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a Amperometric I-t curves of different modified electrodes to subsequent additions of 50 μM NO2⁻ in 0.1 M phosphate buffer (pH 2.5) at an applied potential of +0.8 V (vs. SCE). b The corresponding calibration curve of current versus concentration of NO2⁻ for different modified electrode. c Amperometric (I-t) response of GC/rGO-Nf@Au8 modified electrode in 0.1 M phosphate buffer (pH 2.5) at an applied potential of +0.8 V (vs. SCE) upon successive additions of different concentration of NO2⁻ in a step of 1, 5, and 10 μM. Inset shows the I-t response from 200 to 850 s. d The corresponding calibration curve of current versus concentration of NO2⁻. Inset shows the enlargement of the calibration curve from 1 to 10 μM of NO2⁻ concentration
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The authors show that the electrocatalytic performance toward the detection of nitric oxide (NO) can be enhanced by making use of gold nanoparticles (AuNP) in a matrix consisting of reduced graphene oxide and Nafion (rGO-Nf). The rGO-Nf@Au nanohybrid was synthesized via a hydrothermal method. The spherical AuNP have diameters in the range from 50 t...
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Citations
... This synergistic combination resulted in a fast response time of 3 s and a high sensitivity (5.38 lA/ lM/cm 2 , low detection limit: 133 nM with a S/N ¼ $5.5) for the selective electrochemical detection of NO in living cultured cells. In another study, Yusoff et al. 96 applied a one-step hydrothermal process to develop a reduced GO and Nafion V R (Nf) based film loaded with nearly spherical AuNP (rGO-Nf@Au) with average diameters of $50 to 200 nm and was cast onto the surface of a GCE. Sodium nitrite (NaNO 2 ) was used as NO source, which undergoes a disproportionation reaction to release free NO in an acidic medium. ...
Nitric oxide (NO) signaling plays many pivotal roles impacting almost every organ function in mammalian physiology, most notably in cardiovascular homeostasis, inflammation, and neurological regulation. Consequently, the ability to make real-time and continuous measurements of NO is a prerequisite research tool to understand fundamental biology in health and disease. Despite considerable success in the electrochemical sensing of NO, challenges remain to optimize rapid and highly sensitive detection, without interference from other species, in both cultured cells and in vivo. Achieving these goals depends on the choice of electrode material and the electrode surface modification, with graphene nanostructures recently reported to enhance the electrocatalytic detection of NO. Due to its single-atom thickness, high specific surface area, and highest electron mobility, graphene holds promise for electrochemical sensing of NO with unprecedented sensitivity and specificity even at sub-nanomolar concentrations. The non-covalent functionalization of graphene through supermolecular interactions, including π–π stacking and electrostatic interaction, facilitates the successful immobilization of other high electrolytic materials and heme biomolecules on graphene while maintaining the structural integrity and morphology of graphene sheets. Such nanocomposites have been optimized for the highly sensitive and specific detection of NO under physiologically relevant conditions. In this review, we examine the building blocks of these graphene-based electrochemical sensors, including the conjugation of different electrolytic materials and biomolecules on graphene, and sensing mechanisms, by reflecting on the recent developments in materials and engineering for real-time detection of NO in biological systems.
... The characteristic XRD peaks at the 2θ value of 25.6 • assigned to the (002) plane of the hexagonal graphene structure with an interlayer d-spacing of 3.36 Å corresponded to the rGO [48]. The diffraction peak at 43.35 • with the corresponding d-spacing of 2.1 Å in the XRD pattern was assigned to the disordered turbostaic band of the rGO carbon material [49,50]. [51]. ...
The scarcity of fresh water, which is aggravated by rapid economic development and population growth, is a major threat to the modern world. Solar-driven interfacial desalination and steam generation is a promising strategy that localizes heat at the air-water interface through appropriate thermal management and demonstrates efficient photothermal performance. In the current study, Ag, black TiO2 , and nitrogen-doped 3D reduced graphene oxide (3D black TiO2 /Ag/N@rGO) hierarchical evaporator was fabricated, and its morphology, elemental composition, porosity, broadband solar absorption potential, photothermal performance, and interfacial desalination potential were assessed. The 3D solar evaporator showed efficient solar absorption over the entire broadband UV-visible near-infrared (UV-Vis NIR) region and demonstrated 99% photothermal conversion efficiency and potential freshwater generation of 1.43 kg·m −2 h −1. The specific surface area and porosity analyses demonstrated an ultrahigh specific surface area, high pore volume, and a mesoporous structure, with a predominant pore diameter of 4 nm. The strong photothermal performance can be attributed to the nitrogen doping of the rGO, which boosted the electrocatalytic and photothermal activity of the graphene through the activation of the excess free-flowing π electrons of the sp 2 configuration of the graphene; the broadband solar absorption potential of the black TiO 2 ; and the localized surface plasmon resonance effect of the AgNPs, which induced hot electron generation and enhanced photothermal conversion. Hence, the high photothermal conversion efficiency attained can be attributed to the synergistic photothermal performances of the individual components and the high interfacial surface area, abundant heat, and mass transfer microcavities of the 3D hierarchical porous solar absorber, offering multiple reflections of light and enhanced solar absorption. The study highlights the promising potential of the 3D evaporator for real-word interfacial desalination of seawater, helping to solve the water shortage problem sustainably.
... 28,29 Although several research works have been done on electrochemical NO and nitrite sensing using various metal NPs and graphene-based nanomaterials, very few experimental works were carried out on transition MOS-based electrodes. 30,31 Herein, we have studied electrochemical NO sensing using WO 3 nanoflakes grown on commercially available fluorinedoped tin oxide (FTO) glass substrates. The sensitivity, detection limit, and selectivity of the sensing electrode has been improved after sensitization of Au nanoparticles (Au NPs) with WO 3 nanoflakes. ...
... 6 Current techniques for directly monitoring NO in vivo have proven useful but have drawbacks, such as low resolution (EPR), 14,15 poor sensitivity (MRI), 16,17 or invasiveness (amperometry). 18 A complementary approach is the use of activity-based sensing (ABS) probes 19,20 which exploit the chemical reactivity of the target analyte to report on activity with high selectivity. 21−24 Until recently, most ABS probes for NO have been developed for fluorescence imaging in cellular systems. ...
Nitric oxide (NO) plays a critical role in acute and chronic inflammation. NO's contributions to cancer are of particular interest due to its context-dependent bioactivities. For example, immune cells initially produce cytotoxic quantities of NO in response to the nascent tumor. However, it is believed that this fades over time and reaches a concentration that supports the tumor microenvironment (TME). These complex dynamics are further complicated by other factors, such as diet and oxygenation, making it challenging to establish a complete picture of NO's impact on tumor progression. Although many activity-based sensing (ABS) probes for NO have been developed, only a small fraction have been employed in vivo, and fewer yet are practical in cancer models where the NO concentration is <200 nM. To overcome this outstanding challenge, we have developed BL660-NO, the first ABS probe for NIR bioluminescence imaging of NO in cancer. Owing to the low intrinsic background, high sensitivity, and deep tissue imaging capabilities of our design, BL660-NO was successfully employed to visualize endogenous NO in cellular systems, a human liver metastasis model, and a murine breast cancer model. Importantly, its exceptional performance facilitated two dietary studies which examine the impact of fat intake on NO and the TME. BL660-NO provides the first direct molecular evidence that intratumoral NO becomes elevated in mice fed a high-fat diet, which became obese with larger tumors, compared to control animals on a low-fat diet. These results indicate that an inflammatory diet can increase NO production via recruitment of macrophages and overexpression of inducible nitric oxide synthase which in turn can drive tumor progression.
... Until now many materials either unaided or in the form of composite have been investigated as sensors. These materials include the conduction polymers [2,3], mixed metal oxides [4], carbon-based nanocomposite materials [5,6]. Among the list of all these materials, semiconductorbased metal oxides sensor is the most used sensor material due to their simple preparation method [7], cost-effectiveness [8], stability [9], and simple measurement techniques. ...
Amongst the extended list of metal oxides, Co3O4 has gained envisioned attention in various technological fields. It has a proven record of promising material in optical, optoelectronics, sciences, engineering, medicines and biological fields of studies. Co3O4 is a promising candidate due to its large surface-to-volume ratio, simple preparation methods, higher well-defined electrochemical redox activity, high theoretical capacity, low cost, and stable chemical states. Co3O4 has been used in various applications such as fuel cells, photoelectrochemical water splitting, solar cells, supercapacitors, batteries and electrochemical sensors due to its applicability in various fields. It has shown promising outcomes as an electrochemical sensor in various areas such as in the detection of water contamination, as physiological molecule detectors etc. this mini-review summarizes the fields of contaminated water, as fuel and also in the physiological system.
... In this work, a carbon paste electrode was combined with the outstanding characteristics of AuNPs and GNRs. As an advantage over other well established existing NO sensors that contained gold nanoparticles [36][37][38], the fabrication of this sensor is extremely fast. The often time-consuming synthesis step of the modifying solution or the electrodeposition of the gold particles (usually an additional step) is not required. ...
Various physiological as well as pathophysiological processes in the cardiovascular system, in the immune response or in neurotransmission depend on changes of the concentration of nitric oxide (NO). Due to the instability of this ubiquitous signal molecule in vivo and in vitro, its rapid and direct detection is necessary to obtain meaningful results. Therefore, the development of a method for the rapid electrochemical detection of nitric oxide at 0.72 V (vs. Ag/AgCl) using a carbon paste electrode, modified by drop casting, is presented. As modifying solution, a nanocomposite consisting of Nafion, graphene nanoribbons, and gold nanoparticles was prepared. The voltammetric investigations with the optimized sensor were performed at room temperature in phosphate buffer solution (0.1 M, pH 7.4) as supporting electrolyte. Based on differential pulse voltammetry measurements, the obtained results for the analytical signal showed good linear response in the range of 0.39 - 2.34 μM and 2.34 - 104.7 μM with a correlation coefficient of 0.9941 and 0.9984, respectively. For both linear ranges, the repeatability as well as the reproducibility was < 5% and < 10%, respectively. A concentration of 40 nM was determined for the detection limit, whereas the limit of quantification was 130 nM. In addition, the influence of physiological interferences was also investigated and resulted in negligible effects. Finally, the sensor was successfully used to measure the NO release of NO donors. Based on the results obtained, the new sensor provides a simple and fast method for a direct voltammetric determination of low nitric oxide concentrations in solutions.
... The dispersive energy X-ray (EDX) elementary mapping analysis was employed to detect the distribution of the different elements present in the biosensor 33 . This biosensor consists of carbon, oxygen, silicon and aurum elements. ...
Ferrocene or ferrocenium has been widely studied in the field of organometallic complexes because of its stable thermodynamic, kinetic and redox properties. Novel hexaferrocenium tri[hexa(isothiocyanato)iron(III)]trihydroxonium (HexaFc) complex was the product from the reaction of ferrocene, maleic acid and ammonium thiocyanate and was confirmed by elemental analysis CHNS, FTIR and single crystal X-ray crystallography. In this study, HexaFc was used for the first time as an electroactive indicator for porcine DNA biosensor. The UV–Vis DNA titrations with this compound showed hypochromism and redshift at 250 nm with increasing DNA concentrations. The binding constant (Kb) for HexaFc complex towards CT-DNA (calf-thymus DNA) was 3.1 × 104 M−1, indicated intercalator behaviour of the complex. To test the usefulness of this complex for DNA biosensor application, a porcine DNA biosensor was constructed. The recognition probes were covalently immobilised onto silica nanospheres (SiNSs) via glutaraldehyde linker on a screen-printed electrode (SPE). After intercalation with the HexaFc complex, the response of the biosensor to the complementary porcine DNA was measured using differential pulse voltammetry. The DNA biosensor demonstrated a linear response range to the complementary porcine DNA from 1 × 10−6 to 1 × 10−3 µM (R2 = 0.9642) with a limit detection of 4.83 × 10−8 µM and the response was stable up to 23 days of storage at 4 °C with 86% of its initial response. The results indicated that HexaFc complex is a feasible indicator for the DNA hybridisation without the use of a chemical label for the detection of porcine DNA.
... It is well known, graphene (GR) has the characteristics of large specific surface area, high conductivity, good chemical stability, and is widely used as a carrier for loading metal nanoparticles. So far, many efforts have been made to prepare AuNP-GR composite to enhance the electrochemical catalytic activity of it to nitrite [15][16][17][18][19][20][21][22]. Nevertheless, there is a strong interaction between the GR sheets, so that most of AuNP in the composite are embedded in its sheets. ...
... Table 1 based on AuNP. It can be seen, this AuNP-rGO-MWCNT/ GCE shows the outstanding characteristics of wide linear range, low detection limit and high sensitivity [2,3,[10][11][12][13][14][15][16][17][18][19][20][21][22]. This is because of that this AuNP-rGO-MWCNTs nanocomposite has higher electrocatalytic capability for nitrite under the synergistic action of each component in composite. ...
A nanocomposite consisting of gold nanoparticles (AuNP), reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) was synthesized using a co-reduction strategy in ethylene glycol using sodium citrate as the reducing agent. The nanocomposite was successfully characterized using X-ray powder diffraction, scanning electron microscopy and electrochemical methods. The material was deposited on a glassy carbon electrode and then was found to have high electrocatalytic capability for the electrode process of nitrite. This is attributed to the synergic actions of rGO, MWCNTs and AuNPs. Based on this, an amperometric nitrite sensing scheme was worked out that had attractive features: (a) a wide linear range that extends from 50 nM to 2.2 mM, (b) a working potential of 0.80 V (vs.SCE) at pH 5.0, (c) a 14 nM detection limit (at an SNR of 3), and (d) an electrochemical sensitivity of 1201 μA·mM⁻¹·cm⁻². The sensor was successfully applied to the determination of nitrite in the local river water.
Graphical abstractSchematic presentation of the fabrication of the AuNPs-rGO-MWCNTs composite modified electrode and its application for the nitrite electrochemical sensing.
... Direct electrochemical detection of NO was first reported by Shibuki in 1990, who detected oxygen at a reducing potential on modified Clark electrode [21,22]. Recent reports are focused on electrocatalytic detection of NO with various metal composite materials, including nano-TiO 2 [23], carbon nanotube [24], and gold nanoparticles [25][26][27]. These papers incorporated polymer such as polyvinylpyrrolidone, Nafion, and porphyrin into electrocatalytic oxidation of nitric oxide to improve the selectivity. ...
Here, a nanoporous gold electrode (NAu) was reported with a unique cone-shape nanohole structure for electrochemical sensing of nitric oxide (NO), which was fabricated via a facile sputtering technique on aluminum oxide membrane. Two kinds of nanoporous gold electrodes fabricated on different aluminum oxide membranes with aperture-size of 20 nm (2020NAu) and 200 nm (2040NAu) were obtained and compared in electrochemically active surface area and electro-oxidation activity. Concerning the determination of NO, it exhibited higher selectivity to NO2− and larger electro-oxidation current on 2020NAu electrode than those on 2040NAu electrode when their backsides were used as sensing interfaces. Meanwhile, the anti-interfering ability of bare 2020NAu electrode was also compared with that on Nafion-modified 2020NAu electrode. Results showed that common electroactive interferents such as H2O2, ascorbic acid, and uric acid could be hindered by cone-shape nanohole structure in the backside of 2020NAu electrode. On the basis of cyclic voltammetry, the linear range was from 4.75 × 10−8 to 9.50 × 10−7 M for NO sensing on 2020NAu electrode.
Electrochemical detection of Nitric oxide (NO) has attracted considerable attention due to its central role in different processes of mammalian physiology. In this study, NO is electrochemically detected using lead titanate (PbTiO3) as an electrochemical sensor. The lead titanate (PbTiO3) was prepared successfully through thermal decomposition of bimetallic complex [PbTi(O2CCF3)4(THF)3O]2 containing both lead and titanium metals. A phase of synthesized PbTiO3 powder was studied using X-ray diffraction spectroscopy and Raman spectroscopy, while the morphology and crystallite size were studied by field emission scanning electron microscopy and high-resolution transmission electron microscopy. Further, X-ray photoelectron spectroscopy analysis was also done to determine the elemental composition along with their oxidation states. Finally, the PbTiO3 powder was coated on GCE (glassy carbon electrode) and then further studied electrochemically for sensing NO in NaNO2 solution at pH = 2.5. Moreover, the detection capability of PbTiO3 was analyzed upon adding different concentrations of 1 to 10 mM of NaNO2. As a result, current and concentration followed a linear response. For the interferent studies, uric acid, glucose, dopamine, and ascorbic acid were used as interferents. It was noted that no signals appeared with these interferents in the voltammogram.
