Theoretical Investigation of the Green-Synthesized Carbon-Based Nanomaterial Potential as Inhibitors of ACE2 for Blocking SARS-CoV-2 Binding

Since the emergence of SARS-CoV-2 in 2020, the world has faced a global pandemic, emphasizing the urgent need for effective treatments to combat COVID-19. This study explores the use of green-synthesized carbon-based nanomaterials as potential inhibitors of ACE2, a critical receptor for SARS-CoV-2 entry into host cells. Specifically, the study examines four carbon-based nanomaterials, namely, CD1, CD2, CD3, and CD4 in amino, graphitic, pyridinic, and pyrrolic forms, respectively, synthesized from curcumin, to investigate their binding affinity with ACE2. Molecular docking studies revealed that CD3 (pyridinic form) exhibited the highest binding affinity with ACE2, surpassing that of the control compound, curcumin. Notably, CD3 formed hydrophobic interactions and hydrogen bonds with key ACE2 residues, suggesting its potential to block the binding of SARS-CoV-2 to human cells. Moreover, molecular dynamics simulations demonstrated the stability of these ligand-ACE2 complexes, further supporting the promise of CD3 as an inhibitor. Quantum chemical analyses, including frontier molecular orbitals, natural bond orbital analysis, and the quantum theory of atoms in molecules, unveiled valuable insights into the reactivity and interaction strengths of these ligands. CD3 exhibited desirable chemical properties, signifying its suitability for therapeutic development. The study's findings suggest that green-synthesized carbon-based nanomaterials, particularly CD3, have the potential to serve as effective inhibitors of ACE2, offering a promising avenue for the development of treatments against COVID-19. Further experimental validation is warranted to advance these findings and establish new therapies for the ongoing global pandemic.

Trifunctional electrocatalysts based on a bimetallic nanoalloy and nitrogen-doped carbon with brush-like heterostructure

Trifunctional ORR/OER/HER catalysts are emerging for various sustainable energy storage and conversion technologies. For this function, employing materials with 1D structures leads to catalysts having limited surface area and structural robustness. Instead of 1D catalysts, heterostructured catalysts (i.e., catalysts consisting of interfaces created by combining diverse structural components) have attracted much attention due to their high efficiency. We have fabricated a directly grown 1D-1D heterostructured bimetallic N-doped carbon trifunctional catalyst based on Fe/Co bimetallic-organic frameworks, forming nanobrushes (FeCoNC-NB) with improved resistance to collapsing and substantial numbers of exposed active sites. The secondary 1D structure of this design contributes to creating interparticle conductive networks. By combining the brush-like heterostructure, FeCo alloy active sites, and N-doped carbon as support and for encapsulation of the metal, the catalyst features a high ORR Eonset value (1.046 V), low OER overpotential (363 mV), and comparable HER overpotential (254 mV) in alkaline electrolyte. Zn-air batteries with FeCoNC-NB demonstrate a power density of 195 mW cm-2 and a superior battery life of up to 350 h. Self-powered FeCoNC-NB-based water electrolyzers as energy conversion devices are also demonstrated. This work drives the progress of trifunctional catalysts based on heterostructured nonprecious metal N-doped carbon for energy storage and conversion developments.

Functionalized Phytochemicals-Embedded Carbon Dots Derived from Medicinal Plant for Bioimaging Application

Precise visualization of biological processes necessitates reliable coloring technologies, and fluorescence imaging has emerged as a powerful method for capturing dynamic cellular events. Low emission intensity and solubility of intrinsic fluorescence are still challenging, hindering their application in the biomedical field. The nanostructurization and functionalization of the insoluble phytochemicals, such as chlorophyll and curcumin, into carbon dots (CDs) were conducted to address these challenges. Due to their unique fluorescence characteristics and biocompatibility, CDs derived from medicinal plants hold promise as bioimaging agents. Further, the nitrogen in situ functionalization of the as-synthesized CDs offered tunable optical properties and enhanced solubility. The surface modification aims to achieve a more positive zeta potential, facilitating penetration through biological membranes. This work provides valuable insights into utilizing functionalized phytochemical-embedded carbon dots for bioimaging applications. The doping of nitrogen by adding urea showed an alteration of surface charge, which is more positive based on zeta potential measurement. The more positive CD particles showed that Andrographis paniculata-urea-based CDs were the best particles to penetrate cells than others related to the alteration of the surface charge and the functional group of the CDs, with the optimum dose of 12.5 μg/mL for 3 h of treatment for bioimaging assay.

Porphyrin-derived carbon dots for an enhanced antiviral activity targeting the CTD of SARS-CoV-2 nucleocapsid

BACKGROUND

Since effective antiviral drugs for COVID-19 are still limited in number, the exploration of compounds that have antiviral activity against SARS-CoV-2 is in high demand. Porphyrin is potentially developed as a COVID-19 antiviral drug. However, its low solubility in water restricts its clinical application. Reconstruction of porphyrin into carbon dots is expected to possess better solubility and bioavailability as well as lower biotoxicity.

METHODS AND RESULTS

In this study, we investigated the antiviral activity of porphyrin and porphyrin-derived carbon dots against SARS-CoV-2. Through the in silico analysis and assessment using a novel drug screening platform, namely dimer-based screening system, we demonstrated the capability of the antivirus candidates in inhibiting the dimerization of the C-terminal domain of SARS-CoV-2 Nucleocapsid. It was shown that porphyrin-derived carbon dots possessed lower cytotoxicity on Vero E6 cells than porphyrin. Furthermore, we also assessed their antiviral activity on the SARS-CoV-2-infected Vero E6 cells. The transformation of porphyrin into carbon dots substantially augmented its performance in disrupting SARS-CoV-2 propagation in vitro.

CONCLUSIONS

Therefore, this study comprehensively demonstrated the potential of porphyrin-derived carbon dots to be developed further as a promisingly safe and effective COVID-19 antiviral drug.

Recent Progress in Colloidal Quantum Dot Thermoelectrics

Semiconducting colloidal quantum dots (CQDs) represent an emerging class of thermoelectric materials for use in a wide range of future applications. CQDs combine solution processability at low temperatures with the potential for upscalable manufacturing via printing techniques. Moreover, due to their low dimensionality, CQDs exhibit quantum confinement and a high density of grain boundaries, which can be independently exploited to tune the Seebeck coefficient and thermal conductivity, respectively. This unique combination of attractive attributes makes CQDs very promising for application in emerging thermoelectric generator (TEG) technologies operating near room temperature. Herein, recent progress in CQDs for application in emerging thin-film thermoelectrics is reviewed. First, the fundamental concepts of thermoelectricity in nanostructured materials are outlined, followed by an overview of the popular synthetic methods used to produce CQDs with controllable sizes and shapes. Recent strides in CQD-based thermoelectrics are then discussed with emphasis on their application in thin-film TEGs. Finally, the current challenges and future perspectives for further enhancing the performance of CQD-based thermoelectric materials for future applications are discussed.

Curcumin-derived carbon-dots as a potential COVID-19 antiviral drug

Even entering the third year of the COVID-19 pandemic, only a small number of COVID-19 antiviral drugs are approved. Curcumin has previously shown antiviral activity against SARS-CoV-2 nucleocapsid, but its poor bioavailability limits its clinical uses. Utilizing nanotechnology structures, curcumin-derived carbon-dots (cur-CDs) were synthesized to increase low bioavailability of curcumin. In-silico analyses were performed using molecular docking, inhibition of SARS-CoV-2 nucleocapsid C-terminal domain (N-CTD) and antiviral activity were assessed in dimer-based screening system (DBSS) and in vitro respectively. Curcumin bound with the N-CTD at ΔG = -7.6 kcal/mol, however modifications into cur-CDs significantly improved the binding affinity and %interaction. Cur-CDs also significantly increased protection against SARS-CoV-2 in both DBSS and in vitro at MOI = 0.1. This study demonstrated the effect of post-infection treatment of curcumin and novel curcumin-derived carbon-dots on SARS-CoV-2 N-CTD dimerization. Further investigation on pre-infection and in-vivo treatment of curcumin and cur-CDs are required for a comprehensive understanding on the carbon-dots enhanced antiviral activity of curcumin against SARS-CoV-2.

Novel strategy for high-performance supercapacitors through the polyvinylpyrrolidone (PVP)-assisted in situ growth of FeS2

Iron disulfide or pyrite (FeS₂) has emerged as a promising transition metal sulfide-based supercapacitor owing to its abundance and superb electrochemical properties. However, FeS₂ still faces major hurdles in realizing its full potential, such as a low energy density and poor conductivity. In this study, we report a high-performance FeS₂ supercapacitor synthesized by a direct one-step process with the help of polyvinylpyrrolidone (PVP). The incorporation of PVP on the active materials prevented dendritic expansion and acted as a binding for solving the current FeS₂ limitations, while facilitating a one-step synthesis process. Additionally, PVP could enhance the electrochemical performance by enabling faster ion movement. An FeS₂/PVP nanocomposite was successfully synthesized, and used in an asymmetric supercapacitor, demonstrating a high specific capacity of 735 F g^-1 (at 2 A g^-1) and a high energy density of 69.74 W h kg^-1 (at 911 W kg^-1). The superior electrochemical properties of FeS₂/PVP were enabled by the lower charge-carrier resistance and better surface passivation by PVP, as demonstrated by both electrochemical experiments and first-principles calculations. The high-performance supercapacitor of FeS₂ presented in this study synthesized in situ by an efficient method provides a new insight into novel supercapacitor electrodes.

Interface Analysis of LiCl as a Protective Layer of Li1.3Al0.3Ti1.7(PO4)3 for Electrochemically Stabilized All-Solid-State Li-Metal Batteries

Regardless of the superiorities of Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP), such as stability against oxygen and moisture, high ionic conductivity, and low activation energy, its practical application in all-solid-state lithium metal batteries is still impeded by the formation of ionic-resistance interphase layers. Upon contact with Li metal, electron migration from Li to LATP causes the reduction of Ti⁴⁺ in LATP. As a result, an ionic-resistance layer will be formed at the interface between the two materials. Applying a buffer layer between them is a potential measure to mitigate this problem. In this study, we analyzed the potential role of LiCl to protect the LATP solid electrolyte through a first-principle study-based density functional theory (DFT) calculation. Density-of-states (DOS) analysis on the Li/LiCl heterostructure reveals the insulating roles of LiCl in preventing electron flow to LATP. The insulating properties begin at depths of 4.3 and 5.0 Å for Li (001)/LiCl (111) and Li (001)/LiCl (001) heterostructures, respectively. These results indicate that LiCl (111) is highly potential to be applied as a protecting layer on LATP to avoid the formation of ionic resistance interphase caused by electron transfer from the Li metal anode.

In Vitro and Silico Studies on the N-Doped Carbon Dots Potential in ACE2 Expression Modulation

The alteration of ACE2 expression level, which has been studied in many diseases, makes the topic of ACE2 inducer potential crucial to be explored. The ACE2 inducer could further be designed to control the ACE2 expression level, which is appropriate to a specific case. An in vitro study of well-characterized carbon dots (CDs), made from citric acid and urea, was performed to determine their ability to modulate the ACE2 receptor. Gene expression of ACE2 was quantified using concentrations adjusted for IC50 results from CDs viability assays in HEK 293 and A549 cell lines. RT-qPCR was used to assess the expression of the ACE2 gene and its induction effect in normal cell lines (HEK-293A). According to the results of the tests, ACE2 is expressed in HEK-293A cell lines, and diminazene aceturate can increase ACE2 expression. The effect of CDs on ACE2 gene expression was further examined on the cell lines that had previously been induced with diminazene aceturate, which resulted in upregulation of the ACE2 expression level. An in silico study has been done by using a molecular docking approach. The molecular docking results show that CDs can make strong interactions with ACE2 amino acid residues through hydrophobic interaction, π-π interaction, π-cation interaction, and ionic interaction.

A Free-Standing Polyaniline/Silicon Nanowire Forest as the Anode for Lithium-ion Batteries

Despite its high theoretical capacity, silicon anode has limited intrinsic conductivity and experiences significant volume changes during charge-discharge. To overcome these issues, facile metal-assisted chemical etching and in-situ polymerization of aniline are employed to produce a dense 1D polyaniline/silicon nanowire forest without noticeable agglomeration as a free-standing anode for lithium-ion batteries. This hybrid electrode possesses high cycling performance, delivering a stable capacity capped at 2 mAh cm-2 for 346 cycles of charge-discharge. Maximum capacity of 2 mAh cm-2 is also achievable at high-rate cell testing of 2 mA cm-2, which cannot be obtained by the anode with plain silicon wafer and silicon nanowire only. The introduction of PANI on the silicon nanowire is shown to reduce the solid electrolyte interface (SEI) resistance, stabilize the SEI layer, further alleviate the effect of volume changes, and boost the conductivity of the hybrid anode, resulting in the high electrochemical performance of the anode.

Coke-Resistant Ni/CeZrO2 Catalysts for Dry Reforming of Methane to Produce Hydrogen-Rich Syngas

Dry reforming of methane was studied over high-ratio zirconia in ceria-zirconia-mixed oxide-supported Ni catalysts. The catalyst was synthesized using co-precipitation and impregnation methods. The effects of the catalyst support and Ni composition on the physicochemical characteristics and performance of the catalysts were investigated. Characterization of the physicochemical properties was conducted using X-ray diffraction (XRD), N2-physisorption, H2-TPR, and CO2-TPD. The results of the activity and stability evaluations of the synthesized catalysts over a period of 240 min at a temperature of 700 °C, atmospheric pressure, and WHSV of 60,000 mL g−1 h−1 showed that the 10%Ni/CeZrO2 catalyst exhibited the highest catalytic performance, with conversions of CH4 and CO2 up to 74% and 55%, respectively, being reached. The H2/CO ratio in the product was 1.4, which is higher than the stoichiometric ratio of 1, indicating a higher formation of H2. The spent catalysts showed minimal carbon deposition based on the thermo-gravimetry analysis, which was <0.01 gC/gcat, so carbon deposition could be neglected.

A Sustainable Approach for Preparing Porous Carbon Spheres Derived from Kraft Lignin and Sodium Hydroxide as Highly Packed Thin Film Electrode Materials

A green synthetic strategy to design biomass-derived porous carbon electrode materials with precisely tailored structure and morphology has always been a challenging goal because these materials can fulfill the demands of next-generation supercapacitors and other electrochemical devices. Potassium hydroxide (KOH) is extensively utilized as an activator since it can produce porous carbon with high specific surface area and well-developed porous channels. The exploitation of sodium hydroxide (NaOH) as an activating agent is less referenced in the literature, although it offers some advantages over KOH in terms of low cost, less corrosiveness, and simple handling procedure, all of which are appealing particularly from an industrial viewpoint. The motivation for this present study is to fabricate porous carbon spheres in a sustainable manner via a spray drying approach followed by a carbonization process, using Kraft lignin as the carbon precursor and NaOH as an alternative activation agent instead of the high-cost and high-corrosive KOH for the first time. The structure of carbon particles can be accurately transitioned from a compact to hollow structure, and the surface textural properties can be easily tuned by altering the NaOH concentration. The obtained porous carbon spheres were applied as highly packed thin film electrode materials for supercapacitor devices. The specific capacitance value of porous carbon spheres with a highly compact structure (high packing density) is 66.5 F g^-1, which is higher than that of commercial activated carbon and other biomass-derived carbon. This work provides a green processing for producing low-cost and environment-friendly porous carbon spheres from abundant Kraft lignin and important insight for selecting NaOH as an activator to tailor the morphology and structure, which represents an economical and sustainable approach for energy storage devices.

Correction: Solid-state nitrogen-doped carbon nanoparticles with tunable emission prepared by a microwave-assisted method

Correction for ‘Solid-state nitrogen-doped carbon nanoparticles with tunable emission prepared by a microwave-assisted method’ by Fitri Aulia Permatasari et al., RSC Adv., 2021, 11, 39917–39923, DOI: 10.1039/D1RA07290K.

Revealing the synergetic interaction between amino and carbonyl functional groups and their effect on the electronic and optical properties of carbon dots

Nitrogen and oxygen-based functionalized carbon dots (CDs) surfaces have attracted significant attention due to their ability to tailor the optical and electronic properties of CDs.

Insights into the intermolecular interactions and temperature-concentration dependence of transport in ionic liquid-based EMI–TFSI/LiTFSI electrolytes

DFT calculations and MD simulations show that the EMI–TFSI/LiTFSI system is stabilized by strong nonbonded attractions, and the lithium-ion conductivity depends on the LiTFSI concentration and system temperature.

Vertically Aligned n-Type Silicon Nanowire Array as a Free-Standing Anode for Lithium-Ion Batteries

Due to its high theoretical specific capacity, a silicon anode is one of the candidates for realizing high energy density lithium-ion batteries (LIBs). However, problems related to bulk silicon (e.g., low intrinsic conductivity and massive volume expansion) limit the performance of silicon anodes. In this work, to improve the performance of silicon anodes, a vertically aligned n-type silicon nanowire array (n-SiNW) was fabricated using a well-controlled, top-down nano-machining technique by combining photolithography and inductively coupled plasma reactive ion etching (ICP-RIE) at a cryogenic temperature. The array of nanowires ~1 µm in diameter and with the aspect ratio of ~10 was successfully prepared from commercial n-type silicon wafer. The half-cell LIB with free-standing n-SiNW electrode exhibited an initial Coulombic efficiency of 91.1%, which was higher than the battery with a blank n-silicon wafer electrode (i.e., 67.5%). Upon 100 cycles of stability testing at 0.06 mA cm⁻², the battery with the n-SiNW electrode retained 85.9% of its 0.50 mAh cm⁻² capacity after the pre-lithiation step, whereas its counterpart, the blank n-silicon wafer electrode, only maintained 61.4% of 0.21 mAh cm⁻² capacity. Furthermore, 76.7% capacity retention can be obtained at a current density of 0.2 mA cm⁻², showing the potential of n-SiNW anodes for high current density applications. This work presents an alternative method for facile, high precision, and high throughput patterning on a wafer-scale to obtain a high aspect ratio n-SiNW, and its application in LIBs.

Role of Intrinsic Points Defects on the Electronic Structure of Metal-Insulator Transition h-FeS

Hexagonal iron sulfide (h-FeS) offers huge potential in the development of metal-insulator transition devices. A stoichiometric h-FeS is hard to obtain from its natural iron deficiency. The effect of this iron deficiency on the electronic properties is still obscure. Here, we performed a charged point defect calculation in h-FeS. We found that the most favorable point defect in h-FeS can be tuned with a proper synthesis environment. The single iron vacancy could induce a midgap state with 0.05 eV energy gap, which explains the h-FeS low experimental band gap value. Furthermore, a semiconductor-to-metal transition is observed in h-FeS with higher iron vacancy concentration showing better conductivity from the excess charges. We also observe that iron vacancies will induce a magnetic moment on the antiferromagnetic h-FeS. The findings that the induced MIT behavior and magnetic moment can be tuned by defect concentration may benefit the development of spintronics devices.

Recent advances and rational design strategies of carbon dots towards highly efficient solar evaporation

Solar evaporation using photothermal materials is an environmentally friendly and feasible solution to overcome the water scarcity issue by utilizing the abundant solar energy source. Some key points for efficient solar-to-thermal energy conversion have been extensively studied. Among them, the advancement of solar absorber materials has emerged as an attractive research topic, owing to their potential to enhance the efficiency of solar to thermal conversion significantly. Recently, carbon dots (CDs) have attracted great interest for their applications in this field. CDs have many desirable properties, such as broad light absorption (200-800 nm), high photothermal conversion efficiency (more than 90%), tunable structure and surface functionalization, easy to produce and abundant raw materials that meet the requirements for this application. In this review, the integration of CDs into solar evaporation systems and recent advances in CD-based solar absorbers will be summarized and discussed. Before that, brief knowledge of carbon-based solar thermal evaporation, including its mechanism and strategies to improve the efficiency, is provided, followed by CDs' synthesis and tunable properties that can be optimized for this application. Finally, the challenges and perspectives of research for CD-based solar evaporation are proposed, for example, optimizing solar absorbers by decorating hydroxyl-rich CDs in 2D or 3D structures.

Effect of H2SO4/H2O2 pre-treatment on electrochemical properties of exfoliated graphite prepared by an electro-exfoliation method

The effect of pre-treating graphite sheets in a H2SO4/H2O2 solution before electro-exfoliation is reported. It was revealed that the volume fraction of H2SO4 to H2O2 during pre-treatment could control the degree of exfoliation of the resulting exfoliated graphite (EG). X-ray diffraction (XRD), Raman, and Fourier transform infrared (FTIR) spectroscopy analyses have suggested that EG produced by first pre-treating the graphite sheet in H2SO4/H2O2 solution with the H2SO4 : H2O2 volume fraction of 95 : 5 demonstrates the highest exfoliation degree. This sample also demonstrated excellent electrochemical properties with good electrical conductivity (36.22 S cm-1) and relatively low charge transfer resistance (R ct) of 21.35 Ω. This sample also showed the highest specific capacitance of all samples, i.e., 71.95 F g-1 at 1 mV s-1 when measured at a voltage range of -0.9 to 0 V. Further measurement at an extended potential window down to -1.4 V revealed the superior specific capacitance value of 150.69 F g-1. The superior morphology characteristics and the excellent electrical properties of the obtained EG are several reasons behind its exceptional properties. The pre-treatment of graphite sheets in H2SO4/H2O2 solution allegedly leads to easier and faster exfoliation. The faster exfoliation is allegedly able to prevent massive oxidation, which frequently induces the formation of graphite/graphene oxide (GO) in a prolonged process. However, too large H2O2 volume fraction involved during pre-treatment seems to cause excessive expansion and frail structure of the graphite sheets, which leads to an early breakdown of the structure during electrochemical exfoliation and prohibits layer by layer exfoliation.

The Influence of Surface Charge on the Antiviral Effect of Curcumin Loaded in Nanocarrier System

BACKGROUND

Curcumin is a well-documented bioactive compound present in Curcuma sp., a tropical, medicinal plant. This substance exhibits broad-spectrum biological activities, including antivirus. Despite the lack of pharmaceutical properties of curcumin limits its clinical use.

OBJECTIVE

This study aims to produce curcumin nanoemulsion with different surface charge (curcumin (+) nanoemulsion and curcumin (-) nanoemulsion) and to evaluate its physical characteristics, in vitro cell cytotoxicity, and antiviral activity against dengue virus (DENV) 1 and 2.

METHODS

Two forms of nanoemulsion were prepared, which were differed from their surface charge through spontaneous procedure resulting in similar characteristics except for the zeta potential value. Cytotoxicity was determined using the RT-PCR method in the A549 cell line, and anti- DENV properties were determined by calculation of inhibitory concentration 50 (IC₅₀) value.

RESULTS

The positive charge of curcumin-loaded nanoemulsion showed a better effect in reducing the viral replication represented by a lower IC₅₀ value. In addition, DENV-1 was more sensitive and responsive to curcumin as compared to DENV-2.

CONCLUSION

Positive surface charge of curcumin-loaded nanoemulsion improves the antiviral effect of the curcumin, suggesting a promising approach for alternative treatment for dengue virus infection.

Rapid growth of the CH3NH3PbCl3 single crystal by microwave irradiation

We report a rapid growth of the CH3NH3PbCl3 single crystal through microwave irradiation. A systematic evaluation of the structural and optical properties of the obtained single crystal was also conducted. 1 minute is the optimum microwave irradiation time that generated a large single crystal of dimension (5 × 5 × 2.5) mm3. The obtained crystal exhibits broad absorption in UV range and near-visible light luminescence under UV excitation with an optical bandgap around 2.8 eV. A fast and simple synthesis method of CH3NH3PbCl3 single crystal with these outstanding properties could be potentially applied for any optoelectronic application with scale-up production.

Carbon-Based Quantum Dots for Supercapacitors: Recent Advances and Future Challenges

Carbon-based Quantum dots (C-QDs) are carbon-based materials that experience the quantum confinement effect, which results in superior optoelectronic properties. In recent years, C-QDs have attracted attention significantly and have shown great application potential as a high-performance supercapacitor device. C-QDs (either as a bare electrode or composite) give a new way to boost supercapacitor performances in higher specific capacitance, high energy density, and good durability. This review comprehensively summarizes the up-to-date progress in C-QD applications either in a bare condition or as a composite with other materials for supercapacitors. The current state of the three distinct C-QD families used for supercapacitors including carbon quantum dots, carbon dots, and graphene quantum dots is highlighted. Two main properties of C-QDs (structural and electrical properties) are presented and analyzed, with a focus on the contribution to supercapacitor performances. Finally, we discuss and outline the remaining major challenges and future perspectives for this growing field with the hope of stimulating further research progress.

Solid-state nitrogen-doped carbon nanoparticles with tunable emission prepared by a microwave-assisted method

Tunable emissive solid-state carbon nanoparticles (CNPs) have been successfully synthesized by a facile synthesis through microwave irradiation. Modulating microwave interaction with the sample to generate abrupt localized heating is a long-term challenge to tailor the photoluminescence properties of CNPs. This study systematically revealed that the sample temperature through microwave irradiation plays a crucial role in controlling the photoluminescence properties over other reaction conditions, such as irradiation time and microwave duty cycle. When the sample temperature reached 155 °C in less than three minutes, the CNP sample exhibited a green-yellowish emission with the highest quantum yield (QY) of 14.6%. Time-dependent density functional theory (TD-DFT) study revealed that the tunable photoluminescence properties of the CNPs can possibly be ascribed to their nitrogen concentrations, which were dictated by the sample temperature during irradiation. This study opens up a promising route for the well-controlled synthesis of luminescent CNPs through microwave irradiation.

Tunable emissive solid-state carbon nanoparticles (CNPs) have been successfully synthesized by a facile synthesis through microwave irradiation.

Atomic and molecular adsorption on single platinum atom at the graphene edge: A density functional theory study

We present a density functional theory study of atomic and molecular adsorption on a single Pt atom deposited at the edges of graphene. We investigate geometric and electronic structures of atoms (H, C, N, and O) and molecules (O₂, CO, OH, NO, H₂O, and OOH) on a variety of Pt deposited graphene edges and compare the adsorption states with those on a Pt(111) surface and on a Pt single atom. Furthermore, using the calculated adsorption energy and simple kinetic models, the catalytic activities of a Pt single-atom catalyst for the oxygen reduction reaction and CO oxidation are discussed.

Electrospun nanofiber from various source of expanded polystyrene (EPS) waste and their characterization as potential air filter media

This paper reported on the fabrication of nanofibrous membranes from various sources of expanded polystyrene (EPS) waste using electrospinning technique and their application as air filter media. The filter membranes were made from four EPS waste sources, i.e. food packaging, EPS craft, instant noodle cup, and electronic packaging. The properties of the membranes fabricated from those sources were compared to obtain the best EPS waste source for air filter application. To make the precursor solutions, those samples were dissolved in d-limonene:DMF with the concentration of 15, 20, and 25 wt%. The solid EPS density, solution viscosity, and surface tension were measured. The fiber diameter and morphology of nanofibers were characterized by scanning electron microscopy (SEM) for each EPS variation. The fabricated membrane properties (crystallinity, wettability, and mechanical strength) and filtration properties (pressure drop, PM_2.5 filtration efficiency, and quality factor) were fully characterized and analyzed. Homogeneous fiber diameter with various morphologies (beaded, wrinkled, and smooth fiber) were obtained from all samples with hydrophobic to super-hydrophobic surface (water contact angle ranging from 106 to 153°). Also, the EPS solid density affected the solution viscosity with the expression of η = 0.132 ρ^0.29, which then affected the fabricated membrane packing density, porosity, and mechanical properties. Overall, the experimental results showed that all EPS nanofiber filters had great potential as an air filter media. The EPS filter made from food packaging waste with the solution concentration of 15 wt% exhibited the highest efficiency and quality factor of 99.99% and 0.15 Pa^-1, respectively.

A superhydrophilic bilayer structure of a nylon 6 nanofiber/cellulose membrane and its characterization as potential water filtration media

A bilayer structure of a nylon 6 nanofibrous membrane on a cellulose membrane has been successfully developed for water filter application. The nylon 6 nanofibrous membrane was deposited on the cellulose membrane via the electrospinning technique. The bilayer membrane properties, including mechanical strength, wettability, porosity, and microfiltration performance (flux and rejection), were thoroughly investigated. The membrane properties were studied using nylon 6 nanofibrous membranes having various fiber diameters and membrane thicknesses, which were obtained by adjusting the solution concentration and spinning time. The measurement of solution parameters, i.e., viscosity, conductivity, and surface tension, showed a strong relationship between the solution concentration and these parameters, which later changed the fabricated fiber sizes. The FTIR spectra depicted complete solvent evaporation after the electrospinning process. Smaller nanofiber diameters could improve the mechanical strength of the membranes. The porosity test showed a strong relationship between the nanofiber diameter and the pore size and pore distribution of the membranes. The water contact angle measurement showed the significant influence of the cellulose membrane on increasing the hydrophilicity of the bilayer structure, which then improved the membrane flux. The particle rejection test, using PSL sizes of 308 and 450 nm, showed high rejection (above 98%) for all sample thickness variations. Overall, the bilayer structure of the nylon 6 nanofibers/cellulose membranes showed excellent and promising performance as water filter media.

The SEM image of (a) cellulose membrane and (b) the bilayer structure of a nylon 6 nanofibrous membrane on a cellulose membrane as water filter media.

Controlled morphology of electrospun nanofibers from waste expanded polystyrene for aerosol filtration

This paper reports on the recycling of expanded polystyrene (EPS) waste to be repurposed as EPS nanofibrous mats for air filtration applications. The EPS nanofibrous mats were prepared via electrospinning technique. The EPS solutions for producing the mats were made by dissolving the EPS waste in dimethylformamide (DMF) and d-limonene solvents. The mixing ratio of DMF and d-limonene solvents were varied to obtain EPS solutions with different surface tension and viscosity. As a result, different fiber morphology (smooth fiber, wrinkled fiber, and beaded fiber) and diameter ranging from 314 nm to 3506 nm were obtained. The synthesized EPS nanofibrous mats were characterized by scanning electron microscope, Fourier-transform infrared spectroscopy, x-ray diffraction spectroscopy, differential scanning calorimetry, mechanical strength, porosity, and water contact angle measurement apparatus. The mechanical strength measurement exhibited that the beaded fiber had the highest tensile strength and the lowest elasticity compared to wrinkled and smooth fiber. The water contact angle measurement showed that the EPS nanofibrous mats were classified as ultra-hydrophobic, which was a good criterion for air filter media. Some filtration parameters of the EPS nanofibrous mats were measured, including particle collecting efficiency, pressured drop, and quality factor. The particle collecting efficiency of each EPS nanofibrous mats was measured using monodisperse polystyrene latex (PSL) particles and PM_2.5 from burning incense as the test particles. The EPS nanofibrous mats had a high collecting efficiency (up to 99.99%) and had a low pressure drop (below 70 Pa) for the face velocity of 5.4 cm s^-1. The quality factor of the EPS nanofibrous mats reached 0.10 for PSL filtration and 0.16 for PM_2.5 filtration. Overall, the EPS nanofibrous mats with controlled morphology were suitable to be used as air filtration media with high mechanical strength, ultra-hydrophobic surface, and high quality factor.

The synthesis of nanofiber membranes from acrylonitrile butadiene styrene (ABS) waste using electrospinning for use as air filtration media

Acrylonitrile butadiene styrene (ABS) waste has been successfully recycled into nanofiber membranes by an electrospinning method for air filter applications. The ABS precursor solutions were made by dissolving the ABS waste in three different solvents, DMAc, DMF, and THF, with various concentrations of 10, 20, and 30 wt%. The solvent and solution concentrations affected the fiber properties (size and morphology) and membrane properties (wettability, crystallinity, and mechanical). Accordingly, we tested the fabricated membranes using SEM, FTIR, XRD, water contact angle, and tensile strength test measurements. The SEM images depicted three different morphologies, i.e. beads, beaded fibers, and pure fibers. The FTIR spectra showed that the solvents completely evaporated during the electrospinning process. The water contact angle test exhibited the hydrophobic properties of all the membrane samples. The XRD spectra showed the amorphous structures of all the membranes. The tensile strength test showed that the membranes fabricated using DMF and DMAc solvents had the best mechanical properties. Considering the fiber size, wettability, and mechanical properties, the membranes fabricated using DMAc and DMF solvents had the best criteria as air filter media. Filtration tests on the membranes fabricated using DMAc and DMF solvents with various solution concentrations depicted that the beads affected the membrane pressure drop and efficiency. The beads gave more space among the fibers, which facilitated the air flow through the membrane. The beads greatly reduced the pressure drop without an overly reduced membrane filtration efficiency. This led to a high-quality factor of the membranes that demonstrated their applicability as potential air filter media.

Optimization of surface passivation parameters in [147Pm]-Si planar p-n junction betavoltaic based on analytical 1-D minority carrier diffusion equation approaches

Recombination of the carrier due to the surface state level traps could affect betavoltaic performance. Herein, we employed a theoretical 1-D carrier transport calculation to investigate the surface passivation effect in a planar [¹⁴⁷Pm]-Si p-n junction betavoltaic cell and the results were verified using previous studies. In comparison to the ideal condition of the passivated surface, we predict a 10.74% power loss at the device, thus further research concerning the surface passivation layer for betavoltaic batteries might be necessary.

Biodegradable Polymer-Coated Multifunctional Graphene Quantum Dots for Light-Triggered Synergetic Therapy of Pancreatic Cancer

In this work, we reported the synthesis of an engineered novel nanocarrier composed of biodegradable charged polyester vectors (BCPVs) and graphene quantum dots (GQDs) for pancreatic cancer (MiaPaCa-2 cells) therapy applications. Such a nanocarrier was utilized to co-load doxorubicin (DOX) and small interfering ribonucleic acid (siRNA), resulting in the formation of GQD/DOX/BCPV/siRNA nanocomplexes. The resulting nanocomplexes have demonstrated high stability in physiologically mimicking media, excellent K-ras downregulation activity, and effective bioactivity inhibition for MiaPaCa-2 cells. More importantly, laser light was used to generate heat for the nanocomplexes via the photothermal effect to damage the cells, which was further employed to trigger the release of payloads from the nanocomplexes. Such triggered release function greatly enhanced the anticancer activity of the nanocomplexes. Preliminary colony formation study also suggested that GQD/DOX/BCPV/siRNA nanocomplexes are qualified carrier candidates in subsequent in vivo tests.

Simultaneous ultraviolet and first near-infrared window absorption of luminescent carbon dots/PVA composite film

Liquid Carbon Dots (CDs) were successfully synthesized by hydrothermal method using urea and citric acid as raw materials. TEM images confirmed that the CDs have a spherical shape with a homogeneous distribution. The as-prepared liquid CDs could absorb ultraviolet (UV) and first near infra-red (NIR) window simultaneously. However, the photoluminescence (PL) of the liquid CDs was damaged by their quenching effect. To overcome this issue, the liquid CDs were dispersed in poly(vinyl) alcohol (PVA) to fabricate the composite film. Herein, the dual-peak absorption properties of the CDs/PVA composite films were investigated for the first time. The composite films could maintain the simultaneous UV and first NIR window absorption property even after being preheated up to 200 °C, implying that the structure of CDs was well retained during the transition from the liquid to films. Daylight treatment for seven days produced minimum changes in the UV-vis and PL spectra, which indicates that the CDs/PVA film has more stable optical properties than the liquid CDs.

The simultaneous UV and first NIR absorption of the CDs/PVA composite could be maintained up to 200 °C, with minimum PL changes.

Electrochemical properties of TiOx/rGO composite as an electrode for supercapacitors

This work investigated the electrochemical characteristics of TiO_x and its composite with reduced graphene oxide.

The influence of copper addition on the electrical conductivity and charge transfer resistance of reduced graphene oxide (rGO)

The possible explanations on how the existence of copper, CuO, or Cu₂O influences the electrical conductivity and electrochemical properties of rGO.

Highly conductive nano-sized Magnéli phases titanium oxide (TiOx)

Despite the strong recent revival of Magnéli phase TiO_x as a promising conductive material, synthesis of Magnéli phase TiO_x nanoparticles has been a challenge because of the heavy sintering nature of TiO₂ at elevated temperatures. We have successfully synthesized chain-structured Magnéli phases TiO_x with diameters under 30 nm using a thermal-induced plasma process. The synthesized nanoparticles consisted of a mixture of several Magnéli phases. A post-synthesis heat-treatment was performed to reduce the electrical resistivity without changing the particle morphology. The resistivity of the heat-treated particle was as low as 0.04 Ω.cm, with a specific surface area of 52.9 m² g⁻¹. The effects of heat-treatment on changes in the crystal structure and their correlation with the electron conductivity are discussed based on transmission electron microscopy images, X-ray diffraction spectra, and X-ray adsorption fine structure spectra. Electrochemical characterization using cyclic voltammetry and potentiodynamic scan shows a remarkable electrochemical stability in a strongly oxidizing environment.

Functionalized carbon nanotube (CNT) membrane: progress and challenges

Various approaches have been investigated to functionalize CNT for achieving a high dispersion of CNT as well as high compatibility between CNT and polymer matrix which lead to improvement of membrane properties and performances.

A red emitting of manganese-doped boron carbon oxynitride (BCNO) phosphor materials: facile approach and photoluminescence properties

A bright red emission of manganese-doped BCNO (BCNO:Mn) phosphor was firstly synthesized by solid state method.

Microwave-assisted reduction method under nitrogen atmosphere for synthesis and electrical conductivity improvement of reduced graphene oxide (rGO)

A facile method to synthesize rGO using a microwave-assisted method under N₂-atmosphere conditions is reported.

Heat-treated Escherichia coli as a high-capacity biosorbent for tungsten anions

Adsorption performance in the biosorption of tungsten using Escherichia coli cells can be significantly improved by using cell suspensions that have been heat-treated at ⩽100°C. In the case of E. coli cells suspension heated at 100°C, the aqueous tungsten ions concentration rapidly decreased from 0.8mmol/L to practically zero within 1h. This biosorption time is much shorter than that of non-heat treated E. coli cells (7h). Furthermore, the adsorption saturation amount for cells heat-treated at 100°C was significantly increased up to 1.62mmol-W/g-E. coli compared to the unheated E. coli cells case (0.62mmol-W/g-E. coli). Determination of the surface potential and surface structure along with quantitative analyses of free amino acids of heat-treated E. coli cells were also carried out and revealed that heated cells have a high zeta potential and express a higher concentration of amino acids on the cell surface.

Role of C-N Configurations in the Photoluminescence of Graphene Quantum Dots Synthesized by a Hydrothermal Route

Graphene quantum dots (GQDs) containing N atoms were successfully synthesized using a facile, inexpensive, and environmentally friendly hydrothermal reaction of urea and citric acid, and the effect of the GQDs' C-N configurations on their photoluminescence (PL) properties were investigated. High-resolution transmission electron microscopy (HR-TEM) images confirmed that the dots were spherical, with an average diameter of 2.17 nm. X-ray photoelectron spectroscopy (XPS) analysis indicated that the C-N configurations of the GQDs substantially affected their PL intensity. Increased PL intensity was obtained in areas with greater percentages of pyridinic-N and lower percentages of pyrrolic-N. This enhanced PL was attributed to delocalized π electrons from pyridinic-N contributing to the C system of the GQDs. On the basis of energy electron loss spectroscopy (EELS) and UV-Vis spectroscopy analyses, we propose a PL mechanism for hydrothermally synthesized GQDs.