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Here, a unique heteroatom-doped spongy carbonaceous material from dwarf banana peel has been synthesized successfully using the one-step hydrothermal method. The discarded banana peel was reused as a carbon source for the formation of heteroatom-doped porous carbon. This biowaste-derived heteroatom-doped porous carbonaceous material (BH-PCM) has plenty of interconnected pores with an acceptable surface area of 213 m2 g−1. Thoroughly characterized BH-PCM has been used as electrode material for supercapacitor using a three-electrode system with an aqueous 1 M H2SO4 solution. The as-synthesized BH-PCM holds an excellent specific capacitance of 137 F g−1 at 0.5 A g−1 and an impressive rate performance with a capacitance enduring 51 F g−1 at 5.0 A g−1. After 10,000 galvanostatic charge–discharge cycles, an initial capacitance of 94% was maintained. To show the practical applicability of the BH-PCM, the symmetrical two-electrode cell was fabricated and delivered the gravimetric specific capacitances of 87 F g−1 at 1 A g−1. The excellent electrochemical performance of BH-PCM towards supercapacitor was due to their high surface area, reasonable heteroatom doping rate, and a suitable degree of graphitization. This study offers a green approach for the development of environmental-friendly potential carbon-based electrode, by converting biowaste to clean/green energy.

Spherical-shaped graphene oxide-embedded chitosan/gelatin hydrogel particles (CGGO) were prepared by using inverse suspension method from biopolymers chitosan and gelatin with graphene oxide for the adsorption of heavy metal ions (HM). The prepared CGGO particles were characterized by various physicochemical techniques such as field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy analysis, X-ray diffraction, and Fourier transform infrared spectrometry. HM-Pb(II), Cd(II), Hg(II), and Cr(III) adsorption experiments using CGGO showed 55% removal efficiency of Hg(II) in the single metal system. However, in the multiple metal ion system, all metal ions showed removal efficiency > 70%. This suggests that the prepared hydrogel particles can be effectively used for the removal of HM. The preparation method also paves the way for the large-scale production of hydrogel particles as HM adsorbents.

The iron-oxide nanoparticles (IONPs) filled multi-walled carbon nanotubes (IONP-MWCNTs hybrid) were directly synthesized via chemical vapour deposition method with acetylene as a carbon source. The bare IONPs were synthesized by hydrothermal method and the prepared bare IONPs were employed as a catalytic-support as well as a filling agent for the synthesis of IONP-MWCNTs hybrid at about 800 °C under atmospheric pressure. The synthesized IONP-MWCNTs hybrid was characterized by various physicochemical techniques including X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy and high-resolution transmission electron microscopy. The results demonstrate that the carbon nanotubes were successfully generated on the IONPs with the high yield because of unique carbon-iron metal interactions. An average diameter of synthesized IONPs and MWCNTs are around 9 and 50 nm, respectively. In addition, the HRTEM images and Raman spectrum confirms the obtained IONP-MWCNTs hybrid is well graphitic without major carbonaceous impurities. The electrochemical activity of the synthesized IONP-MWCNTs hybrid was performed in 2 M KOH using a three-electrode cell setup with a saturated Ag/AgCl as a reference electrode and a platinum plate as a counter-electrode by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy techniques. This electrode active material (IONP-MWCNTs hybrid) possess excellent supercapacitive behaviour and has excellent cyclic stability, even after 5000 cycles of charge-discharge at 4 A g−1 as current density. Thus, the synthesized IONP-MWCNTs hybrid will be a suitable as well as an economical electrode active material for high-performance supercapacitors.

Sulphur and nitrogen-rich carbon layers (S/N-CLs) have been derived successfully via a simple calcination for high energy applications including supercapacitor and electrocatalytic hydrogen evolution reaction (HER). The flexible working electrode was fabricated using thoroughly analyzed S/N-CLs composite as an active electrode energy material for supercapacitor and HER. The S/N-CLs composite shows a higher specific capacitance of 266 F g−1 at a current density of 0.5 A g−1 and a satisfied cycling stability with 84% capacitance retention even after 5000 cycles of galvanostatic charge-discharge. On the other hand, the synthesized S/N-CLs composite was used as an electrocatalyst for HER and it exhibits an excellent HER performance with an onset overpotential of −75 mV, and a Tafel slope of 73 mV dec−1 in 0.5 M H2SO4 aqueous electrolyte. Also, the S/N-CLs composite displayed good stability and strong durability. The high electrocatalytic activity and stability of S/N-CLs composite toward HER due to the active site of a compound which may originate from the heteroatom-functional groups including N and S in the carbon structure. Overall, the high-performance supercapacitors and enhancing HER based on heteroatom-doped carbon structures could be promising in replacing traditional supercapacitors for many electronic devices and electrocatalyst for HER.

Heteroatom functionalization on a graphene surface can endow the physical and structural properties of graphene. Here, a one-step in situ polymerization method was used for the noncovalent functionalization of a graphene surface with poly-N-vinyl-2-pyrrolidone (PNVP) and the exfoliation of graphite into graphene sheets. The obtained graphene/poly-N-vinyl pyrrolidone (GPNVP) composite was thoroughly characterized. The surface morphology of GPNVP was observed using field emission scanning electron microscopy and high-resolution transmission electron microscopy. Raman spectroscopy and X-ray diffraction studies were carried out to check for the exfoliation of graphite into graphene sheets. Thermogravimetric analysis was performed to calculate the amount of PNVP on the graphene surface in the GPNVP composite. The successful formation of the GPNVP composite and functionalization of the graphene surface was confirmed by various studies. The cyclic voltammetry measurement at different scan rates (5–500 mV/s) and electrochemical impedance spectroscopy study of the GPNVP composite were performed in the typical three-electrode system. The GPNVP composite has excellent rate capability with the capacitive property. This study demonstrates the one-pot preparation of exfoliation and functionalization of a graphene surface with the heterocyclic polymer PNVP, the resulting GPNVP composite will be an ideal candidate for various electrochemical applications.

Nitrogen-doped carbon dot decorated zinc oxide nanoparticles (N-CDs@ZnO composite) were successfully fabricated by an economical wet-impregnation method and used as a photocatalyst for the degradation of aqueous methylene blue (MB) dye under UV-light at room temperature. The chemical composition and morphological features of the prepared N-CDs@ZnO composite were characterized by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). The photodegradation capability of the N-CDs@ZnO composite was compared with that of bare ZnO nanoparticles, under identical experimental conditions. The results show that the N-CDs@ZnO composite exhibits notably higher photocatalytic activity (degradation efficiency over 99%, 60 min) compared to bare ZnO nanoparticles (75%, 60 min) towards the degradation of MB under UV-light irradiation. Besides, the degradation obeyed the pseudo-first-order kinetics model with a photocatalytic rate constant (k) of 0.0557 min-1, which was ∼2.3 times higher than that of bare ZnO nanoparticles (0.0240 min-1). The crucial roles of N-CDs in the enhancement of the photocatalytic activity of the N-CDs@ZnO composite arise because the N-CDs can efficiently absorb UV-light and trap electrons, thus hindering the recombination of the photo-generated electron-hole pairs and also suppressing the photocorrosion of the ZnO nanoparticles in the N-CDs@ZnO composite. The N-CDs@ZnO composite not only showed good photocatalytic activity but also had good stability since the photocatalytic activity did not significantly decrease after three cycling tests. The present study shows that the N-CDs@ZnO composite can be considered as an ideal photocatalyst in the field of dye degradation. Overall, the present approach obeys green chemistry principles with the simple construction of the N-CDs@ZnO composite and the composite holds promise for the development of efficient photocatalytic systems.

As an efficient photocatalytic titanium dioxide nanoparticles@nitrogen-doped carbon (TiO2 NPs@C) nanocomposite and bright fluorescent with good biocompatible nitrogen-doped carbon dots (N-CDs) were synthesized at once by an affordable hydrothermal method. Physicochemical properties of the synthesized materials were examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM) with energy dispersive X-ray (EDX) and elemental mapping analysis, high resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), ultraviolet–visible (UV–vis) spectroscopy and fluorescence spectroscopy. The photocatalytic efficiency of synthesized TiO2 NPs@C nanocomposite was evaluated in the degradation of methylene blue (MB) under UV-light irradiation. The degradation efficiency of TiO2 NPs@C nanocomposite is about 90% when extending the irradiation time to 40 min, the rate constant is 5 times higher than that of bare TiO2 NPs. The augmentation of photocatalytic activity of TiO2 NPs@C nanocomposite was attributed to the synergistic effect between TiO2 NPs and graphene-like carbon within the nanocomposite. The recycling studies were conducted and the photodegradation efficiency of TiO2 NPs@C nanocomposite did not show any significant changes up to three cycles, suggesting that the synthesized photocatalyst has good repeatability and the considerable stability. In addition, the carbon derived from a natural green source possesses the hydroxyl and nitrogen-containing functional groups on the surface which resulting TiO2 NPs @C nanocomposite with high photocatalytic activity. Also, the obtained N-CDs displays almost zero toxicity towards the Candida albicans cells even at high concentrations which can be utilized as a powerful in-vitro label-free fluorescent probe for live cell imaging. Based on their bright with stable fluorescence and cellular imaging with good biocompatibility, N-CDs would offer a great potential for a wide range of applications in the biomedical and clinical applications in the near future.

Hexagon-shaped composite made up of iron oxide nanoparticles@carbon (IONP@C-HIOP) was successfully synthesized at 185 °C by a simple hydrothermal method. All the analytical results confirmed the formation of IONP@C-HIOP with a uniform size without apparent aggregation. The IONP@C-HIOP composite exhibits excellent catalytic activity towards hydrogen evolution reaction (HER) with lowest onset-potential (−25 mVRHE) and Tafel slope (45 mV dec−1) in 0.5 M H2SO4 aqueous electrolyte. The high electrocatalytic performance of the composite towards HER attributes to the carbon decorated IONPs, providing a conducting network for fast electron transport from IONPs to electrodes. The composite shows high stability representing a synergistic effect between IONPs and carbon for efficient HER. In addition, the supernatant solution (byproduct) of IONP@C-HIOP showed durable fluorescence activity and was used as a label-free fluorescent probe for live cell imaging applications. This method of synthesis is a simple and economic for multi-diverse applications. Thus, the main product of synthesized IONP@C-HIOP might be an ideal choice for environmental-friendly applications HER and the byproduct for cell imaging.

The present work illustrates the potential uses of nitrogen-doped multi-fluorescent carbon dots (N-CDs) for Fe3+ sensing, cellular multi-colour imaging, and fluorescent ink. N-CDs were synthesized using Magnolia liliiflora flower by the simple hydrothermal method. The resulted N-CDs was found to be nearly spherical in shape with the size of about 4 ± 1 nm and showed competitive quantum yield around 11%. The synthesized N-CDs with uniform size distribution and high content of nitrogen and oxygen-bearing functional groups exhibit excellent dispersibility in aqueous media. The N-CDs were able to detect a high concentration of Fe3+ ions (1–1000 μM) with a limit of detection is about 1.2 μM by forming N-CDs-Fe3+ complex due to the functional groups such as nitrogen, carbonyl and carboxyl on the surface of N-CDs. Thus they could be used to remove pollutants from industrial wastewater. The electronic charge on the surface of the N-CDs and N-CDs-Fe3+ complex (zeta potential) is around −36 and 18 mV, respectively. In addition, these N-CDs show excitation-dependent fluorescence that was utilized for multi-colour in vitro cellular imaging in rat liver cells (Clone 9 hepatocytes). The N-CDs are rapidly uptake in the cell cytoplasm and showed high cytocompatibility on cellular morphology. Moreover, as the N-CDs possess strong fluorescence and anti-coagulation they could be utilized in fluorescent ink pens.

Measurement of the interaction force between two materials provides important information on various properties, such as adsorption, binding, or compatibility for coatings, adhesion, and composites. The interaction forces of zwitterionic and ionic monomers with graphite platelets (G) and reduced graphene oxide (rGO) surfaces were systematically investigated by atomic force microscopy (AFM) in air and water. The monomers examined were 2-(methacryloyloxy)ethyl 2-(trimethylammonio)ethyl phosphate (MPC), [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBE), [2-(acryloyloxy)ethyl]trimethylammonium chloride (ATC), and 2-methyl-2-propene-1-sulfonic acid sodium (MSS). The AFM studies revealed that MSS and SBE monomers with sulfonate units have stronger interaction forces with G surface in air and that MPC and ATC monomers with quaternary ammonium units have higher interaction forces in water. In the case of rGO surface, the monomers with quaternary ammonium units showed stronger interactions regardless of the medium. These interactions could be rationalized by the interaction mechanism between the monomers with graphene surfaces, such as cation-π for MPC and ATC and anion-π for MSS and SBE. Overall, cation-π interactions were effective in water, whereas anion-π interactions are effective in air with G surface. The adhesion values of MPC, SBE, ATC, and MSS on rGO were lower than the values measured on G surface. Among the monomers, MPC showed the highest dispersibility for aqueous graphene dispersions. Further, the adsorption of MPC on G and rGO surfaces was verified by high-resolution transmission electron microscopy and X-ray diffraction patterns.

Cobalt oxide nanoparticles@nitrogen-doped reduced graphene oxide (Co3O4@N-rGO) composite and nitrogen-doped graphene dots (N-GDs) were synthesized by a one-pot simple hydrothermal method. The average sizes of the synthesized bare cobalt oxide nanoparticles (Co3O4 NPs) and Co3O4 NPs in the Co3O4@N-rGO composite were around 22 and 24 nm, respectively with an interlayer distance of 0.21 nm, as calculated using the XRD patterns. The Co3O4@N-rGO electrode exhibits superior capacitive performance with a high capability of about 450 F g−1 at a current density of 1 A g−1 and has excellent cyclic stability, even after 1000 cycles of GCD at a current density of 4 A g−1. The obtained N-GDs exhibited high sensitivity and selectivity towards Fe2+ and Fe3+, the limit of detection was as low as 1.1 and 1.0 μM, respectively, representing high sensitivity to Fe2+ and Fe3+. Besides, the N-GDs was applied for bio-imaging. We found that N-GDs were suitable candidates for differential staining applications in yeast cells with good cell permeability and localization with negligible cytotoxicity. Hence, N-GDs may find dual utility as probes for the detection of cellular pools of metal ions (Fe3+/Fe2+) and also for early detection of opportunistic yeast infections in biological samples.

The hybrid composite of ZnO nanoparticles decorated nitrogen-doped graphitic carbon sheets (ZnO@N-C) alongside nitrogen-doped carbon dots (N-CDs) were synthesized by the direct hydrothermal method of peach fruit juice and ZnO nanoparticles (ZnO NPs). The synthesized ZnO@N-C hybrid composite and N-CDs were thoroughly characterized by various physicochemical techniques including powder X-ray diffraction (PXRD), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM) with energy-dispersive X-ray (EDX) spectroscopy, high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, and fluorescence spectroscopy. The ZnO NPs were dispersed in the graphitic carbon structure with an average size of 25 ± 5 nm. The chemical composition of C, O, N, and Zn within the ZnO@N-C hybrid composite exhibits enough graphitization. Methylene blue (MB)-degradation was estimated utilizing the ZnO@N-C hybrid composite, a maximum degradation efficiency of >95% was achieved in a neutral aqueous medium within 60 min under UV-light irradiation. This maximum efficiency allows estimating the contribution of the heterogeneous and homogeneity of ZnO@N-C hybrid composite which is responsible for the MB-degradation. Moreover, the economic natural biosource or bio-waste was employed for the synthesis of ZnO@N-C hybrid composite and displays an excellent photocatalytic degradation under UV-light irradiation which is an alternate for other carbon-based metal oxides. In addition, the resulting N-CDs were utilized as a fluorescence probe for cellular imaging, owing to their tremendous properties such as bright fluorescence with high quantum yield, excellent water solubility, and good biocompatibility. The N-CDs displays a multicolour fluorescence based on their changing of excitation wavelength and these multicolour fluorescence emissions offered a multicolour cellular imaging which could be applicable for real biological system in the near future.

Anchoring electrocatalyst nanoparticles on carbon materials is a promising strategy to establish a hybrid electrocatalyst with unique structure and properties. Deriving carbon support from waste materials is an environmentally green approach. In the present study, the pyrolysis of the heterogeneous mixture containing synthetic disposal material and nickel salt yields N-doped carbon fibers-supported nickel oxide (NiO@CFs) hybrid electrocatalyst. The NiO nanoparticles are well incorporated on the porous carbon base, which has densely packed sharp-edge carbon fibers (CFs). The unique carbon structure incorporated with the NiO nanoparticles that facilitates the adsorption of electrolyte ions, rushes the transfer of electrolyte ions, and thus enhances the electrochemical activity. The as-derived carbon support maximized the electrocatalyst active sites while utilizing low electrocatalyst mass loading. Specifically, the synthetic disposable material-derived-carbon fibers supported NiO (NiO@CFs) hybrid electrocatalyst exhibited remarkably higher surface area and lower charge transfer resistance when compared to that of bare NiO. Intriguingly, the NiO@CFs hybrid electrocatalyst exhibited desirable oxygen evolution reaction (OER) performance (η = 280 mV at 10 mA cm−2) and consistent durability for a 24 h continuous run. This study emphasizes that the utilization of synthetic disposal materials for deriving carbon support is an environmentally effective methodology to incorporate/hybridize electrochemically active materials for the various electrochemical applications.

This article describes a comprehensive study for the preparation of graphene dispersions by liquid-phase exfoliation using amphiphilic diblock copolymers; poly(ethylene oxide)-block-poly(styrene) (PEO-b-PS), poly(ethylene oxide)-block-poly(4-vinylpyridine) (PEO-b-PVP), and poly(ethylene oxide)-block-poly(pyrenemethyl methacrylate) (PEO-b-PPy) with similar block lengths. Block copolymers were prepared from PEO using the Steglich coupling reaction followed by reversible addition-fragmentation chain transfer (RAFT) polymerization. Graphite platelets (G) and reduced graphene oxide (rGO) were used as graphene sources. The dispersion stability of graphene in ethanol was comparatively investigated by on-line turbidity, and the graphene concentration in the dispersions was determined gravimetrically. Our results revealed that the graphene dispersions with PEO-b-PVP were much more stable and included graphene with fewer defects than that with PEO-b-PS or PEO-b-PPy, as confirmed by turbidity and Raman analyses. Gravimetry confirmed that graphene concentrations up to 1.7 and 1.8mg/mL could be obtained from G and rGO dispersions, respectively, using PEO-b-PVP after one week. Distinctions in adhesion forces of PS, VP, PPy block units with graphene surface and the variation in solubility of the block copolymers in ethanol medium significantly affected the stability of the graphene dispersion.

Synthesis of an eco-friendly and efficient antibacterial and antifouling coatings is presented by exploiting urushiol, a natural varnishing material. Since urushiol has inherent outstanding surface-protecting and antimicrobial properties, a series of poly (methyl methacrylate)-urushiol polymer compositions were prepared and fabricated into films. The prepared films were subjected to antimicrobial and antifouling studies. The polymer systems were characterized by various physico-spectroscopic techniques such as 1H NMR, Fourier transform infrared spectroscopy, differential scanning calorimetry, atomic force microscopy, and thermal gravimetric analysis. The confocal laser scanning micrographs, obtained for Pseudomonas aeruginosa biofilm formation, demonstrated an excellent antimicrobial response of the urushiol-incorporated polymers against this bacterial strain. We also demonstrated an inhibitory attachment effect against Navicula incerta, a fouling microalgal strain.

Zinc oxide nanoparticles decorated graphene oxide (ZnO@GO) nanocomposite was successfully prepared using graphene oxide (GO) and zinc oxide nanoparticles (ZnO NPs) as raw materials by simple solvothermal method. The X-ray diffraction pattern, X-ray photoelectron spectroscopic, Fourier transform infrared spectroscopic, and Raman spectroscopic techniques revealed the formation, elemental composition and the purity of ZnO NPs and ZnO@GO nanocomposite. The ZnO NPs were synthesized via simple thermal oxidation, the synthesized ZnO NPs exhibits an excellent near spherical shape with narrow size distribution and mean size of around 20 ± 5 nm which is vividly observed from field emission scanning electron microscopic images. The elemental compositions of ZnO@GO nanocomposite which carbon, oxygen and zinc were revealed by XPS and EDX elemental mapping. The ZnO NPs decorated on GO layers were clearly seen in the high resolution transmission electron microscopic images. The photocatalytic activities of the synthesized pure ZnO NPs and ZnO@GO nanocomposite were investigated by photodegradation of azo-dyes includes neutral red (NR), crystal violet (CV), congo red (CR) and methyl orange (MO) under UV-light irradiation. The results revealed that the ZnO@GO nanocomposite exhibited a remarkably higher photocatalytic efficiency compared to pure ZnO NPs. The enhancement of photocatalytic performance was ascribed to the synergistic effect between ZnO NPs and GO layers. Hence, the synthesized ZnO@GO nanocomposite crucial for efficient degradation of dyes such as NR, CV, CR and MO. The synthesized ZnO@GO nanocomposite exhibits a good photocatalytic activity along with good reproducibility of photodegradation, which is applicable for practical applications.

Graphene oxide grafting titanium dioxide nanoparticles (TiO 2 -GO nanocomposite) was successfully synthesized by a simple solvothermal method. The synthesized TiO 2 -GO nanocomposite were systematically characterized by various physico-chemical techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The XRD results confirm the crystallinity of synthesized bare titanium dioxide nanoparticles (TiO 2 NPs), pristine graphene oxide (GO) and TiO 2 -GO nanocomposite with high pure in nature. The average size of the bare TiO 2 NPs was around 5 nm and were dispersed over the wrinkled graphene layers. Raman spectrum shows the resulting GO and TiO 2 -GO nanocomposite exhibit moderate graphitization with the intensity of D to G value was 1.1 and 1.2, respectively. The chemical state, functionality and composition (carbon, oxygen and titanium) of the resulting TiO 2 -GO nanocomposite were revealed by XPS analysis. The photocatalytic activity of synthesized TiO 2 -GO nanocomposite was investigated on the degradation of hazardous organic dyes (methylene blue (MB) and methyl orange (MO)) under UV-light irradiation and was compared with bare TiO 2 NPs and were presented based on the preferred propagation path of induced electrons that leads to generation of O 2 ─ . The resulting TiO 2 -GO nanocomposite achieve a maximum degradation efficiency of 100 and 84% on MB and MO in a neutral solution within 25 and 240 min, respectively under UV-light irradiation, the results show that the GO plays an important role in the enhancement of photocatalytic performance. The high photocatalytic efficiency due to the increased light absorption, the reduced charge recombination with the introduction of GO. Moreover, the simple and affordable solvothermal derived TiO 2 -GO nanocomposite exhibit rapid photocatalytic degradation on MB in 25 min of UV-light irradiation.

Banana peel is a common solid biowaste. This paper reports a sustainable synthesis of carbon quantum dots (CQDs) from banana peel waste by a simple hydrothermal method. The resulting CQDs have a narrow size distribution, and the average particle size was measured as 5 nm. The nitrogen-containing and oxygen-containing functionalities on/in the surface of carbon structure were observed in the resulting CQDs. CQDs emit intense blue fluorescence under the excitation of UV-light (365 nm) with a good quantum yield of 20% without any surface passivation chemicals. Besides, CQDs exhibit excellent water solubility and excitation-dependent emission performance. Furthermore, the banana peel waste-derived CQDs had almost no photobleaching under UV-light irradiation for a long-time, suggesting that they have high photostability. Since no chemical reagent was involved in the synthesis of CQDs, the synthesized CQDs were confirmed to have lower toxicity for nematodes even at a high concentration of 200 μg mL−1. Because of the intense fluorescence with excellent fluorescence stability and biocompatibility, CQDs can be used for bioimaging in nematodes. The CQDs efficiently stained into the whole body of the nematodes and brightly illuminated the multicolor by varying the excitation wavelength. Therefore, fluorescent CQDs would be a great potential candidate for bioimaging applications.

Hollow carbon nanospheres (HCNSs) supported on monodisperse iron oxide nanoparticles (IONPs) were synthesized by a carbonization route using sucrose as the carbon precursor. The resulting product of the obtained HCNSs possessed a narrow size distribution of 15 nm and an interlayer distance of 0.35 nm. The intensity of the D to G value was less than 1, which confirms the obtained HCNSs with graphitization. This study is expected to pave the way for the application of HCNSs in nanoelectronics.

Hydrophilic nitrogen-doped carbon dots (HN-CDs) were produced by a simple hydrothermal method from biowaste, dwarf banana peel. XRD, Raman spectroscopy, and HRTEM analyses confirmed the graphitic structure and narrow size distribution of the HN-CDs. Nitrogen-doping to the carbon structure/framework and owing rich hydrophilic groups on HN-CDs surface were confirmed by XPS and ATR-FTIR spectroscopy techniques. HN-CDs emitted strong and tunable fluorescence (FL) and possessed a good quantum yield (23%). Thus this novel HN-CDs applied as a nanoprobe for the detection of metal ion (Fe3+ ion) in aqueous solution by the fluorometric method. Excessive or lesser amounts of Fe3+ ion in human bodies lead to diverse diseases. Additionally, the accumulation of Fe3+ ion in the environment will escort to a great threat. The prepared HN-CDs selectively and sensitively detect Fe3+ ions by the FL quenching of HN-CDs with a limit of detection of 0.66 μM in the range of 5–25 μM. Further, the HN-CDs employed as a biocompatible probe for the multicolor bioimaging in rat liver cells. Also, HN-CDs used as fluorescent ink for drawing and writing. Thus, the biowaste/biomass successfully turned to a useful nanoprobe for environmental protection and health care.

In this study, we propose a dye–monomer interaction force measurement technique based on atomic force microscopy (AFM) to predict the performance of polymeric dispersants. Cantilevers modified with functional monomers such as styrene, N-butyl acrylate (BA), and 2-(N-phthalimido)ethyl methacrylate (PEMA) were used to characterize the interaction force between these functional monomers and a target dye (Disperse Blue 359). The interaction forces of each monomer—styrene, BA, and PEMA—with Disperse Blue 359 were measured as 10.75 nN, 7.06 nN, and 21.31 nN, respectively, and their trend was consistent with dipole-moment values obtained from density function theory (DFT) calculations (μ(styrene) = 0.0001, μ(PEMA) = 2.3158, μ(Disperse Blue 359) = 3.0368). We synthesized a series of model polymers containing specific functional monomers (CoPS10, CoBA, CoPPEMAs) with similar molecular weights, molecular-weight distributions, and acid contents and compared their actual performance with that predicted from interaction force measurement data. The results were well correlated with the interaction force measurement data. The effect of the PEMA content on dye dispersion stability was also investigated; the results indicated that both the PEMA content and the type of dye-interacting group greatly influenced the characteristics of the dispersion.

In this work, an ultra-sensing photoelectrochemical (PEC) glucose biosensor has been constructed from the bio-derived nitrogen-doped carbon sheets (NDC) wrapped titanium dioxide nanoparticles (NDC-TiO2 NPs) followed by the covalent immobilization of glucose oxidase (GODx) on them (designated as a GODx/NDC-TiO2NPs/ITO biosensor). Initially, the TiO2 NPs was synthesized by sol-gel method and then NDC-TiO2 NPs was synthesized utilizing a green source of Prunus persica (peach fruit) through a simple hydrothermal process. The synthesized NDC-TiO2 NPs composite was characterized by FESEM, HRTEM, Raman spectroscopy, XRD, ATR-FTIR spectroscopy and XPS to determine composition and phase purity. These fabricated GODx/NDC-TiO2NPs/ITO biosensor exhibited a good charge separation, highly enhanced and stable photocurrent responses with switching PEC behavior under the light (λ > 400 nm). As a result, GODx/NDC-TiO2NPs/ITO PEC glucose sensor exhibits a good photocurrent response to detection of glucose concentrations (0.05–10 μM) with an ultra-low detection limit of 13 nM under optimized PEC experimental conditions. Also, the PEC glucose sensor revealed a high selectivity, good stability, long time durability, and capability to analyze the glucose levels in real human serum. Also, the further development of this work may provide new insights into preparing other bio-derived carbon nanostructure-based photocatalysts for PEC applications.

The graphenated carbon nanotubes (G-CNTs) were synthesized on monodisperse spherical iron oxide nanoparticles (IONPs) using acetylene as carbon precursor by simple chemical vapor deposition method. The reaction parameters such as temperature and flow of carbon source were optimized in order to achieve G-CNTs with excellent quality and quantity. Transmission electron microscopy (TEM) clearly illustrated that the graphene flakes are forming along the whole length on CNTs. The degree of graphitization was revealed by X-ray diffraction (XRD) analysis and Raman spectroscopic techniques. The intensity of D to G value was less than one which confirms the obtained G-CNTs have high degree of graphitization. The optimum reaction temperature for the IONPs to form metallic clusters which in turn lead to the formation of G-CNTs with high carbon deposition yield is at 900 °C. The TEM shows the CNTs diameter is 50 nm with foiled graphene flakes of diameter around 70 nm. Our results advocate for IONPs as a promising catalytic template for quantitative and qualitative productivity of nanohybrid G-CNTs. The produced G-CNTs with high degree of graphitization might be an ideal candidate for nanoelectronic application like super capacitors and so on.

Graphitic carbon nanosheets (GCNS) were synthesized using mesoporous Ti-MCM-41 molecular sieves as catalytic template and acetylene as carbon precursor following chemical vapor deposition method, under atmospheric pressure. The mesoporous Ti-MCM-41 molecular sieves with various Si/Ti ratios were synthesized by direct hydrothermal method. The materials so obtained were characterized by various physico-chemical techniques such as X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. The analytical results indicated that the obtained GCNS possess high thermal stability and good graphitization with an inter layer distance of around 3.45 A. The influence of reaction parameters such as temperature and catalytic templates was studied to improve the quality and quantity of GCNS. The excellent graphitized GCNS material on a large scale was achieved from Ti-MCM-41 at moderate reaction temperature. This work proposes a way for the large scale synthesis of GCNS with applications suitable for nanoelectronics, nanocomposites and so on.

Zinc oxide nanoparticles decorated graphene oxide (ZnO@GO) composite was synthesized by simple solvothermal method where zinc oxide (ZnO) nanoparticles and graphene oxide (GO) were synthesized via simple thermal oxidation and Hummers method, respectively. The obtained materials were thoroughly characterized by various physico-chemical techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Raman spectrum shows the intensity of D to G value was close to one which confirms the obtained GO and ZnO@GO composite possesses moderate graphitization. TEM images shows the ZnO nanoparticles mean size of 15±5nm were dispersed over the wrinkled graphene layers. The photocatalytic performance of ZnO@GO composite on degradation of methylene blue (MB) is investigated and the results show that the GO plays an important role in the enhancement of photocatalytic performance. The synthesized ZnO@GO composite achieves a maximum degradation efficiency of 98.5% in a neutral solution under UV-light irradiation for 15min as compared with pure ZnO (degradation efficiency is 49% after 60min of irradiation) due to the increased light absorption, the reduced charge recombination with the introduction of GO. Moreover, the resulting ZnO@GO composite possesses excellent degradation efficiency as compared to ZnO nanoparticles alone on MB.

The ability to disperse pristine (unfunctionalized) graphene is important for various applications, coating, nanocomposites, and energy related systems. Herein we report that amphiphilic copolymers of poly(4-vinyl pyridine)-block-poly(ethylene oxide) (PVP-b-PEO) are able to disperse graphene with high concentrations about 2.6mg/mL via sonication and centrifugation. Ethanolic and aqueous highly-ordered pyrolytic graphite (HOPG) dispersions with block copolymers were prepared and they were compared with the dispersions stabilized by P-123 Pluronic® (P123) and poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO) synthesized. Transmission electron microscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, Raman and UV-visible spectroscopic studies confirmed that PVP-b-PEO block copolymers are better stabilizers for HOPG graphene than P123 and PS-b-PEO. X-ray photoelectron spectroscopy and force-distance (F-d) curve analyses revealed that the nitrogen of vinyl pyridine plays a vital role in better attractive interaction with surface of graphene sheet. Thermogravimetric analysis showed that larger amount of PVP-b-PEO was adsorbed onto graphene with longer poly(4-vinyl pyridine) (PVP) block length and in aqueous medium, respectively, and which was consistent with electrical conductivity decreases. This study presents the dispersion efficiency of graphene using PVP-b-PEO varies substantially depending on the lengths of their hydrophobic (PVP) domains.