Vertical α-FeOOH nanowires grown on the carbon fiber paper as a free-standing electrode for sensitive H2O2 detection

Highly sensitive, selective, and stable hydrogen peroxide （H2O2） detection using nanozyme-based catalysts are desirable for practical applications. Herein, vertical α-FeOOH nanowires were successfully grown on the surface of carbon fiber paper （CFP） via a low-temperature hydrothermal procedure. The formation of vertical α-FeOOH nanowires is ascribed to the structure-directing role of sodium dodecyl sulfate. The resulting free-standing electrode with one-dimensional （1D） nanowires offers oriented channels for fast charge transfer, excellent electrical contact between the electrocatalyst and the current collector, and good mechanical stability and reproducibility. Thus, it can serve as an efficient electrocatalyst for the reduction and sensitive detection of H2O2. The relation of the oxidation current of H202 with the concentration is linear from 0.05 to 0.5 mM with a sensitivity of -0.194 mA/（mM.cm2） and a low detection limit of 18μM. Furthermore, the portability in the geometric tailor and easy device fabrication allow extending the general applicability of this free-standing electrode to chemical and biological sensors.

H_(2)O_(2)-sensitive nanoscale coordination polymers for photoacoustic tumors imaging via in vivo chromogenic assay

Photoacoustic(PA)imaging with much deeper tissue penetration and better spatial resolution had been widely employed for the prevention and diagnosis of many diseases.In this study,a new type of hydrogen peroxide(H_(2)O_(2)T-activated photoacoustic nanoprobe[Mn-AH nanoscale coordination polymer nanodots(NCPs)]was successfully synthesized by a simple one-step method in water phase containing 2,20-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS),horse radish peroxidase(HRP),and manganese ion(Mn^(2+).After modification by polyethylene glycol(PEG),Mn-AH NCPs exhibited excellent stability and biocompatibility for in vivo H_(2)O_(2)-responsive chromogenic assay with great speci¯city and sensitivity.In the presence of H_(2)O_(2),colorless ABTS would be converted by HRP into the oxidized form with strong near-infrared(NIR)absorbance,enabling photoacoustic detection of endogenous H_(2)O_(2).Using H_(2)O_(2)-activated Mn-AH NCPs,we have successfully performed PA imaging and H_(2)O_(2)detection of subcutaneous murine colon CT26 tumor and deep-seated orthotopic bladder tumor.Due to the inherent Mn element existence inside the Mn-AH,this nanoprobe also serves as a good T1-weighted magnetic resonance imaging(MRI)contrast agent simultaneously.Lastly,after accomplishing its imaging functions,the Mn-AH NCPs could be cleared out from the body without any long-term toxicity,providing a new opportunity for cancer diagnosis and treatment.

DNA-Templated Silver Nanoclusters Formation at Gold Electrode Surface and Its Application to Hydrogen Peroxide Detection

In this work, we have prepared Ag nanoclusters （Ag NCs） at gold electrode surface by using thiol-modified oligodeoxynucleotide consisting of eighteen cytosine deoxyribonucleotides （polyC18） as template and NaBH4 as reducing agent. Experimental results show that Ag nanoclusters （Ag NCs） can be formed around the template polyC18, while the formation can be characterized with electrochemical method. Further studies reveal that the fab- ricated Ag NCs may display high catalytic activity for the reduction of hydrogen peroxide （H2O2）, which can be further used for the detection of H20〉

Highly sensitive electrochemical detection of living cells based on diamond microelectrode arrays

We designed boron-doped nanocrystalline diamond microelectrode arrays（BNCD-MEAs） with 16 channels for the bioanalysis of multicellular samples, which could be readily adapted for a highly sensitive detection of H2 O2[2_TD$IF]released from stimulated cells by ascorbic acid（AA）. Our observations demonstrated that the as-prepared diamond microelectrode arrays could be utilized to distinguish cancer cells from normal cells, and the amperometric study showed the considerable differences in the currents, indicating that the related Hep G2 cancer cells could release more H2 O2 than that of L02 normal cells. This supports the possibility to use diamond-based MEAs for rapid cancer cell detection in future clinic applications.

Multifunctional shape-dependent plasmonic nanoprobe by enzymatic etching of single gold triangular nanoplate

Hydrogen peroxide(H2O2),as a signaling molecule,plays a vital role in a wide variety of signaling transduction processes,aging,and diseases.However,the excessive production of H2O2 causes various diseases.Herein,we develop a novel method for H2O2 detection in live cells via dark-field scattering spectroscopy with gold triangular nanoprisms(AuTNPs)as probes.The corners of AuTNPs would be gradually oxidatively etched by the strong coordination of Br•which is generated by enzymatic reactions in the presence of horseradish peroxidase(HRP),bromide ion and trace hydrogen peroxide.Benefitting from the morphological change,the single AuTNP based plasmonic nanoprobe shows notable blueshifts and scattering color changes which could be real-time monitored under the dark-field microscopy.The peak position in the scattering spectra of individual AuTNP blueshifts linearly with the increase of H2O2 concentration,and exhibits high sensitivity to H2O2 in a large range from 2.5 to 100µM with a low detection limit(LOD)of 0.74µM.Moreover,the experimental results were supported by the simulated results via the finite-difference time-domain(FDTD)method.The nanoprobes have been further used for intracellular H2O2 detection in live cells.Besides,the etching of AuTNP also provides an alternative method to design novel plasmonic logic chips and write-once plasmonic memories.

Facile synthesis of enzyme functional metal-organic framework for colorimetric detecting H_2O_2 and ascorbic acid

In this work,a metal-organic frameworks material MIL-88 was prepared easily using solvent-thermal method,and was first found to have catalytic activities similar to those of biological enzymes such as catalase and peroxidase.The material was characterized by XRD,SEM,TEM,EDX,FT-IR techniques and an N2 adsorption method.It exhibited peroxidase-like activity through catalytic oxidation of the peroxidase substrate 3,3＇,5,5＇-tetramethylbenzidine（TMB） in the presence of H2O2,producing a blue-colored solution.Under optimal conditions,the absorbance at 652 nm is linearly correlated with the concentration of H2O2 from 2.0×10^-6 mol/L to 2.03×10^-5 mol/L（R-2=0.981） with a detection limit of 5.62×10^-7 mol/L（S/N=3）.More importantly,a sensitive and selective method for ascorbic acid detection was developed using this material as a catalyst.The analytical method for ascorbic acid detection was observed to have a linear range from 2.57×10^-6 mol/L to 1.01×10^-5 mol/L（R-2=0.989） with a detection limit of 1.03×10^-6 mol/L（S/N=3）.This work suggests MOFs have advantages of preparing biomimetic catalysts and extends applications of the functional MOFs in the field of biosensor.