Large-scale industrial application of electrochemical water splitting calls for remarkable non-noble metal electrocatalysts. Herein, we report on the synthesis of a NiMo-alloy hollow nanorod array supported on Ti mesh (NiMo HNRs/TiM) using a template-assisted electrodeposition method. The NiMo HNRs/TiM behaves as a durable efficient oxygen evolution anode with 10 mA cm−2 at an overpotential of 310 mV in 1.0 M KOH. Coupled with its superior catalytic performance for hydrogen evolution with 10 mA cm−2 at an overpotential of 92 mV, we made an alkaline electrolyzer using this bifunctional electrode with 10 mA cm−2 at a cell voltage of 1.64 V.

Direct mixing of aqueous dispersions of ultrathin g-C3N4 nanosheets and graphene oxide (GO) under ultrasonication leads to three-dimensional (3D) porous supramolecular architecture. Photoreduction of GO yields conductive porous g-C3N4/rGO hybrid. The resulting 3D architecture possesses high surface area, multilevel porous structure, good electrical conductivity, efficient electron transport network, and fast charge transfer kinetics at g-C3N4/rGO interfaces, which facilitate the diffusion of O2, electrolyte, and electrons in the porous frameworks during oxygen reduction reaction (ORR). Ultrathin g-C3N4 nanosheet also causes effective electron tunneling through g-C3N4 barrier, leading to rich electrode–electrolyte–gas three-phase boundaries, and shortens the electron diffusion distance from rGO to O2. As a novel ORR catalyst, such 3D hybrid exhibits remarkable catalytic performance, outperformed other g-C3N4/rGO composites, and exhibits excellent durability.Keywords: 3D porous supramolecular architecture; electrocatalyst; graphene; oxygen reduction reaction; photoreduction; ultrathin g-C3N4 nanosheets;

•We demonstrate the first one-step fabrication of graphene film-confined MoSx nanoparticles.•Such hybrid film is used as a novel HER electrocatalyst in acidic solution.•Such hybrid film shows high HER activity and good stability.MoSx nanoparticles–graphene hybrid film was deposited onto a glassy carbon electrode by a facile one-step electrodeposition approach using MoS42− and graphene oxide as precursors. As a novel hydrogen evolution reaction (HER) electrocatalyst, this hybrid film exhibits highly catalytic activity and good stability.

•We demonstrate the first solvothermal preparation of ZnCo2O4/NCNT composite.•The composite exhibits high ORR performance in alkaline solution.•The composite has superior methanol tolerance ability and durability to Pt/C catalyst.In this communication, we report on the solvothermal preparation of spinel ZnCo2O4/N-doped carbon nanotube (ZnCo2O4/NCNT) composite. As a novel oxygen reduction reaction (ORR) electrocatalyst, the ZnCo2O4/NCNT composite shows high activity via a four-electron pathway in alkaline solution. Such catalyst also exhibits superior methanol tolerance ability and durability over commercial Pt/C catalyst.

In this communication, for the first time, we demonstrate the shape-controllable synthesis of molybdenum carbide (Mo2C) nanowires (NWs) and nanosheets (NSs) via direct pyrolysis of their MoOx/p-phenylenediamine hybrid precursors under Ar. We further demonstrate the use of such carbides as a highly active hydrogen evolution reaction electrocatalyst with good durability in acidic solution. It also suggests that the Mo2C NWs exhibit superior activity and durability over the Mo2C NSs.

•Two-dimensional mFe2O3–G was developed as a peroxidase mimetic for the first time.•mFe2O3–G exhibits high catalytic activities toward TMB oxidation by H2O2.•mFe2O3–G was used for rapid, highly sensitive and selective optical glucose detection.In this article, for the first time, two-dimensional hybrid mesoporous Fe2O3–graphene (mFe2O3–G) nanostructures were developed as a peroxidase mimetic with catalytic activities superior to those of mFe2O3, G, and previously reported Fe-based peroxidase mimetics. The high-surface-area mFe2O3 not only offers a large number of catalytically active sites, but also facilitates the diffusion of 3,3,5,5-tetramethylbenzidine (TMB) and H2O2 toward G surface. On the other hand, G is π-rich and thus favors the adsorption and enrichment of TMB within these pores. These synergistic effects lead to highly improved catalytic performances. Based on these findings, a simple, rapid, and highly sensitive and selective optical detector of glucose has been developed and demonstrated in buffer solution with a pretty low detection limit of 0.5 μM. In addition, this nanosensor is reusable and can also be used for glucose detection in diluted serum.

In this communication, we demonstrate for the first time that ultrathin graphitic carbon nitride (g-C3N4) nanosheets can serve as a low-cost, green, and highly efficient electrocatalyst toward the reduction of hydrogen peroxide. We further demonstrate its application for electrochemical glucose biosensing in both buffer solution and human serum medium with a detection limit of 11 μM and 45 μM, respectively.

In this article, we demonstrate for the first time that ultrathin graphitic carbon nitride nanosheets (g-C3N4) possess peroxidase activity. Fe doping of the nanosheets leads to peroxidase mimetics with greatly enhanced catalytic performance and the mechanism involved is proposed. We further demonstrate the novel use of such Fe–g-C3N4 as a cheap nanosensor for simple, rapid, highly selective and sensitive optical detection of glucose with a pretty low detection limit of 0.5 μM.

Au nanoparticles (AuNPs) were loaded on graphitic carbon nitride (g-C3N4) nanosheets prepared by ultrasonication-assisted liquid exfoliation of bulk g-C3N4 via green photoreduction of Au(III) under visible light irradiation using g-C3N4 as an effective photocatalyst. The nanohybrids show superior photocatalytic activities for the decomposition of methyl orange under visible-light irradiation to bulk g-C3N4, g-C3N4 nanosheets, and AuNP/bulk g-C3N4 hybrids.Keywords: Au nanoparticles; graphitic carbon nitride; green synthesis; methyl orange; nanosheets; photodegradation;

In this communication, for the first time, we demonstrate the fast and facile preparation of porous FeF3 nanospheres using solvent exchange from FeF3 aqueous solution to ethanol. We further demonstrate the use of such FeF3 nanospheres as cathode materials for rechargeable lithium-ion batteries with good rate capability and cycling performance.Highlights► Porous FeF3 nanospheres were prepared using solvent exchange for the first time. ► The porous FeF3 nanospheres show good rate capability. ► The porous FeF3 nanospheres exhibit excellent cycle stability.

A highly efficient fluorosensor based on ultrathin graphitic carbon nitride (g-C3N4) nanosheets for Cu2+ was developed. In the absence of metal ions, the nanosheets exhibit high fluorescence; the strong coordination of the Lewis basic sites on them to metal ions, however, causes fluorescence quenching via photoinduced electron transfer leading to the qualitative and semiquantitative detection of metal ions. This fluorosensor exhibits high selectivity toward Cu2+. The whole detection process can be completed within 10 min with a detection limit as low as 0.5 nM. The use of test paper enables the naked-eye detection of Cu2+ with a detection limit of 0.1 nmol. The practical use of this sensor for Cu2+ determination in real water samples was also demonstrated.

In this paper, we demonstrate the preparation of reduced graphene oxide (rGO) decorated with FeF3 nanoparticles (FeF3NPs) by adding FeF3 aqueous solution to the rGO ethanol/water dispersion. The obtained FeF3/rGO nanocomposite is further tested as a cathode material for rechargeable lithium batteries and found to have high discharge capacities, good rate capabilities and cycling performance. It can deliver a high discharge capacity of 476 mAh g−1 at a current density of 50 mA g−1 in the voltage range 1.0–4.5 V. It still delivers a discharge capacity of 146 mAh g−1 with 81% capacity retention after 50 charge–discharge cycles under a current density of 1000 mA g−1 in the voltage range 1.7–4.5 V.

In this study, we demonstrate that hydrothermal carbonization of low-cost wastes of willow bark leads to water-soluble, photoluminescent carbon dots (CDs) with diameters ranging from 1 to 4 nm and a quantum yield of approximately 6.0%. We further demonstrate the proof of concept that such CDs can be used as an effective photocatalyst for the simultaneous reduction of Au(III) complex and graphene oxide to form Au nanoparticles decorated reduced graphene oxide (AuNPs–rGO) nanocomposites by UV irradiation of a mixture of GO and HAuCl4 aqueous solution in the presence of CDs. It is found that the resultant AuNPs–rGO nanocomposites exhibit notable catalytic performance for H2O2 reduction and oxidation. Furthermore, we fabricate a glucose biosensor by immobilizing glucose oxidase on the AuNPs–rGO-modified glassy carbon electrode for glucose detection. The linear response range and detection limit are estimated to be from 2 mM to 18 mM (r: 0.995) and 45 μM, respectively. The application of this glucose sensor in human blood serum has also been demonstrated successfully.

•The nickel sulfides/rGO nanocomposites were biomolecule-assisted prepared.•The nanocomposites were applied in supercapacitors with good cycling stability.•The nanocomposites deliver a specific capacitance of 1169 F g−1 at 5 A g−1.•The nanocomposites deliver a specific capacitance of 761 F g−1 at 50 A g−1.The present communication demonstrates the first environmentally friendly hydrothermal synthesis of nickel sulfide nanospheres/reduced graphene oxide (nickel sulfides/rGO) nanocomposites with the use of l-cysteine as a reducing agent, sulfur donor, and linker. The nanosphere consists of ultrafine particles leading to textural pores. The resulting nickel sulfides/rGO nanocomposites were further used as an electrode material for supercapacitors and found to exhibit very high specific capacitances of 1169 F g− 1 and 761 F g− 1 at current rates of 5 A g− 1 and 50 A g− 1, respectively, with good cycling stability.

In this paper, for the first time, we report on the growth of ultrathin Ni(OH)2 nanosheet arrays on a nickel foam (NF) via a novel pH-driven dissolution–precipitation route, carried out by a hydrothermal treatment of the NF in an acidic medium without the introduction of other nickel sources. Acid etching of the NF surface leads to nano-pits and produces Ni(H2O)n2+ ions at the early stage of the reaction. With the elapsed time, an increase in the pH level occurs and the Ni(H2O)n2+ ions gradually hydrolyze and preferentially precipitate on the nano-pits, serving as nucleation sites and leading to ultrathin Ni(OH)2 nanosheet arrays on an NF. The effects of the experimental parameters, such as reaction time, acid type and starting pH value, on the Ni(OH)2 growth are also investigated. Because the nano-pits are integrated parts of the NF and the deposition of Ni(OH)2 nanosheets on such nano-pits ensures intimate contact between them, the Ni(OH)2/NF is robust enough to withstand a violent sonication process and efficient and rapid electron transfer is achieved. As a binder-free anode for Li-ion batteries, the Ni(OH)2/NF exhibits an unexpected ultrahigh capacity of 1689 mA h g−1 and excellent cycling stability.

The present communication reports on the first use of commercially available three-dimensional porous Ni foam (NF) as a novel electrochemical sensing platform for nonenzymatic glucose detection. NF not only acts as a working electrode, but also functions as an effective electrocatalyst for electrooxidation of glucose. The sensor exhibits high selectivity toward glucose. The linear range and limit of detection were 0.05–7.35 mM (R = 0.995) and 2.2 μM with a signal-to-noise ratio of 3, respectively. The application of this glucose sensor in human blood serum has also been demonstrated successfully.

The present paper reports on the facile preparation of novel Ni(II)-based metal–organic coordination polymer nanoparticle/reduced graphene oxide (NiCPNP/rGO) nanocomposites for the first time. The formation of the nanocomposites occurs in a single step, carried out by hydrothermal treatment of the mixture of tannic acid functioned graphene oxide and NiCl2 aqueous solution in N,N-dimethylformamide. It is found that the NiCPNP/rGO nanocomposite-modified electrode shows high electrocatalytic activity for glucose oxidation in alkaline medium. This nonenzymatic glucose sensor exhibits high selectivity toward glucose and the linear range and limit of detection are estimated to be from 0.01 to 8.75 mM (r: 0.997) and 0.14 μM with a signal-to-noise ratio of 3, respectively. The application of this glucose sensor in human blood serum has also been demonstrated successfully.

In this Letter, for the first time, we demonstrated the preparation of a highly efficient electrocatalyst, spinel CuCo2O4 nanoparticles supported on N-doped reduced graphene oxide (CuCo2O4/N-rGO), for an oxygen reduction reaction (ORR) under alkaline media. The hybrid exhibits higher ORR catalytic activity than CuCo2O4 or N-rGO alone, the physical mixture of CuCo2O4 nanoparticles and N-rGO, and Co3O4/N-rGO. Moreover, such a hybrid affords superior durability to the commercial Pt/C catalyst.

The present communication reports on a rapid exfoliation method for high-yield production of few-layer graphene flakes on a large scale from graphite within seconds with the use of chlorosulfonic acid and H2O2 as exfoliating agents.

The present article reports on a simple, economical, and green preparative strategy toward water-soluble, fluorescent carbon nanoparticles (CPs) with a quantum yield of approximately 6.9% by hydrothermal process using low cost wastes of pomelo peel as a carbon source for the first time. We further explore the use of such CPs as probes for a fluorescent Hg2+ detection application, which is based on Hg2+-induced fluorescence quenching of CPs. This sensing system exhibits excellent sensitivity and selectivity toward Hg2+, and a detection limit as low as 0.23 nM is achieved. The practical use of this system for Hg2+ determination in lake water samples is also demonstrated successfully.

In this communication, we develop a facile one-pot green strategy toward CuO–Cu2O–Cu nanorod-decorated reduced graphene oxide (CuNRs–rGO) composites by hydrothermal heating of the mixed solution of GO and Cu(OAc)2 under basic conditions without the use of extra reducing agents. As-synthesized composites have been successfully applied in photocurrent generation in the visible spectral region.

In this communication, we present a green photocatalytic method for the synthesis of highly dispersed Pd nanoparticles (PdNPs) with an average diameter of ca.10 ± 1 nm on the surface of reduced graphene oxide (RGO), using tin(IV) porphyrin (SnP) as a photocatalyst for the reduction of both graphene oxide (GO) and Pd(II). The as-prepared PdNPs–RGO nanocomposites exhibit higher electrocatalytic activities than the commercial Pd/C catalyst for methanol electro-oxidation in alkaline media.

The present communication reports on a novel synthesis of submicrometre-scale polyaniline colloidal spheres (PANICSs) using fluorescent carbon nitride dots (CNDs) as a photocatalyst for the first time. The subsequent treatment of such colloidal spheres with an aqueous AgNO3 solution produces Ag nanoparticles (AgNPs) decorated PANICSs (AgNPs–PANICSs) composites. Such composites exhibit remarkable catalytic performance toward catalytic reduction of 4-nitrophenol and electrochemical reduction of H2O2.

In this paper, we demonstrate our recent finding that CuO nanoflower-decorated reduced graphene oxide (CuONF/rGO) nanocomposites can be successfully prepared by heating the mixture of Cu salts and GO in the presence of poly[(2-ethyldimethylammonioethyl methacrylate ethyl sulfate)-co-(1-vinylpyrrolidone)] (PQ11) and urea for the first time. Several analytical techniques, including UV-vis spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) have been used to characterize the resulting CuONF/rGO nanocomposites. We further demonstrated that such CuONF/rGO nanocomposites can serve as an effective photocatalyst for degradation of rhodamine B (RhB) under UV irradiation. It also suggests that these CuONF/rGO nanocomposites exhibit a higher photocatalytic activity toward degradation of RhB than CuO nanoparticles or rGO samples.

Fe(III)-based coordination polymer nanoparticles (FeCPNPs) have been prepared for the first time by simple mixing of ferric chloride and sodium hexametaphosphate (SHAM) aqueous solutions at room temperature. It was found that such FeCPNPs possess peroxidase-like activity capable of catalyzing the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by H2O2 turning the solution blue in color. Based on these findings, a simple, sensitive and selective colorimetric assay to detect H2O2 was developed, with the linear range and detection limit estimated to be from 1 μM to 50 μM (r = 0.997) and 0.4 μM, respectively. The application of this colorimetric assay to glucose detection both in buffer solution and diluted serum has also been demonstrated successfully. This glucose sensor exhibits excellent performance with a linear range from 2 μM to 20 μM (r = 0.985) and a detection limit of about 1 μM.

Highly stable CuO nanoparticles about 2–4 nm in diameter have been successfully prepared by heating aqueous Cu(OAc)2 and urea solution in the presence of poly[(2-ethyldimethylammonioethyl methacrylate ethyl sulfate)-co-(1-vinylpyrrolidone)] (PQ11). Direct placing of the resultant dispersion on a glassy carbon electrode (GCE) without the use of an immobilization support matrix leads to very stable CuO nanoparticle-containing films with remarkable catalytic performance toward the oxidation of glucose. This sensor shows good response to glucose in comparison to other normally co-existing electroactive species (such as dopamine, ascorbic acid and uric acid). The linear detection range is estimated to be from 5 μM to 2.3 mM (r = 0.994), and the detection limit is estimated to be 0.5 μM at a signal-to-noise ratio of 3. More importantly, it suggests that this glucose sensor can be used for the glucose detection in human blood serum.

Polyaniline nanofibers (PANINFs) have been facilely prepared by electrochemical polymerization of aniline monomers in acidic aqueous media without using any templates and surfactants. The subsequent treatment of such nanofibers with a AgNO3 aqueous solution leads to in situ chemical reduction of Ag+ on them to form Ag nanoparticles decorated PANINFs (AgNPs/PANINFs) nanocomposites. We investigated the catalytic activity and electrochemical properties of these nanocomposites. It is found that such nanocomposites exhibit excellent catalytic activity toward reduction of 4-nitrophenol to 4-aminophenol by NaBH4 and exhibit remarkable catalytic performance for H2O2 reduction. The enzymeless H2O2 sensor constructed using the nanocomposites shows a fast amperometric response time of less than 3 s. The linear range and detection limit are estimated to be from 0.1 mM to 60 mM (r = 0.998) and 1.7 μΜ at a signal-to-noise ratio of 3, respectively. We have fabricated a glucose biosensor by immobilizing glucose oxidase into the AgNPs/PANINFs-modified glassy carbon electrode for glucose detection. This sensor exhibits good response to glucose. The linear response range is estimated to be from 1 mM to 12 mM (r = 0.997) at −0.58 V. The detection limit is estimated to be 0.25 mM at a signal-to-noise ratio of 3.

In this paper, we develop an environmentally friendly, one-pot strategy toward rapid preparation of Ag nanoparticle-decorated reducd graphene oxide (AgNPs/rGO) composites by heating the mixture of GO and AgNO3 aqueous solution in the presence of sodium hydroxide at 80 °C under stirring. The reaction was accomplished within a short period of 10 min without extra reducing agent. As-synthesized AgNPs/rGO composites have been successfully applied in photocurrent generation in the visible spectral region.

The present communication demonstrates the proof of concept of using CoFe layered double hydroxide (CoFe-LDHs) nanoplates as an effective peroxidase mimetic to catalyze the oxidation of peroxidase substrate 3,3′,5,5′-tetramethylbenzidine in the presence of H2O2 to produce a blue solution. We further demonstrate successfully CoFe-LDHs nanoplate-based colorimetric assay to detect H2O2 and glucose.

The present paper reports on the first preparation of 2,4,6-tris(2-pyridyl)-1,3,5-triazine nanobelts (TPTNBs) by adjusting the pH value of the solution and the subsequent synthesis of Ag nanoparticle (AgNP)-decorated TPTNBs (AgNP-TPTNBs) by mixing an aqueous AgNO3 solution with preformed TPTNBs without use of any external reducing agent. It is found that the resultant AgNP-TPTNBs exhibit notable catalytic performance for H2O2 reduction. A glucose biosensor was fabricated by immobilizing glucose oxidase (GOD) onto a AgNP-TPTNBs-modified glassy carbon electrode (GCE) for glucose detection. The constructed glucose sensor has a wide linear response range from 3 mM to 20 mM (r: 0.999) with a detection limit of 190 μM. It is further shown that this glucose biosensor can be used for glucose detection in human blood serum.

The present communication reports on a novel one-pot strategy toward rapid production of N-doped carbon nanoparticles-decorated carbon flakes (N-CNP-CFs) by microwave irradiation of N,N-dimethylformamide in the presence of H3PO4 for the first time. It suggests these N-CNP-CFs exhibit excellent ability to remove dye from water.

In this contribution, we demonstrate a green, cost-effective, one-pot preparative route toward Ag nanoparticles-graphene (AgNPs–G) nanocomposites in aqueous solution with the use of tannic acid (TA), an environmentally friendly and water-soluble polyphenol, as a reducing agent. Such AgNPs–G nanocomposites were synthesized through one-pot reduction of AgNO3 and GO by TA. We investigated surface enhanced Raman scattering (SERS) and electrochemical properties of the resultant AgNPs–G nanocomposites. It is found that such AgNPs–G nanocomposites show excellent SERS activity as SERS substrates and exhibit notable catalytic performance toward the reduction of H2O2. This enzymeless H2O2 sensor has a fast amperometric response time of less than 2 s. The linear range is estimated to be from 1 × 10−4 M to 0.01 M (r = 0.999) and the detection limit is estimated to be 7 × 10−6 M at a signal-to-noise ratio of 3. A glucose biosensor was further fabricated by immobilizing glucose oxidase (GOD) into chitosan–AgNPs–G nanocomposite film on the surface of a glassy carbon electrode (GCE). This sensor exhibits good response to glucose, and the linear response range is estimated to be from 2 to 10 mM (R = 0.996) at −0.5 V. The detection limit of 100 μM was achieved at a signal-to-noise ratio of 3. More importantly, we demonstrate successfully its application for glucose detection in human blood serum.

In this communication, we develop a facile, one-step strategy towards the rapid synthesis of ZnO nanoparticle-decorated reduced graphene oxide (rGO–ZnO) composites by directly immersing Zn plate in a GO solution containing ammonia with the aid of ultrasonication at room temperature. The rGO–ZnO composites obtained have applications in photocurrent generation in the visible spectral region of white light using zinc porphyrin (ZnP) as a photosensitizer.

The present communication reports on a general strategy for the production of photoluminescent carbon nitride dots (CNDs) by microwave heating of organic amines in the presence of acid. The resultant CNDs possess intrinsic peroxidase-like activity and have been successfully used as peroxidase mimetics for the colorimetric detection of H2O2 and glucose for the first time.

In this paper, we demonstrate the novel use of poly(3,4-ethylene dioxythiophene) (PEDOT) nanoparticle as a very effective fluorescent sensing platform for the detection of nucleic acid sequences. The principle of the assay lies in the fact that the adsorption of the fluorescently labeled single-stranded DNA (ssDNA) probe by PEDOT nanoparticle leads to substantial fluorescence quenching, followed by specific hybridization with the complementary region of the target DNA sequence. This results in desorption of the hybridized complex from PEDOT nanoparticle surface and subsequent recovery of fluorescence. A detection limit as low as 30 pM could be achieved in this sensing system. We also demonstrate its application for multiplexed detection of nucleic acid sequences. Furthermore, this sensing system can realize the detection of single-base mismatch even in multiplexed format. It is of importance to note that the successful use of this sensing platform in human blood serum system is also demonstrated.Keywords: blood serum; fluorescent; nanoparticles; nucleic acid detection; poly(3,4-ethylenedioxythiophene)

In this paper, we report on our recent finding that Ag+ can oxidize 3,3′,5,5′,-tetramethylbenzidine (TMB) to develop a blue color in aqueous solution, leading to a simple approach to colorimetric detection of Ag+ with a detection limit of 50 nM. Most importantly, we demonstrate its practical application to detect Ag+ in real sample.

We develop a novel single fluorophore-labeled double-stranded oligonucleotide (OND) probe for rapid, nanostructure-free, fluorescence-enhanced nucleic acid detection for the first time. We further demonstrate such probe is able to well discriminate single-base mutation in nucleic acid. The design takes advantage of an inherent quenching ability of guanine bases. The short strand of the probe is designed with an end-labeled fluorophore that is placed adjacent to two guanines as the quencher located on the long opposite strand, resulting in great quenching of dye fluorescence. In the presence of a target complementary to the long strand of the probe, a competitive strand-displacement reaction occurs and the long strand forms a more stable duplex with the target, resulting in the two strands of the probe being separated from each other. As a consequence of this displacement, the fluorophore and the quencher are no longer in close proximity and dye fluorescence increases, signaling the presence of target.

In this work, we develop a novel environmentally friendly strategy toward one-pot synthesis of CuS nanoparticle-decorated reduced graphene oxide (CuS/rGO) nanocomposites with the use of l-cysteine, an amino acid, as a reducing agent, sulfur donor, and linker to anchor CuS nanoparticles onto the surface of rGO sheets. Upon visible light illumination (λ > 400 nm), the CuS/rGO nanocomposites show pronounced enhanced photocurrent response and improved photocatalytic activity in the degradation of methylene blue (MB) compared to pure CuS. This could be attributed to the efficient charge transport of rGO sheets and hence reduced recombination rate of excited carriers.

In this article, we demonstrate the facile preparation of carbon nanospheres on a large scale by treating graphite with chlorosulfonic acid and their use as very effective quenchers for highly sensitive and selective nucleic acid and thrombin detection. The detection is accomplished by two steps: (1) a carbon nanosphere (CNS) adsorbs and quenches the fluorescence of a dye-labeled single-stranded DNA (ssDNA) probe; (2) in the presence of a target, the biomolecular mutual interaction suppresses fluorescence quenching, which makes the ssDNA detach from the CNS surface, leading to recovery of the dye fluorescence.

The present communication reports on the first preparation of reduced graphene oxide (rGO) viasurface plasmon resonance (SPR)-induced visible light photocatalytic reduction of GO with the use of Ag nanoparticles (AgNPs) as a plasmonic photocatalyst in the presence of an electron donor (ED).

The present paper reports an organic solvent-induced controllable crystallization of a water-soluble inorganic salt Na3[Au(SO3)2] into ultralong nanobelts and hierarchical microstructures of one-dimensional (1D) nanowires. It was found that the morphology of the resulting crystals can be fine tuned by simply varying the experimental parameters, such as the ratios of water to organic solvent and gold salt to organic solvent, as well as the type of organic solvent.

In this communication, we demonstrate for the first time that conducting polymer polyaniline (PANI) nanofibres can serve as a novel fluorescent sensing platform for nucleic acid detection with a high selectivity down to single-base mismatch.

In this article, we report on the use of multi-walled carbon nanotubes (MWCNTs) as an effective fluorescent sensing platform for nucleic acid detection with selectivity down to single-base mismatch. The detection is accomplished with two steps: (1) MWCNTs adsorb and quench the fluorescence of the dye-labeled single-stranded DNA (ssDNA) probe; (2) in the presence of the target, a hybridization event occurs, which produces a double-stranded DNA (dsDNA) that detaches from the MWCNT surface, leading to the restoration of the dye fluorescence. We also compared the sensing responses of MWCNTs and single-walled carbon nanotubes (SWCNTs) under the same experimental conditions.

The present communication demonstrates the use of water-soluble nano-C60 as a novel, effective fluorescent sensing platform for Hg2+ detection for the first time. This sensing system achieves a detection limit as low as 500 pM and exhibits excellent selectivity.

Coordination polymer colloids have been used as an effective fluorescent sensing platform for multiplexing nucleic acid detection capable of distinguishing complementary and mismatched target sequences for the first time.

In this communication, we demonstrate for the first time the proof of concept that carbon nanoparticles (CNPs) can be used as an effective fluorescent sensing platform for nucleic acid detection with selectivity down to single-base mismatch. The dye-labeled single-stranded DNA (ssDNA) probe is adsorbed onto the surface of the CNPvia π–π interaction, quenching the dye. In the target assay, a double-stranded DNA (dsDNA) hybrid forms, recovering dye fluorescence.

In this communication, we develop a novel fluorescent aptasensor for thrombin detection with the use of poly(m-phenylenediamine) (PMPD) rods as an effective sensing platform. This aptasensor exhibits extraordinarily high sensitivity with a detection limit as low as 100 pM and excellent selectivity.

A stable aqueous dispersion of reduced graphene oxide (rGO) has been prepared by the chemical reduction of graphene oxide with the use of benzylamine as a reducing and stabilizing agent. Raman spectroscopy, and X-ray photoelectron spectroscopy were used to characterize the resulting rGO. The rGO could be decorated with Ag nanoparticles (AgNPs) by direct adsorption of preformed, negatively-charged AgNPs. It was found that the resulting hybrid exhibits good catalytic activity toward the reduction of hydrogen peroxide, leading to an enzymeless sensor with a fast amperometric response time of less than 2 s. The linear detection range is estimated to be from 100 μM to 100 mM (r = 0.999), and the detection limit is estimated to be 31.3 μM at a signal-to-noise ratio of 3.

In this paper, we report on the use of 3,4,9,10-perylenetetracarboxylic diimide microfibers (PDIMs) as an effective fluorescent sensing platform for DNA detection for the first time. This sensing system exhibits a detection limit as low as 15 nmol L−1 and has a high selectivity down to single-base mismatch. The general concept used in this approach is based on adsorption of fluorescently labeled single-stranded DNA (ssDNA) probe by PDIM due to the strong π–π stacking between unpaired DNA bases and PDIM. As a result, the fluorophore is brought into close proximity of PDIM, leading to substantial fluorescence quenching. In the presence of the target, the specific hybridization of the probe with its complementary DNA sequence generates a double stranded DNA (dsDNA) which detaches from PDIM, leading to fluorescence recovery. Its generality of this sensing platform for protein detection is also demonstrated.Graphical abstractHighlights► 3,4,9,10-Perylenetetracarboxylic diimide microfibers (PDIMs) can be prepared by sonication. ► PDIMs can serve as a fluorescent sensing platform for DNA and thrombin detection. ► The suggested method has high sensitivity and selectivity down to single-base mismatch. ► A detection limit as low as 15 nM was obtained for DNA detection.

In this communication, we develop a relatively green, and environment friendly route for the synthesis of Au nanostructures on tannic acid (TA)-functionalized graphene oxide (GO) using TA as a reducing and immobilizing agent. The morphologies of Au nanostructures can be controlled by the amount of HAuCl4 used. The resultant Au nanostructures/GO nanocomposites exhibit good catalytic activity toward 4-nitrophenol (4-NP) reduction and the GO supports also enhance the catalytic activityvia a synergistic effect.

In this communication, we demonstrate for the first time that Pd nanoparticles/graphene nanocomposites (PdNPs–G) can be rapidly synthesized through a microwave-assisted, environmentally friendly, one-pot method with the use of tannic acid (TA) as a reducing agent. It is suggested that the loading amount and sizes of PdNPs on a G sheet can be controlled by the ratio of raw materials and microwave irradiation time. It is also found that the electrocatalytic activity and stability of the resultant PdNPs–G nanocomposites are much better than that of commercial Pd/C catalysts towards methanol electrooxidation in alkaline media.

We have recently found that the direct mixing of m-phenylenediamine (MPD) and AgNO3 aqueous solutions at room temperature leads to Ag@poly(m-phenylenediamine) (Ag@PMPD) core–shell nanoparticles (Langmuir, 2011, 27, 2170). In this study, we characterize such core–shell nanoparticles in more detail by X-ray diffraction and IR techniques and further demonstrate that the size of the core and whole particle as well as the ratio of the shell thickness to the core size can be tuned by the molar ratio of MPD to Ag. Furthermore, the PMPD shell can be further used as a reductant to reduce Ag+ into small Ag nanoparticles (AgNPs) which are embedded in the PMPD matrix, leading to nanoparticles with a Ag core and a small AgNP-embedded PMPD shell (Ag@PMPD–Ag core–shell nanoparticles). The Ag core, although buried in the central part of the resultant nanoparticle, can still catalyze the reduction of H2O2, but the embedded AgNPs in the PMPD matrix exhibit superior catalytic performance. With these Ag@PMPD–Ag core–shell nanoparticles, we constructed an enzymeless H2O2 sensor with a fast amperometric response time of less than 2 s, a linear range of 0.1 to 170 mM and a detection limit of 2.5 μM at a signal-to-noise ratio of 3.

In this Communication, we report on the first preparation of conjugation polymer poly(2,3-diaminonaphthalene) (PDAN) microspheres via chemical oxidation polymerization of 2,3-diaminonaphthalene (DAN) monomers by ammonium persulfate (APS) at room temperature. We further demonstrate the use of PDAN microspheres as a novel quencher for fluorescence-enhanced nucleic acid detection.

The chemical oxidation polymerization of m-phenylenediamine (MPD) by ammonium persulfate (APS) at room temperature results in the formation of poly(m-phenylenediamine) (PMPD) microparticles. The subsequent treatment of such microparticles with an aqueous AgNO3 solution produces Ag nanoparticle (AgNP)-decorated PMPD microparticles. It was found that as-formed AgNPs exhibited remarkable catalytic performance toward the reduction of hydrogen peroxide (H2O2). The enzymeless H2O2 sensor constructed with such composites showed a fast amperometric response time of less than 5 s, and the corresponding linear range and detection limit were estimated to be from 0.1 to 30 mM and 4.7 µM, respectively, at a signal-to-noise ratio of 3.

An aqueous dispersion of reduced graphene oxide (rGO) has been successfully prepared via chemical reduction of graphene oxide (GO) by hydrazine hydrate in the presence of aniline for the first time. The noncovalent functionalization of rGO by aniline leads to a rGO dispersion that can be very stable for several months without the observation of any floating or precipitated particles. Several analytical techniques including Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) have been used to characterize the resulting rGO. Taking advantages of the fact reducing ability of aniline toward AgNO3, we further demonstrated the subsequent decoration of rGO with Ag nanoparticles (AgNPs) by in situ chemical reduction of silver salts. It was found that such AgNP/rGO nanocomposites exhibit good catalytic activity toward the reduction of hydrogen peroxide (H2O2), leading to an enzymeless sensor with a fast amperometric response time of less than 2 s. The linear detection range is estimated to be from 100 μM to 80 mM (r = 0.9991), and the detection limit is estimated to be 7.1 μM at a signal-to-noise ratio of 3.Graphical abstractAn aqueous dispersion of reduced graphene oxide has been successfully prepared via chemical reduction of graphene oxide by hydrazine hydrate in the presence of aniline for the first time. We further demonstrated the subsequent decoration of rGO with Ag nanoparticles by in situ chemical reduction of silver salts, and the resultant AgNP/rGO nanocomposites exhibit good catalytic activity toward the reduction of hydrogen peroxide.Highlights► Stable dispersions of rGO were prepared using aniline as stabilizing agent. ► rGO was decorated by Ag nanoparticle via in situ reduction of Ag salt by aniline. ► The resulting AgNP/rGO exhibits notable catalytic activity toward reduction of H2O2.

A novel single-labeled fluorescent oligonucleotide (OND) probe for the detection of nanomolar silver(I) ion in aqueous solution is developed based on the inherent quenching ability of deoxyguanosines. The formation of a hairpin structure of the OND–Ag+ complex brings deoxyguanosines close to a dye, leading to a decreased fluorescence intensity of the dye owning to photoinduced electron transfer from the dye to deoxyguanosines.

In this communication, we demonstrate for the first time that titanium silicalite-1 zeolite microparticles (TSZMs) can effectively catalyze the reduction of H2O2, leading to an enzymeless H2O2 sensor with a linear detection range from 100 μM to 40 mM (r = 0.994) and a detection limit of 0.5 μM at a signal-to-noise ratio of 3.

In this Communication, we report water-soluble nano-C60 in the first use as an effective fluorescent sensing platform for the highly sensitive and selective detection of Ag+. The general concept used in this approach is based on a fluorescently labeled single-stranded DNA (ssDNA) probe that adsorbs on nano-C60, leading to substantial dye fluorescence quenching; however, in the presence of Ag+, C–Ag+–C coordination induces the probe to fold into a hairpin structure, which does not adsorb on nano-C60 and thus retains the dye fluorescence. This sensing system exhibits a detection limit as low as 1 nM and has a high selectivity against other metal ions. Finally and most importantly, we demonstrate its performance in real sample analysis.

In this communication, we demonstrate our recent finding that iron-substituted SBA-15 (Fe-SBA-15) microparticles possess intrinsic peroxidase-like activity and can catalyze the oxidation of peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 to develop a blue color in aqueous solution, leading to a simple approach towards colorimetric detection of H2O2 with a linear detection range from 0.4 μM to 15 μM (r = 0.997) and a detection limit of 0.2 μM.

A stable aqueous dispersion of poly(3,4-ethylenedioxythiophene) (PEDOT) nanorods stabilized by graphene oxide (GO) has been successfully prepared via interface polymerization of EDOT in the presence of GO for the first time. The non-covalent functionalization of PEDOT by GO leads to a PEDOT–GO dispersion that can be stable for several days without the observation of any floating or precipitated particles. Several analytical techniques including Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) have been used to characterize the resultant PEDOT–GO nanocomposites. It is found that such PEDOT–GO nanocomposites exhibit good catalytic activity toward the oxidation of nitrite, leading to a sensor for detection of nitrite. The linear detection range and detection limit are estimated to be 4 μM to 2.48 mM (r = 0.999), and 1.2 μM at a signal-to-noise ratio of 3, respectively.

In this paper, we report on the large-scale, rapid synthesis of coordination polymer microdendrites (CPMDs) assembled from Pd(II) and p-phenylenediamine for the first time. We further explored the use of the CPMDs as an effective fluorescent sensing platform for DNA detection. This sensing system exhibits a low detection limit of 13 nM and a high selectivity down to single-base mismatch. The detection is accomplished in two steps: (1) CPMDs adsorb the dye-labeled single-stranded DNA probe and quenches the fluorescence; (2) in the presence of the target, a hybridization event occurs, which produces a double-stranded DNA that detaches from the CPMD surface, leading to the recovery of the dye fluorescence.

In this communication, we report on acid-driven, microwave-assisted production of fluorescent carbon nitride dots (CNDs) on a large scale by microwave irradiation of N,N-dimethylformamide (DMF) solution in the presence of acids including chlorosulfonic acid (CSA), H2SO4, HCl, or HNO3. It suggests these CNDs are well water-soluble and exhibit strong fluorescence.

In this contribution, we demonstrate that polystyrene (PS) nanospheres can serve as an effective sensing platform for fluorescence-enhanced DNA detection. This kind of assay can be completed by the following two steps: (1) PS quenches the fluorescence of dye-labeled single-stranded DNA (ssDNA) probes very effectively when they are brought into close proximity as a result of the adsorption of ssDNA on PS. The adsorption is ascribed to the strong π–π stacking between unpaired DNA bases and PS. (2) Upon presence of target ssDNA, the specific hybridization of the probe with its target produces a double-stranded DNA (dsDNA). The duplex detaches from PS due to its rigid conformation, the absence of unpaired DNA bases, and electrostatic repulsion between negatively charged dsDNA backbone and PS, leading to recovery of dye fluorescence. This assay system exhibits high selectivity and sensitivity with a detection limit as low as 5 nM. It suggests that this sensing platform can differentiate between perfectly complementary and mismatched targets. The fluorescence enhancement in response to single-base mismatched target T2, two-base mismatched target T3, and three-base mismatched target T4 is about 71%, 63%, and 58% of that from complementary target T1, respectively. The suggested method can also discriminate complementary and single-base mismatched sequences embedded in rather larger strands with short oligonucleotide probes. The fluorescence enhancement in response to single-base mismatched sequence embedded in large strand is 83% of that from the one embedded with complementary sequence. In further experiments, it is demonstrated that the present system can be used for multiple DNA detection. Finally, efforts are made toward its application in human blood serum system to evaluate the ability to withstand the interference arising from real sample.

In this paper we report on the electrodeposition-based construction of film of nano-roughened, hierarchical Au microstructures on indium tin oxide (ITO) surface in a controllable manner. It is found that both the nanotexture and the size of such microstructures can be simply controlled by varying the concentration of Au composition or the deposition potential used. Study on time-evolved microstructure growth further reveals that both the size of the microstructures and the surface coverage of the substrate can be tuned in a continuous mode. It is also found that such Au film exhibits high catalytic activity towards the oxidation of H2O2.Highlights► We report on the construction of Au microstructures on indium tin oxide surface. ► The microstructures can be controlled by varying the concentration of Au composition. ► The microstructures can be controlled by varying the deposition potential. ► The microstrutures and the surface coverage of substrate can be tuned continuously. ► Such Au film exhibits high catalytic activity towards the oxidation of H2O2.

In this communication, we demonstrate our recent findings that carboxyl functionalized mesoporous polymer (CFMP) obtained by solvothermal polymerization of divinylbenzene and methacrylic acid possesses intrinsic peroxidase-like activity and can catalyze the oxidation of peroxidase substrate 3,3,5,5,-tetramethylbenzidine (TMB) by H2O2 to develop a blue color in aqueous solution, providing a simple approach to colorimetric detection of H2O2 with a linear detection range from 1 μM to 8 μM (r = 0.997) and a detection limit of 0.4 μM.

In this communication, we report on the use of tetracyanoquinodimethane nanoparticles (TNs) as an effective fluorescent sensing platform for nucleic acid detection for the first time. The general concept used in this approach is based on adsorption of fluorescently labeled single-stranded DNA (ssDNA) probe by TN, due to the strong π–π stacking between unpaired DNA bases and TN. As a result, the fluorophor is brought into close proximity of TN, leading to substantial fluorescence quenching via photoinduced electron transfer between fluorescent dye and TN. Upon presence of the target ssDNA, specific hybridization with the target takes place to form a double-stranded DNA (dsDNA). The helix cannot be adsorbed by TN due to its rigid conformation and the absence of unpaired DNA bases. Thus, the fluorophor is seperated from TN accompanied by fluorescence recovery. This fluorescence enhancement signals completion of the assay. It also suggests that this sensing platform can well differentiate perfect complementary and mismatched sequences. A detection limit as low as 1.5 nM was obtained.

In this Letter, we demonstrate that chemical oxidation polymerization of o-phenylenediamine (OPD) by potassium bichromate at room temperature results in the formation of submicrometer-scale poly(o-phenylenediamine) (POPD) colloids. Such colloids can absorb and quench dye-labeled single-stranded DNA (ssDNA) very effectively. In the presence of a target, a hybridization event occurs, which produces a double-stranded DNA (dsDNA) that detaches from the POPD surface, leading to recovery of dye fluorescence. With the use of an oligonucleotide (OND) sequence associated with human immunodeficiency virus (HIV) as a model system, we demonstrate the proof of concept that POPD colloid-quenched fluorescent OND can be used as a probe for fluorescence-enhanced nucleic acid detection with selectivity down to single-base mismatch.

In this Letter, we demonstrate the first use of carbon nanoparticles (CNPs) obtained from carbon soot by lighting a candle as a cheap, effective fluorescent sensing platform for Ag+ detection with a detection limit as low as 500 pM and high selectivity. We further demonstrate its practical application to detect Ag+ in a real sample.

Graphene platelet–glucose oxidase (GP–GOD) nanostructures have been prepared through self-assembly of GOD and chitosan (CS) functionalized GPs by electrostatic attraction in aqueous solution. The stable aqueous dispersion of GPs was prepared by chemical reduction of graphene oxide with the use of CS as a reducing and stabilizing agent. UV–vis spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy were used to characterize the resulting GPs and GP–GOD nanostructures. Furthermore, a glucose biosensor was constructed by deposition of the resultant GP–GOD on the surface of glassy carbon electrode. It was found that the resulting biosensor exhibits good response to glucose. The linear detection range is estimated to be from 2 to 22 mM (r = 0.9987), and the detection limit is estimated to be 20 μM at a signal-to-noise ratio of 3.

In this letter, we report on the one-step synthesis of Ag@poly(m-phenylenediamine) core−shell nanoparticles (APCSNPs), carried out by direct mixing of aqueous silver nitrate and m-phenylenediamine solutions at room temperature. We further demonstrate the use of APCSNP as a novel fluorescent sensing platform for nucleic acid detection. In this regard, the detection of DNA is accomplished in two steps. First, APCSNP absorbs and quenches the fluorescence of dye-labeled single-stranded DNA (ssDNA) as a probe. Second, hybridizing of the probe with its target produces a double-stranded DNA (dsDNA) that detaches from APCSNP, resulting in the recovery of dye fluorescence. It suggests that this sensing system has a high selectivity down to single-base mismatch, and the results exhibit good reproducibility. Furthermore, we also demonstrate its application for the multiplex detection of nucleic acid sequences.

The present paper presents the novel use of MC microparticles (MCMPs) as a novel fluorescent sensing platform for thrombin detection. The MCMPs were prepared by a nanocasting method using mesoporous silica (MS) NPs as a hard template. The general concept used in this approach lies in the facts that the non-covalent adsorption of the dye-labeled TA on MCMP driven by π–π stacking of DNA bases on MCMP leads to substantial quenching of dye fluorescence due to their very close proximity. However, the presence of target TB results in the change of TA conformation to quadruplex due to the quadruplex–TB complex formation. Because the binding between the complex and MCMP is not strong enough to guarantee the close proximity of dyes to MCMP surface, fluorescence quenching is suppressed. This sensing system has a low detection limit down to 0.25 nM and exhibits excellent selectivity. We also demonstrate its application in human blood serum system.

In this paper, we report on the first preparation of well-defined SiO2-coated graphene oxide (GO) nanosheets (SiO2/GO) without prior GO functionalization by combining sonication with sol–gel technique. The functional SiO2/GO nanocomposites (F-SiO2/GO) obtained by surface functionalization with NH2 group were subsequently employed as a support for loading Ag nanoparticles (AgNPs) to synthesize AgNP-decorated F-SiO2/GO nanosheets (AgNP/F-SiO2/GO) by two different routes: (1) direct adsorption of preformed, negatively charged AgNPs; (2) in situ chemical reduction of silver salts. The morphologies of these nanocomposites were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). It is found that the resultant AgNP/F-SiO2/GO exhibits remarkable catalytic performance for H2O2 reduction. This H2O2 sensor has a fast amperometric response time of less than 2 s. The linear range is estimated to be from 1 × 10−4 M to 0.26 M (r = 0.998) and the detection limit is estimated to be 4 × 10−6 M at a signal-to-noise ratio of 3, respectively. We also fabricated a glucose biosensor by immobilizing glucose oxidase (GOD) into AgNP/F-SiO2/GO nanocomposite-modified glassy carbon electrode (GCE) for glucose detection. Our study demonstrates that the resultant glucose biosensor can be used for the glucose detection in human blood serum.Highlights► Well-defined SiO2-coated graphene oxide nanosheets are prepared. ► F-SiO2/GO nanosheets are obtained by surface functionalization with NH2 group. ► F-SiO2/GO nanosheets decorated with Ag nanoparticles by two different routes. ► They show remarkable catalytic performance toward H2O2 reduction. ► They can be used for glucose detection in human blood serum.

In this article, carbon nanoparticles (CNPs) were used as a novel fluorescent sensing platform for highly sensitive and selective Hg2+ detection. To the best of our knowledge, this is the first example of CNPs obtained from candle soot used in this type of sensor. The general concept used in this approach is based on that adsorption of the fluorescently labeled single-stranded DNA (ssDNA) probe by CNP via π–π stacking interactions between DNA bases and CNP leads to substantial dye fluorescence quenching; however, in the presence of Hg2+, T–Hg2+–T induced hairpin structure does not adsorb on CNP and thus retains the dye fluorescence. A detection limit as low as 10 nM was achieved. The present CNP-based biosensor for Hg2+ detection exhibits remarkable specificity against other possible metal ions. Furthermore, superior selectivity performance was observed when Hg2+ detection was carried out in the presence of a large amount of other interference ions. Finally, in order to evaluate its potential practical application, Hg2+ detection was conducted with the use of lake water other than pure buffer and it is believed that it holds great promise for real sample analysis upon further development.

The present communication demonstrates a relatively green preparative route toward Au nanoplates in aqueous solution at room temperature with the use of tannic acid (TA), which is an environmentally friendly, soluble polyphenol, as a reducing agent. Such Au nanoplates exhibit notable catalytic performance toward the oxidation and reduction of H2O2. A glucose biosensor was further fabricated by immobilizing glucose oxidase (GOD) into chitosan–Au nanoplate composites film on the surface of glassy carbon electrode (GCE). This sensor exhibits good response to glucose, and the linear response range is estimated to be from 2 to 20 mM (R = 0.999) at 0.65 V and from 2 to 10 mM (R = 0.993) at −0.2 V, respectively. The sensitivity of the sensor determined from the slopes is 49.5 μA mM−1 cm−2 at 0.65 V.

In this article, we report on the first use of fluorescence resonance energy transfer (FRET) dye-labeled probe for fluorescence resonance enhanced DNA detection to greatly improve discrimination ability toward single-base mismatch using conjugation polymer poly(p-phenylenediamine) nanobelts (PNs) as a sensing platform. The suggested FRET dye-labeled probe contains a 5-carboxyfluorescein (FAM) group at 5′ end of the oligomer as a donor and a 6-carboxy-X-rhodamine (ROX) attached to a modified cytosine (C) base as an acceptor, which were separated by three bases. The general concept used in this DNA assay is based on adsorption of the FRET dye-labeled single-stranded DNA (ssDNA) probe by PN, which is accompanied by substantial fluorescence quenching and disappearance of FRET. The subsequent specific hybridization with its target forms a double-stranded DNA (dsDNA), resulting in desorption of the hybridized duplex from PN surface accompanied by reoccurrence of FRET and fluorescence recovery. It suggests that the discrimination ability of this FRET probe based system toward single-base mismatch is about 5.2 times that of the system based on single dye-labeled probe based system.Highlights► FRET dye-labeled probe improves discrimination ability to single-base mismatch. ► It solves the low discrimination ability issue with the nano/microstructure platforms. ► This fluorescent sensing system holds great potential for practical mismatch detection.

Herein, we develop a novel single fluorophore-labeled double-stranded oligonucleotide (OND) probe for rapid fluorescence-enhanced K+ detection, based on an inherent quenching ability of guanine bases and G-rich OND conformation transition from duplex to G-quadruplex. This probe presents high sensitivity and good selectivity for the detection of K+, and the assay process is simple and fast.

In this letter, we report on our interesting finding that the direct mixing of aqueous AgNO3 and NH2OH solutions at room temperature leads to rapid, high-yield production of monodisperse, micrometer-scale, highly crystalline, nanotextured Ag dendrites. The surface-enhanced Raman scattering (SERS) effect of these Ag dendrites was evaluated by using 4-aminothiophenol (p-ATP) as the Raman probe and the results demonstrate that they exhibit strong SERS effects.Keywords: Ag; dendrite; monodisperse; nanoparticle; SERS; wet-chemical synthesis

In this letter, we demonstrate for the first time the electrostatically driven assembly of (3-aminopropyl)triethoxysilane (APTES) and HAuCl4 in aqueous media into novel micrometer-scale supramolecular sheets and their subsequent transformation into small, stable APTES bilayer-capped gold nanoparticles through a thermal process. The nanoparticle formation mechanism is also discussed.

An aqueous dispersion of graphene nanosheets (GNs) has been successfully prepared via chemical reduction of graphene oxide (GO) by hydrazine hydrate in the presence of poly[(2-ethyldimethylammonioethyl methacrylate ethyl sulfate)-co-(1-vinylpyrrolidone)] (PQ11), a cationic polyelectrolyte, for the first time. The noncovalent functionalization of GN by PQ11 leads to a GN dispersion that can be very stable for several months without the observation of any floating or precipitated particles. Several analytical techniques including UV−vis spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) have been used to characterize the resulting GNs. Taking advantages of the fact that PQ11 is a positively charged polymer exhibiting reducing ability, we further demonstrated the subsequent decoration of GN with Ag nanoparticles (AgNPs) by two routes: (1) direct adsorption of preformed, negatively charged AgNPs; (2) in-situ chemical reduction of silver salts. It was found that such Ag/GN nanocomposites exhibit good catalytic activity toward the reduction of hydrogen peroxide (H2O2), leading to an enzymeless sensor with a fast amperometric response time of less than 2 s. The linear detection range is estimated to be from 100 μM to 40 mM (r = 0.996), and the detection limit is estimated to be 28 μM at a signal-to-noise ratio of 3.

In this letter a simple wet-chemical route was developed to prepare silver nanostructures. The formation of the silver nanostructures occurs in a single process, carried out by mixing an AgNO3 aqueous solution and a para-phenylenediamine solution at room temperature without the introduction of other reducing agents and morphology controlling agents. It is found that both the morphology and the size of such silver nanostructures can be facilely controlled by the molar ratio and concentration of the reactants as well as the solvent that was used to dilute para-phenylenediamine aqueous solution. As-formed silver nanostructures were examined by scanning electron microscopy.

The direct mix of aqueous FeCl3 and o-phenylenediamine (OPD) solutions at room temperature leads to supramolecular microfibrils of OPD dimers generated by the oxidation of OPD monomers by FeCl3 (Sun, X.; Hagner, M. Langmuir 2007, 23, 10441). In this Letter, we report on our recent finding that the subsequent treatment of such microfibrils with a AgNO3 aqueous solution transforms them into nanofibers decorated with spherical silver nanoparticles (AgNPs) with sizes in range of 5−20 nm. The possible formation mechanism involved is also discussed. It is interestingly found that as-formed AgNPs exhibit good catalytic activity toward the reduction of H2O2, leading to an enzymeless sensor with a fast amperometric response time of less than 5 s. The linear detection range is estimated to be from 100 μM to 80 mM (r = 0.998), and the detection limit is estimated to be 62 μM at a signal-to-noise ratio of 3.

In this article, we report on the use of multi-walled carbon nanotubes (MWCNTs) as an effective fluorescent sensing platform for nucleic acid detection with selectivity down to single-base mismatch. The detection is accomplished with two steps: (1) MWCNTs adsorb and quench the fluorescence of the dye-labeled single-stranded DNA (ssDNA) probe; (2) in the presence of the target, a hybridization event occurs, which produces a double-stranded DNA (dsDNA) that detaches from the MWCNT surface, leading to the restoration of the dye fluorescence. We also compared the sensing responses of MWCNTs and single-walled carbon nanotubes (SWCNTs) under the same experimental conditions.

The present communication reports on a rapid exfoliation method for high-yield production of few-layer graphene flakes on a large scale from graphite within seconds with the use of chlorosulfonic acid and H2O2 as exfoliating agents.

In this communication, we present a green photocatalytic method for the synthesis of highly dispersed Pd nanoparticles (PdNPs) with an average diameter of ca.10 ± 1 nm on the surface of reduced graphene oxide (RGO), using tin(IV) porphyrin (SnP) as a photocatalyst for the reduction of both graphene oxide (GO) and Pd(II). The as-prepared PdNPs–RGO nanocomposites exhibit higher electrocatalytic activities than the commercial Pd/C catalyst for methanol electro-oxidation in alkaline media.

Polyaniline nanofibers (PANINFs) have been facilely prepared by electrochemical polymerization of aniline monomers in acidic aqueous media without using any templates and surfactants. The subsequent treatment of such nanofibers with a AgNO3 aqueous solution leads to in situ chemical reduction of Ag+ on them to form Ag nanoparticles decorated PANINFs (AgNPs/PANINFs) nanocomposites. We investigated the catalytic activity and electrochemical properties of these nanocomposites. It is found that such nanocomposites exhibit excellent catalytic activity toward reduction of 4-nitrophenol to 4-aminophenol by NaBH4 and exhibit remarkable catalytic performance for H2O2 reduction. The enzymeless H2O2 sensor constructed using the nanocomposites shows a fast amperometric response time of less than 3 s. The linear range and detection limit are estimated to be from 0.1 mM to 60 mM (r = 0.998) and 1.7 μΜ at a signal-to-noise ratio of 3, respectively. We have fabricated a glucose biosensor by immobilizing glucose oxidase into the AgNPs/PANINFs-modified glassy carbon electrode for glucose detection. This sensor exhibits good response to glucose. The linear response range is estimated to be from 1 mM to 12 mM (r = 0.997) at −0.58 V. The detection limit is estimated to be 0.25 mM at a signal-to-noise ratio of 3.

Fe(III)-based coordination polymer nanoparticles (FeCPNPs) have been prepared for the first time by simple mixing of ferric chloride and sodium hexametaphosphate (SHAM) aqueous solutions at room temperature. It was found that such FeCPNPs possess peroxidase-like activity capable of catalyzing the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by H2O2 turning the solution blue in color. Based on these findings, a simple, sensitive and selective colorimetric assay to detect H2O2 was developed, with the linear range and detection limit estimated to be from 1 μM to 50 μM (r = 0.997) and 0.4 μM, respectively. The application of this colorimetric assay to glucose detection both in buffer solution and diluted serum has also been demonstrated successfully. This glucose sensor exhibits excellent performance with a linear range from 2 μM to 20 μM (r = 0.985) and a detection limit of about 1 μM.

In this communication, we demonstrate for the first time that Pd nanoparticles/graphene nanocomposites (PdNPs–G) can be rapidly synthesized through a microwave-assisted, environmentally friendly, one-pot method with the use of tannic acid (TA) as a reducing agent. It is suggested that the loading amount and sizes of PdNPs on a G sheet can be controlled by the ratio of raw materials and microwave irradiation time. It is also found that the electrocatalytic activity and stability of the resultant PdNPs–G nanocomposites are much better than that of commercial Pd/C catalysts towards methanol electrooxidation in alkaline media.

In this communication, we report on the use of tetracyanoquinodimethane nanoparticles (TNs) as an effective fluorescent sensing platform for nucleic acid detection for the first time. The general concept used in this approach is based on adsorption of fluorescently labeled single-stranded DNA (ssDNA) probe by TN, due to the strong π–π stacking between unpaired DNA bases and TN. As a result, the fluorophor is brought into close proximity of TN, leading to substantial fluorescence quenching via photoinduced electron transfer between fluorescent dye and TN. Upon presence of the target ssDNA, specific hybridization with the target takes place to form a double-stranded DNA (dsDNA). The helix cannot be adsorbed by TN due to its rigid conformation and the absence of unpaired DNA bases. Thus, the fluorophor is seperated from TN accompanied by fluorescence recovery. This fluorescence enhancement signals completion of the assay. It also suggests that this sensing platform can well differentiate perfect complementary and mismatched sequences. A detection limit as low as 1.5 nM was obtained.

In this communication, we demonstrate our recent findings that carboxyl functionalized mesoporous polymer (CFMP) obtained by solvothermal polymerization of divinylbenzene and methacrylic acid possesses intrinsic peroxidase-like activity and can catalyze the oxidation of peroxidase substrate 3,3,5,5,-tetramethylbenzidine (TMB) by H2O2 to develop a blue color in aqueous solution, providing a simple approach to colorimetric detection of H2O2 with a linear detection range from 1 μM to 8 μM (r = 0.997) and a detection limit of 0.4 μM.

In this communication, we develop a relatively green, and environment friendly route for the synthesis of Au nanostructures on tannic acid (TA)-functionalized graphene oxide (GO) using TA as a reducing and immobilizing agent. The morphologies of Au nanostructures can be controlled by the amount of HAuCl4 used. The resultant Au nanostructures/GO nanocomposites exhibit good catalytic activity toward 4-nitrophenol (4-NP) reduction and the GO supports also enhance the catalytic activityvia a synergistic effect.

We have recently found that the direct mixing of m-phenylenediamine (MPD) and AgNO3 aqueous solutions at room temperature leads to Ag@poly(m-phenylenediamine) (Ag@PMPD) core–shell nanoparticles (Langmuir, 2011, 27, 2170). In this study, we characterize such core–shell nanoparticles in more detail by X-ray diffraction and IR techniques and further demonstrate that the size of the core and whole particle as well as the ratio of the shell thickness to the core size can be tuned by the molar ratio of MPD to Ag. Furthermore, the PMPD shell can be further used as a reductant to reduce Ag+ into small Ag nanoparticles (AgNPs) which are embedded in the PMPD matrix, leading to nanoparticles with a Ag core and a small AgNP-embedded PMPD shell (Ag@PMPD–Ag core–shell nanoparticles). The Ag core, although buried in the central part of the resultant nanoparticle, can still catalyze the reduction of H2O2, but the embedded AgNPs in the PMPD matrix exhibit superior catalytic performance. With these Ag@PMPD–Ag core–shell nanoparticles, we constructed an enzymeless H2O2 sensor with a fast amperometric response time of less than 2 s, a linear range of 0.1 to 170 mM and a detection limit of 2.5 μM at a signal-to-noise ratio of 3.

In this study, we demonstrate that hydrothermal carbonization of low-cost wastes of willow bark leads to water-soluble, photoluminescent carbon dots (CDs) with diameters ranging from 1 to 4 nm and a quantum yield of approximately 6.0%. We further demonstrate the proof of concept that such CDs can be used as an effective photocatalyst for the simultaneous reduction of Au(III) complex and graphene oxide to form Au nanoparticles decorated reduced graphene oxide (AuNPs–rGO) nanocomposites by UV irradiation of a mixture of GO and HAuCl4 aqueous solution in the presence of CDs. It is found that the resultant AuNPs–rGO nanocomposites exhibit notable catalytic performance for H2O2 reduction and oxidation. Furthermore, we fabricate a glucose biosensor by immobilizing glucose oxidase on the AuNPs–rGO-modified glassy carbon electrode for glucose detection. The linear response range and detection limit are estimated to be from 2 mM to 18 mM (r: 0.995) and 45 μM, respectively. The application of this glucose sensor in human blood serum has also been demonstrated successfully.

In this paper, we demonstrate our recent finding that CuO nanoflower-decorated reduced graphene oxide (CuONF/rGO) nanocomposites can be successfully prepared by heating the mixture of Cu salts and GO in the presence of poly[(2-ethyldimethylammonioethyl methacrylate ethyl sulfate)-co-(1-vinylpyrrolidone)] (PQ11) and urea for the first time. Several analytical techniques, including UV-vis spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) have been used to characterize the resulting CuONF/rGO nanocomposites. We further demonstrated that such CuONF/rGO nanocomposites can serve as an effective photocatalyst for degradation of rhodamine B (RhB) under UV irradiation. It also suggests that these CuONF/rGO nanocomposites exhibit a higher photocatalytic activity toward degradation of RhB than CuO nanoparticles or rGO samples.

The present communication reports on a novel synthesis of submicrometre-scale polyaniline colloidal spheres (PANICSs) using fluorescent carbon nitride dots (CNDs) as a photocatalyst for the first time. The subsequent treatment of such colloidal spheres with an aqueous AgNO3 solution produces Ag nanoparticles (AgNPs) decorated PANICSs (AgNPs–PANICSs) composites. Such composites exhibit remarkable catalytic performance toward catalytic reduction of 4-nitrophenol and electrochemical reduction of H2O2.

In this communication, we develop a facile one-pot green strategy toward CuO–Cu2O–Cu nanorod-decorated reduced graphene oxide (CuNRs–rGO) composites by hydrothermal heating of the mixed solution of GO and Cu(OAc)2 under basic conditions without the use of extra reducing agents. As-synthesized composites have been successfully applied in photocurrent generation in the visible spectral region.

In this communication, we demonstrate for the first time the proof of concept that carbon nanoparticles (CNPs) can be used as an effective fluorescent sensing platform for nucleic acid detection with selectivity down to single-base mismatch. The dye-labeled single-stranded DNA (ssDNA) probe is adsorbed onto the surface of the CNPvia π–π interaction, quenching the dye. In the target assay, a double-stranded DNA (dsDNA) hybrid forms, recovering dye fluorescence.

Coordination polymer colloids have been used as an effective fluorescent sensing platform for multiplexing nucleic acid detection capable of distinguishing complementary and mismatched target sequences for the first time.

In this communication, we develop a novel fluorescent aptasensor for thrombin detection with the use of poly(m-phenylenediamine) (PMPD) rods as an effective sensing platform. This aptasensor exhibits extraordinarily high sensitivity with a detection limit as low as 100 pM and excellent selectivity.

Large-scale industrial application of electrochemical water splitting calls for remarkable non-noble metal electrocatalysts. Herein, we report on the synthesis of a NiMo-alloy hollow nanorod array supported on Ti mesh (NiMo HNRs/TiM) using a template-assisted electrodeposition method. The NiMo HNRs/TiM behaves as a durable efficient oxygen evolution anode with 10 mA cm−2 at an overpotential of 310 mV in 1.0 M KOH. Coupled with its superior catalytic performance for hydrogen evolution with 10 mA cm−2 at an overpotential of 92 mV, we made an alkaline electrolyzer using this bifunctional electrode with 10 mA cm−2 at a cell voltage of 1.64 V.

In this article, we demonstrate the facile preparation of carbon nanospheres on a large scale by treating graphite with chlorosulfonic acid and their use as very effective quenchers for highly sensitive and selective nucleic acid and thrombin detection. The detection is accomplished by two steps: (1) a carbon nanosphere (CNS) adsorbs and quenches the fluorescence of a dye-labeled single-stranded DNA (ssDNA) probe; (2) in the presence of a target, the biomolecular mutual interaction suppresses fluorescence quenching, which makes the ssDNA detach from the CNS surface, leading to recovery of the dye fluorescence.

Highly stable CuO nanoparticles about 2–4 nm in diameter have been successfully prepared by heating aqueous Cu(OAc)2 and urea solution in the presence of poly[(2-ethyldimethylammonioethyl methacrylate ethyl sulfate)-co-(1-vinylpyrrolidone)] (PQ11). Direct placing of the resultant dispersion on a glassy carbon electrode (GCE) without the use of an immobilization support matrix leads to very stable CuO nanoparticle-containing films with remarkable catalytic performance toward the oxidation of glucose. This sensor shows good response to glucose in comparison to other normally co-existing electroactive species (such as dopamine, ascorbic acid and uric acid). The linear detection range is estimated to be from 5 μM to 2.3 mM (r = 0.994), and the detection limit is estimated to be 0.5 μM at a signal-to-noise ratio of 3. More importantly, it suggests that this glucose sensor can be used for the glucose detection in human blood serum.