Graphene Nanoribbon-Supported PtPd Concave Nanocubes for Electrochemical Detection of TNT with High Sensitivity and Selectivity

Vapor phase detection of explosives by surface enhanced Raman scattering under ambient conditions with metal nanogap structures

Non-invasive and passive detection of explosives in the vapor phase is advantageous for military, counter-terrorism, and homeland security applications. Detection of explosives using SERS has been an active research topic. However, the vapor pressures of most explosives are low at room temperature, and consequently, the vapor phase detection by SERS is highly challenging without intentionally heating explosive powder to increase the vapor pressure. In this work, we report the rapid and sensitive detection of 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (2,4-DNT) in the vapor phase, using a gold nanogap (AuNG) SERS substrate. The AuNG SERS substrate was fabricated with electron beam evaporation, rapid thermal annealing, and wet etching. SERS measurements were carried out with an incident power as low as 0.56 mW at 785 nm. To prevent the condensation effect, the TNT and 2,4-DNT powders inside the cuvette were taken out before inserting the nanogap substrate. Our SERS results demonstrate the feasibility of the non-invasive detection of vapor phase explosives under ambient conditions.

A novel electrochemical sensor based on phosphate-stabilized poly-caffeic acid film in combination with graphene nanosheets for sensitive determination of nitro-aromatic energetic materials

This work offers a novel approach and sensor electrode for electrocatalytic reduction of nitro-aromatic explosives (NAEs). This sensor was created by combining electrochemically reduced graphene nanosheets (GNSs) -through cyclic voltammetric reduction of a graphene oxide colloidal solution- with phosphate-stabilized poly-caffeic acid (pCAF) film-modified glassy carbon electrode (GCE). The poly-caffeic acid-modified nonconductive electrode was stabilized with a H2PO4-/HPO42- phosphate buffer at pH 7 and made conductive. The novel electrode, called phosphate stabilized-GC/GNSs/pCAF, was characterized by electrochemical methods and scanning electron microscopy (SEM). The sensor exhibited high performance for trinitrotoluene (TNT) detection with a linear response between 50 and 500 μg L- 1 and a detection limit of 6 μg L-1. In addition to TNT, precise determinations of NAEs such as 2,4-dinitrotoluene (2,4-DNT), tetryl (2,4,6-trinitrophenyl methyl nitramine), trinitro phenol (TNP or picric acid; PA), 2,4-dinitrophenol (2,4-DNP), and 4-amino dinitrotoluene (4A-DNT, an aerobic bacterial degradation product of TNT) were made using the developed sensor electrode and DPV technique. Simultaneous quantification of TNT and DNT was performed with the aid of a computational technique known as multiple linear regression (MLR). The optimized electrode was resistant to interference effects. Satisfactory results on real samples were obtained by applying the modified electrode to the determination of TNT, tetryl, and TNP in contaminated soil. The validation of the proposed method was made against a literature LC-MS/MS method. A statistical comparison of the obtained results was provided using F- and Student's t-tests.

Nanobioengineered surface comprising carbon based materials for advanced biosensing and biomedical application

Carbon-based nanomaterials (CNMs) are at the cutting edge of materials science. Due to their distinctive architectures, substantial surface area, favourable biocompatibility, and reactivity to internal and/or external chemico-physical stimuli, carbon-based nanomaterials are becoming more and more significant in a wide range of applications. Numerous research has been conducted and still is going on to investigate the potential uses of carbon-based hybrid materials for diverse applications such as biosensing, bioimaging, smart drug delivery with the potential for theranostic or combinatorial therapies etc. This review is mainly focused on the classifications and synthesis of various types of CNMs and their electroanalytical application for development of efficient and ultra-sensitive electrochemical biosensors for the point of care diagnosis of fatal and severe diseases at their very initial stage. This review is mainly focused on the classification, synthesis and application of carbon-based material for biosensing applications. The integration of various types of CNMs with nanomaterials, enzymes, redox mediators and biomarkers have been used discussed in development of smart biosensing platform. We have also made an effort to discuss the future prospects for these CNMs in the biosensing area as well as the most recent advancements and applications which will be quite useful for the researchers working across the globe working specially in biosensors field.

A novel 3D-printed graphite/polylactic acid sensor for the electrochemical determination of 2,4,6-trinitrotoluene residues in environmental waters

Here, lab-made graphite and polylactic acid (Gpt-PLA) biocomposite materials were used to additively manufacture electrodes via the fused deposition modeling (FDM) technique for subsequent determination of the explosive 2,4,6-trinitrotoluene (TNT, considered a persistent organic pollutant). The surface of the 3D-printed material was characterized by SEM and Raman, which revealed high roughness and the presence of defects in the graphite structure, which enhanced the electrochemical response of TNT. The 3D-printed Gpt-PLA electrode coupled to square wave voltammetry (SWV) showed suitable performance for fastly determining the explosive residues (around 7 s). Two reduction processes at around -0.22 V and -0.36 V were selected for TNT detection, with linear ranges between 1.0 and 10.0 μM. Moreover, detection limits of 0.52 and 0.66 μM were achieved for both reduction steps. The proposed method was applied to determine TNT in different environmental water samples (tap water, river water, and seawater) without a dilution step (direct analysis). Recovery values between 98 and 106% confirmed the accuracy of the analyses. Additionally, adequate selectivity was achieved even in the presence of other explosives commonly used by military agencies, metallic ions commonly found in water, and also some electroactive camouflage species. Such results indicate that the proposed device is promising to quantify TNT residues in environmental samples, a viable on-site analysis strategy.

A highly sensitive and selective detection of 2,4,6-trinitrotoluene (TNT) using a peptide-functionalized silicon nanowire array sensor

A highly sensitive and specific detection of 2,4,6-trinitrotoluene (TNT), a typical nitrated aromatic explosive, was demonstrated by a silicon nanowire (SiNW) array sensor. The SiNW array devices were self-assembled and functionalized with the anti-TNT peptide to obtain unique sensitivity toward TNT. Also, the effect of the biointerfacing linker's chemistry and Debye screening with varied ionic strength of phosphate buffer solution (PBS) on TNT binding response signals were investigated. The optimization of the peptide-functionalized SiNW array sensor showed high sensitivity for TNT with a detection limit of 0.2 fM, the highest sensitivity reported to date. These initial promising results may help accelerate the development of portable sensors for femtomolar level TNT detection.

A recent advancement on the applications of nanomaterials in electrochemical sensors and biosensors

Industrialization and globalization, both on an international and local scale, have caused large quantities of toxic chemicals to be released into the environment. Thus, developing an environmental pollutant sensor platform that is sensitive, reliable, and cost-effective is extremely important. In current years, considerable progress has been made in the expansion of electrochemical sensors and biosensors to monitor the environment using nanomaterials. A large number of emerging biomarkers are currently in existence in the biological fluids, clinical, pharmaceutical and bionanomaterial-based electrochemical biosensor platforms have drawn much attention. Electrochemical systems have been used to detect biomarkers rapidly, sensitively, and selectively using biomaterials such as biopolymers, nucleic acids, proteins etc. In this current review, several recent trends have been identified in the growth of electrochemical sensor platforms using nanotechnology such as carbon nanomaterials, metal oxide nanomaterials, metal nanoparticles, biomaterials and polymers. The integration strategies, applications, specific properties and future projections of nanostructured materials for emerging progressive sensor platforms are also observed. The objective of this review is to provide a comprehensive overview of nanoparticles in the field of electrochemical sensors and biosensors.

Facile synthesis of surface functionalized Pd2+@P-CDP/COFs for highly sensitive detection of norfloxacin drug based on the host-guest interaction

In this work, β-cyclodextrin porous polymers (P-CDPs) functionalized novel covalent organic frameworks (P-CDPs/COFs) were synthesized by a simple and facile method. After combined with Pd²⁺ via electrostatic interaction, the Pd²⁺@P-CDPs/COFs nanocomposites were prepared and utilized as novel electrode materials to fabricate the non-enzyme electrochemical sensors for high-sensitivity detection of Norfloxacin (NF). Due to the host-guest recognition, excellent adsorption performance and catalytic performance of Pd²⁺@P-CDPs/COFs, the prepared sensor exhibited excellent electrochemical performance for detecting NF under the optimum conditions, which showed two linear ranges of 0.08-7.0 μM and 7.0-100.0 μM with a low detection limit of 0.031 μM (S/N = 3). Additionally, the obtained sensor has also been successfully applied to measure NF with satisfactory results in the real medicinal samples of NF eye-drops. Our findings paved the way for the development of COFs-based sensing platform in drug analysis and testing for human health, food security and the quality control of drugs.

Electrochemical (Bio)Sensors for the Detection of Organophosphorus Pesticides Based on Nanomaterial-Modified Electrodes: A Review

Organophosphorus pesticides were easily remained in fruits and vegetables which would be harm to the environmental safety and human health. In recent years, due to the simple preparation process, fast response and high sensitivity, the electrochemical (bio)sensors have received increasing attention, which were extensively used as the sensing platform for the detection of OPPs. The mechanisms for the determination of OPPs mainly included redox of nitrophenyl OPPs, enzyme hydrolysis and inhibition, immunosensor, aptasensor. Nowadays, the mainly explored electrode material has focused on metal-organic frameworks, metal and metal derivatives, carbon materials (carbon nanotube, graphene, g-C3N4), MXene, etc. These nanomaterials played important roles in the electrochemical (bio)sensors, which included: (a) as an electrocatalyst to promote the redox reaction, (b) as a carrier to load the enzyme or aptamer, (c) as a recognizer to identify the targets. The nanomaterials-based electrochemical (bio)sensor was a rapid, cost-effective methods to detect OPPs with high sensitivity. Besides, this review compared the analytical performance of different nanomaterials-based electrochemical (bio)sensors, and also identified the key challenges in the future. It would provide new ideas and insights to the further development and application of electrochemical (bio)sensors and the detection of pesticides in real samples.

Electrochemical determination of nitroaromatic explosives using glassy carbon/multi walled carbon nanotube/polyethyleneimine electrode coated with gold nanoparticles

The on site/in field detection of explosives has become a rising priority for homeland security and counter-terrorism measures. This work presents the sensitive detection of nitroaromatic explosives using glassy carbon/multi-walled carbon nanotubes/polyethyleneimine (GC/MWCNTs/PEI) electrode coated with gold nanoparticles (AuNPs). MWCNTs and PEI could be well dispersed in ethanol/water solution, giving rise to a thin and homogeneous film on GCE. The GC/MWCNTs/PEI electrode was electrochemically modified with AuNPs and used for the differential pulse voltammetric (DPV) detection of nitroaromatics. The enhanced detection sensitivities were achieved through π-π and charge-transfer (CT) interactions between the electron-deficient nitroaromatic explosives and donor amine groups in PEI to which gold nanoparticles were linked, providing increased analyte affinity toward the modified GCE. Calibration curves of current intensity versus concentration were linear in the range of 0.05-8 mg L^-1 for TNT, 0.2-4 mg L^-1 for 2,4-dinitrotoluene (DNT), 1-20 mg L^-1 for 2,4-dinitrophenol (2,4-DNP), 0.25-10 mg L^-1 for picric acid (PA), and 0.05-4 mg L^-1 for 2,4,6-trinitrophenyl-N-methylnitramine (tetryl) with detection limits (LOD) of 15 μg L^-1, 45 μg L^-1, 135 μg L^-1, 30 μg L^-1, and 12 μg L^-1, respectively. The proposed method was successfully applied to the analysis of nitroaromatics in synthetic explosive mixtures and military composite explosives (comp B and octol). The electrochemical method was not affected by possible interferents of electroactive camouflage materials and common soil ions. Method validation was performed against the reference LC-MS method on TNT and PA-contaminated clay soil samples separately.

Reduced graphene oxide-supported smart plasmonic AgPtPd porous nanoparticles for high-performance electrochemical detection of 2,4,6-trinitrotoluene

Smart plasmonic AgPtPd NPs/rGO exhibited a wide linear range for TNT from 0.1 to 8 ppm with a sensing limit of 0.95 ppb. The remarkable features are probably attributed to the integrated advantages of the plasmonic properties and synergistic effect.

A novel electrochemical sensor for nitroguanidine determination using a glassy carbon electrode modified with multi-walled carbon nanotubes and polyvinylpyrrolidone

The GC/PVP/MWCNTs electrode is the first electrode for the electrochemical determination of insensitive explosive nitroguanidine using intermolecular hydrogen bonding interactions.

Novel electrical properties and applications in kaleidoscopic graphene nanoribbons

As one of the representatives of nano-graphene materials, graphene nanoribbons (GNRs) have more novel electrical properties, highly adjustable electronic properties, and optoelectronic properties than graphene due to their diverse geometric structures and atomic precision configurations. The electrical properties and band gaps of GNRs depend on their width, length, boundary configuration and other elemental doping, etc. With the improvement of the preparation technology and level of GNRs with atomic precision, increasing number of GNRs with different configurations are being prepared. They all show novel electrical properties and high tunability, which provides a broad prospect for the application of GNRs in the field of microelectronics. Here, we summarize the latest GNR-based achievements in recent years and summarize the latest electrical properties and potential applications of GNRs.

Recent advances in graphene nanoribbons for biosensing and biomedicine

In recent years, a new type of quasi-one-dimensional graphene-based material, graphene nanoribbons (GNRs), has attracted increasing attention. The limited domain width and rich edge configurations of GNRs endow them with unique properties and wide applications in comparison to two-dimensional graphene. This review article mainly focuses on the electrical, chemical and other properties of GNRs, and further introduces the typical preparation methods of GNRs, including top-down and bottom-up strategies. Then, their biosensing and biomedical applications are highlighted in detail, such as biosensors, photothermal therapy, drug delivery, etc. Finally, the challenges and future prospects in the synthesis and application of functionalized GNRs are discussed. It is expected that GNRs will have significant practical use in biomedical applications in the future.

Si-doped graphene nanosheets as a metal-free catalyst for electrochemical detection of nitroaromatic explosives

Si-doped graphene nanosheets (SiGNS) have been successfully constructed via high temperature annealing of graphene oxide and tetraethoxysilane mixture in a sealed glass ampoule. The Si atoms doped into graphene's carbon network mainly existed as C₃-Si-O and C₂-Si-O₂ configurations. The as-prepared SiGNS exhibited excellent electrochemical detection ability to nitroaromatic compounds in 0.1 M phosphoric acid buffer solution (PBS, pH = 8.0) via an electrochemical catalytic process. Five nitroaromatic compounds, including nitrobenzene, 2-nitrotoluene, 4-nitrotoluene, 2, 4-dinitrotoluene and 2, 4, 6-trinitrotoluene, were taken as the analyte to demonstrate the electrochemical catalytic ability of SiGNS. Density functional theory (DFT) calculation was carried out to explore the electrochemical catalytic mechanism of SiGNS. A hydrogen bond mediated electrochemical catalytic mechanism was proposed. Both the excellent electrical conductivity and the rich surface hydroxyl groups enhanced the electrochemical detection ability of SiGNS to nitroaromatic compounds. Si atoms in SiGNS played a key role for the excellent electrochemical detection ability of SiGNS due to most of the surface hydroxyl groups anchored on the Si atoms.

Cobalt encapsulated in bamboo-like N-doped carbon nanotubes for highly sensitive electroanalysis of Pb(II): enhancement based on adsorption and catalysis

Carbon nanotubes (CNTs) are recognized as desirable candidates to fabricate electrochemical sensing interfaces owing to their high surface area and excellent electron conductivity. However, the poor catalytic properties of CNTs significantly hinder their further application in electrochemical detection. Herein, for the first time we combined defective CNTs with catalytically active cobalt nanoparticles (Co NPs) to give cobalt encapsulated in a bamboo-like N-doped carbon nanotube nanocomposite (Co/N-CNTs). The novel constructed Co/N-CNTs are used as a modifier on a bare glass carbon electrode for the electrochemical detection of Pb(ii). As a result, the positive effect of adsorption and catalysis on Co/N-CNT shows a significant improvement in the electroanalytical performance towards Pb(ii) with a sensitivity of 69.74 μA μM-1 and a limit of detection of 0.039 μM. Moreover, the stability and practical applications of Co/N-CNTs towards Pb(ii) in real water samples obtained from a mining subsidence area were also considered. This method shows great promise, achieving an outstanding electroanalysis efficiency with noble-metal-free nanocomposite sensors based on the combination of carbon and transition metals.

Synergizing Functional Nanomaterials with Aptamers Based on Electrochemical Strategies for Pesticide Detection: Current Status and Perspectives

Owing to the high toxicity and large-scale use of pesticides, it is imperative to develop selective, sensitive, portable, and convenient sensors for rapid monitoring of pesticide. Therefore, the electrochemical detection platform offers a promising analytical approach since it is easy to operate, economical, efficient, and user-friendly. Meanwhile, with advances in functional nanomaterials and aptamer selection technologies, numerous sensitivity-enhancement techniques alongside a widespread range of smart nanomaterials have been merged to construct novel aptamer probes to use in the biosensing field. Hence, this study intends to highlight recent development and promising applications on the functional nanomaterials with aptamers for pesticides detection based on electrochemical strategies. We also reviewed the current novel aptamer-functionalized microdevices for the portability of pesticides sensors. Furthermore, the major challenges and future prospects in this field are also discussed to provide ideas for further research.

Folic Acid as a Bimodal Optical Probe for the Detection of TNT

Rapid and onsite detection of nitroaromatic explosive 2,4,6-trinitrotoluene (TNT) is very crucial for the safety and security of human life as well as for the environment. In this present work, we demonstrate the feasibility for employing Folic Acid (FA) as a fluorescent as well as a colorimetric probe for the detection of TNT. This probe was synthesized by a simple one-step process. The developed probe shows an emission maximum at 490 nm upon excitation at 420 nm. On adding TNT, the fluorescence of the FA probe is quenched. Also, it shows a good selectivity towards TNT over other similar organic compounds such as 4-nitrophenol (4-NP), 2,4-dinitrophenol (2,4-DNP) and picric acid (PA). The limit of detection (LoD) of TNT was found to be 1.9398 µM. Colorimetric detection was conducted and paper strip assay was developed for the practical applications.

Electrochemical determination of nitroaromatic explosives at boron-doped diamond/graphene nanowall electrodes: 2,4,6-trinitrotoluene and 2,4,6-trinitroanisole in liquid effluents

The study is devoted to the electrochemical detection of trace explosives on boron-doped diamond/graphene nanowall electrodes (B:DGNW). The electrodes were fabricated in a one-step growth process using chemical vapour deposition without any additional modifications. The electrochemical investigations were focused on the determination of the important nitroaromatic explosive compounds, 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitroanisole (TNA). The distinct reduction peaks of both studied compounds were observed regardless of the pH value of the solution. The reduction peak currents were linearly related to the concentration of TNT and TNA in the range from 0.05-15 ppm. Nevertheless, two various linear trends were observed, attributed respectively to the adsorption processes at low concentrations up to the diffusional character of detection for larger contamination levels. The limit of detection of TNT and TNA is equal to 73 ppb and 270 ppb, respectively. Moreover, the proposed detection strategy has been applied under real conditions with a significant concentration of interfering compounds - in landfill leachates. The proposed bare B:DGNW electrodes were revealed to have a high electroactive area towards the voltammetric determination of various nitroaromatic compounds with a high rate of repeatability, thus appearing to be an attractive nanocarbon surface for further applications.

TiO2 Nanoparticles Decorated Graphene Nanoribbons for Voltammetric Determination of an Anti-HIV Drug Nevirapine

In the present study, electrochemical behavior of nevirapine on a glassy carbon electrode (GCE) modified with TiO2 nanoparticles decorated graphene nanoribbons was investigated. Characterization of different components used for modifications was achieved using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The electrochemical behavior of nevirapine on the modified electrodes was examined using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and differential pulse voltammetry (DPV). A considerable oxidation potential decrease of +352 mV for nevirapine in 0.1 M phosphate-buffered saline (PBS), pH 11.0, was achieved due to synergy offered by graphene nanoribbons and TiO2 compared to graphene nanoribbons (+252 mV) and TiO2 (−37 mV), all with respect to the glassy carbon electrode. Under optimized conditions, DPV gave linear calibrations over the range of 0.020–0.14 µM. The detection limit was calculated as 0.043 µM. The developed sensor was used for determination of nevirapine in a pharmaceutical formulation successfully.

Hierarchical ZnO@Hybrid Carbon Core-Shell Nanowire Array on a Graphene Fiber Microelectrode for Ultrasensitive Detection of 2,4,6-Trinitrotoluene

A hierarchical architecture composed of nitrogen (N)-rich carbon@graphitic carbon-coated ZnO nanowire arrays on a graphene fiber (ZnO@C/GF) was fabricated by direct growth of a ZnO@zeolitic imidazolate framework-8 (ZIF-8) core-shell nanowire array on a GF followed by annealing and used as a microelectrode for detection of 2,4,6-trinitrotoluene (TNT). In such a design, ZnO accumulated TNT through a strong nitroxide-zinc interaction and ZIF-8 served as the precursor of the N-rich carbon@graphitic carbon layer that seamlessly connected ZnO with the GF to improve the poor conductivity of ZnO, thus enhancing the sensitivity of the ZnO@C/GF microelectrode. The constructed hierarchical hybrid fiber microsensor exhibited a wide linear response to TNT in a concentration range of 0.1-32.2 μM with a low detection limit of 3.3 nM. This ZnO@C/GF microelectrode was further successfully applied to the detection of TNT in lake and tap water, indicating its promise as a portable sensor for the electrochemical detection of explosive compounds.

Ethylene Glycol Functionalized Gadolinium Oxide Nanoparticles as a Potential Electrochemical Sensing Platform for Hydrazine and p-Nitrophenol

The current work reports the successful synthesis of ethylene glycol functionalized gadolinium oxide nanoparticles (Gd2O3 Nps) as a proficient electrocatalytic material for the detection of hydrazine and p-nitrophenol. A facile hydrothermal approach was used for the controlled growth of Gd2O3 Nps in the presence of ethylene glycol (EG) as a structure-controlling and hydrophilic coating source. The prepared material was characterized by several techniques in order to examine the structural, morphological, optical, photoluminescence, and sensing properties. The thermal stability, resistance toward corrosion, and decreased tendency toward photobleaching made Gd2O3 nanoparticles a good candidate for the electrochemical sensing of p-nitrophenol and hydrazine by using cyclic voltammetric (CV) and amperometric methods at a neutral pH range. The modified electrode possesses a linear range of 1 to 10 µM with a low detection limit of 1.527 and 0.704 µM for p-nitrophenol and hydrazine, respectively. The sensitivity, selectivity, repeatability, recyclability, linear range, detection limit, and applicability in real water samples made Gd2O3 Nps a favorable nanomaterial for the rapid and effectual scrutiny of harmful environmental pollutants.

Versatile Aerogels for Sensors

Aerogels are unique solid-state materials composed of interconnected 3D solid networks and a large number of air-filled pores. They extend the structural characteristics as well as physicochemical properties of nanoscale building blocks to macroscale, and integrate typical characteristics of aerogels, such as high porosity, large surface area, and low density, with specific properties of the various constituents. These features endow aerogels with high sensitivity, high selectivity, and fast response and recovery for sensing materials in sensors such as gas sensors, biosensors and strain and pressure sensors, among others. Considerable research efforts in recent years have been devoted to the development of aerogel-based sensors and encouraging accomplishments have been achieved. Herein, groundbreaking advances in the preparation, classification, and physicochemical properties of aerogels and their sensing applications are presented. Moreover, the current challenges and some perspectives for the development of high-performance aerogel-based sensors are summarized.

A Sensitive Resonance Rayleigh Scattering Method for Na+ Based on Graphene Oxide Nanoribbon Catalysis

The gold nanoparticle reaction of HAuCl₄-H₂O₂ was very slow under 60°C, and the as-prepared graphene oxide nanoribbons (GONRs) exhibited strong catalysis of the reaction to form gold nanoparticles (AuNP) that appeared a resonance Rayleigh scattering (RRS) peak at 550 nm. Upon addition of potassium pyroantimonate (PA) ligand, it was adsorbed on the GONRs surface to inhibit the catalysis to cause the RRS peak decreasing. When the analyte of Na⁺ was added, the coordination reaction between PA and Na⁺ took place to form the stable complexes of [Na₂(PA)] to release free GONRs catalyst that resulted in the RRS peak increasing linearly. Accordingly, a new and sensitive RRS method for Na⁺ was established, with a linear range of 0.69-25.8 nmol/L and a detection limit of 0.35 nmol/L Na⁺.

Fabrication of a self-assembled and flexible SERS nanosensor for explosive detection at parts-per-quadrillion levels from fingerprints

Apart from high sensitivity and selectivity of surface-enhanced Raman scattering (SERS)-based trace explosive detection, efficient sampling of explosive residue from real world surfaces is very important for homeland security applications. Herein, we demonstrate an entirely new SERS nanosensor fabrication approach. The SERS nanosensor was prepared by self-assembling chemically synthesized gold triangular nanoprisms (Au TNPs), which we show display strong electromagnetic field enhancements at the sharp tips and edges, onto a pressure-sensitive flexible adhesive film. Our SERS nanosensor provides excellent SERS activity (enhancement factor = ∼6.0 × 106) and limit of detection (as low as 56 parts-per-quadrillions) with high selectivity by chemometric analyses among three commonly military high explosives (TNT, RDX, and PETN). Furthermore, the SERS nanosensors present excellent reproducibility (<4.0% relative standard deviation at 1.0 μM concentration) and unprecedentedly high stability with a "shelf life" of at least 5 months. Finally, TNT and PETN were analyzed and quantified by transferring solid explosive residues from fingerprints left on solid surfaces to the SERS nanosensor. Taken together, the demonstrated sensitivity, selectivity, and reliability of the measurements as well as with the excellent shelf life of our SERS nanosensors obviate the need for complicated sample processing steps required for other analytical techniques, and thus these nanosensors have tremendous potential not only in the field of measurement science but also for homeland security applications to combat acts of terror and military threats.

Highly-sensitive voltammetric detection of trinitrotoluene on reduced graphene oxide/carbon nanotube nanocomposite sensor

This work presents the highly-sensitive detection of 2,4,6-trinitrotoluene (TNT) on reduced graphene oxide/multi-walled carbon nanotube (rGO/MWCNT) nanocomposite sensor. The formation of a thin film of this nanocomposite occurred at the cyclohexane/water immiscible interface of a mixture of MWCNT and rGO in the biphasic solution. The film was transferred to a boron-doped diamond (BDD) electrode for the square-wave voltammetric detection of TNT, which presented improved analytical characteristics in comparison with bare BDD and after modification with precursors. Electrochemical impedance spectroscopy also revealed the faster electron transfer for a redox probe on the nanocomposite modified surface. The synergistic properties of both carbon nanomaterials in the thin film modified surface resulted in a TNT sensor with a detection limit of 0.019 μmol L^-1 within a wide linear range (0.5-1100 μmol L^-1), with superior performance in comparison with other electrochemical sensors produced with carbon nanomaterials. This new material provides great promises for the highly-sensitive detection of other nitroaromatic explosives as well as other analytes. Moreover, the interfacial method enables the production of homogeneous and stable films on large coated areas as well as the large-scale production of electrochemical sensors.

A sensitive SERS quantitative analysis method for Ni2+ by the dimethylglyoxime reaction regulating a graphene oxide nanoribbon catalytic gold nanoreaction

The nanogold reaction between HAuCl₄ and trisodium citrate (TCA) proceeded very slowly at 60°C in a water bath. The as-prepared graphene oxide nanoribbons (GONRs) exhibited strong catalysis during the reaction to form gold nanoparticles (Au NPs) and appeared as a strong surface-enhanced Raman scattering (SERS) peak at 1616 cm^-1 in the presence of the molecular probe Victoria blue 4R (VB4r). With increase in GONR concentration, the SERS peak increased due to increased formation of Au NPs. Upon addition of dimethylglyoxime (DMG) ligand, which was adsorbed onto the GONR surface to inhibit GONR catalysis, the SERS peak decreased. When Ni²⁺ was added, a coordination reaction between DMG and Ni²⁺ took place to form stable complexes of [Ni (DMG)₂ ]²⁺ and the release of free GONR catalyst that resulted in the SERS peak increasing linearly. A SERS quantitative analysis method for Ni²⁺ was therefore established, with a linear range of 0.07-2.8 μM, and a detection limit of 0.036 μM Ni²⁺ .

Voltammetric sensing based on the use of advanced carbonaceous nanomaterials: a review

This review (with 210 references) summarizes recent developments in the design of voltammetric chemical sensors and biosensors based on the use of carbon nanomaterials (CNMs). It is divided into subsections starting with an introduction into the field and a description of its current state. This is followed by a large section on various types of voltammetric sensors and biosensors using CNMs with subsections on sensors based on the use of carbon nanotubes, graphene, graphene oxides, graphene nanoribbons, fullerenes, ionic liquid composites with CNMs, carbon nanohorns, diamond nanoparticles, carbon dots, carbon nanofibers and mesoporous carbon. The third section gives conclusion and an outlook. Tables are presented on the application of such sensors to voltammetric detection of neurotransmitters, metabolites, dietary minerals, proteins, heavy metals, gaseous molecules, pharmaceuticals, environmental pollutants, food, beverages, cosmetics, commercial goods and drugs of abuse. The authors also describe advanced approaches for the fabrication of robust functional carbon nano(bio)sensors for voltammetric quantification of multiple targets. Graphical Abstract Featuring execellent electrical, catalytic and surface properies, CNMs have gained enormous attention for designing voltammetric sensors and biosensors. Functionalized CNM-modified electrode interfaces have demonstrated their prominent role in biological, environmental, pharmaceutical, chemical, food and industrial analysis.

Methyl parathion detection in vegetables and fruits using silver@graphene nanoribbons nanocomposite modified screen printed electrode

We have developed a sensitive electrochemical sensor for Organophosphorus pesticide methyl parathion (MP) using silver particles supported graphene nanoribbons (Ag@GNRs). The Ag@GNRs nanocomposite was prepared through facile wet chemical strategy and characterized by TEM, EDX, XRD, Raman, UV-visible, electrochemical and impedance spectroscopies. The Ag@GNRs film modified screen printed carbon electrode (SPCE) delivers excellent electrocatalytic ability to the reduction of MP. The Ag@GNRs/SPCE detects sub-nanomolar concentrations of MP with excellent selectivity. The synergic effects between special electrocatalytic ability of Ag and excellent physicochemical properties of GNRs (large surface area, high conductivity, high area-normalized edge-plane structures and abundant catalytic sites) make the composite highly suitable for MP sensing. Most importantly, the method is successfully demonstrated in vegetables and fruits which revealed its potential real-time applicability in food analysis.

Highly sensitive determination of non-steroidal anti-inflammatory drug nimesulide using electrochemically reduced graphene oxide nanoribbons

Preparation of an electrochemically reduced graphene nanoribbon (ER-GONR) film modified screen-printed carbon electrode for the highly sensitive determination of nimesulide.