Carboxyl-modified graphene oxide (GOÀCOOH) is shown to possess intrinsic peroxidase-like activity that can catalyze the reaction of peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H 2 O 2 to produce a blue color reaction. A simple, cheap, and highly sensitive and selective colorimetric method for glucose detection has been developed and been used in buffer solution or diluted blood and fruit juice samples. Our work will facilitate the utilization of the intrinsic peroxidase activity of GOÀCOOH in medical diagnostics and biotechnology.As a novel one-atom-thick planar sheet of sp 2 -bonded carbon atoms, graphene has received much attention in recent years in materials science and biotechnology. [1][2][3][4][5][6][7][8][9][10][11] Significant progress has been made for the utilization of graphene in nanoelectronics, [1,3] nanocomposites, [4,5,7] biosensors, [8,9] and drug delivery. [10,11] Production of graphene sheets in bulk quantity and its modification with functional groups to improve water solubility have been recently reported. [6,11] All these achievements provide new insights into the application of this nanomaterial in medical diagnosis and biosensing. Here, we report that carboxyl-modified graphene oxide (GOÀCOOH) has peroxidase-like activity that can catalyze the reaction of peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H 2 O 2 to produce a blue color reaction. Kinetic studies indicate that GOÀCOOH has even higher catalytic activity to TMB than the natural enzyme, horseradish peroxidase (HRP). Like HRP, the catalytic reaction follows a ping-pong mechanism. Further studies indicate that the observed peroxidase-like activity is not related to the trace amount of metal catalyst in the sample but instead is caused by its own intrinsic property. This is evidenced by energy-dispersive X-ray (EDX) analysis.Peroxidase has great potential for practical application and can be used as a diagnostic kit for hydrogen peroxide (H 2 O 2 ) and glucose. For control of diabetes mellitus, it is important for minimizing diabetic complications to maintain blood glucose concentrations within the normal physiological range. [12] Up to now, a number of glucose sensors have been reported. [13][14][15][16][17][18][19][20][21] Among them, horseradish peroxidase (HRP) has been widely used to fabricate sensors for detection of the products of the glucose oxidase. [16][17][18][19][20][21] In comparison with HRP, GOÀCOOH is low-cost, easy to obtain, more stable to biodegradation, and less vulnerable to denaturation. These advantages indicate that GOÀCOOH can be useful in environmental monitoring and medical diagnostics. In this Communication, using GOÀCOOH peroxidase-like catalytic activity and glucose oxidase (GOx), a colorimetric method for glucose detection has been developed (Scheme 1). The results indicate that this method is simple, cheap, and highly sensitive and selective for glucose detection and has been used in buffer solution and diluted blood or fruit juice samples.GO...

A novel strategy to dissociate amyloid aggregation is presented, using localised heat generation from a clinically used amyloid staining dye, thioflavin-S (ThS)-modified graphene oxide (GO) under NIR laser irradiation. Compared to traditional chemotherapies, photothermal therapy shows reduced side effects and improved selectivity and safety.

Engineering carbon materials as the bifunctional catalysts for both electrocatalytic oxygen reduction/evolution reactions (ORR/OER) is highly promising for the large-scale commercialization of regenerative fuel cells and rechargeable metal-air batteries. Codoping carbons with heteroatoms can achieve unique electronic structures and show tailored electrocatalytic capabilities by rationally regulating their dopants. Sulfur is one of the most important dopants from both experimental and theoretical perspectives. In this work, a novel, highly efficient and environmentally benign method for sulfur incorporation into carbon framework has been developed facilely on the basis of graphene oxide-polydopamine (GD) hybrids to derive the N, S-codoped mesoporous carbon nanosheets. 16.7 at. % S can be conjugated to the GD hybrids associated with the S doping efficiency up to 6.1% after 800 o C pyrolysis, which is higher than most previous S doping approaches. The resultant N, Scodoped mesoporous carbon nanosheets exhibit superior performance with favorable kinetics and excellent durability as a bifunctional ORR and OER catalyst, which is much better than that of most reported metal-free doped carbon, even transition metal and noble metal catalysts. The high concentrations of multiple dopants, abundant porous architecture and good electron transfer ability are believed to significantly expedite the ORR and OER catalytic processes. In the light of physicochemical versatility and structural tunability of polydopamine (PDA), this work provides a universal platform towards further development of PDA-based carbon materials with heteroatom dopants as the highly efficient electrocatalysts.

SWNTs possess intrinsic peroxidase‐like activity, catalyzing the reaction of peroxidase substrate 3,3,5,5‐tetramethylbenzidene (TMB) in the presence of H2O2 to produce a color reaction. Here SWNTs have been used for label‐free colorimetric detection of disease‐associated single‐nucleotide polymorphism with a direct detection limit of 1 nM.

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A facile, economic and green one-step hydrothermal synthesis route using dopamine as source towards photoluminescent carbon nanoparticles (CNPs) is proposed. The as-prepared CNPs have an average size about 3.8 nm. The emission spectra of the CNPs are broad, ranging from approximately 380 (purple) to approximately 525 nm (green), depending on the excitation wavelengths. Due to the favorable optical properties, the CNPs can readily enter into A549 cells and has been used for multicolor biolabeling and bioimaging. Most importantly, the as-prepared CNPs contain distinctive catechol groups on their surfaces. Due to the special response of catechol groups to Fe(3+) ions, we further demonstrate that such wholly new CNPs can serve as a very effective fluorescent sensing platform for label-free sensitive and selective detection of Fe(3+) ions and dopamine with a detection limit as low as 0.32 μM and 68 nM, respectively. The new "mix-and-detect" strategy is simple, green, and exhibits high sensitivity and selectivity. The present method was also applied to the determination of Fe(3+) ions in real water samples and dopamine in human urine and serum samples successfully.

Dual heteroatom-doped carbon materials are efficient electrocatalysts via a synergistic effect. With nitrogen as the primary dopant, boron, sulfur, and phosphorus can be used as secondary elements for co-doped carbons. However, evaluation and analysis of the promotional effect of B, P, and S to N-doped carbons has not been widely researched. Here we report a robust platform that is constructed through polydopamine to prepare N,B-, N,P-, and N,S-co-doped carbon nanosheets, characterized by similar N species content and efficient B, P, and S doping. Systematic investigation reveals S to have the greatest promotional effect in hydrogen evolution reactions (HER) followed by P and that B decreases the activity of N-doped carbons. Experimental and theoretical analyses show the secondary heteroatom promotional effect is impacted by the intrinsic structures and extrinsic surface areas of both materials, i.e., electronic structures exclusively determine the catalytic activity of active sites, while large surface areas optimize apparent HER performance.

carbides, [16,17] and borides [16] for HER and the oxides/hydroxides of Co, [18,19] Ni, [20][21][22] Mn, [23] and Fe [24][25][26][27] for OER. Practically, to achieve an overall water splitting generating oxygen and hydrogen simultaneously, the coupling of HER and OER catalysts in same electrolyte often results in incompatible integration of the catalysts and leads to inferior overall performance. As a result, CoO x , [28] NiFeO x , [29] CoP film, [30] and NiSe nanowire [31] have been developed as efficiently bifunctional HER and OER catalysts. However, inherent corrosion and oxidation susceptibility of these materials in either strongly acidic or alkaline solution largely limit their sustainable utilization, which in most cases underperform noble-metal catalysts.In recent years, nonmetallic heteroatom-doped carbon materials have been intensively studied for energyrelated electrocatalytic reactions such as oxygen reduction reaction (ORR), [32][33][34] OER, [35,36] and HER [37][38][39][40] due to their excellent electrical conductivity, tunable molecular structures, abundance, and strong tolerance to acidic/alkaline environments. Impressively, engineering carbon materials by codoping two or more selected heteroatoms greatly boosts their elctrocatalytic activities through synergistic coupling effect, [39,41] but more importantly, it can realize tailorable catalytic capabilities for specific electrocatalytic reactions by altering doping types, sites, and levels. [42][43][44] Correspondingly, several carbon materials have been synthesized for the bifunctional ORR and OER electrocatalysts with high activity and excellent stability. [43,45,46] Although some of these have recently been successfully developed as the HER electrocatalysts, [37][38][39][40] the employment of carbon-based nanomaterials as the bifunctional HER and OER electrocatalysts has not been reported to date. The possible reason is that the ORR and OER performance of carbon materials can be comparable to or even better than metal-based catalysts, but the HER catalytic efficiency of carbon-based materials still falls far short of that of the metallic benchmarks. [47][48][49] This represents the current bottleneck for the development of bifunctional HER and OER carbon electrocatalysts for overall water splitting.Recently, we demonstrated the unparalleled virtues of polydopamine (PDA) can be applied as an excellent platform for constructing multiple heteroatom-doped carbon materials for electrocatalytic ORR and OER. [46,50] In particular, PDA is extremely reactive to thiol groups via Schiff-base or Overall water splitting involved hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are critical for renewable energy conversion and storage. Heteroatom-doped carbon materials have been extensively employed as efficient electrocatalysts for independent HER or OER processes, while those as the bifunctional catalysts for simultaneously generating H 2 and O 2 by splitting water have been seldom reported. Inspired by the unparalleled virtues of po...