Unlocking the Potential of Colloidal Quantum Dot/Organic Hybrid Solar Cells: Band Tunable Interfacial Layer Approach.

Hybrid colloidal quantum dot (CQD)/organic architectures are promising candidates for emerging optoelectronic devices having high performance and inexpensive fabrication. For unlocking the potential of CQD/organic hybrid devices, enhancing charge extraction properties at electron transport layer (ETL)/CQD interfaces is crucial. Hence, we carefully adjust the interface properties between the ETL and CQD layer by incorporating an interfacial layer for the ETL (EIL) using several types of cinnamic acid ligands. The EIL having a cascading band offset (ΔEC) between the ETL and CQD layer suppresses the potential barrier and the local charge accumulation at ETL/CQD interfaces, thereby reducing the bimolecular recombination. An optimal EIL effectively expands the depletion region that facilitates charge extraction between the ETL and CQD layer while preventing the formation of shallow traps. Representative devices with an EIL exhibit a maximum power conversion efficiency of 14.01% and retain over 80% of initial performances after 300 h under continuous maximum power point operation.

Hybrid nanoparticles with cell membrane and dexamethasone-conjugated polymer for gene delivery into the lungs as therapy for acute lung injury.

Gene therapy has been suggested as a new treatment for acute lung injury (ALI), which is a severe inflammatory disease. Previously, amphiphilic polymeric carriers such as dexamethasone-conjugated polyethylenimine (PEI) (DP) have been used to transport plasmid DNA (pDNA) into the lungs. In the current study, hybrid nanoparticles comprising DP and cell membrane (CM) from LA-4 lung epithelial cells were developed for enhanced delivery of pDNA into the lungs. The CM components of the hybrid nanoparticles may interact with plasma membranes of target cells and facilitate intracellular uptake of pDNA. DP/CM/pDNA nanoparticles had the highest transfection efficiency into LA-4 cells at a weight ratio of 8 : 3 : 1. In vitro transfection assays showed that DP/CM/pDNA nanoparticles improved the cellular uptake and transfection efficiency of pDNA compared with PEI (25 kDa, PEI25k)/pDNA and DP/pDNA nanoparticles. The DP/CM/pDNA nanoparticles were approximately 80 nm in diameter with a zeta potential of +25 mV. To evaluate the therapeutic effects, heme oxygenase-1 pDNA (pHO-1) was administered to ALI animal models by intratracheal instillation. DP/CM/pHO-1 nanoparticles improved gene delivery efficiency compared with PEI25k/pHO-1 and DP/pHO-1 nanoparticles. As a result, inflammation in the lungs was alleviated by DP/CM/pHO-1 nanoparticles more effectively than by other nanoparticles. The results suggest that DP/CM/pDNA hybrid nanoparticles may be useful gene carriers for the treatment of ALI.

Tuning the C1 /C2 Selectivity of Electrochemical CO2 Reduction on Cu-CeO2 Nanorods by Oxidation State Control.

Ceria (CeO2 ) is one of the most extensively used rare earth oxides. Recently, it has been used as a support material for metal catalysts for electrochemical energy conversion. However, to date, the nature of metal/CeO2 interfaces and their impact on electrochemical processes remains unclear. Here, a Cu-CeO2 nanorod electrochemical CO2 reduction catalyst is presented. Using operando analysis and computational techniques, it is found that, on the application of a reductive electrochemical potential, Cu undergoes an abrupt change in solubility in the ceria matrix converting from less stable randomly dissolved single atomic Cu2+ ions to (Cu0 ,Cu1+ ) nanoclusters. Unlike single atomic Cu, which produces C1 products as the main product during electrochemical CO2 reduction, the coexistence of (Cu0 ,Cu1+ ) clusters lowers the energy barrier for C-C coupling and enables the selective production of C2+ hydrocarbons. As a result, the coexistence of (Cu0 ,Cu1+ ) in the clusters at the Cu-ceria interface results in a C2+ partial current density/unit Cu weight 27 times that of a corresponding Cu-carbon catalyst under the same conditions.

Pulmonary delivery of curcumin-loaded glycyrrhizic acid nanoparticles for anti-inflammatory therapy.

Acute lung injury (ALI) is an inflammatory disease of the lungs. Curcumin (Cur) shows protective effects in ALI animal models. However, Cur is a hydrophobic drug and its administration into the lungs is inefficient due to its low bioavailability. In this study, glycyrrhizic acid (GA) micelles were produced and evaluated as a carrier of Cur for treatment of ALI. Cur-loaded GA (GA-Cur) nanoparticles were produced using an oil-in-water emulsion/solvent evaporation method. The size and surface charge of the GA-Cur nanoparticles were 159 nm and -23 mV, respectively. In lipopolysaccharide-activated RAW264.7 cells, the GA-Cur nanoparticles decreased the pro-inflammatory cytokine levels more efficiently than GA, Cur, or a simple mixture of GA and Cur (GA + Cur). This suggests that the GA-Cur nanoparticles improved the therapeutic efficiency by enhanced delivery of GA and Cur. GA-Cur inhibited the nuclear translocation of nuclear factor-κb and induced endogenous heme oxygenase-1 more efficiently than the other treatments. Furthermore, an in vitro toxicity test showed that GA-Cur had little cytotoxicity. In vivo therapeutic effects of GA-Cur were evaluated in ALI mouse models. GA-Cur was administered into the animals by intratracheal instillation. The results showed that GA-Cur reduced pro-inflammatory cytokines in a dose-dependent manner and did so more efficiently than GA, Cur, or GA + Cur. Furthermore, the hemolysis and infiltration of monocytes into the lungs were more effectively inhibited by GA-Cur than the other treatments. The data indicate that GA is an efficient carrier of Cur and an anti-inflammatory drug. Owing to their delivery efficiency and safety, GA-Cur nanoparticles will be useful for treatment of ALI.

Protocol on the fabrication of monocrystalline thin semiconductor via crack-assisted layer exfoliation technique for photoelectrochemical water-splitting.

Thin semiconductors attract huge interest due to their cost-effective, flexible, lightweight, and semi-transparent properties. Here, we present a protocol on the preparation of thin semiconductor via controlled crack-assisted layer exfoliation technique. The protocol details the fabrication procedure for producing thin monocrystalline semiconductors with thicknesses in the range of a few tens of micrometers from thick donor substrates. In addition, we describe proof-of-concept application of the thin semiconductors for photoelectrochemical water-splitting to produce hydrogen fuel. For complete details on the use and execution of this protocol, please refer to Lee et al. (2021).

Mesoporous K-doped NiCo2O4 derived from a Prussian blue analog: high-yielding synthesis and assessment as oxygen evolution reaction catalyst.

The conversion and storage of clean renewable energy can be achieved using water splitting. However, water splitting exhibits sluggish kinetics because of the high overpotentials of the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) and should therefore be promoted by OER and/or HER electrocatalysts. As the kinetic barrier of the former reaction exceeds that of the latter, high-performance OER catalysts are highly sought after. Herein, K-doped NiCo2O4 (HK-NCO) was hydrothermally prepared from a Prussian blue analog with a metal-organic framework structure and assessed as an OER catalyst. Extensive K doping increased the number of active oxygen vacancies and changed their intrinsic properties (e.g., binding energy), thus increasing conductivity. As a result, HK-NCO exhibited a Tafel slope of 49.9 mV dec-1 and a low overpotential of 292 mV at 10 mA cm-2, outperforming a commercial OER catalyst (Ir) and thus holding great promise as a component of high-performance electrode materials for metal-oxide batteries and supercapacitors.

Solvent- and Light-Sensitive AIEE-Active Azo Dye: From Spherical to 1D and 2D Assemblies.

Fluorescent molecular assembly systems provide an exciting platform for creating stimuli-responsive nano- and microstructured materials with optical, electronic, and sensing functions. To understand the relationship between (i) the plausible molecular structures preferentially adopted depending on the solvent polarity (such as N,N-dimethylformamide [DMF], tetrahydrofuran [THF], and toluene), (ii) the resulting spectroscopic features, and (iii) self-assembled nano-, micro-, and macrostructures, we chose a sterically crowded triangular azo dye (3Bu) composed of a polar molecular core and three peripheral biphenyl wings. The chromophore changed the solution color from yellow to pink-red depending on the solvent polarity. In a yellow DMF solution, a considerable amount of the twisted azo form could be kept stable with the help of favorable intermolecular interactions with the solvent molecules. By varying the concentration of the DMF solution, the morphology of self-assembled structures was transformed from nanoparticles to micrometer-sized one-dimensional (1D) structures such as sticks and fibers. In a pink-red toluene solution, the periphery of the central ring became more planar. The resulting significant amount of the keto-hydrazone tautomer grew into micro- and millimeter-sized 1D structures. Interestingly, when THF-H2O (1:1) mixtures were stored at a low temperature, elongated fibers were stacked sideways and eventually developed into anisotropic two-dimensional (2D) sheets. Notably, subsequent exposure of visible-light-irradiated sphere samples to solvent vapor resulted in reversible fluorescence off↔on switching accompanied by morphological restoration. These findings suggest that rational selection of organic dyes, solvents, and light is important for developing reusable fluorescent materials.

Tunable Product Selectivity in Electrochemical CO2 Reduction on Well-Mixed Ni-Cu Alloys.

Electrochemical reduction of CO2 on copper-based catalysts has become a promising strategy to mitigate greenhouse gas emissions and gain valuable chemicals and fuels. Unfortunately, however, the generally low product selectivity of the process decreases the industrial competitiveness compared to the established large-scale chemical processes. Here, we present random solid solution Cu1-xNix alloy catalysts that, due to their full miscibility, enable a systematic modulation of adsorption energies. In particular, we find that these catalysts lead to an increase of hydrogen evolution with the Ni content, which correlates with a significant increase of the selectivity for methane formation relative to C2 products such as ethylene and ethanol. From experimental and theoretical insights, we find the increased hydrogen atom coverage to facilitate Langmuir-Hinshelwood-like hydrogenation of surface intermediates, giving an impressive almost 2 orders of magnitude increase in the CH4 to C2H4 + C2H5OH selectivity on Cu0.87Ni0.13 at -300 mA cm-2. This study provides important insights and design concepts for the tunability of product selectivity for electrochemical CO2 reduction that will help to pave the way toward industrially competitive electrocatalyst materials.

Fully Bottom-Up Waste-Free Growth of Ultrathin Silicon Wafer via Self-Releasing Seed Layer.

The fabrication of ultrathin silicon wafers at low cost is crucial for advancing silicon electronics toward stretchability and flexibility. However, conventional fabrication techniques are inefficient because they sacrifice a large amount of substrate material. Thus, advanced silicon electronics that have been realized in laboratories cannot move forward to commercialization. Here, a fully bottom-up technique for producing a self-releasing ultrathin silicon wafer without sacrificing any of the substrate is presented. The key to this approach is a self-organized nanogap on the substrate fabricated by plasma-assisted epitaxial growth (plasma-epi) and subsequent hydrogen annealing. The wafer thickness can be independently controlled during the bulk growth after the formation of plasma-epi seed layer. In addition, semiconductor devices are realized using the ultrathin silicon wafer. Given the high scalability of plasma-epi and its compatibility with conventional semiconductor process, the proposed bottom-up wafer fabrication process will open a new route to developing advanced silicon electronics.

Thin silicon via crack-assisted layer exfoliation for photoelectrochemical water splitting.

Silicon (Si) has been widely investigated as a feasible material for photoelectrochemical (PEC) water splitting. Compared to thick wafer-based Si, thin Si (<50 µm thickness) could concurrently minimize the material usage allowing the development of cost-effective and flexible photoelectrodes for integrable PEC cells. This work presents the design and fabrication of thin Si using crack-assisted layer exfoliation method through detailed optical simulations and a systematic investigation of the exfoliation method. Thin free-standing Si photoanodes with sub-50 µm thickness are demonstrated by incorporating a nickel oxide (NiOx) thin film as oxygen evolution catalyst, light-trapping surface structure, and a rear-pn+ junction, to generate a photo-current density of 23.43 mA/cm2 with an onset potential of 1.2 V (vs. RHE). Our work offers a general approach for the development of efficient and cost-effective photoelectrodes with Si films with important implications for flexible and wearable Si-based photovoltaics and (opto)electronic devices.

Quasi-graphitic carbon shell-induced Cu confinement promotes electrocatalytic CO2 reduction toward C2+ products.

For steady electroconversion to value-added chemical products with high efficiency, electrocatalyst reconstruction during electrochemical reactions is a critical issue in catalyst design strategies. Here, we report a reconstruction-immunized catalyst system in which Cu nanoparticles are protected by a quasi-graphitic C shell. This C shell epitaxially grew on Cu with quasi-graphitic bonding via a gas-solid reaction governed by the CO (g) - CO2 (g) - C (s) equilibrium. The quasi-graphitic C shell-coated Cu was stable during the CO2 reduction reaction and provided a platform for rational material design. C2+ product selectivity could be additionally improved by doping p-block elements. These elements modulated the electronic structure of the Cu surface and its binding properties, which can affect the intermediate binding and CO dimerization barrier. B-modified Cu attained a 68.1% Faradaic efficiency for C2H4 at -0.55 V (vs RHE) and a C2H4 cathodic power conversion efficiency of 44.0%. In the case of N-modified Cu, an improved C2+ selectivity of 82.3% at a partial current density of 329.2 mA/cm2 was acquired. Quasi-graphitic C shells, which enable surface stabilization and inner element doping, can realize stable CO2-to-C2H4 conversion over 180 h and allow practical application of electrocatalysts for renewable energy conversion.

Relationship between Mental Health and House Sharing: Evidence from Seoul.

While the association between general housing and mental health has been well documented, little is known about the mental health outcomes of house sharing. As shared housing has been viewed as an economically and socially viable housing option for young adults, a broader understanding of how shared housing affects the residents' quality of life, including mental health, is needed. In this context, this study aims to provide empirical evidence about the relationship between mental health and house sharing after controlling for residents' self-selection. We conducted a survey of 834 young single adults living in shared housing and non-shared housing in Seoul, Korea. Then, to control for residential self-selection, we applied the residential dissonance framework. The main findings of this study were two-fold: first, house-sharers with a positive attitude toward shared housing were more likely to respond that their mental health status improved after they started residing in shared housing; second, if young adults are forced to live in shared housing, this could increase the potential risk of social dysfunction of house-sharers. Based on these findings, we suggest policy measures for shared housing, including pre-occupancy interviews, resident behavior codes, and fostering a livable dwelling environment to ensure a healthier life in shared living arrangements.

Where to Ride? An Explorative Study to Investigate Potential Risk Factors of Personal Mobility Accidents.

As a mobility of future, the popularity of personal mobility vehicles (PMs) is rapidly increasing worldwide. However, this boom in the use of PMs has resulted in a substantial number of accidents involving not only PM users but also other road users including pedestrians, bicyclists, and motor vehicle drivers. This study aims to explore the potential risk factors for the occurrence of PM-related accidents and the resulting injury severity using the Traffic Accident Analysis System (TAAS) of South Korea between 2017 and 2019. We found that PM-pedestrian accidents tend to occur on roads with wider sidewalks and bike lanes, possibly because the pedestrian-PM conflict increases in this road condition. There is still ongoing debate on whether it is appropriate for PMs to share the sidewalk with pedestrians. Some countries, including Korea, prohibit the use of PMs on sidewalks; however, in reality, this regulation is not well-observed because using PMs on roadways involves higher crash risk with motor vehicles. This study suggests one potential solution to ensure safety of PM users: expansion of bike lane infrastructure having physically separated bike lanes and sidewalks/motorways in addition to the formation and strict enforcement of appropriate safety rules for PM users.

Direct Identification of Antisite Cation Intermixing and Correlation with Electronic Conduction in CuBi2O4 for Photocathodes.

Cu-based p-type semiconducting oxides have been sought for water-reduction photocathodes to enhance the energy-conversion efficiency in photoelectrochemical cells. CuBi2O4 has recently attracted notable attention as a new family of p-type oxides, based on its adequate band gap. Although the identification of a major defect structure should be the first step toward understanding the electronic conduction behavior, no direct experimental analysis has been carried out yet. Using atomic-scale scanning transmission electron microscopy together with chemical probing, we identify a substantial amount of BiCu-CuBi antisite intermixing as a major point-defect type. Our density functional theory calculations also show that antisite BiCu can seriously hinder the hole-polaron hopping between Cu, in agreement with lower conductivity and a larger thermal activation barrier under a higher degree of intermixing. These findings highlight the value of the direct identification of point defects for a better understanding of electronic properties in complex oxides.

Facile electrochemical synthesis of dilute AuCu alloy nanostructures for selective and long-term stable CO2 electrolysis.

Electrochemical CO production from CO2 electrolysis has been considered the most economically viable approach among various candidate products. AuCu bimetallic alloys are currently receiving attention for their potential to tailor catalytic activity. Here, we synthesized a dilute AuCu alloy nanostructure with an AuCu atomic composition ratio of 3% by using a simple electrochemical treatment method on a 200 nm-thick Au thin film. The dilute AuCu alloy catalyst shows an exceptional CO2 reduction activity in terms of selectivity and overpotential for CO production. In addition, the stability property is more significantly enhanced as compared to pure Au nanostructures. In addition, we describe an in situ tailoring method of catalytic activity for Au nanostructures by repeating an electrochemical treatment process that is performed for forming the Au nanostructure. This approach will be a promising and facile strategy not only for reactive Au catalysts but also to increase the stability activity simultaneously by utilizing Cu impurities existing in an aqueous electrolyte for CO2 reduction.

Template Engineering of CuBi2 O4 Single-Crystal Thin Film Photocathodes.

To develop strategies for efficient photo-electrochemical water-splitting, it is important to understand the fundamental properties of oxide photoelectrodes by synthesizing and investigating their single-crystal thin films. However, it is challenging to synthesize high-quality single-crystal thin films from copper-based oxide photoelectrodes due to the occurrence of significant defects such as copper or oxygen vacancies and grains. Here, the CuBi2 O4 (CBO) single-crystal thin film photocathode is achieved using a NiO template layer grown on single-crystal SrTiO3 (STO) (001) substrate via pulsed laser deposition. The NiO template layer plays a role as a buffer layer of large lattice mismatch between CBO and STO (001) substrate through domain-matching epitaxy, and forms a type-II band alignment with CBO, which prohibits the transfer of photogenerated electrons toward bottom electrode. The photocurrent densities of the CBO single-crystal thin film photocathode demonstrate -0.4 and -0.7 mA cm-2 at even 0 VRHE with no severe dark current under illumination in a 0.1 m potassium phosphate buffer solution without and with H2 O2 as an electron scavenger, respectively. The successful synthesis of high-quality CBO single-crystal thin film would be a cornerstone for the in-depth understanding of the fundamental properties of CBO toward efficient photo-electrochemical water-splitting.

Hierarchically porous Au nanostructures with interconnected channels for efficient mass transport in electrocatalytic CO2 reduction.

Electrocatalytic CO2 reduction is a promising way to provide renewable energy from gaseous CO2 The development of nanostructures improves energy efficiency and selectivity for value-added chemicals, but complex nanostructures limit the CO2 conversion rates due to poor mass transport during vigorous electrolysis. Herein, we propose a three-dimensional (3D) hierarchically porous Au comprising interconnected macroporous channels (200-300 nm) and nanopores (∼10 nm) fabricated via proximity-field nanopatterning. The interconnected macropores and nanopores enable efficient mass transport and large active areas, respectively. The roles of each pore network are investigated using reliable 3D nanostructures possessing controlled pore distribution and size. The hierarchical nanostructured electrodes show a high CO selectivity of 85.8% at a low overpotential of 0.264 V and efficient mass activity that is maximum 3.96 times higher than that of dealloyed nanoporous Au. Hence, the systematic model study shows the proposed hierarchical nanostructures have important value in increasing the efficiency of expensive Au.

Long-term stabilized high-density CuBi2O4/NiO heterostructure thin film photocathode grown by pulsed laser deposition.

Harvesting sustainable hydrogen through water-splitting requires a durable photoelectrode to achieve high efficiency and long lifetime. Dense, uniform CuBi2O4/NiO thin film photocathodes grown by pulsed laser deposition achieved photocurrent density over 1.5 mA cm-2 at 0.4 VRHE and long-term chronoamperometric stability for over 8 hours.

The effect of the oxidation states of supported oxides on catalytic activity: CO oxidation studies on Pt/cobalt oxide.

The strong metal-oxide interaction of platinum nanoparticles (PtNPs) deposited on two types of cobalt oxides, CoO and Co3O4, was investigated using CO oxidation. Two different sizes of PtNPs as well as arc-plasma-deposited (APD) PtNPs without a capping layer were used to reveal the effect of metal-oxide interfaces on catalytic activity. An enhanced catalytic activity was observed on the PtNPs on the Co3O4 substrate, which was ascribed to the reducible support and to the interfacial sites.

Atomic-Layer-Deposited MoN x Thin Films on Three-Dimensional Ni Foam as Efficient Catalysts for the Electrochemical Hydrogen Evolution Reaction.

Future realization of a hydrogen-based economy requires a high-surface-area, low-cost, and robust electrocatalyst for the hydrogen evolution reaction (HER). In this study, the MoN x thin layer is synthesized on to a high-surface-area three-dimensional (3D) nickel foam (NF) substrate using atomic layer deposition (ALD) for HER catalysis. MoN x is grown on NF by the sequential exposure of Mo(CO)6 and NH3 at 225 °C. The thickness of the thin film is controlled by varying the number of ALD cycles to maximize the HER performance of the MoN x/NF composite catalyst. The scanning electron microscopy and transmission electron microscopy (TEM) images of MoN x/NF highlight that ALD facilitates uniform and conformal coating. TEM analysis highlights that the MoN x film is predominantly amorphous with the nanocrystalline MoN grains (4 nm) dispersed throughout it. Moreover, the high-resolution (HR)-TEM analysis shows a rough surface of the MoN x film with an overall composition of Mo0.59N0.41. X-ray photoelectron spectroscopy depth-profile analysis reveals that oxygen contamination is concentrated at the surface because of surface oxidation of the MoN x film under ambient conditions. The HER activity of MoN x is evaluated under acidic (0.5 M H2SO4) and alkaline (0.1 M KOH) conditions. In an acidic electrolyte, the sample prepared with 700 ALD cycles exhibits significant HER activity and a low overpotential (η) of 148 mV at 10 mA cm-2. Under an alkaline condition, it achieves 10 mA cm-2 with η of 125 mV for MoN x/NF (700 cycles). In both electrolytes, the MoN x thin film exhibits enhanced activity and stability because of the uniform and conformal coating on NF. Thus, this study facilitates the development of a large-area 3D freestanding catalyst for efficient electrochemical water-splitting, which may have commercial applicability.