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We investigate the MX2 (M = {Hf, Zr}, X = {S, Se}) transition metal dichalcogenides patterned into armchair (AC) and zigzag (ZZ) nanoribbons (NRs) as potential channel materials in future logic field-effect devices. Ab initio quantum transport simulations are employed to assess the electronic, transport, and ballistic field-effect transistor (FET) properties of devices with such quasi-one-dimensional channels. We report a non-monotonic scaling behavior of MX2NR properties due to strong quantum confinement effects, which is reflected in a strong dependence of the ON-state current (ION) of MX2NR FETs on the nanoribbon configuration. The ∼2 nm-wide HfSe2 and ZrSe2 AC-PFETs have the highest ION of up to 2.6 mA/μm at 10 nA/μm OFF-state current. Surprisingly, MX2NR ZZ-NFETs exhibit a current increase of up to 70% when channel width is scaled down, with ION reaching 2.2 mA/μm in ∼2 nm-wide devices. The high ON-state performance is a direct consequence of high carrier injection velocity, which is explained by analyzing the band structure, transmission, and density of states. We demonstrate that nanostructured MX2 materials can be promising candidates for future logic transistors based on multi-nanowire architectures. [ABSTRACT FROM AUTHOR]

The acid-resistant tungsten trioxide photoelectrochemical solid–liquid ultraviolet (UV) photodetector uses a thin film of tungsten trioxide as the photoelectrode, forming a stable heterojunction with the electrolyte. This study employed band theory and double electron layer theory to analyze the mechanisms underlying the effect of pH on the redox potential and photocurrent, utilizing the ion product constant of water and the Nernst equation. By applying the principles of energy band theory and the two-electron layer model, the electron transfer process was analyzed and explained. These findings hold significant promise for enhancing solid–liquid heterojunction UV photodetectors. Tungsten trioxide has fast response and high sensitivity under extreme conditions. The device performance of WO3 nanosheets fabricated by annealing at 300 °C for one hour is excellent, including a rise time of 0.7 s, decay time of 6.8 s, photosensitivity of 1.90, and photoresponsivity of 2.31 mA/W. 0.5M sulfuric acid produced the highest photocurrent (5.46 μA) and sensitivity (14.07). This material has potential applications in optoelectronics, catalysis, sensing, water treatment, and air purification. [ABSTRACT FROM AUTHOR]

Gallenene is a novel metallic 2D material that can provide a semiconducting counterpart if patterned into quasi-one-dimensional (quasi-1D) nanostructures, i.e., gallenene nanoribbons (GaNRs). We investigate semiconducting GaNRs as a potential channel material for future ultrascaled field-effect transistors (FETs) by employing quantum transport simulations based on Green's functions and tight-binding Hamiltonians with the orbital resolution calibrated on ab initio calculations. The impact of GaNR width downscaling from ∼6 nm down to ∼0.2 nm on the electronic, transport, and ballistic device properties is investigated for the FET channel length of 15 nm. We report current enhancement and injection velocity overshoot effects for sub-1.2 nm-wide nFETs and pFETs, with a maximum current increase of 53% in the 1.2 nm-wide GaNR pFET in comparison to the widest device. In addition, promising current-driving capabilities of n- and p-channel GaNR FETs are observed with top ballistic currents of more than 2.2 mA/μm and injection velocities of up to 2.4 × 107 cm/s. The reported data are explained by analyzing the evolution of band structure and related parameters such as injection velocity, quantum capacitance, effective transport mass etc., with increasing quantum confinement effects in ultranarrow GaNRs. Generally, we find that quasi-1D gallenene is a promising channel material for future nanoscale FETs, especially for transistor architectures based on stacked nanosheets. [ABSTRACT FROM AUTHOR]

Understanding interparticle interactions has been one of the most important topics of research in the field of micro/nanoscale materials. Many significant characteristics of such materials directly stem from the way their building blocks interact with each other. In this work, we investigate the efficacy of a specific category of Machine Learning (ML) methods known as interaction networks in predicting interparticle interactions within colloidal systems. We introduce and study Local Neighborhood Graph Neural Networks (LN-GNNs), defined according to the local environment of colloidal particles derived from particle trajectory data. The LN-GNN framework is trained for unique categories of particle neighborhood environments in order to predict interparticle interactions. We compare the performance of the LN-GNN to a baseline interaction network with a simpler architecture and to an Instance-Based ML algorithm, which is computationally more expensive. We find that the prediction performance of LN-GNN measured as an average normalized mean absolute error outperforms the baseline interaction network by a factor of 2–10 for different local neighborhood configurations. Furthermore, LN-GNN's performance turns out to be very comparable to the instance-based ML framework while being an order of magnitude less expensive in terms of the required computation time. The results of this work can provide the foundations for establishing accurate models of colloidal particle interactions that are derived from real particle trajectory data. [ABSTRACT FROM AUTHOR]

As the channel lengths of electronic devices are scaled down to the nanometer range, the conventional methods to evaluate charge-carrier mobility approach a technical limit that is imposed by interfering effects of the electrode and forcing field. In this study, we demonstrate that electron spectroscopy provides additional (yet hidden) information on unipolar charge transport, which is free from conventional problems. We demonstrate that the estimated effective diffusion current through the target sample allows the measurement that is precise enough (10−4 cm2/V s) to obtain the mobility of electrons μelectron and holes μhole in nanolength organic channels. Using this method, we show how μelectron and μhole are correlated with the local structural order of poly(3-hexylthiophene) at the nanoscale. This method enables in situ charge-resolved observations of μelectron and μhole by eliminating the need for electrode and forcing field and will help to expand our understanding of charge conduction in nanoscale materials. [ABSTRACT FROM AUTHOR]

The study of van der Waals (vdW) materials has seen increased interest in recent years due to the wide range of uses for these materials because of their unique mechanical, electronic, and optical properties. This area has recently expanded further into studying the behavior of vdW nanomaterials as decreasing dimensions open up opportunities to interact with these materials in new ways. However, measuring the band structures of nanomaterials, which is key to understanding how confinement affects material properties and interactions, comes with several challenges. In this review, we survey a range of techniques for synthesizing and characterizing vdW nanomaterials, in order to outline the key material and characterization challenges. This includes controlling the Fermi level in vdW nanoparticles, preparing these particles for either ensemble or individual particle measurement, as well as protecting the pristine surface from oxidation. [ABSTRACT FROM AUTHOR]

Due to their large surface area and novel electronic properties, tungsten disulfide (WS2) nanosheets are promising materials for potential photocatalysis applications. The fabrication of large-scale WS2 nanosheets is a fundamentally important step to realize their applications. The liquid phase exfoliation method, which involves the mechanical exfoliation of layered materials in a solvent, has proven to be a feasible technique for fabricating nanosheets with high yields. Here, we systematically examine the optimization of the fabrication of WS2 nanosheets by exfoliating the WS2 powder in isopropyl alcohol, a low boiling point solvent, using a low-power probe sonicator and ball milling method. We show that prolonged sonication produces a concentration as high as 0.64 mg/ml, and the same concentration can be fabricated in less than half the time if the bulk powder is ball milled prior to the sonication. An atomic force microscopy study reveals that the proportions of monolayers and bilayers can be significantly increased if the nanosheet dispersions are centrifuged at a higher speed or sonicated for a long time. The photodegradation measurements reveal that the decomposition rate of methyl orange with nanosheets is at least 10% higher than that with WS2 powder, suggesting that the photocatalytic activity of WS2 can be enhanced if it is reduced to nanosheets. [ABSTRACT FROM AUTHOR]

It is established that 2D magnetic materials are the ideal platform for building up modern-day electronic and spintronic devices. The popular ways to achieve 2D magnetic materials are mechanical exfoliation and chemical vapor deposition. However, the direct chemical synthesis route of such magnetic 2D materials on a large scale is relatively unexplored. This article reports an easy and cost-effective facile chemical synthesis with a proper capping agent and magnetic study of free-standing 2D Cr2S3 nanosheets and Cr2S3 nanoparticles within the temperature range of 2–300 K under the magnetic field of up to 5 T. Although few magnetic results on 2D Cr2S3 are available in the literature, there is enough scope to work for an in-depth understanding of the magnetic aspects of this 2D material. Here, ferrimagnetic ordering with a sufficiently high coercivity of up to 0.139 T at 2 K along with a tendency to the saturation in magnetization down to a certain temperature limit is observed. Contrary to the strong antiferromagnetic coupling with a Néel temperature, as observed by previous researchers, is also observed for this chemically synthesized 2D Cr2S3 nanosheets. A transition temperature of 117 K is observed for the Cr2S3 nanosheets, whereas for Cr2S3 nanoparticles, a transition temperature of 101.7 K is observed with negligible coercivity. This facile synthesis technique may be applied to achieve other non-van der Waals type 2D magnetic materials. These kinds of non-van der Waals type 2D magnets will be useful to modern-day spintronic devices. [ABSTRACT FROM AUTHOR]

Aluminum (Al)-based reactive materials have recently attracted much attention due to their excellent chemical energy release characteristics. However, there still exists a great challenge to improve the mechanical properties and energy density of Al-based reactive materials. In this work, we reported that core–shell nano-aluminum@fluororubber (nAl@F2311) composites with good mechanical properties and high energy release characteristics were designed and fabricated by the electrical exploding wires method. The results showed that Al nanospheres were coated by F2311 uniformly to form the nAl@F2311 core–shell microstructure with high Al contents. Quasi-static/Split Hopkinson Pressure Bar dynamic compression test results showed axial splitting failure mode of nAl@F2311 composites. nAl@F2311-10 composites with 90 wt. % Al contents had higher compressive strength, with quasi-static and dynamic compressive strength of 117.6 and 304.6 MPa, respectively. nAl@F2311-15 composites with 85 wt. % Al contents had a lower ignition threshold. Furthermore, the impact-induced energy release test showed higher fluorine contents will accelerate energy release, reduce impact ignition threshold, and improve the reaction efficiency of nAl@F2311 composites. The high reaction efficiency (97.79%) of the nAl@F2311-15 composites was obtained at an impact velocity of 1090 m/s. This offered a concept-of-proof work to design and fabrication of nanostructured reaction materials, which had high strength and energy release performance. [ABSTRACT FROM AUTHOR]

The combination of terahertz (THz) pulses with scanning tunneling microscopy (STM) enables us to investigate ultrafast dynamics at material surfaces with high spatial (nanoscale) and temporal (femtosecond) resolution. In this Perspective, we review the basic principles of THz-STM, outline the related literature, and discuss its future outlook capable of advancing nanoscience, especially by introducing further combination of THz-STM with scanning tunneling luminescence spectroscopy, which can extract more fruitful information about nanoscale materials via obtaining luminescence spectra compared to just observing the net tunneling current induced by THz pulses in THz-STM. By shining THz pulses onto an STM tip, we can observe plasmon luminescence locally confined between the tip and the surface, whose spectrum changes with tip conditions. The combined approach is a stepping stone toward investigating the ultrafast excited-state dynamics of nanoscale materials with high spatiotemporal resolution. [ABSTRACT FROM AUTHOR]

Single-molecule tracking (SMT) methods have been widely employed to offer a high-resolution characterization of synthetic polymers under ambient conditions and, thus, have advanced our understanding of their unique material properties. SMT is based on the systematic monitoring of the diffusive motions of individual fluorescent dye molecules in the as-prepared polymer thin films or thicker monoliths. Quantitative assessment of the recorded SMT video data involves the systematic analysis of the generated diffusion trajectories of a single molecule using well-established and reported methods. The results have offered a wealth of new information on the structural alignment, orientational order, and long-range continuity of the polymer microdomains; the nanoscale material heterogeneities governed by defects, misalignment, and ill-controlled preparation conditions; as well as the various forms of probe–host interactions on the single-molecule level. In the first part of this Tutorial review, we describe the fundamental principles and instrumentation of SMT, before offering interested readers and potential future SMT users a practical guidance on the selection of fluorescent probe molecules, preparation of suitable samples, and optimization of experimental conditions and imaging parameters. Then, we highlight several representative SMT studies in microphase-separated block copolymers, and semicrystalline and amorphous homopolymers to further emphasize the usefulness of SMT methods for polymer characterization without neglecting some of their shortcomings. This Tutorial review is written with the motivation to attract new researchers to the fast-growing field and assist them in starting their own SMT research of synthetic polymers and other technologically useful soft matter systems. [ABSTRACT FROM AUTHOR]

Monte Carlo statistical ray-tracing methods are commonly employed to simulate carrier transport in nanostructured materials. In the case of a large degree of nanostructuring and under linear response (small driving fields), these simulations tend to be computationally overly expensive due to the difficulty in gathering the required flux statistics. Here, we present a novel Monte Carlo ray-tracing algorithm with computational efficiency of at least an order of magnitude compared to existing algorithms. Our new method, which is a hybrid of the analytical Boltzmann transport equation and Monte Carlo used a reduced number of ray-tracing particles, avoids current statistical challenges, such as the subtraction of two opposite going fluxes, the application of a driving force altogether, and the large simulation time required for low-energy carriers. We demonstrate the algorithm's efficiency and power in accurate simulations in large domain nanostructures with multiple defects. We believe that the new method we present is indeed more robust and user friendly compared to common methods and can enable the efficient study of transport in nanostructured materials under low-field steady-state conditions. [ABSTRACT FROM AUTHOR]

Boron carbide (B 4 C) has been well studied both theoretically and experimentally in its bulk form due to its exceptional hardness and use as a high-temperature thermoelectric. However, the properties of its two-dimensional nanosheets are not well established. In this paper, using van der Waals-corrected density-functional theory simulations, we show that bulk B 4 C can be cleaved along different directions to form B 4 C nanosheets with low formation energies. We find that there is minimal dependence of formation energies on cleavage planes and surface terminations, even though the bulk is not van der Waals layered. This anomalous stability of B 4 C nanosheets is found to be a result of surface reconstructions that are unique to B-rich systems. While the density of states of the bulk B 4 C indicate that it is a semiconductor, the B 4 C nanosheets are found to be predominantly metallic. We attribute this metallic behavior to a redistribution of charges on the surface bonds of the films. The Seebeck coefficients of the B 4 C films remain comparable to those of the bulk and are nearly constant as a function of temperature. Our results provide guidance for experimental synthesis efforts and future application of B 4 C nanosheets in nanoelectronic and thermoelectric applications. [ABSTRACT FROM AUTHOR]

Two-dimensional transition-metal chalcogenides are one of the most interesting new classes of 2D materials. 2D cobalt selenide nanomaterials are being actively pursued and investigated as well, and recently, the first large-scale synthesis of half-unit-cell-thick Co9Se8 nanosheets has been reported. In the present study, using density functional theory calculations and employing the advanced hybrid HSE06 exchange-correlation functional, the electronic and magnetic structure of Co9Se8 nanosheets is investigated. To allow a comparison with bulk, the electronic and magnetic properties of Co9Se8 bulk are investigated as well. The bulk phase is found to be a ferrimagnetic semiconductor. Reducing the dimensions of Co9Se8 bulk to form a half-unit-cell-thick Co9Se8 nanosheet strongly alters the electronic and magnetic structure of the material. The nanosheet is predicted to have a different type of ferrimagnetic ordering and to be a metal with semimetallic features. Analysis of the X–M segment of the nanosheet's band structure, which mainly determines the electronic transport properties of the material, shows that within this segment, the main band below the Fermi level consists of only spin-up states (Se 4p), while the main band above the Fermi level consists of only spin-down states (Se 4p hybridized with Co 3d). This combination points to possibilities of selective conductivity of either spin-up or spin-down electrons and indicates that ultrathin Co9Se8 nanosheets are a most promising candidate for nanoelectronic and spintronic applications. [ABSTRACT FROM AUTHOR]

Spark discharges in water have great potential for use in various technological fields, including pollutant degradation, precision micromachining, and nanomaterial production. However, the large-scale application of these discharges is limited by the complexity of the implicated physical and chemical phenomena, which cannot be easily controlled. In this study, we assess the effect of an external B-field on the electrical characteristics of multiple successive discharges, as well as on the erosion of the electrode. In addition to the B = 0 condition, two configurations of the B-field are investigated: B-parallel and B-perpendicular to the electrode axis, both at the magnitude of 125 mT. The obtained results demonstrate that discharge electrical characteristics and electrode erosion are significantly affected by the B-field. Using a W electrode, the highest and lowest discharge currents are measured in the case of B-perpendicular and B = 0, respectively. Meanwhile, the highest erosion volume is obtained in the case of B = 0. To assess the influence of electrode nature and magnetic properties on the discharges, the results obtained using W (paramagnetic) electrodes were compared to those obtained with Ni (ferromagnetic). The comparison shows that the discharge electrical data are tightly distributed when the Ni electrode is utilized, regardless of the B-condition, whereas the data obtained with the W electrode exhibit significant statistical variations in the presence of the B-field. Overall, the data reported herein indicate that the electrical properties of a spark discharge may be varied and controlled by applying an external B-field. [ABSTRACT FROM AUTHOR]

In this study, we synthesized VSx transition metal chalcogenides by the hydrothermal method and changed some parameters (reaction time, synthesis temperature, and adding surfactant) in the synthesis process. In this work, the structure of samples has been analyzed (by x-ray diffraction, ultraviolet–visible, Fourier-transform infrared, field-emission scanning electron microscopy). The vanadium sulfide structure phase altered from VS4 to VS2 by increasing the time and temperature of the reaction. Based on Kramers–Kronig equations, the effect of changing synthesis parameters and sheet dimensions on optical and dielectric parameters was investigated. Different components of the complex refractive index and complex dielectric function are increased by decreasing sheet dimensions. Also, the position of transversal and longitudinal optical modes is shifted to lower wavenumbers by increasing sheet dimensions. Moreover, the real part of the dielectric function alters from negative to positive by sheet dimension's alteration. This study demonstrates the great potential of vanadium sulfide compounds for optoelectronics applications. [ABSTRACT FROM AUTHOR]

We study the nature of chemical bonding of the thorium atom with novel BN-based nanomaterials: fullerenes B 30 N 30 , B 12 N 8 , B 8 N 12 , and the BN analog of coronene—B 12 N 12 H 12 , used as a representative molecular fragment of the two dimensional hexagonal BN-sheet. Our ab initio calculations are performed within the dispersion-corrected density functional approach with a hybrid exchange-correlation potential. The smallest 20-atom BN-fullerenes B 12 N 8 , B 8 N 12 proposed by us are shown to be stable and should be observable experimentally. Thorium is found at the center of these structures pushing the outer shell of atoms farther away. The shape of the B 12 N 8 -cage in Th@B 12 N 8 is conserved, while the shape of the B 8 N 12 molecule in Th@B 8 N 12 is largely deformed. The initially planar structure of B 12 N 12 H 12 in the presence of thorium becomes corrugated, demonstrating pronounced off-plane displacements under the thorium atom. Other four-valent metals (Ti, Zr, and Hf) also cause off-plane displacements of B and N atoms albeit to a much smaller scale. In the 60-atom fullerene B 30 N 30 , which is the BN analog of C 60 , two conformations of Th@B 30 N 30 are found: one is with thorium facing the hexagon with one B–B and one N–N covalent bonds and a second, lying 0.79 eV higher, with thorium close to the center of pentagon with one B–B covalent bond. [ABSTRACT FROM AUTHOR]

We report direct, economic, and facile preparation of two-dimensional transition metal dichalcogenide material molybdenum diselenide nanosheets through the ultrasonication assisted liquid exfoliation method. The optical absorption spectra confirm the formation of MoSe2 nanosheets. The Kramers–Kronig expression was used to estimate the refractive index and extinction coefficient values of the prepared nanosheets. The emission properties of the prepared samples were done using photoluminescence spectroscopy. The nonlinear optical studies were performed using an open aperture Z-scan method under nanosecond pulsed laser excitation of a second harmonic generation wavelength of 532 nm. The obtained results demonstrate the strong optical power limiting (OPL) properties of the MoSe2 nanosheets. This OPL is due to two-photon absorption behavior of MoSe2 nanosheets. [ABSTRACT FROM AUTHOR]

Accurate description of solubility and defect ionization energies in low dimensional nanostructures is critical for electronic applications of semiconductors with improved functionalities. Here, we present quantum confinement effect driven strategies for tuning defect level of hydrogen doping in the core region of rutile VO 2 (R) nanowires. The inverse dependence of a bandgap with a diameter (∝ d − 0.48 ) confirms the presence of quantum confinement effect in nanowires. The hydrogen doping in both interstitial and substitution at the O site behaves as a deep donor in low diameter nanowires, where the effect of quantum confinement is significant. The position of a donor charge transition level becomes increasingly shallower with increased nanowire diameters. The ionization energies of hydrogen defects decrease for larger-diameter nanowires due to the dielectric screening effect increment. This indicates the possibility of achieving n-type dopability with large diameter VO 2 (R) nanowires. This study prescribes the strategies for optimizing doping and the defect level for extensive applications of highly correlated 1D nanostructured materials. [ABSTRACT FROM AUTHOR]

Modulating physical and chemical properties of two-dimensional (2D) transition metal dichalcogenides (TMDCs) by defect engineering induced by oxygen plasma is actively pursued. In this work, exfoliated 2D MoS2 layers treated by medium power oxygen plasma for different times (0, 10, 20, 40, and 60 s) are investigated using Kelvin probe force microscopy and tip-enhanced Raman spectroscopy (TERS) besides micro-Raman and photoluminescence (PL) spectroscopy. Under oxygen plasma, defects (mono- and di-sulfur vacancies) and chemical oxidation are predominant from 0 (native defects) up to 40 s, while etching becomes dominant beyond 40 s for mono- (1L), bi- (2L), and tri- (3L) layer MoS2 with optimal defect density for four- (4L) and more layers. While Raman spectra exhibited lattice distortion (broadening of phonon bands) and surface oxidation by the presence of sub-stoichiometric molytrioxide MoO3 (i.e., MoO3–x or MoSxO2–x), the increased spectral weight of trions and quenching in PL spectra are observed with treatment time. The localized nanodomains (∼20–40 nm) and aggregated vacancies as nanovoids and intermixed MoS2/MoO3–x alloy are identified in near-field Raman spectra. The atomic force microscopy also showed defects aggregation, and Kelvin probe force microscopy revealed the work function (WF) increase from 4.98 to 5.56 eV, corroborating the existence of MoO3–x phase which enables doping and shift Fermi level. We also highlight the unique interaction between the gold substrate and the formed MoO3–x facilitating Mo6+ cation reduction to lower oxidation (i.e., Mo4+), thereby yielding intermediate oxidation states responsible for lower WF (ca. theoretical 6.3 eV for stoichiometric MoO3). Strong correlations among the work function and vibrational and optical responses are established while exploring the oxygen plasma-induced defects and changing the landscape on oxygen doping at the nanoscale with varying MoS2 layers, which are useful for heterogeneous electrocatalysis and applicable to other 2D-TMDCs. [ABSTRACT FROM AUTHOR]

Photonic nanostructures have proven useful to enhance the performance of a wide variety of materials and devices for sensing, catalysis, light harvesting, or light conversion. Herein, we discuss the role of nanophotonics in current and next-generation designs of white light-emitting diodes (LEDs). We discuss recent developments on luminescent materials designed as alternatives to rare earth-doped inorganic microcrystals, i.e., phosphors, for color conversion in LEDs, which has opened the door to the integration of resonant photonic architectures. Nanophotonics enables the devised light–matter interaction with luminescent materials in the nanoscale, which allows providing emitting devices with both enhanced performance and novel functionalities to tackle technological challenges ahead. [ABSTRACT FROM AUTHOR]

Carbon fibrous (CF) membranes were fabricated by electrospinning, thermal stabilization, and the carbonization process. The in-depth analyses of the CF membranes' composition, structure, and microwave absorption (MA) property demonstrate that the MA performance of the membranes is strongly correlated with the C/O ratio and CF framework's microstructure. A maximum absorption value of −23.4 dB is achieved at 800 °C, and this was synergistically enhanced to −42.5 dB with the addition of graphene nanosheets (GNSs). The special multilayered membranes containing dielectric loss CNSs and CFs making the balance between excellent impedance matching and the high loss characteristic could deliver an excellent MA property. With the facile and controllable synthesis of the GNS/CF membranes, a new approach to efficiently optimize and regulate its MA behavior is now possible. [ABSTRACT FROM AUTHOR]

Discharges in liquids are very efficient to synthesize nanoparticles by electrode erosion. This simple process is only simple in appearance. Mechanisms responsible for the production of nanoparticles are several depending on the choice of process parameters. They determine size distributions, shapes, composition, and defects of produced particles. They also control their possible assembly into more complex structures. This article describes the basic physics of nanoparticles' synthesis by discharges in liquids using electrodes and gives a summary of the research efforts that have been devoted to the understanding of this process. A special attention is paid to thermodynamics of these systems driven by discharges that are at or close to local equilibrium. Although a complete picture is not available yet, huge progress has been made and offers new capabilities for a better control of these kinds of processes. Finally, among important challenges that are still to tackle, the possibility of forming nanoalloys from immiscible elements or achieving unimodal monodisperse size distributions is questioned from the current mastery reached in this field. [ABSTRACT FROM AUTHOR]

Graphene nanomaterials functionalized with oxygen groups [graphene oxide (GO) and reduced GO (rGO)] are either doped with element nitrogen or nitrogen-containing aromatic moieties followed by the investigation of electrochemical properties that generally show enhanced electroanalytical performance. We studied structural, morphological, and physical–chemical properties using correlative techniques. While we attribute their improved properties promoted simultaneously by topologically interconnected mesoporous network morphology, the presence of heteroatom species, and lattice vibrational structure, the complex interpretation requires the need to supplement the experimental observations with theoretical calculations for further insights. The complex interplay of pore size and redox properties revealing distinctive supercapacitive (ion-adsorption controlled) and pseudocapacitive (diffusion-controlled) energy storage mechanistic contributions arises from the combined effects of oxygen and nitrogen functional groups, most likely located on the basal plane and at the pore edge plane sites. The density functional theory calculations provided band structure and electron transfer from Mulliken and Hirshfeld population analyses helping discern the nature of various functional groups in diverse graphene. Interestingly, while quaternary (N—Q) and pyridinic-N-oxides (N—O) on the basal planes show enhanced capacitance due to positive charge and thus an improved electron transfer at higher current loads identified in nitrogen-doped aerogel (AG/nitrogenated) and GO-derived rGO by chemical and electrochemical properties, the other important functional groups affecting the energy storage are pyridinic (N-6) and pyrrolic (N-5) nitrogen groups on the edge of the rGO nanosheet in association with carboxylic (—COOH) and quinone (C=O) functional groups in nitrogenated functional graphene/graphene aerogel and rGO coated polyaniline, contributing to a pseudocapacitive character. [ABSTRACT FROM AUTHOR]

Persistent phosphors are luminescent sources based on crystalline materials doped with rare-earth or transition metal cations able to produce light after the excitation source vanishes. Although known for centuries, these materials gained renewed interest after the discovery of Eu2+,RE3+ co-doped aluminates and silicates in the late 1990s due to their unprecedented afterglow properties. In contrast, persistent nanophosphors have emerged only recently as a nanoscale alternative to their bulk counterparts, offering exciting opportunities of particular relevance for in vivo imaging, optical data storage, or unconventional light generation. However, taking advantage of the avenues opened by nanoscience demands developing new synthetic strategies that allow precise control of the morphology, surface, and defect chemistry of the nanomaterials, along with a profound understanding of the physical mechanisms occurring in the nanoscale. Besides, advanced physicochemical characterization is required to assess persistent luminescence in a quantitative manner, which allows strict comparison among different persistent nanophosphors, aiming to propel their applicability. Herein, we revisit the main phenomena that determine the emission properties of persistent nanoparticles, discuss the most promising preparation and characterization protocols, highlight recent achievements, and elaborate on the challenges ahead. [ABSTRACT FROM AUTHOR]

Propagons play an important role in tuning the thermal conductivity of nanostructured amorphous materials. Although advances have been made to quantitatively evaluate the relaxation time of propagons with molecular dynamics, the underlying relaxation mechanism remains unexplored. Here, we investigate the relaxation process of propagons in amorphous silicon, amorphous silica, and amorphous silicon nitride at room temperature in terms of the Akhiezer model, the parameters of which were evaluated by performing lattice dynamics and molecular dynamics analysis. The results show that the Akhiezer model can well reproduce experimental results obtained by various types of measurement methods, indicating that the Akhiezer mechanism dominates the relaxation process of propagons at room temperature. Moreover, we show that the appropriate sound speed of propagons is around 80% of the Debye sound speed and comparable to the transversal sound speed. We also reveal that diffusons' contribution to thermal conductivity of these amorphous materials is similar, which is around 1 W/m K, whereas propagons' contribution to the overall heat conduction varies significantly depending on the materials: it is 30% in amorphous silicon and silica but as high as 70% in amorphous silicon nitride. The Akhiezer mechanism offers a deeper understanding of propagon heat transport and sound attenuation in amorphous materials. [ABSTRACT FROM AUTHOR]

The presence of inherent strain and electric field in the Janus transition metal dichalcogenide nanosheets widens their applications in nanodevices. The weak interactions between pristine Janus monolayers and gas molecules limit the applications of Janus sheets in gas sensing devices. However, tuning of structural and electronic properties by doping of foreign atoms in the lattice structure improves the gas sensing property of Janus WSSe monolayers. Herein, the superior gas sensing property of N, P, and As doped Janus WSSe monolayers for CO, NO, and HF gases has been studied using spin-polarized density functional theory. The binding energy analysis shows that the 3.12% doping of N, P, and As at S/Se sites is an exothermic process. New bands have been observed near the Fermi region in doped nanosheets. The simulations also reveal that doping improves the gas sensing properties of the doped sheets because of strong interactions between adsorbate and adsorbent. The interactions between gas molecules and doped WSSe monolayers are examined with the help of density of states plots. The uni-axial tensile strain tends to further improve the adsorption of CO on the nitrogen-doped WSSe nanosheet. Based on the present studies, it is evident that only 3.12% doping of foreign atoms makes WSSe Janus monolayers efficient material for CO, NO, and HF gas sensing without imposing external strain. [ABSTRACT FROM AUTHOR]

Rare-earth ion-doped upconversion (UC) micro/nanoparticles (UCM/NPs) could enable the conversion of near-infrared photons to high-energy emissions in the visible and ultraviolet regions. This unique property makes UCM/NPs highly attractive for applications in diverse fields, including materials science, photophysics, and biomedicine. However, ensemble spectroscopy ignores the heterogeneity in terms of size, shape, defects, surface groups, and charges of single UCM/NPs. Recently, the rapid development of single-particle spectroscopic techniques results in a gradual shift in the investigation of UC materials to heterogeneous nanoscale structures, unique photophysical phenomena, and advanced applications of single UCM/NPs, and the optical performance of a single UCM/NP has become a central topic in the community of UC materials. In this Perspective paper, we outline the characterization methods of a single UCM/NP and provide an overview of recent and on-going progress in investigations on single UCM/NPs, with a focus on their spectroscopic properties and applications in the polarization, waveguide, micro/nano-laser, super-resolution nanoscopy, and nanobarcode. Finally, current challenges and perspectives in this field are highlighted for future research. [ABSTRACT FROM AUTHOR]

Ionic compounds exhibit great structural diversity that can be used for tailoring novel nanostructured materials with distinct technological applications. In particular, significant progress has been made in the development of inorganic nanotubes, where the introduction of polar chemical bonds dramatically affects their physical properties in comparison to their carbon-based analogs. In this work, we apply density functional theory methods combined with plane-wave basis sets and periodic boundary conditions to investigate structural and electronic properties of prototypical lithium fluoride nanotubes featuring armchair, zig-zag, and square sheet (SSNT) configurations. Our results indicate that the zig-zag nanotubes can be formed from the more stable SSNT structures by the application of a positive axial strain, where an upper value of 1.44 eV for the activation energy is obtained. Furthermore, the zig-zag structures become more stable with the increasing nanotube radius, being merely 0.13 eV higher in energy than SSNT for the (10,0) case. All nanotubes investigated herein are insulators, with bandgap energies in the range of 8.33–8.59 eV for armchair and 7.91–8.54 eV for SSNT configurations. The latter nanotubes have higher Young's modulus, and consequently greater stiffness, than the corresponding armchair analogs. The small strain energies computed for the SSNT and armchair nanotubes reveal their high stability, making them promising candidates for experimental realization. [ABSTRACT FROM AUTHOR]

Since the inception of the atomic force microscope (AFM), dynamic methods (dynamic atomic force microscopy) have been very fruitful by establishing methods to quantify dissipative and conservative forces in the nanoscale and by providing a means to apply gentle forces to the samples with high resolution. Here, we discuss developments that cover over a decade of our work on energy dissipation, phase contrast, and the extraction of relevant material properties from observables. We describe the attempts to recover material properties via one-dimensional amplitude and phase curves from force models and explore the evolution of these methods in terms of force reconstruction, fits of experimental measurements, and the more recent advances in multifrequency AFM. We further discuss open questions and key possible paths to advance the field. [ABSTRACT FROM AUTHOR]

Photon upconversion assisted by sensitized triplet–triplet annihilation (sTTA-UC) is a wavelength-shifting technique where high-energy photons are emitted from the radiative recombination of high-energy singlets populated through the annihilation of the metastable triplets of two annihilator/emitter molecules. The emitter triplets are previously populated via energy transfer from a light-harvester/sensitizer moiety that absorbs the incident low-energy photons. In solutions, this process is efficient even at low excitation powers, whereas the limited molecular mobility and short exciton lifetimes typically observed in solid matrices hinder the bi-molecular interactions making the sTTA-UC process rather ineffective. We show here that controlling the confinement of the upconverting dye pairs in nanostructured or nanosized materials results in an increased effective local density of the excitation energy. This also activates a specific sTTA-UC kinetics independent of the triplet excitons' mobility that improves the material performance at low powers. We provide a complete modeling of the sTTA-UC process in confined systems. The results obtained afford useful guidelines for the future development of upconverting photonic devices operating at subsolar irradiances suitable for technological implementation. [ABSTRACT FROM AUTHOR]

In this work, we develop a numerical fitting routine to extract multiple thermal parameters using frequency-domain thermoreflectance (FDTR) for materials having non-standard, non-semi-infinite geometries. The numerical fitting routine is predicated on either a 2D or 3D finite element analysis that permits the inclusion of non-semi-infinite boundary conditions, which cannot be considered in the analytical solution to the heat diffusion equation in the frequency domain. We validate the fitting routine by comparing it with the analytical solution to the heat diffusion equation used within the wider literature for FDTR and known values of thermal conductivity for semi-infinite substrates ( SiO 2 , Al 2 O 3 , and Si). We then demonstrate its capacity to extract the thermal properties of Si when etched into micropillars that have radii on the order of the pump beam. Experimental measurements of Si micropillars with circular and square cross sections are provided and fit using the numerical fitting routine established as part of this work. Likewise, we show that the analytical solution is unsuitable for the extraction of thermal properties when the geometry deviates significantly from the standard semi-infinite case. This work is critical for measuring the thermal properties of materials having arbitrary geometries, including ultra-drawn glass fibers and laser gain media. [ABSTRACT FROM AUTHOR]

In this study, a thermodynamically consistent multiphase phase-field theory has been formulated to describe temperature-induced solid–solid phase transformations via an interfacial phase. This theory satisfies all thermodynamic equilibrium and stability conditions. It allows us to formulate the analytical solutions of the interface profile, energy, width, and velocity for each of the propagating solid–melt and solid–solid interfaces. The formation of the intermediate melt during solid–solid phase transformation has been studied hundreds of degrees below melting temperature in the HMX energetic crystal. The effect of the penalizing term in the phase-field model and two nanoscale material parameters on the appearance and degree of disordering of intermediate melt has been analyzed for the non-equilibrium interface. The developed approach is applicable to phase transitions in geological, pharmaceutical, ferroelectric, colloidal, and superhard materials where phase transformations occur via the intermediate phase. [ABSTRACT FROM AUTHOR]

Nanomagnets form the building blocks for a gamut of miniaturized energy-efficient devices including data storage, memory, wave-based computing, sensors, and biomedical devices. They also offer a span of exotic phenomena and stern challenges. The rapid advancements of nanofabrication, characterization, and numerical simulations during the last two decades have made it possible to explore a plethora of science and technology applications related to nanomagnet dynamics. The progress in the magnetization dynamics of single nanomagnets and one- and two-dimensional arrays of nanostructures in the form of nanowires, nanodots, antidots, nanoparticles, binary and bi-component structures, and patterned multilayers have been presented in detail. Progress in unconventional and new structures like artificial spin ice and three-dimensional nanomagnets and spin textures like domain walls, vortex, and skyrmions has been presented. Furthermore, a huge variety of new topics in the magnetization dynamics of magnetic nanostructures are rapidly emerging. A future perspective on the steadily evolving topics like spatiotemporal imaging of fast dynamics of nanostructures, dynamics of spin textures, and artificial spin ice have been discussed. In addition, dynamics of contemporary and newly transpired magnetic architectures such as nanomagnet arrays with complex basis and symmetry, magnonic quasicrystals, fractals, defect structures, and novel three-dimensional structures have been introduced. Effects of various spin–orbit coupling and ensuing spin textures as well as quantum hybrid systems comprising of magnon–photon, magnon–phonon, and magnon–magnon coupling and antiferromagnetic nanostructures have been included. Finally, associated topics like nutation dynamics and nanomagnet antenna are briefly discussed. Despite showing great progress, only a small fraction of nanomagnetism and its ancillary topics have been explored so far and huge efforts are envisaged in this evergrowing research area in the generations to come. [ABSTRACT FROM AUTHOR]

Graphite ablation by an electric arc or a laser/solar flux is widely used for the synthesis of carbon nanomaterials. Previously, it was observed in multiple arc experiments that the ablation rate is a strong nonlinear function of the arc current and it drastically increases at some threshold current. We developed an analytical model explaining this transition in the rate of ablation by an electric arc or a laser/solar flux. The model not only explains the observations but can also accurately predict the experimentally observed ablation rates. The model takes into account redeposition of carbon back to the ablated surface, which is the key process responsible for the observed effects. [ABSTRACT FROM AUTHOR]

One-dimensional carbon nanomaterials such as carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) are promising for future applications in nanoelectronics and nanophotonics due to their unique characteristics such as topological edge states, chirality, and quantum confinement. Despite the chemical unzipping method of producing GNRs from CNTs, using energetic photons to control light–matter interaction and shape materials at the nanoscale has great promise, especially for chemical-free and on-demand manufacturing. Here, we exploit the high electromagnetic field from a Ti:Sapphire femtosecond laser to interact with CNTs, causing ultrafast energy transfer between the photons and the nanotubes and converting them to GNRs and carbon nanocrystals. Probed with scattering-type scanning near-field optical microscopy, the nanoribbons are identified as semiconducting and/or insulating, a strikingly different electronic phase compared with the original metallic CNTs. Our method of employing high-field and nonequilibrium processes with an ultrafast laser to alter the shape and transform the electronic properties is scalable, does not necessitate high-temperature processes, and is highly spatially controllable—conditions that pave the way for manufacturing nanoscale hybrid materials and devices. [ABSTRACT FROM AUTHOR]

The nanoscale properties of materials can have a great influence on their macroscopic behavior; for instance, the generation and accumulation of defects at the nanoscale, such as point defects, porosity, and interfaces, can change their thermal properties. In this work, we study the role of an interface in the thermal conductivity between two nanoparticles without any external load. We consider a system subjected to a temperature gradient perpendicular to the contact surface and study the thermal conductivity, thermal conductance, thermal resistance, and contact resistance vs nanoparticle size. The thermal resistance at the interface increases linearly with nanoparticles' contact radius a c. A model based on the contact area between two nanoparticles allows us to reasonably explain the obtained numerical results for the thermal conductivity, leading to a net decrease in effective conductivity as the nanoparticle size increases, reasonably well described by a (a c / R) dependence. Simulated thermal conductance was found to be proportional to (a c / R). [ABSTRACT FROM AUTHOR]

We model the highly reduced thermal conductivity of nanostructured materials observed in nanoribbons. For highly scaled structures, such as wires with diameters on the order of 20 nm , physical effects beyond classical boundary scattering, including acoustic softening, become important. To date, work on acoustic softening has focused on reductions in group velocity. However, a reduction in the group velocity implies that the phonon dispersion is modified. Here, we investigate how changes in the phonon dispersion manifest in the mean free path, heat capacity, and group velocity. Including these effects in the modeling of thermal conductivity, we find that softening increases low-temperature thermal conductivity while reducing high temperature thermal conductivity. We further compare the model to experimental data. [ABSTRACT FROM AUTHOR]

In the last few decades, piezoresponse force microscopy (PFM) has been a valuable tool to analyze ferroelectric materials at nanoscale. Domain switching and phase-hysteresis loops acquired by PFM had been taken as a proof of ferroelectricity; however, these two characteristics have been observed in non-ferroelectric materials, generating uncertainty of the characterizations carried out by PFM. To resolve this problem, strategies have been developed but they are difficult to implement or still fail depending on the measurement conditions. In this work, we provide a simple method to effectively differentiate ferroelectric from non-ferroelectric signals in PFM analyses. It is based on the comparison of the phases of the PFM signals obtained at the first and the second harmonics of the contact resonant frequency of the Vac applied between the tip and the bottom electrode. To illustrate the effectiveness and simplicity of the method, analyses were conducted on a ferroelectric PZT film, a non-ferroelectric glass and SrTiO3 sample, and a KNN ceramic with ferroelectric and non-ferroelectric zones. [ABSTRACT FROM AUTHOR]

Barium di-silicide (BaSi2) is a very promising absorber material for high-efficiency thin-film solar cells, due to its suitable bandgap, high light absorption coefficient, and long minority-carrier lifetime. In this study, we compare the nanostructure, layer composition, and point defects of BaSi2 thin films deposited by Radio Frequency (RF) sputtering, Thermal Evaporation (TE), and Molecular Beam Epitaxy (MBE), using Doppler Broadening Positron Annihilation Spectroscopy (DB-PAS) depth profiling, Raman spectroscopy, and x-ray diffraction. Our DB-PAS study on thermally annealed RF-sputter deposited and on TE-deposited BaSi2 layers, in a comparison with high quality BaSi2 films produced by MBE, points to the presence of vacancy-oxygen complexes and Si or Ba mono-vacancies, respectively, in the (poly)crystalline BaSi2 films. The degree of near-surface oxidation increases, going from MBE and TE to the industrially applicable RF-sputtered deposition synthesis. The use of a-Si capping layers on the thermally annealed RF-sputtered BaSi2 films leads to a clear reduction in sub-surface oxidation and improves the quality of the BaSi2 films, as judged from DB-PAS. [ABSTRACT FROM AUTHOR]

In the present study, Cu-based nanomaterials are synthesized by initiating spark discharges between two copper electrodes immersed in de-ionized water. The electrical conductivity of water is varied by adding HCl at very low concentrations. The discharge and water properties are determined by measuring the current-voltage waveforms and monitoring water acidity and conductivity, respectively. Scanning electron and transmission electron microscopy analyses of the produced nanoparticles show that increasing water conductivity, by adding HCl, promotes the synthesis of Cu-based nanomaterials. Depending on the initial water conductivity, various nanostructures are observed, including nanoflakes of cuprite (Cu2O), dendrites with high Cu content, and unordered micrometric aggregates with a mixed Cu/Cu2O content. The initial water conductivity also affects the chemical structure, mainly the relative Cu/Cu2O crystalline content. [ABSTRACT FROM AUTHOR]

Thermoelectric properties of nanocomposites are numerically studied as a function of average grain size or nanoparticle density by simulating the measurements as they would be done experimentally. In accordance with previous theoretical and experimental results, we find that the Seebeck coefficient, power factor, and figure of merit, zT, can be increased by nanostructuring when energy barriers exist around the grain boundaries or embedded nanoparticles. When we simulate the performance of a thermoelectric cooler with the same material, however, we find that the maximum temperature difference, Δ T max , is much less than expected from the given zT. This occurs because the measurements are done in a way that minimizes Joule heating, but the Joule heating that occurs in operating devices has a large effect for these kinds of materials. The same nanocomposite but without energy barriers at the grain boundaries has a lower measured zT but a higher Δ T max . The physical reason for these results is explained. The results illustrate the limitations of zT as a figure of merit for nanocomposites with electrically active grain boundaries. [ABSTRACT FROM AUTHOR]

Leaky mode resonance in tilted fiber Bragg grating (TFBG) has been widely underestimated and ignored. Herein, we theoretically demonstrate that the leaky mode resonance can be greatly enhanced, and it presents a highly sensitive property by virtue of its mode transition. The leaky mode transition consists of five stages from the cladding guided mode to radiationlike and guidedlike leaky modes for both p- and s-polarized modes of bare TFBG. However, the graphene induces only one transition for the s-polarized guidedlike leaky mode, which, in turn, leads to an insensitive wavelength shift. The resonance amplitude depends on the imaginary part of the effective refractive index. Consequently, the enhanced leaky mode resonance (eLMR) in the s-polarized state is obtained and presents higher sensitivity than the widespread surface plasmon resonance (SPR). Furthermore, a general empirical rule associated with the refractive index of nanometer materials for exciting the eLMR in TFBG is obtained (the SPR is also discussed for comparison). The results obtained in this work have shed contemporary light on the undervalued leaky mode resonance, which is of great interest and importance to the development of novel multimodal and multifunctional eLMR-based TFBG devices, such as tunable lasers, optical modulators, and sensors. [ABSTRACT FROM AUTHOR]

Half-Heuslers (HH) represent an emerging family of thermoelectric (TE) materials, wherein intrinsic doping enables a wide range of electronic functionalities. In recent years, the solid-state transformation phenomenonon of spinodal decomposition has been actively explored as an effective paradigm to attain bulk nanostructured TE materials via induced phase separation. In the present work, the implication of intrinsic doping and spinodal decomposition on the thermal and electrical transport parameters of nonstoichiometric (Ti, Zr)CoSb HH systems is examined and corroborated with the help of microstructural characteristics. The synthesized HH nanocomposites were found to contain coherent nanoscale heterogeneities along with nanoscale grain, which severely depress the lattice thermal conductivity, while the intrinsic doping due to interstitial Co and defects induced by excess Co off-stoichiometry favorably tunes the electrical transport. A maximum ZT of ∼0.7 at 873 K was obtained for optimized p-type ZrCo1.03Sb0.8Sn0.2 HH nanocomposites, which is among the highest obtained in p-type HH alloys. The present work thus provides a fundamental basis to the understanding of defect engineering and to achieve highly efficient and cost effective HH compositions. [ABSTRACT FROM AUTHOR]

The high-pressure melting properties of the ternary alloy AlCuSi with face-centred cubic structure are theoretically investigated using the statistical moment method. We calculate the melting temperature for the alloy under pressure up to 80 GPa. The dependence of the melting temperature on the content of alloying elements is also studied. Our results agree well with previous experiments, simulations, and other theoretical calculations. [ABSTRACT FROM AUTHOR]

The utilization of laser spectroscopy has seen a dramatic increase in the past several decades and applications in experimental and theoretical development can be found at present in such areas as biomolecular research and medical practice. To verify the feasibility of a random sensitive means for marking the PLCD1 gene therapy effect on breast cancer, in this paper, the random lasing properties were studied in two groups of human breast xenograft tissues. Both coherent and incoherent random lasing regimes were observed from the AdHu5-EGFP group and the AdHu5-PLCD1 group, respectively. A question remains whether the tumor tissue sample receives PLCD1 gene therapy, and this issue becomes critical to the sample's lasing spectrum performance. The inherent disorder of tumor breast tissues produces more light scatters randomly distributed in the tumor sample, resulting in coherent random lasing emission. Indeed, hematoxylin and eosin staining images attest to the fact that the spatial arrangement of the cells of the breast tumor exhibits more disorder and their organizational structure exhibits more irregularity than that of tumor tissues that receive PLCD1 therapy. Our studies pave the way for a random laser marked gene therapy for breast cancer. [ABSTRACT FROM AUTHOR]

We present the growth and strain deformation of sharp-facetted GaAs/GaAsBi core–shell heterostructure nanowires on a Si (111) substrate. The nanowires have a 90 nm wide GaAs core surrounded by an 80 nm thick GaAsBi shell. The sample was analyzed using microbeam synchrotron x-ray diffraction to resolve the local strain status at the GaAs/GaAsBi heterointerface. GaAsBi showed identical lattice constants for its vertical and lateral lattice planes. From the lattice constants, the Bi concentration in GaAsBi was estimated to be approximately 1.3%. In contrast, the GaAs core showed biaxial strain deformation, exhibiting an enlarged vertical lattice constant identical to that of the GaAsBi shell. These layers are coherently grown at the sidewalls of the nanowires, preserving identical vertical lattice constants between the constituent layers in the heterostructure. [ABSTRACT FROM AUTHOR]

In this study, we report a theoretical model for the temperature and size dependent surface energy of metallic nanomaterials. The model is verified by making a comparison with the available simulation and experimental data. Reasonable agreement has been observed between these results. This study reveals that the decrease of surface energy at high temperatures is caused by cohesive energy weakening and bond expansion. With the same nanomaterial size, the sequence of size effects on the surface energy from weak to strong is thin films, nanowires, and nanoparticles. In particular, this work can provide a theoretical basis for the prediction of size dependent surface energy of metallic nanomaterials at different temperatures, which can help in the understanding of the mechanical and thermodynamic properties of metal surfaces. [ABSTRACT FROM AUTHOR]

Electroactivity of graphene-family nanomaterials and three-dimensional porous architectures is key for various applications at the grand challenges of "energy-water-sensing nexus." It requires well-controlled morphology, manipulation of surface chemistry, interconnected topologic network, as well as electronic properties. Here, we demonstrate by taking advantage of hierarchical mesoporosity, optimized defects number density, nD (edges-plane and pore sites, oxygenated and nitrogenated functionalities), further invoked by synergistic coupling between one-dimensional single-walled carbon nanotube (SWCNT) as "nano" spacers and polymer linker with two-dimensional reduced graphene oxide derived three-dimensional scaffolds (known as aerogels) under hydrothermal conditions, and improved electrochemical (re)activity by enhancing the heterogeneous electron transfer rate (kET). We determined the correlation among nD, in-plane sp2C cluster, La and interdefect distance, LD (all via Raman spectroscopy), and kET (via scanning electrochemical microscopy) to establish "structure–property–functionality–electroactivity" relationships. The prominent Raman bands were also analyzed to determine the sp2-bonded C cluster size (La) for graphene- and nanotube-rich phases. The interplay of (1) rich surface redox chemistry due to carbonyl—C=O, carboxyl—COOH, pryridinic—N and pyrrolic—N functional groups, and geometric defects; (2) protruded edge plane and nanopores sites; (3) topological network; and (4) finite density of states with increased vacancy sites is emphasized and signifies the inherently activated electronic states in functionalized nanoporous composite carbon aerogels, for improved physicochemical processes (following graphene < N-graphene < graphene-SWCNT < N-graphene-SWCNT aerogels) relevant for electrocatalysis, thermo-electrochemical energy harvesting, desalination, and biosensing. [ABSTRACT FROM AUTHOR]

In this work, we report that covalently attached protein to graphene oxide/magnetite (rGO-Fe3O4) nanocomposites can act as a substrate for surface-enhanced Raman spectroscopic studies. The substrate rGO-Fe3O4 synthesized by hydrothermal process was modified with a fluorescently labeled protein, streptavidin (Strp), using silane chemistry. The modification was confirmed by confocal fluorescence microscopy and Fourier-transform infrared spectroscopy, where the fluorescence of the conjugated protein and the presence of the additional peaks were visualized, respectively. The transmission electron microscopy demonstrated a wide distribution of Fe3O4 nanoparticles on rGO sheets. In addition, when the Raman peaks of these bio-nanocomposites (rGO-Fe3O4-Strp) were compared with the GO-Strp sheets and Fe3O4-Strp nanoparticles, an active substrate-mediated surface enhancement Raman spectroscopic effect was observed. It suggests that covalently attached protein on rGO-Fe3O4 nanocomposite substrates acts as a better platform for biosensing application than bare GO sheets or Fe3O4 nanoparticles. [ABSTRACT FROM AUTHOR]