Portable multimodal platform with carbon nano-onions as colorimetric and fluorescent signal output for trypsin detection.

Multimodal biosensors with independent signaling pathways can self-calibrate and improve the reliability of disease biomarker detection. Herein, a colorimetric-fluorescent dual-mode paper-based biosensor with PAN/Fe(III)-CNOs (FPCs) as core components has been developed, which information is recognized by smartphone and naked eye. Using 1-(2-pyridylazo)-2-naphthol (PAN) as a mediator, Fe(III) is enriched on the surface of carbon nano-onions (CNOs), endowing FPCs with excellent mimetic enzyme activity and photothermal conversion ability, which allows it to output amplified colorimetric signals under laser irradiation. In addition, the complexation of PAN with Fe(III) broadens its absorption spectrum, which makes FPCs more suitable to be energy acceptors to quench fluorescence of polymer dots (Pdots), resulting in the changes of output fluorescent signal. Based on the above design, a portable colorimetric-fluorescent dual-mode biosensor is proposed for trypsin detection with Pdots as fluorescence sources and FPCs as fluorescence quenchers and nanoenzymes. This work provides a convenient way for constructing portable visual multimodal biosensors, which is expected to applied in various disease diagnosis.

Electrochemical sensor based on mesoporous g-C3N4/N-CNO/gold nanoparticles for measuring oxycodone.

Oxycodone, often used as an analgesic, is a potent opioid. While its effectiveness has been proven in the control of moderate to acute pain, excessive use of oxycodone imposes heart failure, heart palpitations, reduction of red blood cells, bone pain, and even death. Therefore, monitoring the oxycodone concentration in blood is vital for emergency care. For this purpose, a novel electrochemical sensor was designed based on a glassy carbon electrode modified with mesoporous g-C3N4 (M-C3N4), carbon nano-onions doped with nitrogen (N-CNO), and gold nanoparticles. At first, the SEM and XRD techniques were employed to characterize prepared M-C3N4 and N-CNO samples. The electro-oxidation behavior of the oxycodone was evaluated by cyclic and differential pulse voltammetric methods. Based on the influence of the potential scanning rate and solution pH on the voltammetric response of oxycodone oxidation, a redox mechanism was proposed. A 16 nM detection limit was acquired for the oxycodone analysis with a linear response in the 0.05-150 µM range. This sensor showed a remarkable ability for oxycodone detection in plasma samples. The long-term stability, superior selectivity, and reproducibility of this sensor prove its ability to measure oxycodone accurately and precisely in authentic spices.

Strategic Way of Synthesizing Heteroatom-Doped Carbon Nano-onions Using Waste Chicken Fat Oil for Energy Storage Devices.

An easy way of synthesizing low-cost carbon nanomaterials without the need for high-temperature processing approach is critical for energy storage applications because the demand has increased for affordable, long-term, and environmentally friendly synthesized carbon-based materials. Herein, we synthesized multilayered graphitic carbon nano-onions (CNOs) using an oil-wick flame pyrolysis approach, employing biowaste (chicken fat) oil as a cost-effective precursor. The prepared CNOs can provide enhanced ion movement and less resistance for electron transport by interconnecting CNO particles with one another. Furthermore, heteroatom (S,N)-doped CNOs (h-CNOs) were synthesized to optimize the hydrophilic and conductive properties of carbon materials, which eventually exalted the capacitive charge transfer kinetics. The h-CNOs demonstrated superior, highest specific capacitance of 261 F/g, while the undoped CNOs showed a capacitance of 180.6 F/g at a current density of 1 A/g. In addition to capacitance, the h-CNOs also demonstrated a rate capability of 69% and a good cycling stability of 97.5% under high current densities. An asymmetric supercapacitor was fabricated using the h-CNOs as the negative and MnCo2S4 (MCS) as the positive electrode. The device showed high energy and power performance of 32.8 Wh/kg and 7350 W/kg, respectively, with a capacitance retention of 97% over 5000 cycles. Considering the facile strategic way to produce novel carbonaceous materials derived from biowaste oil (chicken fat oil), this could be considered a potential advantage for commercial energy storage devices and may open the door to producing inexpensive, industrially revolutionizing energy storage devices.

Investigating the Potential of Ghee Precursor-Derived Carbon Nano Onions for Enhancing Interfacial Bonding in Thermoplastic Composites.

In this study, we employed a straightforward flame synthesis process to produce carbon soot containing carbon nano onions (CNOs) using easily accessible ghee oil as a precursor. The ghee oil, with a molecular composition rich in more than 50 carbon atoms, served as an effective source for generating CNOs. The synthesized CNO particles underwent comprehensive characterization through high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analyses, providing a detailed account of their physicochemical properties. In addition, we explored the direct deposition of CNOs on carbon fiber (CF) surfaces for 5 and 10 min via a soot deposition process. The resulting freeze-fracture images obtained from scanning electron microscope (SEM) offered insights into the morphology of the CNO-deposited CF. Our study aims to shed light on the potential applications of CNOs, focusing on their characterization and the possible benefits they may offer in diverse fields, including but not limited to enhancing interfacial bonding in thermoplastic composites.

Enhancing pancreatic ductal adenocarcinoma (PDAC) therapy with targeted carbon nano-onion (CNO)-mediated delivery of gemcitabine (GEM)-derived prodrugs.

Nanotechnology's potential in revolutionising cancer treatments is evident in targeted drug delivery systems (DDSs) engineered to optimise therapeutic efficacy and minimise toxicity. This study examines a novel nanocarrier constructed with carbon nano-onions (CNOs), engineered and evaluated for its ability to selectively target cancer cells overexpressing the hyaluronic acid receptor; CD44. Our results highlighted that the CNO-based nanocarrier coupled with hyaluronic acid as the targeting agent demonstrated effective uptake by CD44+ PANC-1 and MIA PaCa-2 cells, while avoiding CD44- Capan-1 cells. The CNO-based nanocarrier also exhibited excellent biocompatibility in all tested pancreatic ductal adenocarcinoma (PDAC) cells, as well as healthy cells. Notably, the CNO-based nanocarrier was successfully loaded with chemotherapeutic 4-(N)-acyl- sidechain-containing prodrugs derived from gemcitabine (GEM). These prodrugs alone exhibited remarkable efficacy in killing PDAC cells which are known to be GEM resistant, and their efficacy was amplified when combined with the CNO-based nanocarrier, particularly in targeting GEM-resistant CD44+ PDAC cells. These findings demonstrate the potential of CNOs as promising scaffolds in advancing targeted DDSs, signifying the translational potential of carbon nanoparticles for cancer therapy.

Self-Catalyzed Hydrogenated Carbon Nano-Onions Facilitates Mild Synthesis of Transparent Nano-Polycrystalline Diamond.

Transparent nano-polycrystalline diamond (t-NPD) possesses superior mechanical properties compared to single and traditional polycrystalline diamonds. However, the harsh synthetic conditions significantly limit its synthesis and applications. In this study, a synthesis routine is presented for t-NPD under low pressure and low temperature conditions, 10 GPa, 1600 °C and 15 GPa, 1350 °C similar with the synthesis condition of organic precursor. Self-catalyzed hydrogenated carbon nano-onions (HCNOs) from the combustion of naphthalene enable synthesis under nearly industrial conditions, which are like organic precursor and much lower than that of graphite and other carbon allotropes. This is made possible thanks to the significant impact of hydrogen on the thermodynamics, as it chemically facilitates phase transition. Ubiquitous nanotwinned structures are observed throughout t-NPD due to the high concentration of puckered layers and stacking faults of HCNOs, which impart a Vickers hardness about 140 GPa. This high hardness and optical transparency can be attributed to the nanocrystalline grain size, thin intergranular films, absence of secondary phase and pore-free features. The facile and industrial-scale synthesis of the HCNOs precursor, and mild synthesis conditions make t-NPD suitable for a wide range of potential applications.

Functionalized Carbon Nano-Onions as a Smart Drug Delivery System for the Poorly Soluble Drug Carmustine for the Management of Glioblastoma.

The drug delivery system for transporting anticancer agents to targeted tissues in the body is a challenging issue. In search of a suitable biocompatible carrier having controlled and sustained drug release properties of poorly soluble drugs, carbon nano-onions (CNOs) were loaded with an anticancer drug, bis-chloroethyl nitrosourea (BCNU/carmustine). CNOs being autofluorescent, drug-loaded functionalized CNOs (f-CNO-BCNU) can be detected in vivo. Transmission electron microscopy (TEM) and differential light scattering (DLS) techniques were used to analyze the sizes of these f-CNOs. The molecular study revealed that the f-CNO-BCNU readily and noncovalently binds with the folate receptors present on the cancer cell surface in excess. Computer modeling and molecular dynamics simulation followed by binding free energy calculation shows f-CNOs have -29.9 kcal/mol binding free energy, and it noncovalently binds the receptor FRα using loop dynamics of three essential loops present in the protein along with polar stabilization interactions provided by Asp55 and Glu86 residues present in the active site. The f-CNO effectively decreased cancer cell viability with a low IC50 value (the concentration that led to 50% killing of the cells). The cell-based Franz diffusion assay was performed to study the drug release profile. The f-CNO-BCNUs also decreased the mitochondrial membrane potential of U87 cells, increased reactive oxygen species release, and caused a loss of mitochondrial membrane integrity. The f-CNOs also increased the percentage of apoptotic cells observed by the Annexin V assay. Based on observed results, it can be concluded that the f-CNO-BCNU efficiently targets the cancer cells, enhances the bioavailability of carmustine, and can be used as a smart chemotherapeutic agent. This strategy offers better patient compliance and greater bioavailability of the drug.

Sulphonated poly(ethersulfone)/carbon nano-onions-based nanocomposite membranes with high ion-conducting channels for salt removal via electrodialysis.

Herein, we are reporting the carbon nano onions (CNO)-based sulphonated poly(ethersulfone) (SPES) composite membranes by varying CNO content in SPES matrix for water desalination applications. CNOs were cost-effectively synthesized using flaxseed oil as a carbon source in an energy efficient flame pyrolysis process. The physico- and electrochemical properties of nanocomposite membranes were evaluated and compared to pristine SPES. Moreover, the chemical characterisation of composite membranes and CNOs were illustrated using techniques such as nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscope (FE-SEM), thermogravimetric analysis (TGA) and universal tensile machine (UTM). In the series of nanocomposite membranes, SPES-0.25 composite membrane displayed the highest water uptake (WU), ion exchange membrane (IEC) and ionic conductivity (IC) values that were enhanced by 9.25%, ~ 44.78% and ~ 6.10%, respectively, compared to pristine SPES membrane. The electrodialytic performance can be achieved maximum when membranes possess low power consumption (PC) and high energy efficiency (Ee). Therefore, the value of Ee and Pc for SPES-0.25 membrane has been determined to be 99.01 ± 0.97% and 0.92 ± 0.01 kWh kg-1, which are 1.12 and 1.11 times higher than the pristine SPES membrane. Hence, integrating CNO nanoparticles into the SPES matrix enhanced the ion-conducting channels.

Short-Term Intravenous Administration of Carbon Nano-Onions is Non-Toxic in Female Mice.

Background: A nanoscale drug carrier could have a variety of therapeutic and diagnostic uses provided that the carrier is biocompatible in vivo. Carbon nano-onions (CNOs) have shown promising results as a nanocarrier for drug delivery. However, the systemic effect of CNOs in rodents is unknown. Therefore, we investigated the toxicity of CNOs following intravenous administration in female BALB/c mice. Results: Single or repeated administration of oxi-CNOs (125, 250 or 500 µg) did not affect mouse behavior or organ weight and there was also no evidence of hepatotoxicity or nephrotoxicity. Histological examination of organ slices revealed a significant dose-dependent accumulation of CNO aggregates in the spleen, liver and lungs (p<0.05, ANOVA), with a trace amount of aggregates appearing in the kidneys. However, CNO aggregates in the liver did not affect CYP450 enzymes, as total hepatic CYP450 as well as CYP3A catalytic activity, as meased by erythromycin N-demethylation, and protein levels showed no significant changes between the treatment groups compared to vehicle control. CNOs also failed to act as competitive inhibitors of CYP3A in vitro in both mouse and human liver microsomes. Furthermore, CNOs did not cause oxidative stress, as indicated by the unchanged malondialdehyde levels and superoxide dismutase activity in liver microsomes and organ homogenates. Conclusion: This study provides the first evidence that short-term intravenous administration of oxi-CNOs is non-toxic to female mice and thus could be a promising novel and safe drug carrier.

Biomass-derived carbon nano-onions for the effective elimination of organic pollutants and oils from water.

Oil spillage and leakage of organic solvents have caused severe environmental and ecological damages. It is of great significance to develop a cost-efficient and green adsorbent material with high uptake efficiency to separate the oil-water mixture. In this work, biomass-derived CNOs were first time explored in the adsorption of organic pollutants and oils from water. Carbon nano-onions (CNOs) with hydrophobicity and oleophilicity were cost-effectively synthesized in an energy efficient flame pyrolysis process using flaxseed oil as a carbon source. The as-synthesized CNOs without any further surface modification have shown high adsorption efficiency in removing organic solvents and oils from the oil-water mixture. The CNOs could adsorb diverse organic solvents such as pyridine (36.81 mg g-1), dichloromethane (90.95 mg mg-1), aniline (76 mg mg-1), toluene (64 mg mg-1), chloroform (36.25 mg mg-1), methanol (49.25 mg mg-1), and ethanol (42.25 mg mg-1). The uptake capacity for petrol and diesel over CNOs was observed at 36.68 mg mg-1 and 58.1 mg mg-1, respectively. The adsorption of pyridine followed pseudo-second-order kinetics and Langmuir's isotherm model. Moreover, the adsorption efficiency of CNOs towards the remediation of pyridine was almost similar in real-water samples when tested in tap water, dam water, groundwater, and lake water. Similarly, the practical applicability for the separation of petrol and diesel was also verified in the real sample (sea water) and has been proven to be excellent. By simple evaporation, the recovered CNOs can be reused for more than 5 cycles. CNOs exhibit the promising potential to be used in practical applications for oil-polluted water treatment.

Sustainable carbon nano-onions as an adsorbent for the efficient removal of oxo-anions.

The increasing threats of oxo-anions in drinking water have posed a serious threat to human health, aquatic environment, ecology, and sustainability. Accordingly, developments of cost-effective and sustainable nanomaterials for water remediation are on top priority and highly sought in global research community. Carbon nano-onions (CNOs) are one of the emerging nanomaterials for water purification because of its unique morphology, surface reactivity, high density of surface-active sites, and microporous structure. Herein, flaxseed oil-derived CNOs are utilized as efficient adsorbent for the removal of toxic oxo-anions. Aside from the green and economic nature, CNOs provide high adsorption efficiency ~ 806.45 mg g-1 for the removal of [Formula: see text] (99.9%) from aqueous system at ambient temperature, neutral pH in 70 min. The adsorption of [Formula: see text] onto CNOs was well fitted in pseudo-second order kinetics and followed the Langmuir adsorption isotherm model. The adsorption process was determined to be exothermic and spontaneous from the resulting thermodynamic characteristics. Furthermore, the high hydrophobic nature of CNOs make it recycling simpler. The real-life applicability of CNOs towards [Formula: see text] removal was tested in tap water, river water, and dam water. With all these observed results, CNOs show promise for practical water remediation applications.

Self-Assembly of Soot Nanoparticles on the Surface of Resistively Heated Carbon Microtubes in Near-Hexagonal Arrays of Micropyramids.

Almost regular hexagonal arrays of microscopic pyramids consisting of soot nanoparticles are formed on the surface of graphitized hollow filaments, which are resistively heated to ∼1800-2400 °C under an Ar atmosphere containing trace amounts of oxygen (∼300 ppm). At higher temperatures (T > 2300 °C, approximately) the soot particles are represented mainly by multishell carbon nano-onions. The height and width of the pyramids are strongly dependent on the temperature of the resistive heating, diminishing from 5 to 10 µm at T ≈ 1800 °C to ∼1 µm at 2300-2400 °C. Quasi-hexagonal arrays of the micropyramids are organized in the convex "craters" on the surface of the microtubes, which grow with the time of the thermal treatment. The pyramids always point normally to the surface of the craters, except at the boundaries between the craters, where the normal direction is not well-defined. The pyramids are soft and can be easily destroyed by touching them but can be hardened by heating them under an oxygen-free atmosphere. The pyramids are observed only on the exterior surface of the microtubes, not on their inner surface. This suggests that the thermophoretic force generated by a strong temperature gradient near the external surface of the tubes may be the cause of the micropyramid formation. Electrostatic charging of the soot nanoparticles due to thermionic emission may also be relevant to this phenomenon. The micropyramids can function as field emission point sources, as demonstrated with the use of a micronanoprobing station, mounted in a scanning electron microscope.

A Metal Coordination-Based Supramolecular Elastomer with Shape Memory-Assisted Self-Healing Effect.

Rubber materials are widely used in aerospace, automotive, smart devices and artificial skin. It is significant to address the aging susceptibility of conventional vulcanized rubber and to impart it rapid self-healing performance for destructive crack damage. Herein, a novel supramolecular rubber elastomer is prepared by introducing metal coordination between carboxyl-terminated polybutadiene and polystyrene-vinylpyridine copolymer. Based on the metal coordination interaction, the elastomer exhibits shape memory and self-healing properties. Moreover, a rapid closure-repair process of destructive cracks is achieved by presetting temporary shapes. This shape memory-assisted self-repair model is shown to be an effective means for rapid repair of severe cracks. An approach to enhance the mechanical and self-healing properties of elastomer was demonstrated by adding appropriate amounts of oxidized carbon nano-onions (O-CNO) into the system. The tensile strength of the elastomer with an O-CNOs content of 0.5 wt% was restored to 83 ± 10% of the original sample after being repaired at 85 °C for 6 h. This study confirms that metal coordination interaction is an effective method for designing shape memory self-healing rubber elastomer. The shape memory-assisted self-healing effect provides a reference for the rapid self-repairing of severe cracks.

Supramolecular Functionalisation of B/N Co-Doped Carbon Nano-Onions for Novel Nanocarrier Systems.

Boron/nitrogen co-doped carbon nano-onions (BN-CNOs) are spherical nanoparticles that consist of multiple inter-nestled fullerene layers, giving them an onion-like internal structure. They have potential as nanocarriers due to their small size, aqueous dispersibility, and biocompatibility. The non-covalent attachment of a biocompatible polymer to BN-CNOs is a simple and effective method of creating a scaffold for a novel nanocarrier system as it allows for increased aqueous dispersibility whilst preventing the immune system from recognising the particle as a foreign object. The non-covalent approach also preserves the electronic and structural properties of the BN-CNOs. In this study, we attached a hyaluronic acid-phospholipid (HA-DMPE) conjugate polymer to the BN-CNO's surface to improve its hydrophilicity and provide targetability toward HA-receptor overexpressing cancer cells. To this end, various ratios of HA-DMPE to BN-CNOs were investigated. The resulting supramolecular systems were characterised via UV-Vis absorption and FTIR spectroscopy, dynamic light scattering, and zeta potential techniques. It was found that the HA-DMPE conjugate polymer was permanently wrapped around the BN-CNO nanoparticle surface. Moreover, the resulting BN-CNO/HA-DMPE supramolecular systems displayed enhanced aqueous solubility compared to unfunctionalised BN-CNOs, with excellent long-term stability observed in aqueous dispersions.

Carbon Nanomaterials (CNMs) and Enzymes: From Nanozymes to CNM-Enzyme Conjugates and Biodegradation.

Carbon nanomaterials (CNMs) and enzymes differ significantly in terms of their physico-chemical properties-their handling and characterization require very different specialized skills. Therefore, their combination is not trivial. Numerous studies exist at the interface between these two components-especially in the area of sensing-but also involving biofuel cells, biocatalysis, and even biomedical applications including innovative therapeutic approaches and theranostics. Finally, enzymes that are capable of biodegrading CNMs have been identified, and they may play an important role in controlling the environmental fate of these structures after their use. CNMs' widespread use has created more and more opportunities for their entry into the environment, and thus it becomes increasingly important to understand how to biodegrade them. In this concise review, we will cover the progress made in the last five years on this exciting topic, focusing on the applications, and concluding with future perspectives on research combining carbon nanomaterials and enzymes.

Co-doped In-Situ Engineered Carbon Nano-Onions Enabled High-Performance Supercapacitors.

The feasibility of achieving in situ sulfur (S) and nitrogen (N) co-doped carbon nano-onions (CNOs and SN-CNOs) via a simple flame-pyrolysis technique without using sophisticated high-vacuum annealing or expensive nanodiamond-based complex processes is demonstrated for the first time. The characteristic onion-like feature of 0.34 nm remained intact with a high degree of ordering and graphitization, even though the S and N heteroatoms were co-doped simultaneously. The in situ co-doped SN-CNO demonstrated high supercapacitor device performance with a high energy density of 25 Wh kg-1 at a maximum power density of 18 kW kg-1, maintaining 98% specific capacitance over 10,000 cycles at 10 A g-1. These are the highest achieved device performance values of a fullerene family electrode material to date.

Supramolecular Hydrogels from a Tripeptide and Carbon Nano-Onions for Biological Applications.

Nanocomposite hydrogels have attracted researchers' attention in recent years to achieve superior performances in a variety of materials applications. In this work, we describe the outcome of three different strategies to combine a self-assembling tripeptide and carbon nano-onions (CNOs), through covalent and non-covalent approaches, into supramolecular and nanostructured hydrogels. Importantly, the tripeptide coated the nano-onions and extended their aqueous dispersions' stability by several hours. Furthermore, CNOs could be loaded in the tripeptide hydrogels at the highest level ever reported for nanocarbons, indicating high compatibility between the components. The materials were formed in phosphate-buffered solutions, thus paving the way for biological applications, and were characterized by several spectroscopic, microscopic, thermogravimetric, and rheological techniques. In vitro experiments demonstrated excellent cytocompatibility.

Temperature-dependent synthesis of multi-walled carbon nanotubes and hydrogen from plastic waste over A-site-deficient perovskite La0.8Ni1-xCoxO3-δ.

Thermochemical conversion of plastic wastes into carbon nanotubes (CNTs) and hydrogen is a promising management option to eliminate their hazardous effect. The yields and morphologies of CNTs strongly depend on the catalyst design and reaction conditions. To boost the efficiency, tuning of bimetallic nanoparticles as catalyst is an effective approach. For that reason, A-site-deficient perovskite La0·8Ni1-xCoxO3-δ (LN1-xCx, x = 0.15, 0.5, 0.85) was developed and used as a catalyst precursor to achieve in situ formation of bimetallic Ni-Co nanoparticles. At an optimized Ni-to-Co ratio, the LN0.5C0.5 exhibited the highest yields of multi-walled CNTs, namely 840 and 853 mg/gcatalyst from high density polyethylene and polypropylene, respectively. This could be attributed to the higher catalytic capability of LN0.5C0.5 catalyst for the decomposition of hydrocarbons into hydrogen and carbon. In both cases, multi-walled CNTs had regular shapes when the reaction temperature was 700 °C. At higher reaction temperatures, the morphological changes of carbon products were observed from multi-walled CNTs to carbon nano-onions. The Raman spectra showed that compared with the commercial multi-walled CNTs, the as-prepared multi-walled CNTs had a lower degree of defects.

Effect of Sn Doping on Pd Electro-Catalysts for Enhanced Electro-Catalytic Activity towards Methanol and Ethanol Electro-Oxidation in Direct Alcohol Fuel Cells.

Carbon nano-onions (CNOs) were successfully synthesized by employing the flame pyrolysis (FP) method, using flaxseed oil as a carbon source. The alcohol reduction method was used to prepare Pd/CNOs and Pd-Sn/CNOs electro-catalysts, with ethylene glycol as the solvent and reduction agent. The metal-nanoparticles were supported on the CNO surface without adjusting the pH of the solution. High-resolution transmission electron microscopy (HRTEM) images reveal CNOs with concentric graphite ring morphology, and also PdSn nanoparticles supported on the CNOs. X-ray diffractometry (XRD) patterns confirm that CNOs are amorphous and show the characteristic diffraction peaks of Pd. There is a shifting of Pd diffraction peaks to lower angles upon the addition of Sn compared to Pd/CNOs. X-ray photoelectron spectroscopy (XPS) results also confirm the doping of Pd with Sn to form a PdSn alloy. Fourier transform infrared spectroscopy (FTIR) displays oxygen, hydroxyl, carboxyl, and carbonyl, which facilitates the dispersion of Pd and Sn nanoparticles. Raman spectrum displays two prominent peaks of carbonaceous materials which correspond to the D and G bands. The Pd-Sn/CNOs electro-catalyst demonstrates improved electro-oxidation of methanol and ethanol performance compared to Pd/CNOs and commercial Pd/C electro-catalysts under alkaline conditions.

Insight into the Multistate Emissive N, P-doped Carbon Nano-Onions: Emerging Visible-Light Absorption for Photocatalysis.

Carbon dots (CDs) have become one of the most emerging materials as an alternative solar light-induced photocatalyst in contrast to traditional metal-based systems. However, one of the major challenges is the lack of visible light absorption. Herein, we have fabricated unique N, P-co-doped CDs with a self-assembled onion-like layered structure by using a bottom-up facile synthesis technique from chitosan gel and phosphoric acid as molecular precursors. This typical layered structure of N, P-co-doped carbon nano onions (N, P-CNOs), with an average size of 25-50 nm, displays an enhanced visible light absorption. Detailed structural and elemental characterizations confirm the extensive aromatic domain with P-containing surface functionalities, while electrochemical study clarifies the lowering of band gaps as well as the creation of new electronic states in comparison to the pristine N-CDs. Furthermore, the intrinsic structural features are correlated with the underpinning photophysical processes by steady-state and time-resolved fluorescence spectroscopy. In addition, steady-state polarized emission and thermo-responsive PL properties have been carried out to unveil further the structure-property correlation of N, P-CNOs, and their comparative study with pristine N-CDs at the different excitation wavelengths. Finally, N, P-CNOs exhibit efficient visible-light-induced photocatalysis, and the detailed mechanistic study is carried out by trapping the photogenerated species in an aqueous medium. The prepared N, P-CNOs displayed an excellent visible-light photocatalytic performance over MB dye with a degradation efficiency of 75.8% within 120 min along with a degradation rate constant of ∼0.0109 min-1 . It is concluded that the easy to synthesize and low-cost N, P-CNOs with a unique morphology hold great potential for application in visible-light photocatalysis.