Analytical methods for determining environmental contaminants of concern in water and wastewater.

Control and prevention of environmental pollution have emerged as paramount global concerns. Anthropogenic activities, such as industrial discharges, agricultural runoff, and improper waste disposal, introduce a wide range of contaminants into various ecosystems. These pollutants encompass organic and inorganic compounds, particulates, microorganisms, and disinfection by-products, posing severe threats to human health, ecosystems, and the environment. Effective monitoring methods are indispensable for assessing environmental quality, identifying pollution sources, and implementing remedial measures. This paper suggests that the development and utilization of highly advanced analytical tools are both essential for the analysis of contaminants in water samples, presenting a foundational hypothesis for the review. This paper comprehensively reviews the development and utilization of highly advanced analytical tools which is mandatory for the analysis of contaminants in water samples. Depending on the specific pollutants being studied, the choice of analytical methods widely varies. It also reveals insights into the diverse applications and effectiveness of these methods in assessing water quality and contaminant levels. By emphasizing the critical role of the reviewed monitoring methods, this review seeks to deepen the understanding of pollution challenges and inspire innovative monitoring solutions that contribute to a cleaner and more sustainable global environment.•Urgent global concerns: control and prevention of pollution from diverse sources.•Varied contaminants, diverse methods: comprehensive review of analytical tools.•Inspiring a sustainable future: innovative monitoring for a cleaner environment.

Detection of SARS-CoV-2 in clinical and environmental samples using highly sensitive reduced graphene oxide (rGO)-based biosensor.

Quantitative RT-PCR (qRT-PCR) is the most commonly used diagnostic tool for SARS-CoV-2 detection during the COVID-19 pandemic. Despite its sensitivity and accuracy, qRT-PCR is a time-consuming method that requires expensive laboratories with highly trained personnel. In this work, on-site detection of SARS-CoV-2 in municipal wastewater was investigated for the first time. The wastewater was unprocessed and did not require any prefiltration, prior spiking with virus, or viral concentration in order to be suitable for use with the biosensor. The prototype reported here is a reduced graphene oxide (rGO)-based biosensor for rapid, sensitive and selective detection of SARS-CoV-2. The biosensor achieved a limit of detection (LOD) of 0.5 fg/mL in phosphate-buffered saline (PBS) and exhibited specificity when exposed to various analytes. The response time was measured to be around 240 ms. To further explore the capabilities of the biosensor in real clinical and municipal wastewater samples, three different tests were performed to determine the presence or absence of the virus: (i) qRT-PCR, (ii) a rapid antigen-based commercially available test (COVID-19 Test Strips), and (iii) the biosensor constructed and reported here. Taken together, our results demonstrate that a biosensor that can detect SARS-CoV-2 in clinical samples as well as unfiltered and unprocessed municipal wastewater is feasible.

Optimization of an rGO-based biosensor for the sensitive detection of bovine serum albumin: Effect of electric field on detection capability.

Despite significant progress in the field of biosensing, the impact of electric field on biosensor detection capability and the feasibility of the biosensor application in wastewater has yet to be investigated. The objective of this study was to develop a low-cost, highly sensitive, and selective reduced graphene oxide (rGO)-based biosensor. The constructed biosensor consists of an in-house prepared GO and a four-terminal Kelvin sensing. Spin-coating was chosen as the deposition technique and results revealed an optimal GO number of layers and concentration of 7 and 2 mg/mL, respectively. Experiments to determine the effects of electric field on the performance of the biosensor showed significant changes in the biosensor surface, also presenting a direct impact on the biosensor functionality, such that the biosensor showed an increase in limit of detection (LOD) from 1 to 106 fg/mL when the applied voltage was increased from 0.0008 to 0.2 V. Furthermore, this study successfully explores a pilot scale setup, mimicking wastewater flow through sewage pipelines. The demonstrated improvements in the detection capability and sensitivity of this biosensor at optimized testing conditions make it a promising candidate for further development and deployment for the detection of protein analytes present at very low concentrations in aqueous solutions. In addition, the application of this biosensor could be extended to the detection of protein analytes of interest (such as the spike protein of SARS-CoV-2) in much more complex solutions, like wastewater.

Recent advances in the biosensors application for the detection of bacteria and viruses in wastewater.

The presence of disease-causing pathogens in wastewater can provide an excellent diagnostic tool for infectious diseases. Biosensors are far superior to conventional methods used for regular infection screening and surveillance testing. They are rapid, sensitive, inexpensive portable and carry no risk of exposure in their detection schemes. In this context, this review summarizes the most recently developed biosensors for the detection of bacteria and viruses in wastewater. The review also provides information on the new detection methods aimed at screening for SARS-CoV-2, which has now caused more than 4 million deaths. In addition, the review highlights the potential behind on-line and real-time detection of pathogens in wastewater pipelines. Most of the biosensors reported were not targeted to wastewater samples due to the complexity of the matrix. However, this review highlights on the performance factors of recently developed biosensors and discusses the importance of nanotechnology in amplifying the output signals, which in turn increases the accuracy and reliability of biosensors. Current research on the applicability of biosensors in wastewater promises a dramatic change to the conventional approach in the field of medical screening.

Nanojunction Material Effect on the Photoelectric Response of Single-Wall Carbon Nanotube Rectennas.

To optimize the performance of carbon nanotube (CNT)-based rectennas, we have studied the effect of metal work function on the photodetection characteristics. Two materials of conducting nanoprobes, namely, gold (Au) and platinum (Pt), have been used to form a rectifying diode at the interface with the CNT. The electrical and optical characteristics of single-wall carbon nanotubes (SWCNTs) dispersed on top of a SiO2/Si substrate have been investigated using a conductive mode atomic force microscope (C-AFM). The I-V measurements performed for both diodes have exhibited an explicit rectification behavior with high sensitivity of a CNT-based rectenna to light. It has been observed that the lower work function metal (Au) leads to a higher on/off current ratio than the high work function metal (Pt). These experimental observations will be explained using the material characterization of the complete system along with representative energy-band diagrams.

Single wall carbon nanotube based optical rectenna.

We present an optical rectenna by engineering a rectifying diode at the interface between a metal probe of an atomic force microscope (AFM) and a single wall carbon nanotube (SWCNT) that acts as a nano-antenna. Individual SWCNT electrical and optical characteristics have been investigated using a conductive AFM nano-probe in contact with two device structures, one with a SWCNT placed on a CuO/Cu substrate and the other one with a SWCNT on a SiO2/Si substrate. The I-V measurements performed for both designs have exhibited an explicit rectification behavior and the sensitivity of carbon nanotube (CNT)-based rectenna to light. The measured output current at a set voltage value demonstrates the significant effect of the light irradiation on the current signal generated between the Au nano-probe and CNT interface. This effect is more prominent in the case of the CuO/Cu substrate. Detailed analysis of the system, including the energy band diagram, materials characterization and finite element simulation, is included to explain the experimental observations. This work will pave the way for more investigations and potential applications of CNTs as nano-rectennas in optical communication and energy harvesting systems.

Carbon Nanotube Inkjet Printing Based Resettable Sensor for Online Scale Monitoring.

In this paper, a new type of sensor and associated system for complete online monitoring of scale deposition with great accuracy and reliability is fabricated and characterized. The system is based on carbon nanotubes (CNTs), which have unique sensing/electronic properties along with physical and chemical stability in corrosive and hostile environments required for the oil and gas application. CNTs inkjet printing technique is used to fabricate the CNTs sensor. The sensitivity of the films, real time monitoring of brine solution, stability of the films in various solvents and fluids and the ability of setting and resetting of the sensor are studied. The results of these studies indicate that adding of one brine solution on the surface of the CNTs inkjet printing increases the resistance from 0.50 kΩ to 1.50 kΩ. The CNTs inkjet printing sample is found to be stable even after 48 hours of soaking the whole sample in DI-water. This sensor not only shows good sensing response for detection of the deposition of brine, but can also be easily reset back many times by just wash it with DI-water. This simple sensor is ideally suited for real time monitoring and the response time of the film is found to be from 15­30 s.