Host-Guest Mechanism via Induced Fit Fullerene Complexation in Porphin Receptor to Probe Salivary Alpha-Amylase in Dental Caries for Clinical Applications.

Salivary α-amylase is the most abundant protein of human saliva that potentially binds to streptococcus and other bacteria via specific surface-exposed α-amylase-binding proteins and plays a significant role in caries development. The detection of α-amylase in saliva can be used as a bioindicator of caries development. Herein, a facile strategy has been applied, tailoring the photochemical properties of 5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H-porphine (TPPOH) and the fullerene C60 complex. The fluorescence emission of TPPOH is quenched by starch-coated fullerene C60 via charge-transfer effects, as determined by UV absorption and fluorescence spectroscopic studies. The starch-coated C60 has been thoroughly characterized via Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), optical microscopy, thermal gravimetric analysis (TGA), static water contact angle measurements, and zeta potential measurements. The analytical response of the assay showed a linear fluorescent response in α-amylase concentrations ranging from 0.001-0.1 Units/mL, with an LOD of 0.001 Units/mL. The applicability of the method was tested using artificial saliva with quantitative recoveries in the range 95-100%. The practicability of the procedure was verified by inspecting saliva samples of real clinical samples covering all age groups. We believe that the proposed method can serve as an alternative analytical method for caries detection and risk assessment that would also minimize the cost of professional preventive measures and treatments.

Growth of diazonium-functionalized ZnO nanoflakes on flexible carbon cloth for electrochemical sensing of acetone in the liquid phase.

Simple detection of acetone is indispensable due to its health and environmental concerns. Surface-modified electrodes are promising for the detection of acetone. In the present study, the facile fabrication of ZnO nanoflakes on carbon cloth (CC) is reported. The electrode was fabricated by decorating the CC with ZnO nanoparticles (ZnO NPs), followed by the hydrothermal treatment and modification with diazonium salt using linear sweep voltammetry (LSV) forming ZnO nanoflakes (ZnO NFs) on ZnO NPs/CC. The as-prepared ZnO/CC electrode was used for the detection of acetone at room temperature using cyclic voltammetry. Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) analyses were used for the chemical and physical characterization of the CC before and after each modification step. The obtained data manifested that ZnO NFs functionalized with diazonium salt increased the roughness of the CC surface, which was advantageous to promote the interaction between CC and acetone target. The modified sensing platform showed excellent performance in terms of the wide working range (0.1-2000 ppm) and low detection limit (0.03 ppm), making it a promising and cost-effective sensor of acetone in the liquid phase.

Fabrication of polydopamine decorated carbon cloth as support material to anchor CeO2 nanoparticles for electrochemical detection of ethanol.

A flexible CeO2 nanostructured polydopamine-modified carbon cloth (CeO2/PDA/CC) interface was fabricated via electrodeposition for ethanol detection. The fabrication method involved two consecutive electrochemical steps in which dopamine was firstly electrodeposited on carbon fibers, followed by the electrochemical growth of CeO2 nanoparticles. The CeO2/PDA-based electroactive interface exerts an impressive electrochemical performance on the flexible sensor due to strong synergistic effect of the PDA functionalization with more active sites. Moreover, catalytic activity of CeO2 nanostructures anchored on highly conductive CC incorporate superior electrocatalytic performance of the fabricated interface. The designed electrochemical sensor showed a wide response to ethanol in the linear range 1 to 25 mM with a detection limit of 0.22 mM. The CeO2/PDA/CC flexible sensor showed good anti-interference ability and excellent repeatability and reproducibility (RSD = 1.67%). The fabricated interface performed well in saliva samples with satisfactory recoveries, corroborating the viability of CeO2/PDA/CC integrated interface for practical implementation.

In-situ synthesized ZIF-67 graphene oxide (ZIF-67/GO) nanocomposite for efficient individual and simultaneous detection of heavy metal ions.

Heavy metals are ubiquitous in water bodies as a result of anthropogenic activities and over time they accumulate in body thus posing serious health problems. Therefore, it is essential to improve sensing performance, for determination of heavy metal ions (HMIs), of electrochemical sensors. In this work, cobalt-derived MOF (ZIF-67) was in-situ synthesized and incorporated onto the surface of graphene oxide (GO) by simple sonication method. The prepared material (ZIF-67/GO) was characterized by FTIR, XRD, SEM, and Raman spectroscopy. Afterwards, a sensing platform was made by drop-casting synthesized composite onto glassy carbon electrode for individual and simultaneous detection of heavy metal ions pollutants (Hg2+, Zn2+, Pb2+, and Cr3+) with estimated detection limits of 2 nM, 1 nM, 5 nM, and 0.6 nM, respectively, when determined simultaneously, that are below the permissible limit by World Health Organization. To the best of our knowledge, this is first report of HMIs detection by ZIF-67 incorporated GO sensor which can successfully determine the Hg+2, Zn+2, Pb+2, and Cr+3 ions simultaneously with lower detection limits.

Graphene oxide reinforced silk fibroin nanocomposite as an electroactive interface for the estimation of dopamine.

The fabrication of 2D materials and polymer-based nanocomposites deposited on flexible conductive interfaces has unblocked new horizons to expedite reaction kinetics for developing highly selective and sensitive electrochemical biosensors. Herein, we developed a novel biosensing platform, comprising graphene oxide and a silk fibroin-based nanocomposite, drop-cast on a carbon cloth electrode. The fabricated interface was expected to be a robust and miniaturized sensing platform for precise detection of dopamine (DA). Characterization was performed by SEM, EDX, FTIR, XRD, UV-visible spectroscopy, contact angle measurement, fluorescence spectroscopy, particle size, and zeta potential analysis. CV, EIS, DPV, and chronoamperometry demonstrated the superior electrochemical properties of the working interface and revealed its enhanced active surface area, increased conductivity, and accelerated electron transfer rate. The designed interface exhibited low LoD (0.41 µM), admirable stability, good sensitivity (2.46 µA µM-1 cm-2), wide linearity ranging from 100-900 µM, excellent reproducibility, and superb selectivity against dopamine even in the presence of possible interfering analytes. These findings endorse the feasibility of the practical execution of such an integrated system in real sample analysis.

Multifunctional Smart ZnSe-Nanostructure-Based Fluorescent Aptasensor for the Detection of Ochratoxin A.

Herein, we present a comprehensive investigation of rationally designed zinc selenide (ZnSe) nanostructures to achieve highly negatively charged ZnSe nanostructures. A Microwave-assisted hydrothermal synthesis method was used to synthesize three types of ZnSe nanostructures, i.e., nanorods, µ-spheres and nanoclusters, as characterized by a zeta potential analyzer, X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and BET, which were labeled as type A, B and C. Three different solvents were used for the synthesis of type A, B and C ZnSe nanostructures, keeping other synthesis conditions such as temperature, pressure and precursors ratio constant. Based on two heating time intervals, 6 and 9 h, types A, B and C were further divided into types A6, A9, B6, B9, C6 and C9. ZnSe nanostructures were further evaluated based on their fluorescent quenching efficiency. The maximum fluorescence quenching effect was exhibited by the ZnSe-B6 type, which can be attributed to its highly negative surface charge that favored its strong interaction with cationic dye Rhodamine B (Rh-B). Further, the optimized ZnSe-B6 was used to fabricate an aptasensor for the detection of a food-based toxin, ochratoxin-A (OTA). The developed aptasensor exhibited a limit of detection of 0.07 ng/L with a wide linear range of 0.1 to 200 ng/L.

N-Doped graphene quantum dots (N-GQDs) as fluorescent probes for detection of UV induced DNA damage.

UV induced DNA damage can lead to the development of skin cancer, skin aging and cell death. In this study, we fabricated a fluorescence-based biosensor that can be applied to the detection of DNA damage caused by UV radiation with the help of nitrogen doped graphene quantum dots (N-GQDs) as the probe material. In this paper, N-GQDs with good fluorescence efficiency have been synthesized by the hydrothermal method and were used as a fluorescent probe for the detection of UV damaged DNA. The fluorescence intensity of N-GQDs was quenched by the static quenching of UV damaged DNA through the formation of a N-GQD/UV damaged DNA complex. Moreover, the effects of different values of pH, NaCl and glucose on analytical performances of the sensor were also studied. Thus, using a fluorescence based approach, we demonstrated a quite simple, rapid, and inexpensive biosensor for the detection of DNA damage caused by UV radiation.

Functionalized organic filler based integrated membranes for environmental remediation.

Mixed matrix membranes (MMMs) are synthesized for efficient CO2 separation released from various anthropogenic sources, which are due to global environmental concerns. The synergetic effect of porous nitrogen-rich, CO2-philic filler and polymer in mixed matrix-based membranes (MMMs) can separate CO2 competent. The development of various loadings of porphyrin poly(N-isopropyl Acryl Amide) (P-NIPAM)as functionalized organic fillers (5-20%) in polysulfone (PSU) through solution casting is carried out followed by the various characterizations including field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), Fourier Transform Infrared Spectrometer(FT-IR) analysis and pure and mixed gas permeations ranging from 2 to 10 bar feed pressure. Due to both organic species interactions in the matrix, well-distributed fillers and homogenous surfaces, and cross-sectional structures were observed due to π-π interactions and Lewis's basic functionalities. The strong affinity of porous nitrogen-rich and CO2-philic fillers through gas permeation analysis showed high CO2/CH4 and CO2/N2 gas performance that surpassed Robeson's upper bound limit. Comparatively, MMMs showed improved CO2/CH4 permeabilities from 87.5 ± 0.5 Barrer to 88.2 ± 0.9 Barrer than pure polymer matrix. For CO2/N2, CO2 permeabilities improved to 75 ± 0.8 Barrer than pure polymer matrix. For both gas pairs (CO2/CH4, CO2/N2), respective pureselectivities (84%; 86%) and binary selectivities (85% and 85%)were improved. Various theoretical gas permeation models were used to predict CO2 permeabilities for MMMs from which the modified Maxwell-Wagner-Sillar model showed the least AARE% of 0.87. The results showed promising results for efficient CO2 separation due to exceptional functionalized P-PNIPAM affinitive properties. Finally, cost analysis reflected the inflated cost of membranes production for industrial setup using indigenous resources.

Functionalized thiazolidone-decorated lanthanum-doped copper oxide: novel heterocyclic sea sponge morphology for the efficient detection of dopamine.

Herein, we synthesized lanthanum (La)-doped sea sponge-shaped copper oxide (CuO) nanoparticles and wrapped them with novel O-, N- and S-rich (2Z,5Z)-3-acetyl-2-((3,4-dimethylphenyl)imino)-5-(2-oxoindolin-3-ylidene)thiazolidin-4-one (La@CuO-DMT). The shape and composition of the designed materials were confirmed by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and Raman spectroscopy. The graphitic pencil electrode (GPE) fabricated using La@CuO-DMT showed excellent sensing efficacy against dopamine (DA) with good selectivity, reproducibility and ideal stability. The unique morphology and massive surface defects by La@CuO offer good accessibility to DA and enhance smooth and robust channeling of electrons at the electrode-electrolyte interface. Consequently, these properties resulted in improved reaction kinetics and robust DA oxidation with an amplified faradaic response. Meanwhile, O-, N-, and S-enriched carbon support, i.e. DMT, inhibited the leaching of electrode matrixes, resulting in a superior detection limit of 423 nm and an improved sensitivity of 13.9 µA µM-1 cm-2 in the linear range of 10 µM to 1500 µM. Additionally, the developed sensing interface was successfully employed to analyze DA from tear samples with excellent percentage recoveries. We expect that such engineered morphology-based nanoparticles with a O-, N-, and S-rich C support will facilitate the development of DA sensors for in vitro screening of rarely studied tear samples with good sensitivity and selectivity.

Insight into prognostics, diagnostics, and management strategies for SARS CoV-2.

The foremost challenge in countering infectious diseases is the shortage of effective therapeutics. The emergence of coronavirus disease (COVID-19) outbreak has posed a great menace to the public health system globally, prompting unprecedented endeavors to contain the virus. Many countries have organized research programs for therapeutics and management development. However, the longstanding process has forced authorities to implement widespread infrastructures for detailed prognostic and diagnostics study of severe acute respiratory syndrome (SARS CoV-2). This review discussed nearly all the globally developed diagnostic methodologies reported for SARS CoV-2 detection. We have highlighted in detail the approaches for evaluating COVID-19 biomarkers along with the most employed nucleic acid- and protein-based detection methodologies and the causes of their severe downfall and rejection. As the variable variants of SARS CoV-2 came into the picture, we captured the breadth of newly integrated digital sensing prototypes comprised of plasmonic and field-effect transistor-based sensors along with commercially available food and drug administration (FDA) approved detection kits. However, more efforts are required to exploit the available resources to manufacture cheap and robust diagnostic methodologies. Likewise, the visualization and characterization tools along with the current challenges associated with waste-water surveillance, food security, contact tracing, and their role during this intense period of the pandemic have also been discussed. We expect that the integrated data will be supportive and aid in the evaluation of sensing technologies not only in current but also future pandemics.

Nickel -doped iron oxide nanoparticle-conjugated porphyrin interface (porphyrin/Fe2O3@Ni) for the non-enzymatic detection of dopamine from lacrimal fluid.

Herein, we synthesized nickel (Ni)-doped iron oxide nanoparticles (Fe2O3). The presence of the dopant afforded anchoring sites for the porphyrinic hetero cavity of 5,10,15,20-(tetra-4-carboxyphenyl)porphyrin to produce the porphyrin/Fe2O3@Ni composite. The crystalline structure and morphology of porphyrin/Fe2O3@Ni were assessed using various tools including Fourier transform spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Raman spectroscopy. Porphyrin/Fe2O3@Ni has proven to be an excellent dopamine (DA) probe material with good selectivity, reproducibility, stability and reliability owing to its clever morphology, which induces numerous active sites along with good active surface area. It consequently provides good accessibility to DA and allows for the smooth tunneling of electrons between the analyte and sensing interface. Meanwhile, the porphyrin molecules provide good carbon-based resilient support, inhibit the leaching of the electrode matrix and enhance electron shuttling, resulting in the robust oxidation of DA with amplified transduction signals. The designed porphyrin/Fe2O3@Ni interface showed a low detection limit (1.2 nm) with good sensitivity (1.2 nM) in the linear bounds of 10 µM to 3500 µM. Additionally, the interface was employed successfully to analyze DA from lacrimal fluid with good percentage recoveries (99.8% to 100.1%). We anticipate that such a design will simplify the in vitro screening of DA in rarely studied tear samples with sensitivity and selectivity.

Fabrication of ionic liquid stabilized MXene interface for electrochemical dopamine detection.

Development of MXene (Ti3C2Cl2)-based sensing platforms by exploiting their inherent active electrochemistry is highly challenging due to their characteristic poor stability in air and water. Herein, we report a cost-effective methodology to deposit MXene on a conductive graphitic pencil electrode (GPE). MXenes can provide active surface area due to their clever morphology of accordion-like sheets; however, the disposition to stack together limits their potential applications. A task-specific ionic liquid (1-methyl imidazolium acetate) is utilized as a multiplex host material to engineer MXene interface via π-π interactions as well as to act as a selective binding site for biomolecules. The resulting IL-MXene/GPE interface proved to be a highly stable interface owing to good interactions between MXene and IL that inhibited electrode leaching and boosted electron transfer at the electrode-electrolyte interface. It resulted in robust dopamine (DA) oxidation with amplified faradaic response and enhanced sensitivity (9.61 µA µM-1 cm-2) for DA detection. This fabricated sensor demonstrated large linear range (10 µM - 2000 µM), low detection limit (702 nM), high reproducibility, and good selectivity. We anticipate that such platform will pave the way for the development of stable and economically viable MXene-based sensors without sacrificing their inherent properties. Scheme 1 Schematic illustration of the IL-MXene/GPE fabrication and oxidative process towards non-enzymatic dopamine sensor.

Perylene diimide/MXene-modified graphitic pencil electrode-based electrochemical sensor for dopamine detection.

The synthesis of novel architecture comprising perylene diimide (PDI)-MXene (Ti3C2TX)-integrated graphitic pencil electrode for electrochemical detection of dopamine (DA) is reported. The good electron passage between PDI-MXene resulted in an unprecedented nano-adduct bearing enhanced electrocatalytic activity with low-energy electronic transitions. The anionic groups of PDI corroborated enhanced active surface area for selective binding and robust oxidation of DA, thereby decreasing the applied potential. Meanwhile, the MXene layers acted as functional conducive support for PDI absorption via strong H-bonding. The considerable conductivity of MXene enhanced electron transportation thus increasing the sensitivity of sensing interface. The inclusively engineered nano-adduct resulted in robust DA oxidation with ultra-sensitivity (38.1 µAµM-1cm-2), and low detection limit (240 nM) at very low oxidation potential (-0.135 V). Moreover, it selectively signaled DA in the presence of physiological interferents with wide linearity (100-1000 µM). The developed transducing interface performed well in human serum samples with RSD (0.1 to 0.4%) and recovery (98.6 to 100.2%) corroborating the viability of the practical implementation of this integrated system. Graphical abstract Schematic illustration of the oxidative process involved on constructed sensing interface for the development of a non-enzymatic dopamine sensor.

Sustainable mixed matrix membranes containing porphyrin and polysulfone polymer for acid gas separations.

The synergetic effect of nitrogen-rich and CO2-philic filler and polymer in mixed matrix-based membranes (MMMs) can separate CO2 competently. The introduction of well-defined nanostructured porous fillers of pores close to the kinetic diameter of the gas molecule and polymer matrix compatibility is a challenge in improving the gas transportation characteristics of MMMs. This study deals with the preparation of porphyrin filler and the polysulfone (PSf) polymer MMMs. The fillers demonstrated uniform distribution, uniformity, and successful bond formation. MMMs demonstrated high thermal stability with a glass transition temperature in the range of 480-610 °C. The porphyrin filler exhibited microporous nature with the presence of π-π bonds and Lewis's basic functionalities between filler-polymer resulted in a highly CO2-philic structure. The pure and mixed gas permeabilities and selectivity were successfully improved and surpass the Robeson's upper bound curve's tradeoff. Additionally, the temperature influence on CO2 permeability revealed lower activation energies at higher temperatures leading to the gas transport facilitation. This can be granted consistency and long-term durability in polymer chains. These results highlight the unique properties of porphyrin fillers in CO2 separation mixed matrix membranes and offer new knowledge to increase comprehension of PSf performance under various contents or environments.

Copper oxide integrated perylene diimide self-assembled graphitic pencil for robust non-enzymatic dopamine detection.

Exploring a robust, extremely sensitive, cost-effective and reliable assay platform for the precise analysis of dopamine (DA) has become a big challenge predominantly at the clinical level. To participate in this quest, herein, we fabricated a perylene diimide (PDI) self-assembled graphitic surface of the graphitic pencil electrode (GPE) anchored copper oxide (CuO). The self-assembled N-rich PDI led to the fast movement of ions by decreasing the bandgap and improved the electron transport kinetics with more exposed catalytic active sites, thus resulting in the robust electrochemical sensing of DA. The designed sensor exhibited good sensitivity (4 µM-1 cm-2), high structural stability, repeatability and excellent reproducibility with an RSD value of 2.9%. Moreover, the developed system showed a wide linear range (5 µM to 500 µM) and reliable selectivity even in the presence of co-existing interferants, such as ascorbic acid and uric acid. The fabricated nanohybrid was eventually employed to analyze DA in spiked physiological fluids and provided satisfactory recoveries. The designed PDI-CuO based interface also showed a very low detection limit of 6 nM (S/N = 3), consequently confirming its suitability for clinical and biological applications.

Fluorescence quenching mediated detection of hydrogen peroxide using tungsten incorporated graphitic carbon nitride nanoflakes.

A reliable, non-enzymatic detection for H2O2 with high sensitivity and accuracy is of profound importance and getting considerable interest due to its usefulness in biological systems. Therefore, this work was aimed to develop a sensitive method for the detection of H2O2 using rhodamine B as a fluorescence system and tungsten doped graphitic carbon nitride (W/GCN) as catalysts. Fluorescence quenching and colorimetric properties of the chromogenic-dye probe were used as a detection strategy of H2O2. The enhanced catalytic property of nanoflakes of W/GCN was attributed to the unique structural characteristics, influenced by the dopant, that not only tuned its bandgap but also enhanced separation of electron-hole pairs as compared to planar and larger sized nanosheets of pristine GCN. This low-cost and rapid assay offered a very low limit of detection of 8 nM for the fluorescence quenching method and 20 nM for the colorimetric method. The linear range for fluorescence quenching and colorimetric H2O2 assays were from 10-500 nM and 35-400 nM, respectively. Therefore, this novel method of using W/GCN nanoflakes in fluorescence quenching and colorimetric based detections of H2O2 is expected to catch more interest on the topic of using non-enzymatic platforms for sensitive and selective detection of different analysts.

MIP-Based Impedimetric Sensor for Detecting Dengue Fever Biomarker.

In this study, molecular imprinted polymer (MIP)-based impedimetric sensor has been developed to detect dengue infection at an early stage. Screen-printed carbon electrode (SPCE) was modified with electrospun nanofibers of polysulfone (PS) and then, coated with dopamine while using NS1 (non-structural protein 1-a specific and sensitive biomarker for dengue virus infection) as template during polymerization. The self-polymerization of dopamine at room temperature helps to retain exact structure of template (NS1) which results in generating geometrically fit imprinted sites for specific detection of target analyte. The electrochemical properties of MIP-modified SPCEs were studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) at every step of modification. Under optimal conditions, impedimetric measurements showed linear response in the range from 1 to 200 ng/mL. The developed sensor can selectively detect NS1 concentrations as low as 0.3 ng/mL. Moreover, impedimetric sensor system was also employed for NS1 determination in real human serum samples and satisfying recoveries varying from 95 to 97.14% were obtained with standard deviations of less than 5%.

Construction of sponge-like graphitic carbon nitride and silver oxide nanocomposite probe for highly sensitive and selective turn-off fluorometric detection of hydrogen peroxide.

In the present work, spongy graphitic carbon nitride (GCN) and silver oxide nanocomposites were prepared through a facile hydrothermal method at 160 °C for 4 h using GCN, silver nitrate, and dipotassium hydrogen phosphate as the starting materials. The prepared samples were characterized by scanning electron microscopy, energy dispersive X-ray spectrometry, Brunauer-Emmett-Teller method, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), UV-Visible diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, Raman, and photoluminescence techniques. SEM images showed Ag2O loaded GCN nanocomposite has a sponge-like structure due to the interconnecting of the enormous layer on the planar structure of GCN. XRD of samples showed the diffraction planes due to the hexagonal structure of carbon nitride with a decrease in intensity of peaks with increasing silver oxide (Ag2O) in the nanocomposite. Further, the addition of silver oxide improved the electrical properties of the nanocomposite by reducing the recombination of electron and hole pairs as shown by photoluminescence spectra. XPS spectra have confirmed the oxidation state of Ag as well as the coexistence of Ag2O and GCN in the nanocomposite. BET results indicated the increase in surface area for Ag2O/GCN-4.2% nanocomposite as compared to GCN. FTIR study indicated that the graphitic structure in GCN remained intact with the loading of Ag2O. A fluorescent quenching based H2O2 sensor was constructed by simultaneous oxidation of Rhodamine B in the presence of hydrogen peroxide and nanocomposite as the catalyst. In phosphate buffer saline at room temperature, Rhodamine B displayed a strong fluorescence emission peak around 577 nm under an excitation wavelength of 554 nm. This fluorescence signal of Rhodamine B was quenched in the presence of H2O2 and nanocomposite. The catalytic fluorescence quenching was increased with the increase in H2O2 concentration in the reaction system. The detection conditions of the prepared sensor were optimized as a reaction temperature of 25 °C, Rhodamine B concentration as 66 ng mL-1 and nanocomposite concentration as 56 µg mL-1. The catalytic fluorescence quenching response of the biosensor exhibited a linear range and limit of detection for H2O2 as 30-300 nM and 22 nM respectively.

Nitrogen-doped graphene oxide as a catalyst for the oxidation of Rhodamine B by hydrogen peroxide: application to a sensitive fluorometric assay for hydrogen peroxide.

The authors report that nitrogen-doped graphene oxide (NGO) catalyzes the oxidative decomposition of the fluorophore Rhodamine B (RhB) by hydrogen peroxide. The catalytic decomposition of hydrogen peroxide yields free hydroxyl radicals that destroy RhB so that the intensity of the yellow fluorescence is reduced. Nitrogen doping enhances the electronic and optical properties and surface chemical reactivities of GO such as widening of bandgap, increase in conductivity, enhanced quenching and adsorbing capabilities etc. The catalytic properties of NGO are attributed to its large specific surface and high electron affinity of nitrogen atoms. The chemical and structural properties of GO and NGO were characterized by XRD, FTIR, SEM, UV-visible and Raman spectroscopies. The method was optimized by varying the concentration of RhB, nitrogen dopant and hydrogen peroxide. The fluorescent probe, best operated at excitation/emission wavelengths of 554/577 nm, allows hydrogen peroxide to be determined in concentrations as low as 94 pM with a linear range spanning from 1 nM to 1 µM. Graphical abstract Schematic illustration of a fluorescence quenching method for the determination of H2O2. Upon addition of H2O2, nitrogen-doped graphene oxide (NGO) catalyzes the oxidation of Rhodamine B dye due to hydroxyl radical generation, which leads to a sensitive quenchometric methd for H2 O2.

N-Doped Graphene Oxide Decorated with PtCo Nanoparticles for Immobilization of Double-Stranded Deoxyribonucleic Acid and Investigation of Clenbuterol-Induced DNA Damage.

We demonstrate here a facile hydrothermal-assisted formation of PtCo alloy nanoparticles (NPs) and their simultaneous anchoring on the graphitic surface of N-doped graphene oxide (NGO). Doping induced nanopores in the carbon surface to facilitate the uniform and homogeneous anchoring of alloy nanoparticles. It was revealed that the formation of PtCo NPs on an NGO interface plodded excellent tendency toward double-stranded deoxyribonucleic acid (dsDNA). The dsDNA immobilization was enabled by the presence of several oxidation states of Pt and Co. The same property was further used to monitor the direct detection of dsDNA damage induced by clenbuterol via screen-printed carbon electrodes. Cyclic voltammetric and electrochemical impedance spectroscopic characterization traced well the dsDNA attachment on the modified electrode surface. Differential pulsed voltammetry was further used as a tool to monitor the characteristic guanine peak before and after incubating with clenbuterol used as a damage probe for the dsDNA. The findings can further be appurtenant in exploring dsDNA immobilization protocols and developing analytical methods for determination of various dsDNA damaging agents.