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The exhaustion of the ozone layer in the atmosphere has caused an escalation of dangerous UV radiation penetrating the earth's surface. Reactive oxygen species generated under UV exposure through photocatalytic reactions can lead to severe skin health risks, such as skin cancer and premature aging. Although chemical sunscreens are widely used for protection against UV radiation, their long‐term use poses safety concerns and causes environmental damage. In this regard, we have developed carbon dots (CDs) with excellent UV absorption along with extraordinary antioxidant activity, photostability, and biocompatibility from green tea as the main precursor and alpha‐hydroxy acids (AHA) as the co‐precursors, including gluconic acid (GA), citric acid (CA), and tartaric acid (TA). All CDs have a strong UV absorption, especially in the UVB and UVC regions, with G‐CDs having the highest UV absorption. The G‐CDs also have the highest antioxidant activity, which is also higher than that of their parent green tea, AHAs, and ascorbic acid, a well‐known antioxidant. The photostability and cell viability of the G‐CDs were also excellent. The potential of G‐CDs as multifunctional materials makes them a promising candidate for cosmetic applications, particularly for their ability to absorb UV radiation with exceptionally high antioxidant activity, photostability, and biocompatibility. [ABSTRACT FROM AUTHOR]

Passivation of the sulfur cathode by insulating lithium sulfide restricts the reversibility and sulfur utilization of Li−S batteries. 3D nucleation of Li2S enabled by radical conversion may significantly boost the redox kinetics. Electrolytes with high donor number (DN) solvents allow for tri‐sulfur (S3⋅−) radicals as intermediates, however, the catastrophic reactivity of such solvents with Li anodes pose a great challenge for their practical application. Here, we propose the use of quaternary ammonium salts as electrolyte additives, which can preserve the partial high‐DN characteristics that trigger the S3⋅− radical pathway, and inhibit the growth of Li dendrites. Li−S batteries with tetrapropylammonium bromide (T3Br) electrolyte additive deliver the outstanding cycling stability (700 cycles at 1 C with a low‐capacity decay rate of 0.049 % per cycle), and high capacity under a lean electrolyte of 5 μLelectrolyte mgsulfur−1. This work opens a new avenue for the development of electrolyte additives for Li−S batteries. [ABSTRACT FROM AUTHOR]

Passivation of the sulfur cathode by insulating lithium sulfide restricts the reversibility and sulfur utilization of Li−S batteries. 3D nucleation of Li2S enabled by radical conversion may significantly boost the redox kinetics. Electrolytes with high donor number (DN) solvents allow for tri‐sulfur (S3⋅−) radicals as intermediates, however, the catastrophic reactivity of such solvents with Li anodes pose a great challenge for their practical application. Here, we propose the use of quaternary ammonium salts as electrolyte additives, which can preserve the partial high‐DN characteristics that trigger the S3⋅− radical pathway, and inhibit the growth of Li dendrites. Li−S batteries with tetrapropylammonium bromide (T3Br) electrolyte additive deliver the outstanding cycling stability (700 cycles at 1 C with a low‐capacity decay rate of 0.049 % per cycle), and high capacity under a lean electrolyte of 5 μLelectrolyte mgsulfur−1. This work opens a new avenue for the development of electrolyte additives for Li−S batteries. [ABSTRACT FROM AUTHOR]

Novel amine‐incorporated zinc complex/carbon dots composites were created and used as supercapacitor electrode materials in this study. By using a one‐step gamma irradiation, the amine‐incorporated zinc complex/carbon dots composites were prepared from zinc acetate dihydrate, ethylenediamine, and carbon dots. The impacts of ethylenediamine and carbon dots on the performance of the supercapacitor were examined. The highest specific capacitance obtained in this work was 179.9 F g−1 along with an excellent 91 % capacitance retention after 10,000 cycles. To clarify the mechanistic insights on the improved supercapacitor performance, an electrochemical analysis was performed, and it was found that amine incorporation improved the diffusion process of charge transfer, which led to better charge storage and higher capacitance. We have demonstrated that gamma irradiation is a simple and efficient method for creating electro‐active materials based on amine‐incorporated zinc complex/carbon dots composites for supercapacitors with improved performance and electrochemical properties. [ABSTRACT FROM AUTHOR]

Lithium metal is considered as a highly desirable anode for high-energy and safe quasi-solid-state batteries. Nevertheless, the terrible wettability of molten lithium does not permit it to spread out on the lithiophobic current collectors, limiting their practical applications. Herein, we report an ultrathin lithium–molybdenum (Li–Mo) composite anode to settle this hurdle by reacting molten Li with α-MoO3 nanobelts. The experimental characterizations and density functional theory calculations reveal that the interfacial binding energy between molten Li and copper (Cu) foil can be decreased by adding α-MoO3, which improves the wettability toward Cu current collector and helps to realize uniform spreading of an ultrathin Li with a thickness of ∼35 μm. As a demonstration, the ultrathin Li–Mo is stabilized to provide a high average Coulombic efficiency of ∼95.2% over 300 cycles at a high current density of 1 mA cm−2, and a capacity retention of 100% is realized for a quasi-solid-state battery paired with LiFePO4 and poly(1,3-dioxolane) electrolyte. These findings open up a promising option for enhancing the wettability of molten lithium and provide a sustainable strategy for the large-scale production of ultrathin lithium for realizing next-generation high-energy and safe quasi-solid-state batteries. [ABSTRACT FROM AUTHOR]

Tuberculosis (TB) is a deadly disease and needs a fast, cheap, and effective method of detection at an early stage. Methyl nicotinate (MN) is an important TB biomarker, but there are only a few reports on MN sensing. In this study, fluorescence-based sensors and optical electronic nose sensors from carbon dots (CDs) were developed for the highly sensitive and selective detection of MN. They were able to detect MN in the solution phase via the inner filter effect (IFE) and strong π–π interactions between the pyridine ring and the CDs. The limit of detection was found to be dependent upon the excitation wavelength and concentration of CDs. The use of 0.05 mg mL−1 CDs and 260 nm excitation provided the best linearity range of over 5–500 μM and the lowest detection limit of 3 nM. The CDs showed excellent photostability and good selectivity towards MN in the presence of several interferences. This work demonstrated the practical use of the CDs when tested in MN spiked biological samples, with 98.8–102.9% recovery percentage. The fabrication of reusable paper-based sensors was also demonstrated. The CD thin film integrated in the optical electronic nose could sense MN vapor and distinguish MN from other biomarkers. The CDs developed in this work can be potentially used as dual-mode sensors for early TB detection. [ABSTRACT FROM AUTHOR]

In this work, bio‐renewable, high‐performance supercapacitors were prepared from sugarcane wastes. Activated carbon and carbon dots (CDs) was prepared from sugarcane bagasse and leaves, whereas electrolyte, for the first time in any kind of electrochemical device, was prepared from molasses. The supercapacitors were then fabricated from activated carbon electrodes and molasses electrolyte. The supercapacitors using bagasse‐ and leaf‐derived activated carbon and molasses aqueous solution yielded a specific capacitance of 101 and 80 F g−1, respectively, at a scan rate of 30 mV s−1. When the molasses electrolyte was prepared in H2SO4 solution, the specific capacitance increased to 308 and 268 F g−1, respectively. Interestingly, when the CDs were added to molasses/H2SO4 electrolyte, the specific capacitance was further boosted to 456 and 356 F g−1, which are equivalent to 148 % and 133 % increases. In addition to enhancing the specific capacitance, the use of CDs also improved the cycling stability of the supercapacitors. A combination of enhanced surface capacitance and reduced interfacial resistance offered by the CDs led to a significantly enhanced performance. This work thus demonstrates a value‐adding strategy for sugarcane wastes and the fabrication of novel, high‐performance supercapacitors. [ABSTRACT FROM AUTHOR]

Exploring solid electrolytes with promising electrical properties and desirable compatibility toward electrodes for safe and high-energy sodium metal batteries remains a challenge. In this work, these issues are addressed via an in situ hybrid strategy, viz., highly conductive and thermally stable 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide is immobilized in nanoscale silica skeletons to form ionogel via a non-hydrolytic sol-gel route, followed by hybridizing with polymeric poly(ethylene oxide) and inorganic conductor Na3Zr2Si2PO12. Such hybrid design yields the required solid electrolyte, which shows not only a stable electrochemical stability window of 5.4 V vs Na/Na+ but also an extremely high ionic conductivity of 1.5 × 10−3 S cm−1 at 25 °C, which is demonstrated with the interacted and monolithic structure of the electrolyte by SEM, XRD, thermogravimetric (TG), and XPS. Moreover, the capabilities of suppressing sodium metal dendrite growth and enabling high-voltage cathode Mg-doped P2-type Na0.67Ni0.33Mn0.67O2 are verified. This work demonstrates the potential to explore the required solid electrolytes by hybridizing an in situ ionogel, a polymer, and an inorganic conductor for safe and high-energy solid-state sodium metal batteries. [ABSTRACT FROM AUTHOR]

Detection of trace magnesium ion (Mg2+) is important in environmental and health monitoring. In this work, high‐performance Mg2+ sensor was developed from label‐free carbon dots. The novel carbon dots were prepared for the first time from natural rubber through the two‐step pyrolysis and hydrothermal method. They showed selectivity towards Mg2+ against a range of metal ions in solution and yielded a detection limit of 4.3 μM. The Mg2+ detection in real water samples showed an excellent recovery of 97.21 to 99.21 %. A paper‐based sensor was also fabricated as a portable device, showing a detection limit of 8.0 μM. UV‐vis and X‐ray absorption studies provided some evidences of the unique dynamic interactions between carbon dots and Mg2+ ions. In summary, the novelty of this work lies upon (i) developing a methodology of converting abundant, low‐cost natural rubber into carbon dots and (ii) fabricating sensitive and selective sensors from the label‐free carbon dots for the detection of Mg2+ both in solution and as paper‐based devices. The findings in this work will therefore have potential for environmental and health monitoring applications. [ABSTRACT FROM AUTHOR]

In this work, the novel, simple Ni2+ sensors with high sensitivity, selectivity, accuracy, practicality, and adsorption capacity were developed from the label‐free carbon dots. The carbon dots were prepared from polyurethane through a one‐step pyrolysis method. They exhibited excitation‐independent photoluminescence and offered a fluorescence quantum yield of 24 %. They were then tested for metal ion sensing, showing selectivity towards Ni2+ against a range of metal ions with a detection limit of 3.14 μM, the best for the carbon dots reported to date. A carbon dot‐loaded paper‐based sensor was also fabricated for Ni2+ detection, showing a limit of detection of 43.3 μM. The detection of Ni2+ in real water samples showed excellent recovery of 95.6 to 99.2 %. The selective detection of Ni2+ by the carbon dots arose from the inner filter effect and complex formation, leading to fluorescence quenching of the carbon dots. X‐ray absorption analysis further confirmed the unique interaction and electron transfer from the carbon dots to Ni2+. In addition to high‐performance sensing, the carbon dots demonstrated high adsorbent capacity towards Ni2+, in which one nanoparticle could accommodate up to 182 Ni2+ ions, equivalent to 234.8 mg g−1. This work demonstrates the unique sensing and adsorbent properties of polyurethane‐derived carbon dots towards Ni2+, which can be applied for simultaneous monitoring and cleaning. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) are fascinating nanomaterials with technologically relevant properties; however, the effects of heteroatom doping on several properties of CDs have not been studied. In this work, a facile method for the synthesis and heteroatom doping of carbon dots from table sugar was developed using nitric acid, phosphoric acid, and sulfuric acid as simultaneous catalysts and dopants. The optical properties, phenolic content, antioxidant activity, photostability, and cytotoxicity of the CDs were measured and compared. Lascorbic acid, a well-known antioxidant, and avobenzone and oxybenzone, common UV absorbers in sunscreens, were used for comparison. Interestingly, heteroatom doping has adverse effects on several properties of the CDs as the undoped CDs yielded the highest UV-vis absorption, phenolic content, antioxidant activity, photostability, and biocompatibility. Only fluorescence quantum yields were improved by heteroatom doping. These findings will be crucial for choosing precursors for the synthesis of CDs because heteroatoms inherently present in precursors can have negative effects on the properties of the resulting CDs. [ABSTRACT FROM AUTHOR]

Temperature-responsive polymers are smart materials that respond to changes in temperature and have a wide range of applications, ranging from sensing to biomedical fields. In this work, we investigated the synthesis and temperature-responsive behavior of responsive elastomer based on N-isopropylacrylamide-grafted natural rubber. The grafting reaction was carried out using deproteinized natural rubber (DPNR) latex and potassium persulfate as free radical initiator. The temperature responsiveness of the graft copolymers was investigated using water swelling and contact angle measurements, and compared with that of pure DPNR. The lower critical solution temperature of the graft copolymer was found to be in the range 30-34 °C, whereas the DPNR was not responsive to temperature. Furthermore, the graft copolymer exhibited temperature responsiveness in a solid state. As the temperature responsiveness of the graft copolymer is close to the human body temperature, it can be used in biomedical applications. Dye adsorption studies revealed the Langmuir isotherm, indicating monolayer coverage. The technique proposed in this study produces a temperature-responsive natural rubber, with potential applications as a responsive material for use in sensing and biomedical products. [ABSTRACT FROM AUTHOR]

We investigated the synthesis of a pH-responsive graft copolymer of natural rubber and 4-vinylpyridine. The grafting reaction was carried out using deproteinized natural rubber (DPNR) latex, with potassium persulfate as a free radical initiator. The pH responsiveness of the graft copolymer was investigated using water swelling and contact angle measurements, and was compared with that of pure DPNR. The graft copolymer was found to become responsive in solution at a pH of around 4. Indigo carmine adsorption studies identified the Langmuir isotherm, suggesting monolayer coverage. The adsorbed indigo carmine, a model anionic drug, and carbon dots, an emerging nanosized fluorophore, could be released from the graft copolymer by lowering the pH of the solution. The graft copolymer was tested as a heavy metal adsorbent, and demonstrated selectivity to copper(II) ions. The graft copolymer of 4-vinylpyridine and DPNR developed in this study is therefore a multifunctional, pH-responsive material with a wide range of potential applications, including sensing and catalysis, as a biomedical material and as an adsorbent. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

A straightforward method for functionalizing natural rubber (NR) with poly( N-vinylcaprolactam) (PNVCL), a temperature-responsive polymer having lower critical solution temperature (LCST) near human body temperature, has been successfully developed using free radical crosslinking reaction. Effects of polymer and initiator concentrations, reaction temperature, and reaction time on immobilization percentage of the synthesized polymer were investigated. Results showed 100% immobilization percentage when using 100 phr of PNVCL, 10 phr of benzoyl peroxide at 75 °C within 36 h. For the temperature responsiveness, the water swelling, water contact angle, and dye release of the crosslinked NR were measured. Its LCST ca. 32-34 ˚C was close to that of the pristine PNVCL. The dye adsorption studies revealed the Langmuir isotherm indicating monolayer coverage. Dye release could be triggered by increasing the temperature above the LCST, suggesting its potential uses in drug release technology. In addition, this temperature-responsive NR would potentially be used as a novel responsive rubber-based material in various applications, such as sensors and biomedical materials. [ABSTRACT FROM AUTHOR]

Stimuli-responsive elastomers are smart materials for sensing applications. Natural rubber ( NR) is a renewable elastomer with excellent elasticity and fatigue resistance. In this work, a straightforward method for the preparation of pH-responsive crosslinked materials from NR and poly(4-vinylpyridine) ( P4VP) via free radical crosslinking reaction using benzoyl peroxide ( BPO) as an initiator is described. The effects of P4VP and BPO concentrations, reaction time and reaction temperature on immobilization percentage were investigated. It was found that the immobilization percentage reached 90% when using a P4VP concentration of 150 phr and a BPO concentration of 10 phr for 24 h at 90 °C. The pH responsiveness of the crosslinked materials was studied via water swelling, water contact angle and dye release measurements. Unlike unmodified rubber, the P4VP-crosslinked NR was found to be pH-responsive in acidic solution. Indigo carmine adsorption studies showed the Langmuir isotherm suggesting monolayer coverage of dye on the rubber surface. The dye could also be released upon increasing the pH of solution above 4. Based on these results, the introduction of pH responsiveness to NR will lead to novel responsive rubber-based materials that can be used in biomedical and sensing applications. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Stimuli-responsive polymers are considered as smart materials as they can respond to subtle changes in external stimuli, such as pH, temperature, light, magnetic field, etc. Natural rubber (NR) is one of the most important renewable resources, offering excellent flexibility and fatigue resistance. In this work, temperature responsiveness was introduced to NR via a crosslinking reaction with poly( N-isopropylacrylamide) (PNIPAM) using benzoyl peroxide as a free radical crosslinker. PNIPAM was chosen because it is a well-known temperature-responsive polymer with a lower critical solution temperature near the human body temperature, enabling applications in biomedical fields. The crosslinked materials between PNIPAM and NR were characterized using Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The effects of polymer and crosslinker concentration, reaction temperature, and reaction time on the gel content were studied. The temperature responsiveness of the crosslinked polymers was investigated and the lower critical solution temperature was found to be in the range 30-34 °C. Based on these results, we demonstrated a straightforward strategy for preparing crosslinked polymers between PNIPAM and NR. The introduction of temperature responsiveness into NR will lead to new responsive rubber-based materials and expand the range of potential applications. [ABSTRACT FROM AUTHOR]

A polymerization method for the preparation of an interpenetrating network polymer with poly(ethylene terephthalate) is reported. Two types of monomer, styrene and 4-vinylpyridine, were chosen as hydrophobic and hydrophilic representatives, respectively, in order to show the versatility of this polymerization method. The polymer-immobilized poly(ethylene terephthalate) samples were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The immobilization efficiency of styrene as a function of reaction temperature, monomer-to-initiator molar ratio, reaction time, addition of solvent, surface hydrophilicity and immersion in initiator was studied. The maximum immobilization percentage of styrene reaches 111%. The immobilization efficiency is proportional to polymer molecular weight and sample thickness. Based on these results, this strategy is shown to be an efficient, versatile method for preparing interpenetrating network polymers and can be used as a means to modify the structures and properties of polymeric substrates. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Photoinduced charge transfer modifies the device properties of illuminated pentacene field effect transistors (FETs) incorporating ZnO quantum dots at the gate insulator/pentacene interface. The transferred charge is trapped on electronic states associated with the ZnO quantum dots, with a steady state population approximately proportional to the rate of organic-inorganic charge transfer. Trapped charge shifts the threshold voltage of the FETs, providing the means to evaluate the rate of organic/inorganic charge transfer and the effects of interface modification. Monolayers of the wide-gap alkane stearic acid and the conjugated oligomer terthiophene attached to the ZnO suppress or permit charge transfer, respectively. [ABSTRACT FROM AUTHOR]

A C60-terminated self-assembled monolayer can be used to place molecular acceptor states at the interface between the semiconductor and gate insulator of an organic field effect transistor. The time dependence of the photoinduced charge transfer between pentacene and C60 has a fast component with a characteristic time of 1.9 s and slower component with a time constant of 32 and 48 s at the beginning and end of a transient increase in illumination, respectively. Variation in the threshold voltage shift with the thickness of the pentacene results from the competing length scales for light absorption and exciton diffusion. [ABSTRACT FROM AUTHOR]