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The development of single-atom catalysts anchored on two-dimensional (2D) conductive matrix with well exposed active sites has great significance in electrocatalytic energy storage yet remains challenging. Inspired by the power of biomolecular self-assembly in making delicate nanostructures, we report a novel template-free folic acid (FA) self-assembly strategy to achieve the facile preparation of ultrathin N-doped carbon nanosheet confining single-metal-atom catalysts (M-N-C SAC, M = Co, Ni, Zn, Fe). The 2D association of FA is developed for the first time via the ribbon-like H bonding pattern and metal-FA coordination in a mixed solvent. A tunable metal loading content of the catalysts is facilely realized through a pH-tuned FA partial dissociation chemistry. As a proof of demonstration, Co-N-C SAC shows an excellent performance for lean electrolyte lithium-sulfur battery. Our findinging suggest a new and potentially scalable route for facile fabrication of M-N-C SACs for broad energy storage applications.

Numerous scientists are in the pursuit of energy storage materials with high energy and high power density by assembly of electrochemically active materials into conductive scaffolds, owing to the emerging need for next-generation energy storage devices. In this architectures, the active materials bonded to the conductive scaffold can provide a robust and free-standing structure, which is crucial to the fabrication of materials with high gravimetric capacity. Thus, hierarchical copper-cobalt-nickel ternary oxide (CuCoNi-oxide) nanowire arrays grown from copper foam were successfully fabricated as free-standing anode materials for lithium ion batteries (LIBs). CuCoNi-oxide nanowire arrays could provide more active sites owing to the hyperbranched structure, leading to a better specific capacity of 1191 mAh/g, cycle performance of 73% retention in comparison to CuO nanowire structure, which exhibited a specific capacity of 1029 mAh/g and capacity retention of 43%, respectively.

Biomolecules with a broad range of structure and heteroatom-containing groups offer a great opportunity for rational design of promising electrocatalysts via versatile chemistry. In this study, uniform folic acid–Co nanotubes (FA–Co NTs) were hydrothermally prepared as sacrificial templates for highly porous Co and N co-doped carbon nanotubes (Co–N/CNTs) with well-controlled size and morphology. The formation mechanism of FA–Co NTs was investigated and FA–Co-hydrazine coordination interaction together with the H-bond interaction between FA molecules was characterized to be the driving force for growth of one-dimensional nanotubes. Such distinct metal–ligand interaction afforded the resultant CNTs rich Co–Nx sites, hierarchically porous structure and Co nanoparticle-embedded conductive network, thus an overall good electrocatalytic activity for oxygen reduction. Electrochemical tests showed that Co–N/CNTs-900 promoted an efficient 4e− ORR process with an onset potential of 0.908 V vs. RHE, a limiting current density of 5.66 mA cm−2 at 0.6 V and a H2O2 yield lower than 5%, comparable to that of 20% Pt/C catalyst. Moreover, the catalyst revealed very high stability upon continuous operation and remarkable tolerance to methanol.

Electrocatalytic seawater splitting has been considered as a transformative technology for industrial-scale hydrogen generation. However, the competition between the oxygen evolution reaction (OER) and chlorine evolution reaction (CER) at the anode with sluggish kinetics is the main bottleneck. Herein, an organic-oxidation-assisted strategy has been demonstrated, in which the thermodynamically favorable methanol selective oxidation reaction (MSOR) is used to suppress the undesired OER/CER using carbon paper supported Pt–Co3O4 electrocatalysts (denoted as Pt–Co3O4/CP), leading to hydrogen and value-added formate generation simultaneously with significantly low energy consumption. In the integrated two-electrode electrolyzer using Pt–Co3O4/CP bifunctional electrocatalysts, the required cell voltage at 10 mA cm−2 is only 0.555 V when adding 2.0 M methanol, which is 1022 mV lower than that in alkaline seawater. The integrated cell also produces hydrogen and formate simultaneously with high faradaic efficiency and considerable durability. The findings in this work represent a new direction for energy-saving production of hydrogen from seawater.

γ-MnO2 nanorod-assembled hierarchical micro-spheres with abundant oxygen defects are synthesized by a simple thermal treatment approach as oxygen reduction electrocatalysts for Al (aluminum) - air batteries. The rich oxygen vacancies on the surface of γ-MnO2 are verified by morphology, structure, electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) results. The oxygen reduction reaction (ORR) electrocatalytic activity of γ-MnO2 is significantly improved by the incoming oxygen vacancies. The γ-MnO2 nanorod-assembled hierarchical micro-spheres calcined under 300 °C in Ar atmosphere show the best ORR performance. The primary Al-air batteries using γ-MnO2 catalysts as the cathode, which demonstrates excellent peal power density of 318 mW cm−2 when applying the γ-MnO2 catalysts with optimal amount of oxygen vacancies.

Pseudocapacitors with high power density, long-term durability, as well as reliable safety, play a key role in energy conversion and storage. Designing electrode materials combing the features of high specific capacitance, excellent rate performance, and outstanding mechanical stability is still a challenge. Herein, a facile partial sulfurization strategy has been developed to modulate the electronic structure and crystalline texture of cobalt hydroxide nanosheets (denoted as Co(OH)2) at room temperature. The resultant cobalt hydroxysulfide nanosheet (denoted as CoSOH) electrode with abundant low-valence cobalt species and amorphous structure, exhibits a high specific capacitance of 2110 F g−1 at 1 A g−1 with an excellent capability retention rate of 92.1% at 10 A g−1, which is much larger than that of Co(OH)2 precursor (916 F g−1 at 1 A g−1 and 80% retention at 10 A g−1). Furthermore, the fabricated asymmetric supercapacitor device con structed with CoSOH and active carbon displays a considerable high energy density of 44.9 W h kg−1 at a power density of 400 W kg−1, and exceptional stability after 8000 cycles.

Metal nanoparticles stabilized on a support material have been explored extensively to boost heterogeneous catalysis. Herein, the effect of metal-support interaction between bismuth (Bi) nanoparticles and reduced graphene oxide nanosheets (Gr) on the electroreduction of CO2 towards value-added formate is explored. The obtained Bi/Gr hybrid catalysts exhibit a superior catalytic activity towards electrochemical reduction of CO2, which gives the maximum faradic efficiency of 92.1 % at -0.97 V (vs. RHE) for formate generation. Particularly, the hydride shows an enhancement to the catalysts of bare Bi and physical mixture of Bi and Gr, with a high current density of 28.1 mA∙cm−2 and production rate of 0.53 mol∙cm−2 h-1 at -1.17 V (vs. RHE) for formate generation. The electrochemical analysis reveals that the metal-support interactions substantially boost CO2 electroreduction activity through modification the electronic structure and improving interfacial electron transfer between Bi and Gr. This work not only deepens an understanding of metal-support interaction effect but also sheds light on the design of high-efficiency catalysts toward CO2 electroreduction by virtue of the interactions between active metals and carbon-like support.

Electrocatalytic N

Electrochemical reduction of CO2 to value-added products with high selectivity has attracted significant research interest. The development of earth-abundant and low-cost electrocatalysts is the key in this process. Herein, an efficient CO2 reduction electrocatalyst, comprising Ni and N in situ co-doped into porous and Ni nanoparticle-embedded carbon nanotubes (NiNxCNT), is developed from a sustainable and representative bioligand – folic acid. The synthesis process is straightforward, with the crucial step being the chelation of folic acid and Ni ions into uniform tubular metal–organic complex precursor. The resulted NiNxCNT catalyst exhibits a CO partial current density of 9.0 mA cm−2 at −0.676 V versus RHE and a high selectivity towards CO (>98%) in a wide potential range of −0.676 to −0.976 V versus RHE. Furthermore, the electrode shows little current decay over a period of total 44 h continuous operation at different potentials. The notable performance here is attributed to the synergistic effect of rich Ni–Nx sites and hierarchically porous nanotube structure. The findings of this study will open new avenues for developing inexpensive and high-performance CNT-based electrocatalysts for CO2 utilization.

Interfaces of metal-oxide heterostructured electrocatalyst are critical to their catalytic activities due to the significant interfacial effects. However, there are still obscurities in the essence of interfacial effects caused by crystalline defects and mismatch of electronic structure at metal-oxide nanojunctions. To deeply understand the interfacial effects, we engineered crystalline-defect Pd-Cu2O interfaces through non-epitaxial growth by a facile redox route. The Pd-Cu2O nanoheterostructures exhibit much higher electrocatalytic activity toward glucose oxidation than their single counterparts and their physical mixture, which makes it have a promising potential for practical application of glucose biosensors. Experimental study and density functional theory (DFT) calculations demonstrated that the interfacial electron accumulation and the shifting up of d bands center of Cu-Pd toward the Fermi level were responsible for excellent electrocatalytic activity. Further study found that Pd(3 1 0) facets exert a strong metal-oxide interface interaction with Cu2O(1 1 1) facets due to their lattice mismatch. This leads to the sinking of O atoms and protruding of Cu atoms of Cu2O, and the Pd crystalline defects, further resulting in electron accumulation at the interface and the shifting up of d bands center of Cu-Pd, which is different from previously reported charge transfer between the interfaces. Our findings could contribute to design and development of advanced metal-oxide heterostructured electrocatalysts.

Highlights A manganese single-atom catalyst is developed via a facile folic acid self-assembly strategy.The catalyst exhibits outstanding activity and selectivity for electrochemical reduction of nitrogen to ammonia (NRR).Electrocatalytic mechanism of Mn–N3 site for NRR is unveiled by a combination of experimental and computational study. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00651-1., Graphic Abstract Efficient and robust single-atom catalysts (SACs) based on cheap and earth-abundant elements are highly desirable for electrochemical reduction of nitrogen to ammonia (NRR) under ambient conditions. Herein, for the first time, a Mn–N–C SAC consisting of isolated manganese atomic sites on ultrathin carbon nanosheets is developed via a template-free folic acid self-assembly strategy. The spontaneous molecular partial dissociation enables a facile fabrication process without being plagued by metal atom aggregation. Thanks to well-exposed atomic Mn active sites anchored on two-dimensional conductive carbon matrix, the catalyst exhibits excellent activity for NRR with high activity and selectivity, achieving a high Faradaic efficiency of 32.02% for ammonia synthesis at − 0.45 V versus reversible hydrogen electrode. Density functional theory calculations unveil the crucial role of atomic Mn sites in promoting N2 adsorption, activation and selective reduction to NH3 by the distal mechanism. This work provides a simple synthesis process for Mn–N–C SAC and a good platform for understanding the structure-activity relationship of atomic Mn sites. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00651-1.

While increasing worldwide energy consumption demands for better storage devices, the environmental impact of these is often neglected. More sustainable energy storage in terms of greener battery materials would be desirable. In this regard, bioderived quinone containing molecules may serve as active battery material. Here, dopamine, among others an important neurotransmitter or active in mussel adhesion, is copolymerized with pyrrole to form a rod-like mixed copolymer. n-type charge storage in the quinone functionalities is combined with p-type charge storage in the conjugated doped polymer backbone from pyrrole and dopamine units with decreased polaron delocalization length compared to neat polypyrrole. The resulting sustainable polymer can be used as a cathode material due to a favorable redox potential of approx. 3.0–3.5 V vs. Li+/Li. It can reversibly store 160 mA h g−1 at a discharging rate of 100 mA g−1 and hence achieve similar capacities than inorganic, unsustainable, cathode materials and significantly higher capacities than other sustainable cathodes. Capacity is stable for more than 50 cycles, and even at high discharging rate of 800 mA g−1, approximately 90 mA h g−1 are reversibly stored with coulombic efficiency of almost 100%.

Three-dimensional (3D) graphene were synthesized by chemical vapor deposition (CVD) under atmospheric pressure, and then it was used as an electrode support for electrochemical deposition of CdTe quantum dots. We further systemically analyzed the electrical properties of the obtained graphene/CdTe composite through semiconductor device analyzer and four-probe measurements. It shows that the conductivity of this composite material exhibits strong dependant behavior with temperature, it can reach up to 15668 S cm−1 at 345 K, which is the twice higher value compared with the conductivity of 7677 S cm−1 at 80 K. Meanwhile, the composite displays a nonlinear relationship between the logarithm of the conductivity and the reciprocal of the temperature. The surface-trap states are most likely responsible for the thermally activated transport behavior of this composite. Our results give a guide for its practical photoelectric applications based on graphene/CdTe heterostructures.

Developing high-efficient and durable electrocatalysts for CO2 electroreduction reaction (CO2RR) at high current density is attractive but still challenging. In this study, ultrasmall Bi nanoparticles confined in carbon nanosheets are successfully prepared by directly annealing of dipped carbon cloth. Benefited from the uniform distribution of the ultrasmall Bi nanoparticles and the in‐situ‐formed carbon nanosheets, the resultant self-supported electrocatalysts exhibit excellent CO2RR activity in a synergistic way. The optimized Bi-PVP/CC600 exhibits high formate faradaic efficiency of over 81 % at high current densities in a wide potential range. Impressively, high durability is also achieved for this binder-free electrode, with a remarkable high current density of 54 mA∙cm−2 for nearly 40 h. The high performance associated with this facile and potentially scalable synthetic method suggests the great application potential of ultrasmall Bi nanoparticles in CO2RR. The strategy developed herein is versatile and can be extended to prepare other high‐performance ultrasmall metal nanoparticles catalysts.

The rational design of earth-abundant catalysts with excellent water splitting activities is important to obtain clean fuels for sustainable energy devices. In this study, mixed transition metal oxide nanoparticles encapsulated in nitrogendoped carbon (denoted as AB2O4@NC) were developed using a one-pot protocol, wherein a metal–organic complex was adopted as the precursor. As a proof of concept, MnCo2O4@NC was used as an electrocatalyst for water oxidation, and demonstrated an outstanding electrocatalytic activity with low overpotential to achieve a current density of 10 mA·cm−1 (η 10 = 287 mV), small Tafel slope (55 mV·dec−1), and high stability (96% retention after 20 h). The excellent electrochemical performance benefited from the synergistic effects of the MnCo2O4 nanoparticles and nitrogen-doped carbon, as well as the assembled mesoporous nanowire structure. Finally, a highly stable all-solid-state supercapacitor based on MnCo2O4@NC was demonstrated (1.5% decay after 10,000 cycles).

Electro-oxidative organic upgrading is recently considered as a promising strategy for energy saved H2 co-generation but still challenging for high productivity of value-added chemicals at large current density. Herein, the synthesized defects-rich Ni3S2-CNFs nanoheterostructures exhibit robust electrocatalytic performance for selectively catalyzing methanol to value-added formate with high productivity and without CO2 emission, in which the large current density (> 700 mA cm−2) is achieved with high faradaic efficiency (> 90%). By replacing the sluggish OER, the methanol upgrading reaction can greatly boost H2 co-generation from water with reduced energy consumption. DFT calculations indicate the in situ formed Ni–OOH and SOx species with synergistic effect can effectively modulate the d band center of Ni3S2 in Ni3S2-CNFs nanoheterostructures, acting as unique collaborative active sites for the thermodynamically favorable conversion from methanol to formate and suppressing the further oxidation to CO2, resulting in the high activity and selectivity of CO2-emission-free methanol upgrading reaction.

Solid oxide cells (SOCs) including solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) are advanced electrochemical energy storage and conversion devices. However, the lack of highly active and stable fuel electrode materials impedes their practical applications. Herein, in-situ exsolved CoFe nanoparticles on perovskite matrixes with abundant defects are developed as bifunctional fuel electrocatalysts for SOCs from the Sr2FeMo1-xCoxO6−δ (x = 0, 0.15, 0.25, 0.45) precursor. Increasement of Co doping promotes CoFe alloy exsolution and the formation of more defects in the remaining perovskite matrix under reducing atmosphere at high temperatures. Consequently, with increasing Co dopant content, the electrocatalytic activity towards CO2 electrolysis and hydrogen (H2) fuel oxidation are both significantly enhanced for the reduced Sr2FeMo1-xCoxO6−δ. The reduced Sr2FeMo1-xCoxO6−δ with high Co doping content of x = 0.45 electrocatalysts also exhibits respectable coking resistance and excellent long-term stability. The high performance may be owing to the unique simultaneously in-situ formed nanoalloy-oxide heterostructure and electron-ion mixed conductive perovskite matrixes with abundant defects.

Graphene quantum dots (GQDs) are emerging fluorescence reporters attractive for optical sensing, owing to their high photostability, highly tunable photoluminescence, molecular size, atomically thin structure, biocompatibility, and ease of functionalization. Herein, we present a fluorometric sensing platform based on tyramine-functionalized GQDs, which is able to detect a spectrum of metabolites with high sensitivity and specificity. Furthermore, multiparametric blood analysis (glucose, cholesterol, l-lactate, and xanthine) is demonstrated. This convenient metabolite profiling technique could be instrumental for diagnosis, study, and management of metabolic disorders and associated diseases, such as diabetes, obesity, lactic acidosis, gout, and hypertension. NMRC (Natl Medical Research Council, S’pore) MOE (Min. of Education, S’pore)

Cross-distributed MoS2 nanospheres and nanosheets were uniformly deposited on a 3D graphene foam by a hydrothermal approach. Attributable to their synergistic effect, the as-fabricated free-standing electrodes display excellent electrocatalytic activity and outstanding cycling stability towards hydrogen evolution.

Owing to its extraordinary properties, graphene materials have changed the landscapes in many technical areas. However, their applications (e.g., in energy conversion and storage) are often limited due to the lack of intrinsic electrochemical activity and restacking between graphene sheets. In this study, we demonstrate the synthesis of a heteroatom-doped graphene–bacteria composite using chemically-exfoliated graphene oxide as the precursor and E. coli as the reducing agent, spacer and doping source. As a proof-of-concept demonstration, we show that the carbonaceous rGO/E. coli composites are excellent electrode materials for the oxygen reduction reaction and lithium ion batteries.

In comparison to randomly oriented nanorods (NRs), self-assembly of the colloidal CdX (X = S, Se) NRs into well-organized large-scale structures results in unique collective properties. Moreover, the anisotropic structural features of self-assemblies preserved from colloidal CdX (X = S, Se) NRs have opened up exciting opportunities in the field of nanotechnology applications. We present the latest strategies for the self-assembly of colloidal NRs on solid substrates, and further focus on the self-assembled NRs for applications in devices. Advanced progress in the preparation of NR building blocks on the basis of nanofabrication techniques and comprehensive studies on the interactions of NRs with substrates will remarkably expand the application of colloidal semiconductor NRs. Understanding and mastering the driving forces behind the assembly of the NRs is the key goal of engineering future functional structures based on NRs.

Two-dimensional materials have attracted increasing research interest owing to their unique electronic, physical, optical, and mechanical properties. We thus developed a general strategy for the fabrication of ultralong hybrid microfibers from a mixture of reduced graphene oxide and transition-metal dichalcogenides (TMDs), including MoS2, TiS2, TaS2, and NbSe2. Furthermore, we prepared fiber-based solid-state supercapacitors as a proof-of-concept application. The performance of thus-prepared supercapacitors was greatly improved by the introduction of the TMDs. ASTAR (Agency for Sci., Tech. and Research, S’pore)

A novel three-dimensional (3D) electrochemical sensor was developed for highly sensitive detection of hydrogen peroxide (H2O2). Monolithic and macroporous graphene foam grown by chemical vapor deposition (CVD) served as the electrode scaffold. Using in-situ polymerized polydopamine as the linker, the 3D electrode was functionalized with thionine molecules which can efficiently mediate the reduction of H2O2 at close proximity to the electrode surface. Such stable non-enzymatic sensor is able to detect H2O2 with a wide linear range (0.4 to 660 μM), high sensitivity (169.7 μA mM−1), low detection limit (80 nM), and fast response (reaching 95% of the steady current within 3 s). Furthermore, this sensor was used for real-time detection of dynamic release of H2O2 from live cancer cells in response to a pro-inflammatory stimulant. Keywords: 3D graphene, Electrochemical sensing, Hydrogen peroxide, Thionine, Polydopamine

Quantum dots (QDs) derived from the atomically-thin two-dimensional (2D) sheets (graphene, transition metal dichalcogenide, graphitic carbon nitride, hexagonal boron nitride, and phosphorene) are emerging extraordinary zero-dimensional materials. Covering a broad spectrum of interesting optical, catalytic, electronic, chemical and electrochemical properties, these 2D-QDs promise a wide range of novel applications including imaging, sensing, cancer therapy, optoelectronics, display, catalysis, and energy. In this article, we discuss the synthesis methods and the properties of these 2D-QDs and emphasize their applications in electrocatalysis, photocatalysis, supercapacitors, batteries, and photovoltaics.

A simple approach was developed to synthesize the three-dimensional (3D) hybrid of manganese dioxide (MnO 2 ) and graphene foam. The morphology of the MnO 2 nanostructures can be readily controlled by the solution acidity. Furthermore, we demonstrate that, serving as a free-standing supercapacitor electrode, this novel three-dimensional hybrid gives a remarkable specific capacitance (560 F/g at the current density of 0.2 A/g) and excellent cycling stability.

In this work, simultaneous isolation of lactoferrin (Lf) and lactoperoxidase (Lp) from defatted bovine colostrum by one-step cation exchange chromatography with SPEC 70 SLS ion-exchange resin was investigated. A RP-HPLC method for Lf and Lp determination was developed and optimized as the following conditions: detection wavelength of 220 nm, flow rate of 1 mL/min and acetonitrile concentration from 25% to 75% within 20 min. The adsorption process of Lf on SPEC 70 SLS resin was optimized using Lf standard as substrate. The maximum static binding capacity of SPEC 70 SLS resin was of 22.0 mg/g resin at 15 °С, pH 7.0 and adsorption time 3 h. The Lf adsorption process could be well described by the Langmuir adsorption isotherm model, with a maximum adsorption capacity of 21.73 mg/g resin at 15 °С. In batch fractionation of defatted colostrum, the binding capacities of SPEC 70 SLS resin for adsorbing Lf and Lp simultaneously under the abovementioned conditions were 7.60 and 6.89 mg/g resin, respectively, both of which were superior to those of CM Sepharose F.F. or SP Sepharose F.F. resins under the same conditions. As a result, SPEC 70 SLS resin was considered as a successful candidate for direct and economic purification of Lf and Lp from defatted colostrum.

Quantum dots (QDs) derived from the atomically-thin two-dimensional (2D) sheets (graphene, transition metal dichalcogenide, graphitic carbon nitride, hexagonal boron nitride, and phosphorene) are emerging extraordinary zero-dimensional materials. Covering a broad spectrum of interesting optical, catalytic, electronic, chemical and electrochemical properties, these 2D-QDs promise a wide range of novel applications including imaging, sensing, cancer therapy, optoelectronics, display, catalysis, and energy. In this article, we discuss the synthesis methods and the properties of these 2D-QDs and emphasize their applications in electrocatalysis, photocatalysis, supercapacitors, batteries, and photovoltaics.

Electrochemical energy storage using lignin as a renewable electrode material is a cheap and sustainable approach for future organic batteries. Previous reports mainly focus on lignosulfonates (LS) or composites with conductive polymer additives with inherent problems, such as still expensive monomers. Here, composite electrodes are used from more available Kraft lignin and sustainable conductive carbon. Charge storage is evaluated in terms of electrical double layer storage and redox reactions, aiming at a better understanding of desired lignin properties for electrochemical energy storage. Using unmodified, commercial lignin and high surface area conductive carbon, reasonable capacity of ≈80 mAh g−1 is achieved in samples in which a thin layer of lignin covers the interface of high surface area carbon. Non-faradaic contribution to charge storage is as large as in comparable pure carbon electrodes, and redox reactions in lignin contribute to additional, faradaic charge storage, significantly enhancing capacity in these systems. Resulting electrodes are cheap, reliable, and stable.

Owing to their extraordinary physicochemical, electrical, and mechanical properties, carbon nanotubes (CNTs) and graphene materials have been widely used to improve energy storage and conversion. In this article, we briefly review the latest development on fabrication of 3D porous structures of CNTs or graphene sheets or their hybrids, and their applications in various energy devices including supercapacitors, (bio-) fuel cells, and lithium ion batteries.

Owing to their small size, biocompatibility, unique and tunable photoluminescence, and physicochemical properties, graphene quantum dots (GQDs) are an emerging class of zero-dimensional materials promising a wide spectrum of novel applications in bio-imaging, optical, and electrochemical sensors, energy devices, and so forth. Their widespread use, however, is largely limited by the current lack of high yield synthesis methods of high-quality GQDs. In this contribution, a facile method to electrochemically exfoliate GQDs from three-dimensional graphene grown by chemical vapor deposition (CVD) is reported. Furthermore, the use of such GQDs for sensitive and specific detection of ferric ions is demonstrated.

Microfiber devices are able to extend the micro/nano functionalities of materials or devices to macroscopic scale with excellent flexibility and weavability, promising a variety of unique applications and, sometimes, also improved performance as compared with bulk counterparts. The fiber electrodes in these devices are often made of carbon materials (e.g., carbon nanotubes and graphene) because of their exceptional electrical, mechanical, and structural properties. Covering the latest developments and aiming to stimulate more exciting applications, we comprehensively review the preparation and applications of carbon-microfiber devices on energy conversion and storage, electronics, sensors and actuators. ASTAR (Agency for Sci., Tech. and Research, S’pore) Published version

Heteroatom doping can endow graphene with various new or improved electromagnetic, physicochemical, optical, and structural properties. This greatly extends the arsenal of graphene materials and their potential for a spectrum of applications. Considering the latest developments, we comprehensively and critically discuss the syntheses, properties and emerging applications of the growing family of heteroatom-doped graphene materials. The advantages, disadvantages, and preferential doping features of current synthesis approaches are compared, aiming to provide clues for developing new and controllable synthetic routes. We emphasize the distinct properties resulting from various dopants, different doping levels and configurations, and synergistic effects from co-dopants, hoping to assist a better understanding of doped graphene materials. The mechanisms underlying their advantageous uses for energy storage, energy conversion, sensing, and gas storage are highlighted, aiming to stimulate more competent applications. ASTAR (Agency for Sci., Tech. and Research, S’pore) Published version

In this work, a nanoporous thin film consisting of sieve-like tin oxide (SnO2) sheets was prepared by anodization of tin foil in aqueous ammonia and applied as a photoelectrode for dye-sensitized solar cell (DSSC). Compared to the conventional SnO2 nanoparticle-based photoelectrode, the anodized nanoporous SnO2 electrode offers higher short circuit current (6.85 vs. 3.64 mA/cm2) and open circuit voltage (0.56 vs. 0.51 V) due to better charge transportation and better suppression of charge recombination. Consequently, the power conversion efficiency of the DSSC equipped with the anodized SnO2 electrode is enhanced by 63%. Published version

Hierarchically porous carbons are attracting tremendous attention in sustainable energy systems, such as lithium ion battery (LIB) and fuel cell, due to their excellent transport properties that arise from the high surface area and rich porosity. The state-of-the-art approaches for synthesizing hierarchically porous carbons normally require chemical- and/or template-assisted activation techniques, which is complicate, time consuming, and not feasible for large scale production. Here, a molecular-level design principle toward large-scale synthesis of nitrogen and phosphorus codoped hierarchically porous carbon (NPHPC) through an in situ self-activation process is proposed. The material is fabricated based on the direct pyrolysis of a well-designed polymer, melamine polyphosphate, which is capable of in situ self-activation to generate large specific surface area (1479 m2 g−1) and hierarchical pores in the final NPHPC. As an anode material for LIB, NPHPC delivers a high reversible capacity of 1073 mAh g−1 and an excellent cyclic stability for 300 cycles with negligible capacity decay. The peculiar structural properties and synergistic effect of N and P codopants also enable NPHPC a promising electrocatalyst for oxygen reduction reaction, a key cathodic reaction process of many energy conversion devices (for example, fuel cells and metal air batteries). Electrochemical measurements show NPHPC a comparable electrocatalytic performance to commercial Pt/C catalyst (onset potential of 0.88 V vs reversible hydrogen electrode in alkaline medium) with excellent stability (89.8% retention after 20 000 s continuous operation) and superior methanol tolerance.

Using a simple hydrothermal procedure, cobalt oxide (Co(3)O(4)) nanowires were in situ synthesized on three-dimensional (3D) graphene foam grown by chemical vapor deposition. The structure and morphology of the resulting 3D graphene/Co(3)O(4) composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. The 3D graphene/Co(3)O(4) composite was used as the monolithic free-standing electrode for supercapacitor application and for enzymeless electrochemical detection of glucose. We demonstrate that it is capable of delivering high specific capacitance of ∼1100 F g(-1) at a current density of 10 A g(-1) with excellent cycling stability, and it can detect glucose with a ultrahigh sensitivity of 3.39 mA mM(-1) cm(-2) and a remarkable lower detection limit of25 nM (S/N = 8.5).

Bovine colostrum is the milk secreted by cows during the first few days after parturition. It contains many essential nutrients and bioactive components, including growth factors, immunoglobulins (Igs), lactoperoxidase (Lp), lysozyme (Lys), lactoferrin (Lf), cytokines, nucleosides, vitamins, peptides and oligosaccharides, which are of increasing relevance to human health. Much research work has been done on the structure and function of bovine colostrum proteins. IgG was widely utilised in the immunological supplementation of foods, specifically in infant formulate, and yielded sales of approximately US$100 million in 2007 (Gapper, et al., 2007). In the highly competitive and valuable international market for IgG-containing products, some of the products are usually priced based on IgG content. Another important protein from bovine colostrum is lactoferrin. Its diverse range of biological activities such as anti-infective activities toward a broad spectrum of species, antioxidant activities and promotion of iron transfer are expanding the demand in the market. It also exhibits the potential for chemoprevention of colon and other cancers as a natural gradient. Apart from the two kinds of bovine colostrum proteins, ┙-lactalbumin has been claimed as an important food additive in infant formula due to its high content in tryptophan and as a protective against ethanol and stress-induced gastric mucosal injury. ┚Lactoglobulin is commonly used to stabilize food emulsions for its surface-active properties. Bovine serum albumin (BSA) has gelation properties and it is of interest in a number of food and therapeutic applications (Almecija, et al., 2007). Therefore, fractionation for the recovery and isolation of these proteins has a great scientific and commercial interest. As a result of this growth in the commercial use of bovine colostrum proteins, there is great interest in establishing more efficient, robust and low cost processes to purify them. Although great deals of studies have been done for the separation and purification of colostrum proteins due to their wide application in food industry, medicine and as supplements, large scale production system for the downstream processing of recombinant antibodies still represents the major issue. Lu (Lu, et al., 2007) designed a two-step ultrafiltration process followed by a fast flow strong cation exchange chromatography to isolate LF from bovine colostrum in a production scale. A stepwise procedure for purification of the crude LF was conducted using a preparative-scale strong cation exchange

The influence of cellulose:lignin ratios on liquid hydrocarbons (crude oil) production by hydrothermal conversion of biomass was investigated. Crude oil was recovered with acetone and analysised by GC-MS. The oil from the high ratio of cellulose: lignin consists of ketone and cyclopentene derivatives mainly whereas that of low ratio consists of phenolic compounds. The yields of crude oil were increased from 27.8% to 35.4% (w/w) with the lignin content decreasing from 100% to 25 % (w/w), and were decreased from 34% to 27% (w/w) with increasing cellulose content from 75% to 100% (w/w), which has no obvious relationship with the lignin content in the substrates.

Graphene quantum dots (GQDs) are emerging zero-dimensional materials promising a wide spectrum of novel applications including development of optical sensors. Herein, a GQD-based fluorometric sensor is devised to detect acetylcholinesterase (AChE, a critical enzyme in central nervous system and neuromuscular junctions) with an ultralow detection limit (0.58 pM with S/N of 5.0), using a photoluminescence 'turn-off' mechanism. This simple 'mix-and-detect' platform can also be employed to sense a variety of compounds that can directly or indirectly inhibit the enzymatic activities of AChE, such as nerve gases, pesticides, and therapeutic drugs. As the proof-of-concept demonstrations, we show the sensitive detection of paraoxon (a pesticide), tacrine (a drug to treat Alzheimer's disease), and dopamine (an important neurotransmitter). NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version

Biofuel cells (BFCs), which use enzymes as catalysts to harvest energy from green and sustainable fuels abundantly producible from biological systems, are promising next-generation energy devices. However, the poor stability and high specificity to only one fuel type of these bio-catalysts largely limits the practical use of current BFCs. In this contribution, we demonstrate a unique fuel cell which, equipped with two identical enzyme-free electrodes based on Co3O4 coated 3D graphene, is able to efficiently harvest electricity from various sweet biofuels (glucose, sucrose, or lactose). Taking advantage of the dual catalytic ability of nanostructured Co3O4 for both glucose oxidation and oxygen reduction as well as the exceptional electrical and structural properties of 3D graphene, our glucose-powered fuel cell, with good long-term stability, offers high open circuit voltage (∼1.1 V) and power density output (2.38 ± 0.17 mW cm−2). NRF (Natl Research Foundation, S’pore) ASTAR (Agency for Sci., Tech. and Research, S’pore) MOE (Min. of Education, S’pore)

A novel graphene–cobalt oxide hybrid needle-like electrode was fabricated for non-enzymatic glucose detection. Taking advantage of its small size, the needle electrode can probe glucose in a micro-droplet with high sensitivity.