ABSTRACT
Building a polarization center is an effective avenue to boost charge separation and molecular activation in photocatalysis. However, a limited number of polarization centers are usually created. Here, a polarization plane based on two-dimensional (2D) atomic layers is designed to maximize the surface polarization centers. The Mn in a 2D crystal lattice is etched from the MnIn2S4 atomic layers to build a consecutive symmetry-breaking structure of isolated InO1S5 sites. More charges aggregate around O, making the isolated InO1S5 sites highly polarized. Due to the formation of the InO1S5 polarization plane, an enormous polarized electric field is formed perpendicular to the 2D atomic layers and the carrier lifetime can be prolonged from 93.2 ps in MnIn2S4 to 1130 ps in amorphous MnxIn2Sy. Meantime, the formed large charge density gradient favors coupling and activation of small molecules. Benefiting from these features, a good NH3 photosynthesis performance (515.8 µmol g-1 h-1) can be realized over amorphous MnxIn2Sy, roughly 2.5 and 48.9 times higher than those of MnIn2S4 atomic layers and bulk MnIn2S4, respectively. The apparent quantum yields reach 5.4 and 3.3% at 380 and 400 nm, respectively. Meanwhile, a greatly improved CO2 reduction activity is also achieved over MnxIn2Sy. This strategy provides an accessible pathway for designing an asymmetrical polarization plane to motivate photocatalysis optimization.
ABSTRACT
The limitations of two-dimensional (2D) graphene in broadband photodetector are overcome by integrating nitrogen (N) doping into three-dimensional (3D) structures within silicon (Si) via plasma-assisted chemical vapor deposition (PACVD) technology. This contributes to the construction of vertical Schottky heterojunction broad-spectrum photodetectors and applications in logic devices and image sensors. The natural nanoscale resonant cavity structure of 3D-graphene enhances photon capture efficiency, thereby increasing photocarrier generation. N-doping can fine-tune the electronic structure, advancing the Schottky barrier height and reducing dark current. The as-fabricated photodetector exhibits exceptional self-driven photoresponse, especially at 1550 nm, with an excellent photoresponsivity (79.6 A/W), specific detectivity (1013 Jones), and rapid response of 130 µs. Moreover, it enables logic circuits, high-resolution pattern image recognition, and broadband spectra recording across the visible to near-infrared range (400-1550 nm). This research will provide new views and technical support for the development and widespread application of high-performance semiconductor-based graphene broadband detectors.
ABSTRACT
The graph representation of complex materials plays a crucial role in the field of inorganic and organic materials investigations for developing data-centric materials science, such as those using graph neural networks (GNNs). However, the currently prevalent GNN models are primarily employed for investigating periodic crystals and organic small molecule data, yet they still encounter challenges in terms of interpretability and computational efficiency when applied to polymer monomers and organic macromolecules data. There is still a lack of graph representation of organic polymers and macromolecules specifically tailored for GNN models to explore the structural characteristics. The Polymer-unit Graph, a novel coarse-grained graph representation method introduced in study, is dedicated to expressing and analyzing polymers and macromolecules. By incorporating the Polymer-unit Graph into the GNN models and analyzing the organic semiconductor (OSC) materials database, it becomes possible to uncover intricate structure-property relationships involving branched-chain engineering, fluoridation substitution, and donor-acceptor combination effects on the elementary structure of OSC polymers. Furthermore, the Polymer-unit Graph enables visualizing the relationship between target properties and polymer units while reducing training time by an impressive 98% and minimizing molecular graph representation models. In conclusion, the Polymer-unit Graph successfully integrates the concept of Polymer-unit into the field of GNNs, enabling more accurate analysis and understanding of organic polymers and macromolecules.
ABSTRACT
A breakthrough in the performance of bionic optical structures will only be achieved if we can obtain an in-depth understanding of the synergy mechanisms operating in natural optical structures and find ways to imitate them. In this work, inspired by feline eyes, an optical substrate that takes advantage of a synergistic effect that occurs between resonant and reflective structures was designed. The synergistic effect between the reflective and resonant components leads to a Raman enhancement factor (EF) of 1.16 × 107, which is much greater than that achieved using the reflective/resonant cavities on their own. Finite-difference time-domain (FDTD) simulations and experimental results together confirm that the mechanism of this synergistic effect is achieved by realizing multiple reflections and repeated absorptions of light, generating a strong local electric field. Thus, a 2-3 order of magnitude increase in sensitivity could be achieved. More importantly, with the homemade centrifugal device, above optical substrates were further used to develop a rapidly highly sensitive household health monitoring system (detection time <3 min). It can thus be used to give early warning of acute diseases with high risk (e.g., acute myocardial infarction (AMI) and cerebral peduncle). Due to the good reusability and storability (9% and 8% reduction in EF after washing 30 times and 9 months of storage, respectively) of the substrates, the substrates thus reduce detection costs (to â¼$1), making them much cheaper to use than the current gold-standard methods (e.g., â¼$16 for gout detection).
Subject(s)
Spectrum Analysis, Raman , Cats , Animals , Humans , Spectrum Analysis, Raman/methods , Chronic DiseaseABSTRACT
Studying the phosphorescent mechanisms of carbon nanostructures synthesized by the "bottom-up" approach is key to understanding the structure modulation and the interfacial properties of carbon nanostructures. In this work, the relationships among symmetry of precursors in the "bottom-up" synthesis, structures of products, and phosphorescence lifetimes of graphene quantum dots (GQDs) are studied. The symmetry matching of precursors in the formation of a D6h graphene-like framework is considered the key factor in controlling the separability of sp2 domains in GQDs. As the separability of sp2 domains in GQDs increases, the phosphorescence lifetimes (14.8-125.5 ms) of GQDs in the solid state can be tuned. Machine learning is used to define the degree of disorder (S) of the GQD structure, which quantitatively describes the different space groups of precursors. The negative correlation between S and the oscillator strength of GQDs is uncovered. Therefore, S can be recognized as reflective of oscillator strength in the GQD structure. Finally, based on the correlations found between the structures and phosphorescence lifetimes of GQDs, GQDs with an ultralong phosphorescence lifetime (28.5 s) are obtained. Moreover, GQDs with visible phosphorescence emission (435-618 nm) are synthesized.
ABSTRACT
Enhancing the thermoelectric transport properties of conductive polymer materials has been a long-term challenge, in spite of the success seen with molecular doping strategies. However, the strong coupling between the thermopower and the electrical conductivity limits thermoelectric performance. Here, we use polaron interfacial occupied entropy engineering to break through this intercoupling for a PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulfonate)) thin film by using photochromic diarylethene (DAE) dopants coupled with UV-light modulation. With a 10-fold enhancement of the thermopower from 13.5 µV K-1 to 135.4 µV K-1 and almost unchanged electrical conductivity, the DAE-doped PEDOT:PSS thin film achieved an extremely high power factor of 521.28 µW m-1 K-2 from an original value of 6.78 µW m-1 K-2. The thermopower was positively correlated with the UV-light intensity but decreased with increasing temperature, indicating resonant coupling between the planar closed DAE molecule and PEDOT. Both the experiments and theoretical calculations consistently confirmed the formation of an interface state due to this resonant coupling. Interfacial entropy engineering of polarons could play a critical role in enhancing the thermoelectric performance of the organic film.
ABSTRACT
A magnetic relaxation switch (MRS) that targets small molecules such as H2O2 is difficult to realize because of the small size of the targets, which cannot gather enough MRS probes to form aggregates and generate a difference in magnetic relaxation times. Therefore, the development of small molecule-targeted MRS is strongly dependent on changes in the interfacial structure of the probe, which modulates the proton transport behavior near the probe. Herein, functionalized graphene quantum dots (GQDs) consisting of GQDs with disulfide bonds, polyethylene glycol (PEG), and paramagnetic Gd3+ were used as the MRS probe to sense H2O2. The structure of GQDs changed after reacting with H2O2. The PEG assembled a tube for transmitting changes in GQDs via proton transport and thus enabled the magnetic relaxation response of the probe towards H2O2. Pentaethylene glycol was experimentally and theoretically proven to have the strongest ability to transport protons. Such a probe can be applied in the differentiation of healthy and senescent cells/tissues using in vitro fluorescent imaging and in vivo magnetic resonance imaging. This work provides a reliable solution for building a proton transport route, which not only enables the response of the MRS probe towards the targets but also demonstrates the design of carbon nanostructures with proton transport behaviors.
Subject(s)
Graphite , Quantum Dots , Protons , Graphite/chemistry , Quantum Dots/chemistry , Hydrogen Peroxide , Magnetic Resonance Imaging , Oxidative StressABSTRACT
Osmotic power, a clean energy source, can be harvested from the salinity difference between seawater and river water. However, the output power densities are hampered by the trade-off between ion selectivity and ion permeability. Here we propose an effective strategy of double angstrom-scale confinement (DAC) to design ion-permselective channels with enhanced ion selectivity and permeability simultaneously. The fabricated DAC-Ti0.87 O2 membranes possess both Ti atomic vacancies and an interlayer free spacing of ≈2.2â Å, which not only generates a profitable confinement effect for Na+ ions to enable high ion selectivity but also induces a strong interaction with Na+ ions to benefit high ion permeability. Consequently, when applied to osmotic power generation, the DAC-Ti0.87 O2 membranes achieved an ultrahigh power density of 17.8â W m-2 by mixing 0.5/0.01â M NaCl solution and up to 114.2â W m-2 with a 500-fold salinity gradient, far exceeding all the reported macroscopic-scale membranes. This work highlights the potential of the construction of DAC ion-permselective channels for two-dimensional materials in high-performance nanofluidic energy systems.
ABSTRACT
Transition metal oxides are promising electrocatalysts for zinc-air batteries, yet surface reconstruction caused by the adsorbate evolution mechanism, which induces zinc-ion battery behavior in the oxygen evolution reaction, leads to poor cycling performance. In this study, we propose a lattice oxygen mechanism involving proton acceptors to overcome the poor performance of the battery in the OER process. We introduce a stable solid base, hydroxy BaCaSiO4, onto the surfaces of PrBa0.5Ca0.5Co2O5+δ perovskite nanofibers with a one-step exsolution strategy. The HO-Si sites on the hydroxy BaCaSiO4 significantly accelerate proton transfer from the OH* adsorbed on PrBa0.5Ca0.5Co2O5+δ during the OER process. As a proof of concept, a rechargeable zinc-air battery assembled with this composite electrocatalyst is stable in an alkaline environment for over 150 hours at 5 mA cm-2 during galvanostatic charge/discharge tests. Our findings open new avenues for designing efficient OER electrocatalysts for rechargeable zinc-air batteries.
ABSTRACT
Facet engineering was realized to enhance the CO2 photoreduction performance of the Ni2P/ZnIn2S4 heterostructure, in which the commonly exposed (1 0 2) face of ZnIn2S4 was converted to the (1 0 1) face due to the unique properties of the phosphide. The variation in the crystal plane strengthened the intense interfacial contact between Ni2P and ZnIn2S4, resulting in the promotion of utilization and absorption efficiency for incident light and boosting the surface reaction rate. Combined with the significant metallicity of Ni2P, inhibited recombination and strengthened transfer efficiency were achieved, leading to an obvious enhancement of photoreduction activity over Ni2P/ZnIn2S4 compared to pure samples. In particular, the optimal NZ7 composite (the mass ratio of Ni2P to ZnIn2S4) reached 68.31 µmol h-1 g-1 of CH4, 10.65 µmol h-1 g-1 of CH3OH, and 11.15 µmol h-1 g-1 of HCOOH. The mechanism of the CO2 photoreduction process was elucidated using ESR and in situ DRIFTS techniques.
ABSTRACT
High-performance organic semiconductors (OSCs) can be designed based on the identification of functional units and their role in the material properties. Herein, we present a polymer-unit fingerprint (PUFp) generation framework, "Python-based polymer-unit-recognition script" (PURS), to identify the subunits "polymer unit" in the polymer and generate polymer-unit fingerprint (PUFp). Using 678 collected OSC data, machine learning (ML) models can be used to determine structure-mobility relationships by using PUFp as a structural input, and the classification accuracy reaches 85.2%. A polymer-unit library consisting of 445 units is constructed, and the key polymer units affecting the mobility of OSCs are identified. By investigating the combinations of polymer units with mobility performance, a scheme for designing OSCs by combining ML approaches and PUFp information is proposed. This scheme not only passively predicts OSC mobility but also actively provides structural guidance for high-mobility OSC material design. The proposed scheme demonstrates the ability to screen materials through pre-evaluation and classification ML steps and is an alternative methodology for applying ML in high-mobility OSC discovery.
ABSTRACT
Direct photoelectrochemical 2-electron water oxidation to renewable H2 O2 production on an anode increases the value of solar water splitting. BiVO4 has a theoretical thermodynamic activity trend toward highly selective water oxidation H2 O2 formation, but the challenges of competing 4-electron O2 evolution and H2 O2 decomposition reaction need to overcome. The influence of surface microenvironment has never been considered as a possible activity loss factor in the BiVO4 -based system. Herein, it is theoretically and experimentally demonstrated that the situ confined O2 , where coating BiVO4 with hydrophobic polymers, can regulate the thermodynamic activity aiming for water oxidation H2 O2 . Also, the hydrophobicity is responsible for the H2 O2 production and decomposition process kinetically. Therefore, after the addition of hydrophobic polytetrafluoroethylene on BiVO4 surface, it achieves an average Faradaic efficiency (FE) of 81.6% in a wide applied bias region (0.6-2.1 V vs RHE) with the best FE of 85%, which is 4-time higher than BiVO4 photoanode. The accumulated H2 O2 concentration can reach 150 µm at 1.23 V versus RHE under AM 1.5 illumination in 2 h. This concept of modifying the catalyst surface microenvironment via stable polymers provides a new approach to tune the multiple-electrons competitive reactions in aqueous solution.
ABSTRACT
Herein, we demonstrate the use of large-scale reactive molecular dynamics simulations to identify the influence of nanostructures, size effects, and temperature for the decomposition processes of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). The bulk-phase and six types of HMX nanoparticle (30-70 Å) systems were investigated at two high temperatures (2000 K and 3000 K). The evolution of the potential energy (PE) and total number of molecules (TM) of HMX crystals and their six nanoparticle systems were analyzed and addressed, and it was revealed that the nanostructure has a great accelerative effect on the thermal decomposition of HMX. The temperature distribution, initial decomposition process, and main intermediate and gas products were traced, and showed that the initial decomposition of HMX nanoparticles is triggered by the dissociation of the N-NO2 bond. With the increase in temperature, the total amount of gas molecules in HMX nanoparticles rapidly increases, which shows that the high temperature can accelerate the decomposition rate for HMX nanoparticles.
ABSTRACT
The contradiction between energy and safety of explosives is better balanced by the host-guest inclusion strategy. To deeply analyze the role of small guest molecules in the host-guest system, we first investigated the intermolecular contacts of host and guest molecules through Hirshfeld surfaces, 2-D fingerprint plots and electrostatic interaction energy. We then examined the strength and nature of the intermolecular interactions between CL-20 and various small molecules in detail, using state-of-the-art quantum chemistry calculations and elaborate wavefunction analyses. Finally, we studied the effect of the small molecules on the properties of CL-20, using density functional theory (DFT). The results showed that the spatial arrangement of host and guest molecules and the interaction between host and guest molecules, such as repulsion or attraction, may depend on the properties of the guest molecules, such as polarity, oxidation, hydrogen content, etc. The insertion of H2O2, H2O, N2O, and CO2 had significant influence on the electrostatic potential (ESP), van der Waals (vdW) potential and chemical bonding of CL-20. The intermolecular interactions, electric density and crystal orbital Hamilton population (COHP) clarified and quantified the stabilization effect of different small molecules on CL-20. The insertion of the guest molecules improved the stability of CL-20 to different extents, of which H2O2 worked best.
ABSTRACT
Three-dimensional graphene (3D-graphene) is used in surface-enhanced Raman spectroscopy (SERS) because of its plasmonic nanoresonator structure and good ability to interact with light. However, a thin (3-5 nm) layer of amorphous carbon (AC) inevitably appears as a template layer between the 3D-graphene and object substrate when the 3D-graphene layer is synthesized, weakening the enhancement factor. Herein, two-dimensional graphene (2D-graphene) is employed as a template layer to directly synthesize 3D-graphene on a germanium (Ge) substrate via plasma-assisted chemical vapor deposition, bypassing the formation of an AC layer. The interaction and photoinduced charge transfer ability of the 3D-graphene/Ge heterojunction with incident light are improved. Moreover, the high density of electronic states close to the Fermi level of the heterojunction induces the adsorbed probe molecules to efficiently couple to the 3D-graphene-based SERS substrate. Our experimental results imply that the lowest concentrations of rhodamine 6G and rhodamine B that can be detected on the 3D/2D-graphene/Ge SERS substrate correspond to 10-10 M; for methylene blue, it is 10-8 M. The detection limits of the 3D/2D-graphene/Ge SERS substrate with respect to 3-hydroxytyramine hydrochloride and melamine (in milk) are both less than 1 ppm. This work may provide a viable and convenient alternative method for preparing 3D-graphene SERS substrates. It also constitutes a new approach to developing SERS substrates with remarkable performance levels.
ABSTRACT
Two-dimensional (2D) CsPbI3 is developed to conquer the phase-stability problem of CsPbI3 by introducing bulky organic cations to produce a steric hindrance effect. However, organic cations also inevitably increase the formation energy and difficulty in crystallization kinetics regulation. Such poor crystallization process modulation of 2D CsPbI3 leads to disordered phase-arrangement, which impedes the transport of photo-generated carriers and worsens device performance. Herein, a type of C3 N quantum dots (QDs) with ordered carbon and nitrogen atoms to manipulate the crystallization process of 2D CsPbI3 for improving the crystallization pathway, phase-arrangement and morphology, is introduced. Combination analyses of theoretical simulation, morphology regulation and femtosecond transient absorption (fs-TA) characterization, show that the C3 N QDs induce the formation of electron-rich regions to adsorb bulky organic cations and provide nucleation sites to realize a bi-directional crystallization process. Meanwhile, the quality of 2D CsPbI3 film is improved with lower trap density, higher surface potential, and compact morphology. As a result, the power conversion efficiency (PCE) of the optimized device (n = 5) boosts to an ultra-high value of 15.63% with strengthened environmental stability. Moreover, the simple C3 N QDs insertion method shows good universality to other bulky organic cations of Ruddlesden-Popper and Dion-Jacobson, providing a good modulation strategy for other optoelectronic devices.
ABSTRACT
5-diphosphoinositol pentakisphosphate (5-IP7) is a signalling metabolite linked to various cellular processes. How extracellular stimuli elicit 5-IP7 signalling remains unclear. Here we show that 5-IP7 in ß cells mediates parasympathetic stimulation of synaptotagmin-7 (Syt7)-dependent insulin release. Mechanistically, vagal stimulation and activation of muscarinic acetylcholine receptors triggers Gαq-PLC-PKC-PKD-dependent signalling and activates IP6K1, the 5-IP7 synthase. Whereas both 5-IP7 and its precursor IP6 compete with PIP2 for binding to Syt7, Ca2+ selectively binds 5-IP7 with high affinity, freeing Syt7 to enable fusion of insulin-containing vesicles with the cell membrane. ß-cell-specific IP6K1 deletion diminishes insulin secretion and glucose clearance elicited by muscarinic stimulation, whereas mice carrying a phosphorylation-mimicking, hyperactive IP6K1 mutant display augmented insulin release, congenital hyperinsulinaemia and obesity. These phenotypes are absent in mice lacking Syt7. Our study proposes a new conceptual framework for inositol pyrophosphate physiology in which 5-IP7 acts as a GPCR second messenger at the interface between peripheral nervous system and metabolic organs, transmitting Gq-coupled GPCR stimulation to unclamp Syt7-dependent, and perhaps other, exocytotic events.
Subject(s)
Exocytosis , Inositol Phosphates/metabolism , Insulin/metabolism , Receptors, G-Protein-Coupled/metabolism , Synaptotagmins/metabolism , Animals , Mice , Phosphorylation , Signal TransductionABSTRACT
It is well believed that machine learning models could help to predict the formation energies of materials if all elemental and crystal structural details are known. In this paper, it is shown that even without detailed crystal structure information, the formation energies of binary compounds in various prototypes at the ground states can be reasonably evaluated using machine-learning feature abstraction to screen out the important features. By combining with the "white-box" sure independence screening and sparsifying operator (SISSO) approach, an interpretable and accurate formation energy model is constructed. The predicted formation energies of 183 experimental and 439 calculated stable binary compounds (E hull = 0) are predicted using this model, and both show reasonable agreements with experimental and Materials Project's calculated values. The descriptor set is capable of reflecting the formation energies of binary compounds and is also consistent with the common understanding that the formation energy is mainly determined by electronegativity, electron affinity, bond energy, and other atomic properties. As crystal structure parameters are not necessary prerequisites, it can be widely applied to the formation energy prediction and classification of binary compounds in large quantities.
ABSTRACT
The design of contrast agents (CAs) with high magnetic relaxivities is a key issue in the field of magnetic resonance imaging (MRI). The traditional strategy employed is aimed at optimizing the structural design of the magnetic atoms in the CA. However, it is difficult to obtain an agent with magnetic relaxivity over 100 mM-1 s-1 using this approach. In this work, we demonstrate that modulation of the localized superacid microenvironment of certain CAs (Gd3+ loaded polyethylene glycol modified graphene oxide quantum dots or 'GPG' for short) can effectively enhance the longitudinal magnetic relaxivities (r1) by accelerating proton exchange. r1 values of a series of GPGs are significantly increased by 20-30 folds compared to commercially available CAs over a wide range of static magnetic field strengths (e.g. 210.9 mM-1 s-1vs. 12.3 mM-1 s-1 at 114 µT, 127.0 mM-1 s-1vs. 4.9 mM-1 s-1 at 7.0 T). GPG aided MRI images is then acquired both in vitro and in vivo with low biotoxicities. Furthermore, folic-acid-modified GPG is demonstrated suitable for MRI-fluorescence dual-modal tumor targeting imaging in animals with more than 98.3% specific cellular uptake rate.
Subject(s)
Graphite , Neoplasms , Quantum Dots , Animals , Contrast Media , Magnetic Resonance Imaging , Tumor MicroenvironmentABSTRACT
Temperature-induced morphological changes are one of the strategies for designing crystal shapes, but the role of temperature in enhancing or inhibiting crystal growth is not well understood yet. To meet the requirements of high density and low sensitivity, we need to control the crystal morphology of the energetic materials. We studied the crystal morphology of 1,1-diamino-2,2-dinitroethylene (FOX-7) in dimethyl sulfoxide/water mixed solvent by using the modified Hartman-Perdok theorem. Molecular dynamics simulations were used to determine the interaction of FOX-7 and solvents. The results showed that the crystal shape of FOX-7 is hexagonal, the (101) face is the largest exposed face and is adjacent to six crystal faces at 354 K. As the temperature goes down, the area of the (001) face is significantly reduced. The crystal morphology of FOX-7 at 324 K has a smaller aspect ratio of 4.72, and this temperature is suitable for tuning the morphology from slender hexagon into diamond. The prediction results are in remarkable agreement with the experiments. Moreover, we predicted the evolution path of FOX-7 morphology by Gibbs-Curie-Wulff theorem and explained the variation of crystal shape caused by different external conditions in the actual crystallization process.