In the past detonation nanodiamonds (DNDs), sized 3–5 nm, have been praised for their colloidal stability in aqueous media, thereby attracting vast interest in a wide range of applications including nanomedicine. More recent studies have challenged the consensus that DNDs are monodispersed after their fabrication process, with their aggregate formation dynamics poorly understood. Here we reveal that DNDs in aqueous solution, regardless of their post-synthesis de-agglomeration and purification methods, exhibits hierarchical aggregation structures consisting of chain-like and cluster aggregate morphologies. With a novel characterization approach of combining machine learning with direct cryo-transmission electron microscopy, in combination with X-ray scattering and vibrational spectroscopy, we show in detail that their aggregate morphologies of chain and cluster ratios and the corresponding size and fractal dimension distributions vary with the post-synthesis treatment methods. In particular DNDs with positive ζ-potential subject to a hierarchical structure that assembles aggregates into large networks. Moreover, DNDs purified with the gas phase annealing and oxidation tend to have more chain-like aggregates. Our findings provide important contribution in understanding the DND interparticle interactions, which give pathways to controlling the size, polydispersity and aggregation of DNDs tailored to their desired applications.

The present work delineates the heat transfer potential of the semiconducting graphitic carbon nitride (g-C3N4) nanofluid. The paper also discusses the eco-friendly green synthesis of g-C3N4 nanoparticles from the natural carbon precursor portobello mushroom by the hydrothermal method. The nanoparticles synthesised are subjected to structural, morphological, thermal, and optical characterizations. The flower-like laminar structure of the sample revealed through field emission scanning electron microscope (FESEM) analysis exhibited a semiconducting nature with an optical bandgap of 2.58 eV. The formation of g-C3N4 is confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray photoelectron (XPS) and Raman spectroscopic analyses. The thermogravimetric analysis (TGA) reveals good thermal stability up to 500 °C, which suggests possible applications in heat transfer fluids. The concentration-dependent thermal diffusivity variation of the g-C3N4 semiconductor nanofluid, investigated using the sensitive mode mismatched dual beam thermal lens technique, divulges its potential as an organic, metal-free additive in engine coolants for automobile applications.

A composite of graphene oxide (GO) and oleate-protected iron oxide nanoparticles (IONPs) has been developed, synthesized, and characterized by SEM, TEM, AFM, and FTIR spectroscopy. The dispersion of GO/IONPs in an organic medium in the presence of an external magnetic field exhibits a magneto-optical effect that was used to obtain a composite material based on the NPEL-128 amino-cured epoxy resin. The viscosity of the composition was adjusted by adding n-butylglycidyl ether (BGE), the optimal composition was chosen with a BGE content of 30 wt%. The samples were obtained without nanoadditives, with the addition of GO, IONPs, and GO/IONPs particles, the latter were cured without applying a magnetic field, as well as parallel and perpendicular to the direction of the magnetic field. The obtained samples were tested for wear with the determination of the friction coefficient and wear rate, as well as the analysis of the wear profile. It has been established that samples with GO/IONP cured in a magnetic field were subjected to the greatest wear. Conclusions are drawn about the core role of the orientation of GO/IONPs flakes in a magnetic field in the mechanism of wear of polymer nanocomposite samples.

Friedrich-Wintgen (FW) bound states in the continuum (BICs), as a kind of optical BICs, basically relie on changing the angle of incidence and polarization for its dynamic implementation. Here, we explore the realization of an FW BIC in a hybrid guided-mode resonance (GMR) and Fabry-Pérot resonance (FPR) system consisting of two layers of graphene and dielectric SiO2. The band structure and field distribution demonstrate the location of the proposed BIC is at 44 THz. Further studies show that changes in the Fermi level of graphene1 can dynamically achieve the FW BIC. Considering the significant difference in the electric field intensity corresponding to the GMR and FW BIC states, the dynamic near-field display can be achieved by applying different gate voltages. This work provides theoretical guidance for FW BIC in image display and data encryption.

Photoelectrocatalysis is one of the most promising strategies to address ever-growing wastewater problems. A novel heterojunction photoanode formed by depositing a photocatalyst on a boron-doped diamond (BDD) layer has been considered an ideal material for the practical application of photoelectrocatalytic (PEC) degradation due to its advantages of light responsiveness, excellent charge transport, and robustness. In this study, various BiVO4/BDD heterojunction photoanodes with different diamond crystalline qualities and electrical conductivities were successfully fabricated by tuning the boron (B) doping concentration of the BDD layer. It was proposed that the charge transport efficiency of the photoanodes is promoted by optimizing the crystalline qualities and electrical conductivities of BDD films, thereby enhancing the PEC activity of the BiVO4/BDD heterojunction photoanode. Our results suggested that the electrical conductivity of BDD increased and the crystalline quality of BDD deteriorated with increasing B doping concentration. As a result, the PEC activity of the BiVO4/BDD heterojunction photoanode first increased and then decreased. The optimal PEC activity of the BiVO4/BDD heterojunction photoanode was achieved corresponding to the [B]/[C] gas ratio at 500 ppm, producing a current density of 3.3 mA/cm2 at 1.6 VRHE (the potential versus a reversible hydrogen electrode) in 0.1 M Na2SO4 under AM 1.5 irradiation, which was 1.7 times (1.9 mA/cm2) that of the photoanode with a [B]/[C] gas ratio of 3000 ppm. Meanwhile, the optimized tetracycline hydrochloride (TCH) degradation efficiency was 63.5 % within 9 min (500 ppm gas phase), which was 2.5 times (25.1 %) that of the highly doped photoanode with a [B]/[C] gas ratio of 3000 ppm. This study revealed that the excellent PEC performance benefited from the high crystalline quality and high electrical conductivity of BDD, which depended on the optimized B doping concentration. The idea of enhancing the PEC activity of the photoanode by optimizing the properties of the conductive electrode material proposed in this study provides a conceptual reference for fabricating potential high-performance photoanodes in the future.

Single-crystal diamond presents as an ideal semiconductor material for high-performance and high-reliability MEMS devices, on account of its outstanding mechanical and physical properties. A smart-cut technology based on ion-implantation was proposed to fabricate the SCD-on-SCD MEMS resonators. However, the ion-implantation damage induced defects would degrade the quality (Q) factors of the diamond MEMS resonators. Here, we systematically investigate the effect of ultra-high vacuum annealing on the resonance properties of SCD cantilevers. It is observed that the Q factors are markedly improved by nearly twice after annealing at 1100 °C due to the annihilation of the ion implantation induced damage in the resonators. Therefore, reducing the defects in the resonators by high-temperature annealing the as-fabricated SCD MEMS cantilevers is one of the strategies to improve the Q factors. This work also proves out that MEMS represents a more sensitive tool for characterizing the crystalline quality of diamond, compared with the conventional structural methods.

This paper aimed to construct carboxymethyl cellulose (CMC) nanocomposite films incorporated with carbon nanotubes (CNTs) and silver nanoparticles (Ag NPs) by an eco-friendly approach and compared their alternative properties with the pure CMC film. The novelty in this article is the investigation of the dielectric properties of CMC/CNT/Ag, the enhancement of the CMC solubility by citric acid, and the preparation of Ag NPs in a domestic microwave. Treatment of the CMC/CNT/Ag films with citric acid decreased the water solubility and water adsorption by 13.7–83 % and 6–14.3 %, respectively, while enhancing the tensile strength (TS) and elongation at break (EB) by 4–5 % and 81–115 %, respectively, compared to the pristine CMC film. In addition, the pore size and surface area of the prepared films increased due to the incorporation of CNTs. Adding 10 and 20 wt% CNTs and Ag NPs to the treated films decreased the water solubility and adsorption, increasing tensile properties and electrical conductivity. The addition of different concentrations of CNT/Ag to the membrane led to variations in the membrane's electrical properties. CNTs and Ag NPs might be alternatives to nano-fillers for improving the CMC film properties. These CNT/Ag and CMC films could be used as alternative materials in eco-friendly safer lithium-ion batteries.

Two different reduced graphene oxide, i.e. the chemical reduced GO grafted with the polyamide (PGO) and common thermal reduced graphene oxide (RGO), had been used to modify epoxy/Zn composite coatings and their anticorrosive behavior was studied and compared. PGO was innovatively incorporated into the epoxy composite coating during preparing the paint via the solve-thermal treatment of GO in polyamide-651 at 90 °C. Various analyses revealed that GO was reduced in situ and simultaneously grafted with polyamide macromolecules during the solve-thermal treatment. Compared to pristine GO and RGO, PGO displayed improved dispersibility in the resin diluent and its superior effect on improving the anti-corrosive performance of epoxy/Zn coating was confirmed by different corrosion test and surface analysis technique. Moreover, its optimum content in the composite paint was only 0.3 wt%. The excellent anti-corrosion performance of the composite coating could be attributed to the great barrier properties of PGO in the epoxy coating, as well as its good dispersion and compatibility to epoxy matrix.

A simple, sensitive, and rapid method of determining phenolic acids, i.e. caffeic, ferulic, syringic, and vanillic using boron-doped diamond electrode (BDDE) by differential pulse voltammetry (DPV) was described. To the best of our knowledge, this is the first presentation of an electrochemical method to determine these compounds on BDDE. Under the conditions presented, the mentioned analytes undergo irreversible oxidation controlled by diffusion. The measurement conditions and composition of the supporting electrolyte were developed and optimized. Optimal measurement parameters ensure the usage of 0.02 mol L−1 ammonium citrate buffer pH 3.0 as a supporting electrolyte. The calibration graphs were linear with a correlation coefficient (r) >0.9959. The detection limits for the phenolic acids were within 0.01–0.03 mg L−1. Repeatability in all experiments, expressed by RSD%, was better than 5 %. The influence of interfering metal ions, such as Bi3+, Cd2+, Cu2+, Pb2+ and Tl+, was studied. The proposed method was successfully verified by measuring recoveries of phenolic acids in the model wine solution. The standard addition method was also applied in the determination of syringic acid in homemade and commercially available products: walnuts, walnut tincture, fresh and dried thyme. Effective application of the described analytical approach with the usage of BDDE not only enables the electrochemical detection of these four phenolic acids but also helps to reduce operational costs.

In this study, we investigated the upper pressure limit of diamond. A method for predicting the upper pressure limit of diamonds under multiaxial stress is developed by introducing stress angles α based on first-principles calculations. The normal stresses of diamond in three mutually orthogonal orientations [111], 112¯, and 11¯0 are set as σ111tanα=σ112¯=σ11¯0. The three most important characteristics, namely, the theoretical strength, maximum dynamic stability stress, and phase transition stress, are evaluated and analysed to further determine the upper pressure limit of diamond. The calculated results indicate that the upper pressure limit of diamond can reach up to 1.265 TPa in the [111] orientation under multiaxial compressions, which is approximately 1.25 times higher than that of our calculated phase transition stress (σ[111] = 1008.3 GPa) and 1.18–1.28 times higher than that of the current upper pressure limit 990 (Phys. Rev. Lett. 108 (2012) 045704)–1075 GPa (Proc. Natl Acad. Sci. U. S. A. 103 (2006) 1204) at a hydrostatic pressure, which is a new record. This study provides a possible approach to obtain a high pressure limit by multiaxial compression, which will advance the progress of in-situ high-pressure anvil technology.

Preparation of carbon dots (CDs) and nitrogen-doped carbon dots (NCDs) with germanium oxide (GeO2/GeO) using a facile one-step microwave-assisted synthesis procedure is presented. Iso-ascorbic acid, urea and Ge-132 were used as carbon, nitrogen and germanium sources, respectively. Studies have shown that the CDs, NCDs and GeO2/GeO nanoparticles individually have excellent qualities for bio-imaging applications including photoluminescence, biocompatibility, good stability and low toxicity. While CDs have been thoroughly explored in literature, CDs with germanium oxide on their surface are an avenue that has scarce information. Hence the synthesis and physicochemical characterizations of CDs- /NCDs- GeO2/GeO composites were studied using different microscopic and spectroscopic techniques to explore their compatibility for bio-imaging applications. In the presence of Ge, the approximate particle sizes of both the CDs and NCDs increased from 2.5 nm to 5.8 nm and the spherical or quasi-spherical shape was maintained. The X-ray photoelectron spectroscopy survey spectrum showed that the surface of Iso-N-Ge-CDs contained nitrogen and germanium, indicating the successful synthesis of nitrogen-doped carbon dots (NCDs) with germanium oxide (GeO2/GeO). Photoluminescence emissions of longer wavelengths suitable for cell imaging were observed for Iso-N-Ge-CDs (350 nm) and Iso-Ge-CDs (430 nm) and the Iso-N-Ge-CDs are able to fluoresce under the red and blue wavelengths. The Ge-NCDs demonstrated excitation-dependent emission wavelength behaviour, pH sensitivity and Fe3+ sensitivity which may be used as a probe for Fe3+ metal ions and intracellular pH measurements.

The urgent need for sustainable energy development is contingent on pollution-free technologies, which has sparked widespread interest in exploring environmentally favorable methods employing inexpensive and abundant starting materials. In this study, 3D honeycomb-like hierarchical porous carbons were prepared using a green molten salt activation method, with renewable biomass waste cotonier catkin (CC) as the carbon source and non-toxic salt KHCO3 as the activating agent and were used as electrodes for supercapacitors. Specifically, the optimal CC-HPC-1:3 sample has a 3D honeycomb-like structure with a high specific surface area (970.5 m2 g−1) and a relatively applicable pore volume (0.54 cm3 g−1) as well as abundant multi-heteroatoms doping (nitrogen: 3.64 at. %, oxygen: up to 11.22 at. %). As anticipated, the CC-HPC-1:3 electrode exhibits intriguing electrochemical properties in aqueous solution, including an excellent specific capacitance of up to 284.5 F g−1 at 0.5 A g−1, good rate capacitive behavior (194.2 F g−1 retain at 10 A g−1) and low resistance. Notably, the assembled symmetric supercapacitors based on CC-HPC-1:3 carbon materials with a wide voltage window of 1.8 V result in a high energy density of 16.1 Wh kg−1 at 180 W kg−1 and good stability with a capacitance ratio >96 % after 10,000 cycles. Our work presented a very competitive strategy for synthesizing sustainable new green electrode materials for high-performance and low-cost energy storage devices due to the simple and environmentally friendly preparation of CC-HPC.

The development of high-performance electromagnetic wave-absorbent materials from inexpensive biomass feedstock is currently the subject of considerable interest. In this study, we developed Co/C composites with excellent electromagnetic wave absorption properties using a simple carbonization method with mangosteen shells as a precursor. The Co/C composite has a minimum reflection loss value (RLmin) of −61.88 dB and a maximum effective absorption bandwidth of 6.32 GHz. For thicknesses ranging from 1 to 5.5 mm, the effective absorption frequency range could cover the entire C, X, and Ku bands. The magnetic loss produced by Co and the dielectric loss, dipole polarization, interfacial polarization, and multiple reflections of biomass carbon synergies enhance the impedance matching capabilities and microwave absorption performance of the composites. The results demonstrate that the activated mangosteen shell magnetic composite has a wider effective absorption bandwidth and greater absorption intensity. This work provides a good potential method for preparation of magnetic particle/biomass-derived carbon microwave absorbing structural materials.

Numerous researches were interestingly considered with investigation of unique strategies for industrialization of efficacious textiles to find wide-scaled applicability in different purposes. The demonstrated approach represents unique strategy for manufacturing of fluorescent/UV-resistant/microbicide cotton via exploitation of silver nanoparticles (AgNPs), carbon quantum dots (CQDs) and silver nanoparticles-doped carbon quantum dots (AgNPs-CQDs) to be applicable as efficacious textiles. Whereas, both CQDs and AgNPs were formerly clustered from alginate biopolymer. Topographical features and particle size of AgNPs (7.5 ± 2.6 nm), CQDs (4.9 ± 1.7 nm) & AgNPs-CQDs (4.0 ± 1.4 nm) were investigated via microscopic images and Zetasizer data. Spectral mapping data for the photoluminescent emission showed that, AgNPs, CQDs & AgNPs-CQDs were exhibited with two intense peaks at 370 nm & 490 nm. Cotton fabrics were sequentially treated with CQDs, Ag-CQDs & AgNPs-CQDs to prepare CQDs@Cotton, Ag-CQDs@Cotton and AgNPs-CQDs@Cotton, respectively. Thermal stability, colorimetric properties/color strength, UV-resistance and antimicrobial potentiality were studied for all the prepared samples. AgNPs-CQDs@Cotton exhibited excellent UV-resistance (UPF, 43.4) and antimicrobial activity, whereas the diameter of inhibition zone was estimated for its affinity against S. aureus, E. coli and C. albicans, to be 14 mm, 18 mm and 16 mm, respectively.

In this work, Fe3O4/FeS2/g-C3N4 nanocomposites were developed for catalytic hydrogen generation from sodium borohydride. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and environmental scanning electron microscopy (ESEM) were used to analyze these nanocomposites. The XRD diffraction peaks of Fe3O4 and FeS2 cubic phase showed an average crystal size of calculation of 15 and 20 nm. ESEM micrographs showed a 2D broken up sheet structure having more edge sites. The BET surface areas for S@g-C3N4, 1.0, 2.0, and 3.0 wt% Fe3O4/FeS2 were 40, 109, 137 and 162 m2/g, respectively. Even though FeS2 were incorporated into the nanosheet, the pore size was increased from 2.0 to 2.15 nm. S@g-C3N4 has an average band gap of 2.60 eV that decreased to 2.30, 2.21 and 2.18 eV at 1.0, 2.0 and 3.0 wt% of FeS2. In addition, Fe3O4/FeS2/g-C3N4 nanosheets showed an emission band at 460 nm. Moreover, the intensity of this band decreased as the content of Fe3O4/FeS2 reached 3.0 wt%. The rate of hydrogen production is accelerated as the percentage of Fe3O4/FeS2 increased from 1.0 to 3.0 wt%. The sample 3.0 wt% Fe3O4/FeS2 showed the best rate of hydrogen production (8480 mL/g·min).

To improve the heat dissipation performance of Nd:YAG lasers, sandwich-type Nd:YAG laser crystal with a diamond cap is analyzed by using a 2D numerical model, and the effect of the diamond cap thickness on the temperature distribution and thermal aberration is investigated. The simulation results reveal that the diamond cap with a thickness of 1 mm can reduce the maximum temperature inside the Nd:YAG to 309.7 K, which is 38 K lower than that of the laser crystal without a cap. Thermal aberration causes the optical path difference (OPD) inside laser crystal, and the total OPD of the Nd:YAG with the 1-mm-thickness diamond cap is lower compared to that of Nd:YAG without or with a 1-mm-thickness YAG cap. As the diamond cap thickness increases from 0.2 mm to 1 mm, the maximum temperature inside Nd:YAG decreases by 2.3 K and the near-axis OPD of the composite structure changes from negative to positive. Moreover, the spherical thermal aberration is described by the dioptric power and the absolute value of the dioptric power decreases with the increase of the diamond cap thickness. The dioptric power reaches zero at a diamond cap thickness of 0.59 mm, which means that a certain thickness of diamond cap can correct spherical thermal aberration. Therefore, to achieve better laser beam quality and higher output power, the optimal thickness of the diamond cap can be designed by considering the effects of temperature distribution and thermal aberration of the laser crystal.

Corn husk, an abundant agro-industrial waste was employed to produce activated carbon for energy storage. The sponge-like activated carbons were produced with environmentally friendly potassium carbonate (K2CO3) at different impregnation ratio (corn husk:K2CO3; 1:1 to 1:3) and activation temperatures (500–800 °C). The obtained activated carbon was used to produce electrodes for supercapacitor application. The results revealed that corn husk: K2CO3 ratio of 1:2 and 650 °C promoted mainly nanopores (0.773 nm) with appreciably higher specific surface area (1115 m2/g) and a sponge morphology. The electrochemistry performance test on the materials shows specific capacitances of up to 269 F/g at 5 mV/s scan rate for a material obtained at 650 °C. The textural characteristics, morphology, and heteroatoms of sulfur and nitrogen significantly promoted higher energy storage capacity. This activated carbon was employed to assemble a symmetric supercapacitor in acidic electrolyte (0.5 M H2SO4) that delivered up to ~10 Wh/kg and was very stable, maintaining about 99.5 % of its original energy after 20,000 charge/discharge cycles.

Boron-doped diamond (BDD) electrodes have achieved excellent selectivity and switchable product formation for electrochemical CO2 reduction reaction (eCO2RR), although the current should be improved. Surface morphology modulation is a promising approach for improving it by exposing a larger electroactive area. Herein, we fabricated a porous 1 % BDD film (p-BDD) and a rough-surfaced 1 % BDD film (r-BDD) by modifying the surface of a flat 1 % BDD film (f-BDD). Fundamental electrochemical properties, including potential window, differential capacitance, and active area were examined, followed by eCO2RR activity evaluation. The synthetic r-BDD electrode enabled approximately 1.7-fold increases in current density and yield rate (17.6 μmol h−1) toward CO production compared to f-BDD (10.3 μmol h−1). This improvement in eCO2RR is ascribed to the larger electroactive area with a comparable kinetic performance, in comparison to f-BDD. On the other hand, p-BDD possesses the largest real area, but showed the lowest activity for eCO2RR (1.2 μmol h−1 for CO), which could result from hindered diffusion of CO2 inside the pores. X-rays photoelectron spectroscopy and electrochemical impedance spectroscopy were employed to disentangle the morphological structure effect from the chemical reactivity of the electrode surface.

The present work reports a study on the magnetic properties of graphene oxide decorated with magnetite nanoparticles (GO·Fe3O4), at room temperature. A total of ten samples were prepared via co-precipitation method, controlling the magnetite incorporation on the GO surface. Magnetic characterization was performed using a vibrating sample magnetometer. Transmission electron microscopy and X-ray diffraction were employed for structural investigation. All systems presented magnetisation loops that resemble a Langevin function at the high field region, but also have non-zero coercivity and remanent magnetisation. These features are attributed to the size distribution of the magnetic nanoparticles. A portion of the magnetite particles small enough present superparamagnetic behaviour, while the bigger ones are ferrimagnetic. Using the in-field δMR interaction-plots technique, it was observed that demagnetizing interactions are predominant. Magnetic parameters like coercivity and remanent magnetisation, however, are mainly governed by average particle size, and not by such interactions.

This study presents the development of green and sustainable supercapacitor electrodes using activated carbons derived from industrial waste from red pepper (RPW) via conventional chemical activation using ZnCl2 at various carbonization/activation temperatures. The activated carbon samples were subjected to various analytical techniques, including elemental analysis, N2 adsorption-desorption, Raman, FT-IR, and SEM-EDS. The resulting carbon samples were then used to prepare standard coin-sized supercapacitor cells, which were tested using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques with a 6 M KOH electrolyte. The BET surface area and surface functionality of the samples decreased as the temperature increased. The material produced at the highest temperature (AC800) exhibited the lowest gravimetric capacitance value (131 F/g). However, it demonstrated perfectly reversible electrochemical behavior with the highest capacitance retention of 50 % (between 0.5 A/g and 10 A/g) and cyclic stability (>96 %) over 10,000 cycles among all the other materials. Conversely, the electrode material produced at the lowest temperature (AC600) had the highest gravimetric capacitance value of 175 F/g but the lowest electrochemical stability due to the contribution of pseudo faradaic processes in the storage mechanism.