Jayaraman Balamurugan

Effective seed-assisted synthesis of gold nanoparticles anchored nitrogen-doped graphene for electrochemical detection of glucose and dopamine.

A novel gold nanoparticle-anchored nitrogen-doped graphene (AuNP/NG) nanohybrid was synthesized through a seed-assisted growth method, as an effective electrocatalyst for glucose and dopamine detection. The AuNP/NG nanohybrids exhibited high sensitivity and selectivity toward glucose and dopamine sensing applications. The as-synthesized nanohybrids exhibited excellent catalytic activity toward glucose, with a linear response throughout the concentration range from 40μM to 16.1mM, a detection limit of 12μM, and a short response time (∼ 10s). It also exhibited an excellent response toward DA, with a wide detection range from 30nM to 48μM, a low detection limit of 10nM, and a short response time (∼ 8s). Furthermore, it also showed long-term stability and high selectivity for the target analytes. These results imply that such nanohybrids show a great potential for electrochemical biosensing application.

Facile fabrication of Co2CuS4 nanoparticle anchored N-doped graphene for high-performance asymmetric supercapacitors

A novel strategy for the synthesis of high-quality ternary cobalt copper sulfide nanoparticles (NPs) anchored on nitrogen doped graphene nanosheets (Co2CuS4/NG) was developed via a one-pot solvothermal method. FE-SEM and TEM images showed that the Co2CuS4 NPs with an average size of ∼21 nm were anchored to NG nanosheets. The NG nanosheets provide a large surface area to reduce self-aggregation and confine the shape of the Co2CuS4 NPs for a highly conductive network to boost the charge transport properties of energy storage devices. Impressively, the synergetic Co2CuS4/NG composite showed a high specific capacitance of ∼1005 F g−1 at 1 A g−1, excellent rate capability (770 F g−1 at 50 A g−1), and outstanding stability (96.3% capacitance retention after 5000 cycles). The electrochemical performance of the Co2CuS4/NG composite was superior to that of monometallic CoS/NG, Cu2S/NG composite, pure Co2CuS4, and NG. An asymmetric supercapacitor device fabricated using the Co2CuS4/NG composite as the positive electrode material and NG as the negative electrode material illustrates the outstanding performance for practical energy storage devices. The asymmetric supercapacitor device delivers superb energy density (53.3 W h kg−1), high power density (∼10 936 W kg−1 at 38.4 W h kg−1), and a long-cycle life (∼4000 times).

Novel porous gold-palladium nanoalloy network-supported graphene as an advanced catalyst for non-enzymatic hydrogen peroxide sensing.

In an effort to develop electrocatalysts associated with effective design, testing, and fabrication, novel porous gold-palladium nanoalloy network-supported graphene (AuPd@GR) nanohybrids were successfully synthesized via electroless deposition followed by a chemical vapor deposition (CVD) method for the first time. The AuPd@GR nanohybrids were obtained as a continuous, porous, transparent, bendable, and ultrathin film with good assembly of the AuPd nanoalloy particles (<10nm) within the GR. The AuPd@GR nanohybrids exhibited excellent catalytic activity towards H2O2 detection with a wide detection range (5μM-11.5mM), high sensitivity (186.86μAmM(-1)cm(-2)), low limit of detection (1μM), fast response (3s), and long-term working stability (2500s). Furthermore, the AuPd@GR nanohybrids demonstrated outstanding durability, along with negligible interference from ascorbic acid, dopamine, uric acid, urea, potassium ions, chloride ions, and glucose. These findings open a new pathway to fabricate electrocatalysts for application in high performance electrochemical sensors and bioelectronics.

Facile synthesis of 3D hierarchical N-doped graphene nanosheet/cobalt encapsulated carbon nanotubes for high energy density asymmetric supercapacitors

A novel three-dimensional (3D) hierarchical hybrid architecture, consisting of in situ designed cobalt-encapsulated nitrogen doped carbon nanotubes (Co–NCNTs) grown on nitrogen doped graphene (NG), is fabricated for asymmetric supercapacitors. When evaluated as an electrode material for supercapacitors, the 3D hybrid has an excellent energy density, outstanding rate capability and long-cycle life compared with commercial electrode materials. The decent electrochemical performance is comparable to most of the earlier reported results and the synergistic effect boosts the pseudocapacitive performance. The constructed hybrid exhibits excellent energy storage characteristics, which result in an ultra-high specific capacitance of 2568 F g−1 at 2 A g−1 and excellent rate capability with an extraordinary capacitance of 1594 F g−1 at 100 A g−1 (96.64% capacitance retention after 20000 cycles). The improvement in the outstanding electrochemical performance can be attributed to the unique morphology, extraordinary porosity, excellent conductive networks, and the intense networking of Co–NCNT and NG nanosheets in the 3D hybrid. An asymmetric supercapacitor fabricated using the 3D NG/Co–NCNT hybrid as the positive electrode and NG as the negative electrode demonstrates exceptional performance for practical energy storage devices. The assembled asymmetric supercapacitors provide a greater energy density (∼88.44 W h kg−1), an ultra-high power density (∼17991 W kg−1 at 56.97 W h kg−1), and outstanding cyclability (∼10000 times).

A novel hierarchical 3D N-Co-CNT@NG nanocomposite electrode for non-enzymatic glucose and hydrogen peroxide sensing applications.

A novel 3D nanocomposite of nitrogen doped Co-CNTs over graphene sheets (3D N-Co-CNT@NG) have been successfully fabricated via a simple, scalable and one-step thermal decomposition method. This 3D hierarchical nanostructure provides an admirable conductive network for effective charge transfer and avoids the agglomeration of NG matrices, which examine direct as well as non-enzymatic responses to glucose oxidation and H2O2 reduction at a low potential. The novel electrode showed excellent electrochemical performance towards glucose oxidation, with high sensitivity of 9.05μAcm-2mM-1, a wide linear range from 0.025 to 10.83mM, and a detection limit of 100nM with a fast response time of less than 3s. Furthermore, non-enzymatic H2O2 sensors based on the 3D N-Co-CNT@NG electrode exhibited high sensitivity (28.66μAmM-1cm-2), wide linear range (2.0-7449μM), low detection limit of 2.0μM (S/N=3), excellent selectivity, decent reproducibility and long term stability. Such outstanding electrochemical performance can be endorsed to the large electroactive surface area, unique porous architecture, highly conductive networks, and synergistic interaction between N-Co-CNTs and nitrogen doped graphene (NG) in the novel 3D nanocomposite. This facile, cost-effective, sensitive, and selective glucose as well as H2O2 sensors are also proven to be appropriate for the detection of glucose as well as H2O2 in human serum.

3D hierarchical CoO@MnO2 core–shell nanohybrid for high-energy solid state asymmetric supercapacitors

A unique morphology, high specific surface area, extraordinary porosity, and excellent conductive networks are typical favorable properties of pseudocapacitors; however, fully comprehending and interpreting this substantive topic still remains a great challenge. Herein, we present a new strategy for the direct growth of a cobalt monoxide@manganese oxide core–shell nanostructure on 3D Ni foam (CoO@MnO2/Ni foam). This is accomplished by simple, scalable, in situ fabrication methods to produce a material that can be employed as an advanced electrode material for high-energy solid state asymmetric supercapacitors (ASCs). The cost-effective, binder-free 3D CoO@MnO2 core–shell nanostructure delivers excellent electrochemical properties with an ultra-high specific capacitance (1835 F g−1 at a current density of 1 A g−1), tremendous rate capabilities with an extraordinary capacitance of 1198 F g−1 at a current density of 20 A g−1, and outstanding stability (97.7% capacitance retention after 10 000 cycles). ASCs with a maximum potential window of 1.8 V are fabricated by using a 3D CoO@MnO2 core–shell nanohybrid as the positive electrode and N-doped graphene (NG) as the negative electrode in order to validate the outstanding performance for practical energy storage devices. Impressively, the ASCs delivered a high specific capacitance (191 F g−1 at 1 A g−1), excellent energy density (∼85.9 W h kg−1), an ultra-high power density (∼16 769 W kg−1 at 51.7 W h kg−1), and remarkable cycle stability (86.8% capacitance retention after 10 000 cycles). These findings provide a new method to design 3D CoO@MnO2 core–shell nanostructures that are cost-effective and binder-free electrode materials for the development of high-performance energy storage devices.

Facile fabrication of FeN nanoparticles/nitrogen-doped graphene core-shell hybrid and its use as a platform for NADH detection in human blood serum

Herein, we present a novel strategy for the synthesis of an iron nitride nanoparticles-encapsulated nitrogen-doped graphene (FeN NPs/NG) core-shell hierarchical nanostructure to boost the electrochemical performance in a highly sensitive, selective, reproducible, and stable sensing platform for nicotinamide adenine dinucleotide (NADH). This core-shell hierarchical nanostructure provides an excellent conductive network for effective charge transfer and avoids the agglomeration and restacking of NG sheets, which provides better access to the electrode material for NADH oxidation. The FeN NPs/NG core-shell hierarchical nanostructure demonstrates direct and mediatorless responses to NADH oxidation at a low potential. This material displays a high sensitivity of 0.028μA/μMcm(2), a wide linear range from 0.4 to 718μM, and a detection limit of 25nM with a fast response time of less than 3s. The interferences from common interferents, such as glucose, uric acid, dopamine, and ascorbic acid, are negligible. The fabricated sensor was further tested for the determination of NADH in human blood serum. The resulting high sensitivity, excellent selectivity, outstanding stability, and good reproducibility make the proposed FeN NPs/NG core-shell hierarchical nanostructure as a promising candidate for biomedical applications.

Hierarchical 3D Cobalt-Doped Fe3O4 Nanospheres@NG Hybrid as an Advanced Anode Material for High-Performance Asymmetric Supercapacitors

Hierarchical nanostructure, high electrical conductivity, extraordinary specific surface area, and unique porous architecture are essential properties in energy storage and conversion studies. A new type of hierarchical 3D cobalt encapsulated Fe3 O4 nanosphere is successfully developed on N-graphene sheet (Co-Fe3 O4 NS@NG) hybrid with unique nanostructure by simple, scalable, and efficient solvothermal technique. When applied as an electrode material for supercapacitors, hierarchical Co-Fe3 O4 NS@NG hybrid shows an ultrahigh specific capacitance (775 F g-1 at a current density of 1 A g-1 ) with exceptional rate capability (475 F g-1 at current density of 50 A g-1 ), and admirable cycling performance (97.1% capacitance retention after 10 000 cycles). Furthermore, the fabricated Co-Fe3 O4 NS@NG//CoMnO3 @NG asymmetric supercapacitor (ASC) device exhibits a high energy density of 89.1 Wh kg-1 at power density of 0.901 kW kg-1 , and outstanding cycling performance (89.3% capacitance retention after 10 000 cycles). Such eminent electrochemical properties of the Co-Fe3 O4 NS@NG are due to the high electrical conductivity, ultrahigh surface area, and unique porous architecture. This research first proposes hierarchical Co-Fe3 O4 NS@NG hybrid as an ultrafast charge-discharge anode material for the ASC device, that holds great potential for the development of high-performance energy storage devices.

Hierarchical design of Cu1−xNixS nanosheets for high-performance asymmetric solid-state supercapacitors

Novel supercapacitor electrodes comprising hierarchical architectures with high specific surface areas, unique porosities, excellent conductivities, and admirable mechanical stabilities are necessary for developing high-performance solid-state supercapacitors. Herein, a novel ultra-thin copper nickel sulfide (Cu1−xNixS) nanosheet array supercapacitor electrode was constructed on a 3D Ni backbone through a powerful anion exchange technique and it demonstrated a unique architecture with a substantial degree of porosity. Accordingly, Cu1−xNixS plays an imperative role in the electrochemical energy storage characteristics of the electrode by accomplishing an ultra-high areal capacitance of 5.88 F cm−2 and a specific capacitance of 2672 F g−1 at a current density of 2 mA cm−2 with an excellent rate capability (71.26% capacitance retention at 20 mA cm−2) and a superior cycling performance (97.33% capacitance retention after 10 000 cycles). To design asymmetric supercapacitors (ASCs), Cu1−xNixS and N, S co-doped graphene nanosheets (NSGNSs) are employed as positive and negative electrodes, respectively. Remarkably, the fabricated ASC exhibits a potential window of ∼1.8 V, which demonstrates an ultra-high energy density of ∼94.05 W h kg−1 at 1.09 kW kg−1 as well as an excellent life cycle (95.86% capacitance retention after 10 000 cycles). Owing to this fact, this investigation offers a simple, scalable, and cost-effective approach for the fabrication of other ternary transition metal sulfides (TMSs), emphasizing great prospects in next-generation energy storage applications.

Enhanced Electrochemical and Photocatalytic Performance of Core–Shell CuS@Carbon Quantum Dots@Carbon Hollow Nanospheres

A controlled structural morphology, high specific surface area, large void space, and excellent biocompatibility are typical favorable properties in electrochemical energy storage and photocatalytic studies; however, a complete understanding about this essential topic still remains a great challenge. Herein, we have developed a new type of functionalized carbon hollow-structured nanospheres based on core-shell copper sulfide@carbon quantum dots (CQDs)@carbon hollow nanosphere (CHNS) architecture. This CuS@CQDs@C HNS is accomplished by a simple, scalable, in situ single-step hydrothermal method to produce the material that can be employed as an electrode for electrochemical energy storage and photocatalytic applications. Impressively, the CuS@CQDs@C HNS nanostructure delivers exceptional electrochemical energy storage characteristics with high specific capacitance (618 F g-1 at a current density of 1 A g-1) and an excellent rate capability with an extraordinary capacitance (462 F g-1 at current density of 20 A g-1) and long cycle life (95% capacitance retention after 4000 cycles). Further, the proposed photocatalyst exhibited superior photocatalytic activity under solar light due to the efficient electron transfer, which was revealed by photoluminescence studies. Such superior electrochemical and photocatalytic performance can be ascribed to the mutual contribution of CuS, CQDs, and CHNS and unique core-shell architecture. These results exhibit that the core-shell CuS@CQDs@C HNS nanostructure is one of the potential candidates for supercapacitors and photocatalytic applications.