Pd Nanoparticles on Functionalized Graphene for Excellent Detection of Nitro aromatic Compounds

A Wearable Electrochemical Biosensor Utilizing Functionalized Ti3C2Tx MXene for the Real-Time Monitoring of Uric Acid Metabolite

Wearable, noninvasive sensors enable the continuous monitoring of metabolites in sweat and provide clinical information related to an individual's health and disease states. Uric acid (UA) is a key indicator highly associated with gout, hyperuricaemia, hypertension, kidney disease, and Lesch-Nyhan syndrome. However, the detection of UA levels typically relies on invasive blood tests. Therefore, developing a wearable device for noninvasive monitoring of UA concentrations in sweat could facilitate real-time personalized disease prevention. Here, we introduce 1,3,6,8-pyrene tetrasulfonic acid sodium salt (PyTS) as a bifunctional molecule functionalized with Ti3C2Tx via π-π conjugation to design nonenzymatic wearable sensors for sensitive and selective detection of UA concentration in human sweat. PyTS@Ti3C2Tx provides many oxidation-reduction active groups to enhance the electrocatalytic ability of the UA oxidation reaction. The PyTS@Ti3C2Tx-based electrochemical sensor demonstrates highly sensitive detection of UA in the concentration range of 5 μM-100 μM, exhibiting a lower detection limit of 0.48 μM compared to the uricase-based sensor (0.84 μM). In volunteers, the PyTS@Ti3C2Tx-based wearable sensor is integrated with flexible microfluidic sweat sampling and wireless electronics to enable real-time monitoring of UA levels during aerobic exercise. Simultaneously, it allows for comparison of blood UA levels via a commercial UA analyzer. Herein, this study provides a promising electrocatalyst strategy for nonenzymatic electrochemical UA sensor, enabling noninvasive real-time monitoring of UA levels in human sweat and personalized disease prevention.

Advances in Graphene/Inorganic Nanoparticle Composites for Catalytic Applications

Graphene-based nanocomposites with inorganic (metal and metal oxide) nanoparticles leads to materials with high catalytic activity for a variety of chemical transformations. Graphene and its derivatives such as graphene oxide, highly reduced graphene oxide, or nitrogen-doped graphene are excellent support materials due to their high surface area, their extended π-system, and variable functionalities for effective chemical interactions to fabricate nanocomposites. The ability to fine-tune the surface composition for desired functionalities enhances the versatility of graphene-based nanocomposites in catalysis. This review summarizes the preparation of graphene/inorganic NPs based nanocomposites and their use in catalytic applications. We discuss the large-scale synthesis of graphene-based nanomaterials. We have also highlighted the interfacial electronic communication between graphene/inorganic nanoparticles and other factors resulting in increased catalytic efficiencies.

Silver cluster (Ag6) decorated coronene as non-enzymatic sensor for glucose and H2O2

Silver-graphene quantum dots are promising electrochemical sensors due to their unique electronic properties. Herein, we report the comprehensive DFT study to explore the electronic properties of silver cluster (Ag₆) decorated coronene as model for silver graphene quantum dots. The current study aims to investigate the sensing ability of silver-coronene complex for non-enzymatic electrochemical detection of glucose & H₂O₂. The stability of the complexes of analytes with silver decorated coronene is supported by their greater interaction energies (-36.7 to -44.9 kcal mol^-1)_. NBO charge analysis and charge decomposition analysis (CDA) reveal donor-acceptor charge transfer interactions in the complexes. Frontier molecular orbital analysis illustrates that charge is transferred from analytes to silver decorated coronene during excitation from HOMO to LUMO. The Uv-visible results show that λ_max is red shifted during interactions of analytes with silver decorated coronene. The NCI analysis illustrates the strong non-covalent (M … O) and unusual M … H-O interactions in the complexes. The precedent sensing performance of Ag₆-coronene might be attributed to the synergistic effect of both silver clusters and coronene in the composite. The evaluated results validate the excellent sensing ability of silver-graphene quantum dots for the detection of glucose & H₂O₂. The outcome of the current study and its prospects will open the avenue for the rational development of smart sensors.

Characterization of Room-Temperature Ionic Liquids to Study the Electrochemical Activity of Nitro Compounds

Over the past few years, room-temperature ionic liquid (RTIL) has evolved as an important solvent-cum-electrolyte because of its high thermal stability and excellent electrochemical activity. Due to these unique properties, RTILs have been used as a solvent/electrolyte/mediator in many applications. There are many RTILs, which possess good conductivity as well as an optimal electrochemical window, thus enabling their application as a transducer for electrochemical sensors. Nitroaromatics are a class of organic compounds with significant industrial applications; however, due to their excess use, detection is a major concern. The electrochemical performance of a glassy carbon electrode modified with three different RTILs, [EMIM][BF4], [BMIM][BF4] and [EMIM][TF2N], has been evaluated for the sensing of two different nitroaromatic analytes: 2,6-dinitrotoluene (2,6 DNT) and ethylnitrobenzene (ENB). Three RTILs have been chosen such that they have either a common anion or cation amongst them. The sensory response has been measured using square wave voltammetry (SQWV). We found the transducing ability of [EMIM][BF4] to be superior compared to the other two RTILs. A low limit of detection (LOD) of 1 ppm has been achieved with a 95% confidence interval for both the analytes. The efficacy of varying the cationic and anionic species of RTIL to obtain a perfect combination has been thoroughly investigated in this work, which shows a novel selection process of RTILs for specific applications. Moreover, the results obtained from testing with a glassy carbon electrode (GCE) have been replicated using a miniaturized sensor platform that can be deployed easily for on-site sensing applications.

Nanostructured Graphene Oxide Dots: Synthesis, Characterization, Photoinduced Electron Transfer Studies, and Detection of Explosives/Biomolecules

Herein, we report the preparation of graphene oxide dots (GO dots) by fine-tuning the carbonization degree of citric acid. The structure of GO dots was characterized by absorption spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, as well as high-resolution scanning electron microscopy and transmission electron microscopy analyses. The typical particle size of the GO dots was 42 nm. The fluorescent characteristics of the GO dots were analyzed by fluorescence spectroscopy. Once excited at 360 nm, the GO dots were fluorescent in the range of 450-550 nm, which was dependent on the excitation wavelength. Further, GO dots were effectively utilized for multifarious applications such as photoinduced electron transfer and detection of explosives and biomolecules. The emission property of GO dots was competently quenched by viologens, picric acid (PA), and bilirubin (BR). The mechanism of quenching by viologens and explosives/biomolecules was found to be due to photoinduced electron transfer and the internal filter effect, respectively. Intriguingly, the detection minimum of PA is in the nanomolar level. Toward commercialization, the economic test strips have also been introduced for the identification of PA. Furthermore, the GO dots have been applied as an efficient luminescent bioprobe for a selective and perceptive finding of BR.

A novel Ag(i)-calix[4]arene coordination polymer for the sensitive detection and efficient photodegradation of nitrobenzene in aqueous solution

Nitrobenzene (NB) is a widespread and highly toxic organic pollutant in water, and consequently its detection and removal have attracted considerable attention. In the present study, we designed and synthesized a novel coordination polymer, [AgL_0.5(NO₃)]_n (1), {L = 25,26,27,28-tetra[(3-pyridylmethyl)oxy]calix[4]arene}, from AgNO₃ and a tetra-pyridyl-functionalized calix[4]arene ligand, which possessed a 2D network based on [Ag₄L(NO₃)₄] units. The 1-modified glassy carbon electrode (1/GCE) exhibited good electrocatalytic activity toward the reduction of NB, offering the selective detection of NB in a wide linear range (1-2450 μM) and a low detection limit (0.62 μM). Furthermore, it displayed excellent photocatalytic activity for the degradation of NB in aqueous solution under UV light. The kinetics of the catalytic degradation reaction and the stability of the catalyst were also studied. These results indicated that compound 1 is a favorable material for the effective determination and degradation of NB, which makes it a promising candidate in both monitoring water quality and treating wastewater.

Electrochemical behavior of amaranth and its sensitive determination based on Pd-doped polyelectrolyte functionalized graphene modified electrode

In this work, poly(sodium p-styrenesulfonate) (PSS)-functionalized graphene supported palladium nanoparticles (Pd) composites were fabricated with simple ultrasonic bath method. The morphology and structure of PSS-GR-Pd composites were characterized using UV-vis absorption spectra, X-ray diffraction and Transmission Electron Microscopy. By combining the merits of the PSS-GR and Pd NPs, a new electrochemical sensor was erected to detect amaranth based on the PSS-GR-Pd nanocomposites. The electrochemical behavior of amaranth was investigated systematically in 0.1molL^-1 phosphate buffer solution (PBS 2.0). At the optimum parameter, I_pa was found to be linearly dependent on the concentrations of amaranth (1×10^-7-9×10^-6molL^-1). The detection limit was 7nM (S/N=3) and sensitivity was 5.85μAμM^-1. Finally, this system was utilized for determining amaranth in soft drink using the standard addition method.

A Study of Electrocatalytic and Photocatalytic Activity of Cerium Molybdate Nanocubes Decorated Graphene Oxide for the Sensing and Degradation of Antibiotic Drug Chloramphenicol

In this present work, "killing two birds with one stone" strategy was performed for the electrochemical trace level detection and photocatalytic degradation of antibiotic drug chloramphenicol (CAP) using Ce(MoO₄)₂ nanocubes/graphene oxide (CeM/GO) composite for the first time. The CeM/GO composite was synthesized via simple hydrothermal treatment followed by sonication process. The successful formation of CeM/GO composite was confirmed by several analytical and spectroscopic techniques. The CeM/GO composite modified glassy carbon electrode (GCE) showed excellent electrocatalytic activity toward the reduction of CAP in terms of decrease the potential and increase the cathodic peak current in comparison with different modified and unmodified electrodes. The electrocatalytic reduction of CAP based on the CeM/GO modified GCE exhibited high selectivity, wide linear ranges, lower detection limit, and good sensitivity of 0.012-20 and 26-272 μM, 2 nM ,and 1.8085 μA μM^-1 cm^-2, respectively. Besides, when CeM/GO/GCE was used to analyze the CAP in real samples, such as honey and milk, the satisfactory recovery results were obtained. On the other hand, the CeM/GO composite played excellent catalyst toward the photodegradation of CAP. The obtained results from the UV-vis spectroscopy clearly suggested that CeM/GO composite had high photocatalytic activity compared to pristine Ce(MoO4)₂ nanocubes. The degradation efficiency of CeM/GO toward CAP is observed about 99% within 50 min under visible irradiation and it shows a good stability by observing the reusability of the catalyst. The enhanced photocatalytic performance was attributed to the increased migration efficiency of photoinduced electrons and holes.

Au-Pt bimetallic nanoparticles supported on functionalized nitrogen-doped graphene for sensitive detection of nitrite

In this work, we report a novel Au-Pt bimetallic nanoparticles (Au-PtNPs) decorated on the surface of nitrogen-doped graphene (NG) functionalized with 1, 3, 6, 8-pyrene tetra sulfonic acid sodium salt (PyTS) by direct electrodeposition method. The results of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and electrochemical impendence spectrum (EIS) reveal that the Au-PtNPs were successfully anchored on the surface of NG sheets with a diameter of 20-40nm. Further, the prepared Au-PtNPs/PyTS-NG nanocomposite exhibits superior catalytic activity for the oxidation of nitrite. Under optimal experimental conditions, an amperometric sensor with a linear range of 0.5-1621μM and a detection limit of 0.19μM (S/N=3) for the detection of nitrite was set up and applied to real samples.

Green synthesized silver nanoparticles decorated on reduced graphene oxide for enhanced electrochemical sensing of nitrobenzene in waste water samples

In the present work, an electrochemical sensor for nitrobenzene has been developed based on a green synthesized silver nanoparticle (AgNP) decorated reduced graphene oxide (RGO) modified glassy carbon electrode (GCE).

Highly selective detection of trinitrophenol by luminescent functionalized reduced graphene oxide through FRET mechanism

Among different nitro compounds, trinitrophenol (TNP) is the most common constituent to prepare powerful explosives all over the world. A few works on the detection of nitro explosives have already been reported in the past few years; however, selectivity is still in its infant stage. As all the nitroexplosives are highly electron deficient in nature, it is very difficult to separate one from a mixture of different nitro compounds by the usual photoinduced electron transfer (PET) mechanism. In the present work, we have used a bright luminescent, 2,6-diamino pyridine functionalized graphene oxide (DAP-RGO) for selective detection of TNP in the presence of other nitro compounds. The major advantage of using this material over other reported materials is not only to achieve very high fluorescence quenching of ∼96% but also superior selectivity >80% in the detection of TNP in aqueous medium via both fluorescence resonance energy transfer and PET mechanisms. Density functional theory calculations also suggest the occurrence of an effective proton transfer mechanism from TNP to DAP-RGO, resulting in this tremendous fluorescence quenching compared to other nitro compounds. We believe this graphene based composite will emerge a new class of materials that could be potentially useful for selective detection, even for trace amounts of nitro explosives in water.