≤ 1) layered double perovskite nanocrystals with controlled Mn-Mn coupling interaction.

Lead-free perovskites and their analogues have been extensively studied as a class of next-generation luminescent and optoelectronic materials. Herein, we report the synthesis of new colloidal Cs4M(ii)Bi2Cl12 (M(ii) = Cd, Mn) nanocrystals (NCs) with unique luminescence properties. The obtained Cs4M(ii)Bi2Cl12 NCs show a layered double perovskite (LDP) crystal structure with good particle stability. Density functional theory calculations show that both samples exhibit a wide, direct bandgap feature. Remarkably, the strong Mn-Mn coupling effect of the Cs4M(ii)Bi2Cl12 NCs results in an ultra-short Mn photoluminescence (PL) decay lifetime of around 10 µs, around two orders of magnitude faster than commonly observed Mn2+ dopant emission in NCs. Diluting the Mn2+ ion concentration through forming Cs4(Cd1-xMnx)Bi2Cl12 (0 < x < 1) alloyed LDP NCs leads to prolonged PL lifetimes and enhanced PL quantum yields. Our study provides the first synthetic example of Bi-based LDP colloidal NCs with potential for serving as a new category of stable lead-free perovskite-type materials for various applications.

Mn2+/Yb3+ Codoped CsPbCl3 Perovskite Nanocrystals with Triple-Wavelength Emission for Luminescent Solar Concentrators.

Doping metal ions into lead halide perovskite nanocrystals (NCs) has attracted great attention over the past few years due to the emergence of novel properties relevant to optoelectronic applications. Here, the synthesis of Mn2+/Yb3+ codoped CsPbCl3 NCs through a hot-injection technique is reported. The resulting NCs show a unique triple-wavelength emission covering ultraviolet/blue, visible, and near-infrared regions. By optimizing the dopant concentrations, the total photoluminescence quantum yield (PL QY) of the codoped NCs can reach ≈125.3% due to quantum cutting effects. Mechanism studies reveal the efficient energy transfer processes from host NCs to Mn2+ and Yb3+ dopant ions, as well as a possible inter-dopant energy transfer from Mn2+ to Yb3+ ion centers. Owing to the high PL QYs and minimal reabsorption loss, the codoped perovskite NCs are demonstrated to be used as efficient emitters in luminescent solar concentrators, with greatly enhanced external optical efficiency compared to that of using solely Mn2+ doped CsPbCl3 NCs. This study presents a new model system for enriching doping chemistry studies and future applications of perovskite NCs.

Stereoselective C-C Oxidative Coupling Reactions Photocatalyzed by Zwitterionic Ligand Capped CsPbBr3 Perovskite Quantum Dots.

Semiconductor quantum dots (QDs) have attracted tremendous attention in the field of photocatalysis, owing to their superior optoelectronic properties for photocatalytic reactions, including high absorption coefficients and long photogenerated carrier lifetimes. Herein, by choosing 2-(3,4-dimethoxyphenyl)-3-oxobutanenitrile as a model substrate, we demonstrate that the stereoselective (>99 %) C-C oxidative coupling reaction can be realized with a high product yield (99 %) using zwitterionic ligand capped CsPbBr3 perovskite QDs under visible light illumination. The reaction can be generalized to different starting materials with various substituents on the phenyl ring and varied functional moieties, producing stereoselective dl-isomers. A radical mediated reaction pathway has been proposed. Our study provides a new way of stereoselective C-C oxidative coupling via a photocatalytic means using specially designed perovskite QDs.

Phase Modulation by Vacuum Poling toward Enhanced Performance of Quasi-Two-Dimensional Bromide Perovskite-Based Light-Emitting Diodes.

As a new kind of highly efficient luminescent materials, quasi-two-dimensional (quasi-2D) perovskites show great potential in industrial display applications. In this work, the poling methods are used in modulating the phase arrangement in quasi-2D perovskite light-emitting diodes (PeLEDs). We find the effective modulation of different phase components in uniform arrangement can enhance both brightness and current efficiency to 30 810 cd/m2 and 8.3 cd/A, about 2 times in comparison to results for the control devices. Upon further investigation by optical and impedance spectroscopy, we find the phase modulation can improve the balance of charge carrier injection without sacrificing the transport ability. We believe our studies can provide new inspiration on the influence of phase arrangement in PeLED devices.