Nanoparticles as components of electrochemical sensing platforms for the detection of petroleum pollutants: A review

Detection of Crude Oil in Subsea Environments Using Organic Electrochemical Transistors

Current methods for detecting pipeline oil leaks depend primarily on optical detection, which can be slow and have deployment limitations. An alternative non-optical approach for earlier and faster detection of oil leaks would enable a rapid response and reduce the environmental impact of oil leaks. Here, we demonstrate that organic electrochemical transistors (OECTs) can be used as non-optical sensors for crude oil detection in subsea environments. OECTs are thin film electronic devices that can be used for sensing in a variety of environments, but they have not yet been tested for crude oil detection in subsea environments. We fabricated OECTs with poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) as the channel and showed that coating the channel with a polystyrene film results in an OECT with a large and measurable response to oil. Oil that comes in contact with the device will adsorb onto the polystyrene film and increases the impedance at the electrolyte interface. We performed electrochemical impedance spectroscopy measurements to quantify the impedance across the device and found an optimal thickness for the polystyrene coating for the detection of oil. Under optimal device characteristics, as little as 10 μg of oil adsorbed on the channel surface produced a statistically significant change in the source-drain current. The OECTs were operable in seawater for the detection of oil, and we demonstrated that the devices can be transferred to flexible substrates which can be easily implemented in vehicles, pipelines, or other surfaces. This work demonstrates a low-cost device for oil detection in subsea environments and provides a new application of OECT sensors for sensing.

Research progress of sensors based on molecularly imprinted polymers in analytical and biomedical analysis

Molecularly imprinted polymers (MIPs) have had tremendous impact on biomimetic recognition due to their precise specificity and high affinity comparable to that of antibodies, which has shown the great advantages of easy preparation, good stability and low cost. The combination of MIPs with other analytical technologies can not only achieve rapid extraction and sensitive detection of target compounds, improving the level of analysis, but also achieve precise targeted delivery, in-vivo imaging and other applications. Among them, the recognition mechanism plays a vital role in chemical and biological sensing, while the improvement of the recognition element, such as the addition of new nanomaterials, can greatly improve the analytical performance of the sensor, especially in terms of selectivity. Currently, due to the need for rapid diagnosis and improved sensing properties (such as selectivity, stability, and cost-effectiveness), researchers are investigating new recognition elements and their combinations to improve the recognition capabilities of chemical sensing and bio-sensing. Therefore, this review mainly discusses the design strategies of optical sensors, electrochemical sensors and photoelectric sensors with molecular imprinting technology and their applications in environmental systems, food fields, drug detection and biology including bacteria and viruses.

Magnetic Fe3O4 nanoparticles decorated phosphorus-doped biochar-attapulgite/bismuth film electrode for smartphone-operated wireless portable sensing of ultra-trace multiple heavy metal ions

Pollution caused by both forestry wastes and heavy metals has increasingly drawn attention owing to environmental safety concerns. After essential oil is extracted from Cinnamomum camphoras (L.), the branches are used as forestry wastes to prepare a phosphorus-doped biochar-attapulgite/bismuth film electrode decorated with magnetic Fe₃O₄ nanoparticles (MBA-BiFE). The smartphone-operated wireless portable sensor is employed for the simultaneous ultratrace voltammetric detection of multiple heavy metal ions (Cd²⁺, Pb²⁺, and Hg²⁺). Cd²⁺, Pb²⁺, and Hg²⁺ exhibit excellent electrochemical responses in linear ranges of 0.1 nM-5 μM, 0.01 nM-7 μM, and 0.1 nM-3 μM with limits of detection equal to 0.036, 0.003, and 0.011 nM, respectively. The recoveries of MBA-BiFE for Cd²⁺, Pb²⁺, and Hg²⁺ are 93.6-109.9%, 86.0-107.5%, and 94.8-104.6%, respectively, and the RSD values for repeated measurements of Cd²⁺, Pb²⁺, and Hg²⁺ are 4.2%, 2.8%, and 3.3%, respectively. A machine learning model based on an artificial neural network algorithm is constructed to enable a smart determination of ultratrace hazardous multiple metal ions. The portable sensor based on the screen-printed integrated three-electrode sensor modified using MBA-BiFE demonstrates advantages and practicability in outdoor detection, compared with conventional sensors based on MBA-BiFE. This study provides a smartphone-operated wireless portable sensing technique for high-potential applications in environmetallomics or agrometallomics using forestry waste-derived biochar as substrate for electrode preparation. HIGHLIGHTS: • Fe₃O₄ decorated phosphorus-doped biochar-attapulgite/bismuth film electrode. • A smartphone-operated sensor for analysis of multiple heavy metal ions. • An Artificial neural network model for smart analysis of Cd²⁺, Pb²⁺, and Hg²⁺.

Plasma-Assisted Fabrication of Molecularly Imprinted NiAl-LDH Layer on Ni Nanorod Arrays for Glyphosate Detection

An inorganic-framework molecularly imprinted NiAl layered double hydroxide (MI-NiAl-LDH) with specific template molecule (glyphosate pesticide, Glyp) recognition ability was prepared on Ni nanorod arrays (Ni NRAs) through electrodeposition followed by a low-temperature O₂ plasma treatment. The freestanding Ni/MI-NiAl-LDH NRA electrode had highly enhanced sensitivity and selectivity. The electrocatalytic oxidation of Glyp was proposed to occur at Ni³⁺ centers in MI-NiAl-LDH, and the current response depended linearly on the Glyp concentration from 10.0 nmol/L to 1.0 μmol/L (R² = 0.9906), with the limit of detection (LOD) being 3.1 nmol/L (S/N = 3). An exceptional discriminating capability with tolerance for other similar organophosphorus compounds was achieved. Molecular imprinting (N and P residues) affected the electronic structure of NiAl-LDH, triggering the formation of highly active NiOOH sites at relatively lower anodic potentials and substantially enhancing the electrocatalytic oxidation ability of the NiAl-LDH interface toward the C-N bonds in Glyp. In combination with the surface enrichment effect of MI-NiAl-LDH toward template molecules, the electrochemical oxidation signal intensity of Glyp increased significantly, with a greater peak separation from interfering molecules. These results challenge the common belief that the excellent performance of inorganic-framework molecularly imprinted interfaces arises from their specific adsorption of template molecules, providing new insight into the development of high-performance organic-pollutant-sensing electrodes.

Computational investigation of a covalent triazine framework (CTF-0) as an efficient electrochemical sensor

In the current study, a covalent triazine framework (CTF-0) was evaluated as an electrochemical sensor against industrial pollutants i.e., O₃, NO, SO₂, SO₃, and CO₂. The deep understanding of analytes@CTF-0 complexation was acquired by interaction energy, NCI, QTAIM, SAPT0, EDD, NBO and FMO analyses. The outcome of interaction energy analyses clearly indicates that all the analytes are physiosorbed onto the CTF-0 surface. NCI and QTAIM analysis were employed to understand the nature of the non-covalent interactions. Furthermore, SAPT0 analysis revealed that dispersion has the highest contribution towards total SAPT0 energy. In NBO analysis, the highest charge transfer is obtained in the case of SO₃@CTF-0 (−0.167 e⁻) whereas the lowest charge transfer is observed in CO₂@CTF-0. The results of NBO charge transfer are also verified through EDD analysis. FMO analysis revealed that the highest reduction in the HOMO–LUMO energy gap is observed in the case of O₃ (5.03 eV) adsorption onto the CTF-0 surface, which indicates the sensitivity of CTF-0 for O₃ analytes. We strongly believe that these results might be productive for experimentalists to tailor a highly sensitive electrochemical sensor using covalent triazine-based frameworks (CTFs).

In the current study, a covalent triazine framework (CTF-0) was evaluated as an electrochemical sensor against industrial pollutants i.e., O₃, NO, SO₂, SO₃, and CO₂.

Green Synthesis: An Eco-friendly Route for the Synthesis of Iron Oxide Nanoparticles

Green approach has received major attention for the synthesis of metal oxide nanoparticles. One such metal oxide nanoparticles are iron oxide nanoparticles (IONPs). IONPs have fetched a great deal of interest in recent era because of their magnetic nature, as they can be easily recovered from the reaction mixture by applying an external magnetic field. Although, a variety of chemical and physical methods of synthesis are known, green synthesis is safer, sustainable and biologically acceptable. Plants and microbes are the main biological materials used for the green synthesis. In present review, the synthesis of IONPs by using plants, bacteria, fungi and algae have been highlighted. IONPs produced by plants, fungi, bacteria and algae usually falls in 1–100 nm range and are of distinct shapes like cubic, tetragonal crystalline, spherical, cylindrical, elliptical, octahedral, orthorhombic, hexagonal rods, nanosphere and quasi spherical. Furthermore, these biomaterials play role of reducing, capping, stabilizing and fabricating agents in green synthesis of nanoparticles. The review put forward a comprehensive report of various routes used for synthesizing IONP, biologically. Intuition into the procedures for synthesis of nanoparticles will help to nourish our learning in the area of nanotechnology.

Emerging electrochemical sensing and biosensing approaches for detection of Fumonisins in food samples

Fumonisins (FBs) can be found extensively in feedstuffs, foodstuffs, and crops. The consumption of the fumonisin-contaminated corn can result in esophageal cancer. In addition, the secondary metabolites of fungi termed mycotoxins may have some adverse effects on animals and humans such as estrogenicity, immunotoxicity, teratogenicity, mutagenicity, and carcinogenicity. Hence, developing sensitivity techniques for mycotoxins determination is of great importance. This paper reports the latest developments of nanomaterial-based electrochemical biosensing, apta-sensing, sensing, and immunosensing analyses to detect fumonisins. A concise study of the occurrence, legislations, toxicity, and distribution of FBs in levels monitoring was done. The techniques, different detection matrices, and approaches to highly selective and sensitive sensing methods were reviewed. The review also summarizes the salient features and the necessity of biosensing assessments in FBs detection, and diverse immobilization techniques. Furthermore, this review defined the performance of various electrochemical sensors using different detection elements couples with nanomaterials fabricated applying different detection elements coupled with nanomaterials (metal oxide nanoparticles (NPs), metal NPs, CNT, and graphene), the factors limiting progress, and the upcoming tasks in successful aptasensor fabrication with the functionalized nanomaterials.

Biosensing strategies for the electrochemical detection of viruses and viral diseases - A review

Viruses are the causing agents for many relevant diseases, including influenza, Ebola, HIV/AIDS, and COVID-19. Its rapid replication and high transmissibility can lead to serious consequences not only to the individual but also to collective health, causing deep economic impacts. In this scenario, diagnosis tools are of significant importance, allowing the rapid, precise, and low-cost testing of a substantial number of individuals. Currently, PCR-based techniques are the gold standard for the diagnosis of viral diseases. Although these allow the diagnosis of different illnesses with high precision, they still present significant drawbacks. Their main disadvantages include long periods for obtaining results and the need for specialized professionals and equipment, requiring the tests to be performed in research centers. In this scenario, biosensors have been presented as promising alternatives for the rapid, precise, low-cost, and on-site diagnosis of viral diseases. This critical review article describes the advancements achieved in the last five years regarding electrochemical biosensors for the diagnosis of viral infections. First, genosensors and aptasensors for the detection of virus and the diagnosis of viral diseases are presented in detail regarding probe immobilization approaches, detection methods (label-free and sandwich), and amplification strategies. Following, immunosensors are highlighted, including many different construction strategies such as label-free, sandwich, competitive, and lateral-flow assays. Then, biosensors for the detection of viral-diseases-related biomarkers are presented and discussed, as well as point of care systems and their advantages when compared to traditional techniques. Last, the difficulties of commercializing electrochemical devices are critically discussed in conjunction with future trends such as lab-on-a-chip and flexible sensors.

Metallic-Nanoparticle-Based Sensing: Utilization of Mixed-Ligand Monolayers

The last two decades have seen great advancements in fundamental understanding and applications of metallic nanoparticles stabilized by mixed-ligand monolayers. Identifying and controlling the organization of multiple ligands in the nanoparticle monolayer has been studied, and its effect on particle properties has been examined. Mixed-ligand protected particles have shown advantages over monoligand protected particles in fields such as catalysis, self-assembly, imaging, and drug delivery. In this Review, the use of mixed-ligand monolayer protected nanoparticles for sensing applications will be examined. This is the first time this subject is examined as a whole. Mixed-ligand nanoparticle-based sensors are revealed to be divided into four groups, each of which will be discussed. The first group consists of ligands that work cooperatively to improve the sensors' properties. In the second group, multiple ligands are utilized for sensing multiple analytes. The third group combines ligands used for analyte recognition and signal production. In the final group, a sensitive, but unstable, functional ligand is combined with a stabilizing ligand. The Review will conclude by discussing future challenges and potential research directions for this promising subject.

Insights into the Formation of DNA-Magnetic Nanoparticle Hybrid Structures: Correlations between Morphological Characterization and Output from Magnetic Biosensor Measurements

Understanding the binding mechanism between probe-functionalized magnetic nanoparticles (MNPs) and DNA targets or amplification products thereof is essential in the optimization of magnetic biosensors for the detection of DNA. Herein, the molecular interaction forming hybrid structures upon hybridization between DNA-functionalized magnetic nanoparticles, exhibiting Brownian relaxation, and rolling circle amplification products (DNA-coils) is investigated by the use of atomic force microscopy in a liquid environment and magnetic biosensors measuring the frequency-dependent magnetic response and the frequency-dependent modulation of light transmission. This approach reveals the qualitative and quantitative correlations between the morphological features of the hybrid structures with their magnetic response. The suppression of the high-frequency peak in the magnetic response and the appearance of a new peak at lower frequencies match the formation of larger sized assemblies upon increasing the concentration of DNA-coils. Furthermore, an increase of the DNA-coil concentration induces an increase in the number of MNPs per hybrid structure. This study provides new insights into the DNA–MNP binding mechanism, and its versatility is of considerable importance for the mechanistic characterization of other DNA-nanoparticle biosensor systems.

Structure, synthesis, and sensing applications of single-walled carbon nanohorns

Single-walled carbon nanohorns (SWCNHs), a type of tapered carbon nanomaterials, are generally prepared by laser ablation method, arc method, and Joule heating method without the addition of metal catalysts, which makes them pure and environmentally friendly. The obtained aggregates of SWCNHs mainly have three different types of structure, dahlia-like, bud-like, and seed-like. Over the past few decades, they have been widely used in the fields of energy, medicine, chemistry, and sensing. The SWCNHs-based sensors have shown high sensitivity, rapid response, and excellent stability, which are mainly attributed to the excellent electrical conductivity, large electrochemical window, large specific surface area, and mechanical strength of SWCNHs. In this review, we systematically summarizes the structures, synthesis methods, and sensing applications of SWCNHs, including electrochemical sensors, photoelectrochemical sensors, electrochemiluminescence sensors, fluorescent sensors, and resistive sensors. Moreover, the development prospects of SWCNHs in this field are also discussed.