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1.
Nature ; 612(7940): 470-476, 2022 12.
Article in English | MEDLINE | ID: mdl-36517715

ABSTRACT

Quantitative determination and in situ monitoring of molecular chirality at extremely low concentrations is still challenging with simple optics because of the molecular-scale mismatch with the incident light wavelength. Advances in spectroscopy1-4 and nanophotonics have successfully lowered the detection limit in enantioselective sensing, as it can bring the microscopic chiral characteristics of molecules into the macroscopic scale5-7 or squeeze the chiral light into the subwavelength scale8-17. Conventional nanophotonic approaches depend mainly on the optical helicity density8,9 by localized resonances within an individual structure, such as localized surface plasmon resonances (LSPRs)10-16 or dielectric Mie resonances17. These approaches use the local chiral hotspots in the immediate vicinity of the structure, whereas the handedness of these hotspots varies spatially. As such, these localized resonance modes tend to be error-prone to the stochasticity of the target molecular orientations, vibrations and local concentrations18,19. Here we identified enantioselective characteristics of collective resonances (CRs)20 arising from assembled 2D crystals of isotropic, 432-symmetric chiral gold nanoparticles (helicoids)21,22. The CRs exhibit a strong and uniform chiral near field over a large volume above the 2D crystal plane, resulting from the collectively spinning, optically induced dipoles at each helicoid. Thus, energy redistribution by molecular back action on the chiral near field shifts the CRs in opposite directions, depending on the handedness of the analyte, maximizing the modulation of the collective circular dichroism (CD).

2.
Proc Natl Acad Sci U S A ; 120(28): e2219231120, 2023 07 11.
Article in English | MEDLINE | ID: mdl-37399389

ABSTRACT

Real-time monitoring of various neurochemicals with high spatial resolution in multiple brain regions in vivo can elucidate neural circuits related to various brain diseases. However, previous systems for monitoring neurochemicals have limitations in observing multiple neurochemicals without crosstalk in real time, and these methods cannot record electrical activity, which is essential for investigating neural circuits. Here, we present a real-time bimodal (RTBM) neural probe that uses monolithically integrated biosensors and multiple shanks to study the connectivity of neural circuits by measuring multiple neurochemicals and electrical neural activity in real time. Using the RTBM probe, we demonstrate concurrent measurements of four neurochemicals-glucose, lactate, choline, and glutamate without cross-talking each other-and electrical activity in real time in vivo. Additionally, we show the functional connectivity between the medial prefrontal cortex and mediodorsal thalamus through the simultaneous measurement of chemical and electrical signals. We expect that our device will contribute to not only elucidating the role of neurochemicals in neural circuits related to brain functions but also developing drugs for various brain diseases related to neurochemicals.


Subject(s)
Brain Diseases , Brain , Humans , Brain/physiology , Electrophysiological Phenomena , Glutamic Acid , Electrophysiology
3.
Nat Mater ; 23(7): 977-983, 2024 Jul.
Article in English | MEDLINE | ID: mdl-38693448

ABSTRACT

Homochirality is an important feature in biological systems and occurs even in inorganic nanoparticles. However, the mechanism of chirality formation and the key steps during growth are not fully understood. Here we identify two distinguishable pathways from achiral to chiral morphologies in gold nanoparticles by training an artificial neural network of cellular automata according to experimental results. We find that the chirality is initially determined by the nature of the asymmetric growth along the boundaries of enantiomeric high-index planes. The deep learning-based interpretation of chiral morphogenesis provides a theoretical understanding but also allows us to predict an unprecedented crossover pathway and the resulting morphology.

4.
Brain ; 147(6): 2114-2127, 2024 Jun 03.
Article in English | MEDLINE | ID: mdl-38227798

ABSTRACT

Mutations in the Microrchidia CW-type zinc finger 2 (MORC2) GHKL ATPase module cause a broad range of neuropathies, such as Charcot-Marie-Tooth disease type 2Z; however, the aetiology and therapeutic strategy are not fully understood. Previously, we reported that the Morc2a p.S87L mouse model exhibited neuropathy and muscular dysfunction through DNA damage accumulation. In the present study, we analysed the gene expression of Morc2a p.S87L mice and designated the primary causing factor. We investigated the pathological pathway using Morc2a p.S87L mouse embryonic fibroblasts and human fibroblasts harbouring MORC2 p.R252W. We subsequently assessed the therapeutic effect of gene therapy administered to Morc2a p.S87L mice. This study revealed that Morc2a p.S87L causes a protein synthesis defect, resulting in the loss of function of Morc2a and high cellular apoptosis induced by high hydroxyl radical levels. We considered the Morc2a GHKL ATPase domain as a therapeutic target because it simultaneously complements hydroxyl radical scavenging and ATPase activity. We used the adeno-associated virus (AAV)-PHP.eB serotype, which has a high CNS transduction efficiency, to express Morc2a or Morc2a GHKL ATPase domain protein in vivo. Notably, AAV gene therapy ameliorated neuropathy and muscular dysfunction with a single treatment. Loss-of-function characteristics due to protein synthesis defects in Morc2a p.S87L were also noted in human MORC2 p.S87L or p.R252W variants, indicating the correlation between mouse and human pathogenesis. In summary, CMT2Z is known as an incurable genetic disorder, but the present study demonstrated its mechanisms and treatments based on established animal models. This study demonstrates that the Morc2a p.S87L variant causes hydroxyl radical-mediated neuropathy, which can be rescued through AAV-based gene therapy.


Subject(s)
Genetic Therapy , Animals , Humans , Mice , Adenosine Triphosphatases/genetics , Adenosine Triphosphatases/metabolism , Charcot-Marie-Tooth Disease/genetics , Charcot-Marie-Tooth Disease/metabolism , Charcot-Marie-Tooth Disease/therapy , Dependovirus/genetics , Fibroblasts/metabolism , Genetic Therapy/methods , Hydroxyl Radical/metabolism , Transcription Factors/genetics , Transcription Factors/metabolism
5.
Nano Lett ; 24(33): 10380-10387, 2024 Aug 21.
Article in English | MEDLINE | ID: mdl-39120059

ABSTRACT

The advancement of effective nasal mucoadhesive delivery faces challenges due to rapid mucociliary clearance (MCC). Conventional studies have employed mucoadhesive materials, mainly forming spherical nanoparticles, but these offer limited adhesion to the nasal mucosa. This study hypothesizes that a 2D nanoscale structure utilizing adhesive polyphenols can provide a superior strategy for countering MCC, aligning with the planar mucosal layers. We explore the use of tannic acid (TA), a polyphenolic molecule known for its adhesive properties and ability to form complexes with biomolecules. Our study introduces an unprecedented 2D nanopatch, assembled through the interaction of TA with green fluorescent protein (GFP), and cell-penetrating peptide (CPP). This 2D nanopatch demonstrates robust adhesion to nasal mucosa and significantly enhances immunoglobulin A secretions, suggesting its potential for enhancing nasal vaccine delivery. The promise of a polyphenol-enabled adhesive 2D nanopatch signifies a pivotal shift from conventional spherical nanoparticles, opening new pathways for delivery strategies through respiratory mucoadhesion.


Subject(s)
Nasal Mucosa , Polyphenols , Tannins , Tannins/chemistry , Polyphenols/chemistry , Polyphenols/administration & dosage , Nasal Mucosa/metabolism , Nasal Mucosa/immunology , Animals , Nanoparticles/chemistry , Humans , Cell-Penetrating Peptides/chemistry , Green Fluorescent Proteins/metabolism , Green Fluorescent Proteins/chemistry , Adhesives/chemistry , Mucociliary Clearance/drug effects , Immunoglobulin A , Mice
6.
J Am Chem Soc ; 2024 Oct 10.
Article in English | MEDLINE | ID: mdl-39388348

ABSTRACT

Chiral inorganic nanomaterials hold significant promise for various applications, including enantioselective catalysis, polarization-controlling optical devices, metamaterials, and enantioselective molecular sensors. In our previous work, we presented a method for synthesizing chiral Au 432 helicoid III (Au helicoids) from peptides and amino acids, where helical gaps are intricately arranged with 432 symmetry within single cubic nanoparticles. In this study, we have achieved the fabrication of chiral silica molds through Au etching subsequent to the silica coating of Au helicoids. We demonstrate that these molds serve as geometrically confined reactors capable of producing chiral Ag, Pd, and Pt 432 helicoid III (Ag, Pd, and Pt helicoids). The morphology of the synthesized Ag, Pd, and Pt helicoids closely resembles that of the Au helicoids, exhibiting a superior g-factor compared to other reported chiral structures of each material. Notably, the Ag and Pd helicoids are found to be single-crystalline, with high-index planes exposed within the gaps. We believe that this silica mold-based approach can be generalized to synthesize chiral nanomaterials of various metal and even oxide materials.

7.
Anal Chem ; 2024 Aug 15.
Article in English | MEDLINE | ID: mdl-39146475

ABSTRACT

Merging two droplets into a droplet to add and mix two contents is one of the common droplet microfluidic functions with droplet generation and sorting, performing broad ranges of biological and chemical assays in droplets. However, traditional droplet-merging techniques often encounter unsynchronized droplets, causing overmerging or mis-merging, and unwanted merging outside of the desired zone. This is more severe when the incoming droplets to be merged are polydisperse in their sizes, often observed in assays that require long-term incubation, elevated-temperature, and/or multiple droplet processing steps. Here, we developed an interdigitated electrode (IDE)-based droplet merger consisting of a droplet autosynchronizing channel and a merging channel. The autosynchronizing channel provides >95% merging efficiency even when 20% polydispersity in the droplet size exists. The highly localized and enhanced dielectrophoretic force generated by the IDEs on the channel bottom allows droplet merging at an extremely low voltage (4.5 V) and only locally at the IDE region. A systematic evaluation of how various design and operation parameters of the IDE merger, such as IDE finger dimensions, dielectric coating layer thickness, droplet size, and droplet flow speed impact the performance was conducted. The optimized device showed consistent performance even when operating for up to 100 h consecutively at high throughput (100 droplets/s). The presented technology has been integrated into a droplet microfluidics workflow to test the lytic activities of bacteriophage on bacterial host cells with 100% merging efficiency. We expect this function to be integrated into droplet microfluidic systems performing broad ranges of high-throughput chemical and biological assays.

8.
Small ; 20(35): e2401248, 2024 Aug.
Article in English | MEDLINE | ID: mdl-38639029

ABSTRACT

Chlorine has been supplied by the chlor-alkali process that deploys dimensionally stable anodes (DSAs) for the electrochemical chlorine evolution reaction (ClER). The paramount bottlenecks have been ascribed to an intensive usage of precious elements and inevitable competition with the oxygen evolution reaction. Herein, a unique case of Ru2+-O4 active motifs anchored on Magnéli Ti4O7 (Ru-Ti4O7) via a straightforward wet impregnation and mild annealing is reported. The Ru-Ti4O7 performs radically active ClER with minimal deployment of Ru (0.13 wt%), both in 5 m NaCl (pH 2.3) and 0.1 m NaCl (pH 6.5) electrolytes. Scanning electrochemical microscopy demonstrates superior ClER selectivity on Ru-Ti4O7 compared to the DSA. Operando X-ray absorption spectroscopy and density functional theory calculations reveal a universally active ClER (over a wide range of pH and [Cl-]), through a direct adsorption of Cl- on Ru2+-O4 sites as the most plausible pathway, together with stabilized ClO* at low [Cl-] and high pH.

9.
Cerebellum ; 23(1): 56-66, 2024 Feb.
Article in English | MEDLINE | ID: mdl-36633829

ABSTRACT

Cerebellar brain inhibition (CBI), a neural connection between the cerebellum and primary motor cortex (M1), has been researched as a target pathway for neuromodulation to improve clinical outcomes in various neurological diseases. However, conflicting results of anodal cerebellar transcranial direct current stimulation (acb-tDCS) on M1 excitability indicate that additional investigation is required to examine its precise effect. This study aimed to gather evidence of the neuromodulatory effect of acb-tDCS on the M1 using functional near-infrared spectroscopy (fNIRS). Sixteen healthy participants were included in this cross-over study. Participants received real and sham acb-tDCS randomly, with a minimum 1-week washout period between them. The anode and cathode were placed on the right cerebellum and the right buccinator muscle, respectively. Stimulation lasted 20 min at an intensity of 2 mA, and fNIRS data were recorded for 42 min (including a 4-min baseline before stimulation and an 18-min post-stimulation duration) using eight channels attached bilaterally on the M1. acb-tDCS induced a significant decrease in oxyhemoglobin (HbO) concentration (inhibitory effect) in the left (contralateral) M1, whereas it induced a significant increase in HbO concentration (excitatory effect) in the right (ipsilateral) M1 compared to sham tDCS during (p < 0.05) and after stimulation (p < 0.01) in a group level analysis. At the individual level, variations in response to acb-tDCS were observed. Our findings demonstrate the neuromodulatory effects of acb-tDCS on the bilateral M1 in terms of neuronal hemodynamics.


Subject(s)
Motor Cortex , Transcranial Direct Current Stimulation , Humans , Transcranial Direct Current Stimulation/methods , Spectroscopy, Near-Infrared , Motor Cortex/physiology , Cross-Over Studies , Cerebellum/physiology , Electrodes , Evoked Potentials, Motor/physiology
10.
Langmuir ; 40(4): 1961-1970, 2024 Jan 30.
Article in English | MEDLINE | ID: mdl-38224073

ABSTRACT

A key issue in lithium-ion batteries is understanding the solid electrolyte interphase (SEI) resulting from a reductive reaction on the anode/electrolyte interface. The presence of the SEI layer affects the transport behavior of the ions and electrons between the anode and electrolyte. Despite the influence on interfacial properties, the formation and evolution mechanism of the SEI layer are unclear owing to their complexity and dynamic nature. Atomistic-scale simulations have promoted the understanding of the reaction mechanism on the anode/electrolyte interface, the formation and evolution of the SEI layer, and their fundamental properties. This Perspective discusses the modeling and interpretations of anode/SEI/electrolyte interfaces through computational methods at the atomic-scale and highlights interfacial modeling techniques for a realistic interface design, which can overcome the limited time and length scale with high accuracy.

11.
Nanotechnology ; 35(24)2024 Mar 26.
Article in English | MEDLINE | ID: mdl-38461550

ABSTRACT

Opto-neuromorphic operation is critical for biological system to recognize the visual objects and mimicking such operation is important for artificial prosthesis as well as machine vision system for industrial applications. To sophisticatedly mimic biological system, regulation of learning and memorizing efficiency is needed, however engineered synthetic platform has been lack of controllability, which makes huge gap between biological system and synthetic platform. Here we demonstrated controllable learning and memorizing opto-neuromorphic operation at plasmonic hot electron transistor. Especially, circularly polarized light (CPL) sensitive synaptic characteristics and learning experience capability are enabled by incorporating chiral plasmonic nanoparticle. Furthermore, gate voltage gives rise to controllable neuromorphic operation due to hot electron injection and trapping effect, resulting in high remaining synaptic weight of ∼70% at negative gate voltage under CPL excitation. We believe that this discovery makes significant leap toward on-demand in-sensor computing as well as toward bio-realistic device.

12.
J Chem Phys ; 160(6)2024 Feb 14.
Article in English | MEDLINE | ID: mdl-38341778

ABSTRACT

Molecular chirality is represented as broken mirror symmetry in the structural orientation of constituent atoms and plays a pivotal role at every scale of nature. Since the discovery of the chiroptic property of chiral molecules, the characterization of molecular chirality is important in the fields of biology, physics, and chemistry. Over the centuries, the field of optical chiral sensing was based on chiral light-matter interactions between chiral molecules and polarized light. Starting from simple optics-based sensing, the utilization of plasmonic materials that could control local chiral light-matter interactions by squeezing light into molecules successfully facilitated chiral sensing into noninvasive, ultrasensitive, and accurate detection. In this Review, the importance of plasmonic materials and their engineering in chiral sensing are discussed based on the principle of chiral light-matter interactions and the theory of optical chirality and chiral perturbation; thus, this Review can serve as a milestone for the proper design and utilization of plasmonic nanostructures for improved chiral sensing.

13.
BMC Med Educ ; 24(1): 92, 2024 Jan 26.
Article in English | MEDLINE | ID: mdl-38279179

ABSTRACT

BACKGROUND: This study aims to improve nursing students' ability to care for critically ill patients through education in extracorporeal membrane oxygenation (ECMO) nursing. METHODS: This study developed a virtual reality (VR) simulation program for the five-step ECMO nursing of the Analysis, Design, Development, Implement, and Evaluation (ADDIE) model and used an equivalent control group pre-test and post-test no-synchronized design to verify the effect. The participants of this study were fourth-year nursing students enrolled in nursing departments at three universities in Seoul, Gangwon, and Gyeonggi in South Korea; it included 66 participants, 33 in each of the experimental and control groups. The program consisted of pre-training, orientation, VR simulation, and debriefing. RESULTS: The interaction effect of the intervention and control groups with time points using the ECMO nursing VR simulation program was rejected due to no statistically significant difference in knowledge (F = 1.41, p = .251), confidence (F = 1.97, p = .144), and clinical reasoning capacity (F = 2.85, p = .061). However, learning immersion (t = 3.97, p < .001) and learning satisfaction (t = 4.25, p < .001) were statistically significantly higher in the experimental group than in the control group. CONCLUSION: VR simulation program for ECMO nursing developed in this study is a potential educational method that positively affects the learning immersion and learning satisfaction of nursing students.


Subject(s)
Education, Nursing, Baccalaureate , Education, Nursing , Extracorporeal Membrane Oxygenation , Students, Nursing , Virtual Reality , Humans , Education, Nursing, Baccalaureate/methods , Learning
14.
J Craniofac Surg ; 35(4): e312-e316, 2024 Jun 01.
Article in English | MEDLINE | ID: mdl-38315743

ABSTRACT

This case study systematically assessed diverse approaches to sinus augmentation in the presence of sinus pathology. Three patients were carefully selected and categorized as pseudocyst (PsC) (type 1), mucous retention cyst (MRC) smaller than 20 mm (type 2), and MRC larger than 20 mm in size (type 3). All patients underwent sinus augmentation procedures, with each case utilizing a unique surgical approach. Spontaneous drainage was performed for the patient with PsC (type 1), followed by uncomplicated sinus augmentation. For the patient with an MRC smaller than 20 mm (type 2), aspiration of the cyst contents preceded sinus augmentation. Conversely, the patient with a larger MRC (type 3) underwent cyst enucleation followed by sinus augmentation after complete recovery of the sinus membrane. No complications were noted in any of the cases, and follow-up revealed stable implant installation at the site of sinus augmentation. Within the constraints of this study, the choice of surgical procedure, whether involving spontaneous drainage, aspiration, or enucleation, should be guided by an anticipated pathologic diagnosis and the size of the sinus cyst. This informed approach empowers clinicians to make well-informed decisions for the best possible outcomes and sustained results. Overall, this study offers valuable insights for clinicians seeking to optimize sinus augmentation procedures in the presence of sinus pathology.


Subject(s)
Cysts , Sinus Floor Augmentation , Humans , Male , Middle Aged , Cysts/surgery , Dental Implantation, Endosseous/methods , Drainage/methods , Maxillary Sinus/surgery , Mucocele/surgery , Paranasal Sinus Diseases/surgery , Sinus Floor Augmentation/methods , Aged
15.
J Craniofac Surg ; 2024 May 07.
Article in English | MEDLINE | ID: mdl-38710039

ABSTRACT

Closed treatment of mandibular condylar fractures has been used for its indications based on the fracture site, fracture status, and patient age. Posttreatment mandibular condyle size is associated with mandibular function; however, a few studies have reported bone remodeling patterns and volume changes in the condyle and glenoid fossa after mandibular condylar head fractures (CHFs). Therefore, volumetric changes in the mandibular condyle and glenoid fossa were analyzed in the present study, and bone remodeling patterns were evaluated after mandibular CHFs. The present study included 16 condyles from 12 patients who received closed treatment for CHF. After reconstruction of a 3-dimensional skull model, including the mandible, using computed tomography data taken immediately after injury and 6 months after treatment, volume changes in the mandibular condyle and glenoid fossa were analyzed. The condylar volume increased by 0.32±0.66 cm3 during the 6-month healing period without statistical significance (P=0.093). Regarding the glenoid fossa, the fossa showed a statistically significant volume increase of 0.41±0.59 cm3 (P=0.021), and 12 glenoid fossae (75%) showed downward bone apposition; however, no change or only mild bone resorption was observed in 4 glenoid fossae (25%). The results of this study indicated that the volume changes in the mandibular condyle after closed treatment of a mandibular CHF are not significant, and the glenoid fossa adapts to the displaced mandibular condyle through downward growth accompanied by volume increase.

16.
Int J Mol Sci ; 25(7)2024 Mar 26.
Article in English | MEDLINE | ID: mdl-38612500

ABSTRACT

Increased intraocular pressure (IOP) is the most important risk factor for glaucoma. The role of IOP fluctuation, independently from elevated IOP, has not yet been confirmed in glaucoma. We investigated the effects of IOP fluctuation itself on retinal neurodegeneration. Male rats were treated with IOP-lowering eyedrops (brinzolamide and latanoprost) on Mondays and Thursdays (in the irregular instillation group) or daily (in the regular instillation group), and saline was administered daily in the normal control group for 8 weeks. The IOP standard deviation was higher in the irregular instillation group than the regular instillation group or the control group. The degree of oxidative stress, which was analyzed by labeling superoxide, oxidative DNA damage, and nitrotyrosine, was increased in the irregular instillation group. Macroglial activation, expressed by glial fibrillary acidic protein in the optic nerve head and retina, was observed with the irregular instillation of IOP-lowering eyedrops. Microglial activation, as indicated by Iba-1, and the expression of TNF-α did not show a significant difference between the irregular instillation and control groups. Expression of cleaved caspase-3 was upregulated and the number of retinal ganglion cells (RGCs) was decreased in the irregular instillation group. Our findings indicate that IOP fluctuations could be induced by irregular instillation of IOP-lowering eyedrops and this could lead to the degeneration of RGCs, probably through increased oxidative stress and macrogliosis.


Subject(s)
Glaucoma , Intraocular Pressure , Male , Animals , Rats , Retina , Glaucoma/drug therapy , Retinal Ganglion Cells , Ophthalmic Solutions
17.
Biol Proced Online ; 25(1): 17, 2023 Jun 16.
Article in English | MEDLINE | ID: mdl-37328878

ABSTRACT

BACKGROUND: Deinococcus radiodurans is a robust bacterium that can withstand harsh environments that cause oxidative stress to macromolecules due to its cellular structure and physiological functions. Cells release extracellular vesicles for intercellular communication and the transfer of biological information; their payload reflects the status of the source cells. Yet, the biological role and mechanism of Deinococcus radiodurans-derived extracellular vesicles remain unclear. AIM: This study investigated the protective effects of membrane vesicles derived from D. radiodurans (R1-MVs) against H2O2-induced oxidative stress in HaCaT cells. RESULTS: R1-MVs were identified as 322 nm spherical molecules. Pretreatment with R1-MVs inhibited H2O2-mediated apoptosis in HaCaT cells by suppressing the loss of mitochondrial membrane potential and reactive oxygen species (ROS) production. R1-MVs increased the superoxide dismutase (SOD) and catalase (CAT) activities, restored glutathione (GSH) homeostasis, and reduced malondialdehyde (MDA) production in H2O2-exposed HaCaT cells. Moreover, the protective effect of R1-MVs against H2O2-induced oxidative stress in HaCaT cells was dependent on the downregulation of mitogen-activated protein kinase (MAPK) phosphorylation and the upregulation of the nuclear factor E2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway. Furthermore, the weaker protective capabilities of R1-MVs derived from ΔDR2577 mutant than that of the wild-type R1-MVs confirmed our inferences and indicated that SlpA protein plays a crucial role in R1-MVs against H2O2-induced oxidative stress. CONCLUSION: Taken together, R1-MVs exert significant protective effects against H2O2-induced oxidative stress in keratinocytes and have the potential to be applied in radiation-induced oxidative stress models.

18.
Small ; 19(32): e2300963, 2023 Aug.
Article in English | MEDLINE | ID: mdl-37066701

ABSTRACT

Two essential characteristics that are required for hybrid electrocatalysts to exhibit higher oxygen and hydrogen evolution reaction (OER and HER, respectively) activity are a favorable electronic configuration and a sufficient density of active sites at the interface between the two materials within the hybrid. In the present study, a hybrid electrocatalyst is introduced with a novel architecture consisting of coral-like iron nitride (Fe2 N) arrays and tungsten nitride (W2 N3 ) nanosheets that satisfies these requirements. The resulting W2 N3 /Fe2 N catalyst achieves high OER activity (268.5 mV at 50 mA cm-2 ) and HER activity (85.2 mV at 10 mA cm-2 ) with excellent long-term durability in an alkaline medium. In addition, density functional theory calculations reveal that the individual band centers experience an upshift in the hybrid W2 N3 /Fe2 N structure, thus improving the OER and HER activity. The strategy adopted here thus provides a valuable guide for the fabrication of cost-effective multi-metallic crystalline hybrids for use as multifunctional electrocatalysts.

19.
Small ; 19(11): e2204850, 2023 Mar.
Article in English | MEDLINE | ID: mdl-36642858

ABSTRACT

Three-dimensional topological insulators (3D TI) exhibit conventional parabolic bulk bands and protected Dirac surface states. A thorough investigation of the different transport channels provided by the bulk and surface carriers using macroscopic samples may provide a path toward accessing superior surface transport properties. Bi2 Te3 materials make promising 3D TI models; however, due to their complicated defect chemistry, these materials have a high number of charge carriers in the bulk that dominate the transport, even as nanograined structures. To partially control the bulk charge carrier density, herein the synthesis of Te-enriched Bi2 Te3 nanoparticles is reported. The resulting nanoparticles are compacted into nanograined pellets of varying porosity to tailor the surface-to-volume ratio, thereby emphasizing the surface transport channels. The nanograined pellets are characterized by a combination of resistivity, Hall- and magneto-conductance measurements together with (THz) time-domain reflectivity measurements. Using the Hikami-Larkin-Nagaoka (HLN) model, a characteristic coherence length of ≈200 nm is reported that is considerably larger than the diameter of the nanograins. The different contributions from the bulk and surface carriers are disentangled by THz spectroscopy, thus emphasizing the dominant role of the surface carriers. The results strongly suggest that the surface transport carriers have overcome the hindrance imposed by nanoparticle boundaries.

20.
Small ; 19(5): e2204905, 2023 Feb.
Article in English | MEDLINE | ID: mdl-36446633

ABSTRACT

To separately explore the importance of hydrophilicity and backbone planarity of polymer photocatalyst, a series of benzothiadiazole-based donor-acceptor alternating copolymers incorporating alkoxy, linear oligo(ethylene glycol) (OEG) side chain, and backbone fluorine substituents is presented. The OEG side chains in the polymer backbone increase the surface energy of the polymer nanoparticles, thereby improving the interaction with water and facilitating electron transfer to water. Moreover, the OEG-attached copolymers exhibit enhanced intermolecular packing compared to polymers with alkoxy side chains, which is possibly attributed to the self-assembly properties of the side chains. Fluorine substituents on the polymer backbone produce highly ordered lamellar stacks with distinct π-π stacking features; subsequently, the long-lived polarons toward hydrogen evolution are observed by transient absorption spectroscopy. In addition, a new nanoparticle synthesis strategy using a methanol/water mixed solvent is first adopted, thereby avoiding the screening effect of surfactants between the nanoparticles and water. Finally, hydrogen evolution rate of 26 000 µmol g-1  h-1 is obtained for the copolymer incorporated with both OEG side chains and fluorine substituents under visible-light irradiation (λ > 420 nm). This study demonstrates how the glycol side chain strategy can be further optimized for polymer photocatalysts by controlling the backbone planarity.

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