Nanomolar Level Detection Research Articles

Nanomolar level detection of phosphodiesterase 5 inhibitor drug tadalafil based on halide perovskite@HNTs nanocomposite electrode

As halide perovskites have taken a central role in the evolution of semiconductor materials, they are setting new standards for performance and revolutionizing the energy sectors. Unfortunately, little light is shed on the material's electrochemical sensing capabilities. This work reports the synthesis and characterization of a novel double halide perovskite Cs2CaSnCl6 (HDP) integrated with halloysite nanotubes (HNTs) for the electrochemical detection of Tadalafil (TAD). HDP@HNTs nanocomposite is synthesized using a simple solvothermal method and is characterized using various techniques like SEM, TEM, UV-visible, FT-IR, TGA/DTA, XRD and BET analysis. The results obtained from these characterizations confirmed the successful formation of the nanocomposite, revealed the material's endurance to high temperatures and the availability of a large surface area for reaction. Electrochemical characterization techniques like cyclic voltammetry (CV) and linear sweep voltammetry (LSV) demonstrated a linear correlation with the concentrations of TAD. Computational analysis of the TAD structure optimization, molecular electrostatic potential (MEP) of TAD and calculations regarding the HOMO-LUMO molecular orbitals are all carried out using the DFT/B3LYP method. The HDP@HNTs sensor is capable of achieving the lowest detection limit of 1.68 nM and the limit of quantification of 5.09 nM. The material showcased a remarkable sensitivity of 0.0104 µA nM-1 cm-2 from all the electrochemical parameters. Its reliability and stable performance even in the presence of real samples makes it a promising material for sensing applications. Thus, the reported framework contributes to the advancement in the development of sensors and enhanced healthcare outcomes.

Customizable OpenGUS immunoassay: A homogeneous detection system using β-glucuronidase switch and label-free antibody

We developed a customizable OpenGUS immunoassay that enables rapid and sensitive detection of analytes without requiring antibody modification. This immunoassay employs label-free whole antibodies, an antibody-binding Z domain (ZD) derived from Staphylococcal protein A, and a β-glucuronidase (GUS) switch mutant, allowing for easy replacement of antibodies to tailor the immunoassays for various targeted antigens. The working principle is that the OpenGUS probe, the fusion protein of ZD and a GUS switch, converts the antibody-antigen interaction into GUS activation in a one-pot reaction. To enhance the signal-to-background ratio of the immunoassay, a GUS switch mutant that exhibits reduced background activation was developed by screening several additional mutations at the diagonal interface residue H514. Moreover, we optimized the composition of the reaction buffer, including organic solvents, salt, and surfactant. Under optimal conditions, we customized OpenGUS immunoassays for Cry j 1, human C-reactive protein, and human lactoferrin, achieving around 10–20-fold maximum fluorescence (15 min) or colorimetric (2 h) responses with picomolar to low nanomolar level detection limit, simply by using commercially available IgGs. Additionally, the three analytes were successfully detected in complex matrices similar to those used in practical applications. We believe that this customizable OpenGUS immunoassay will pave the way for the prompt development of rapid and sensitive homogeneous immunoassays for point-of-care diagnostics, high-throughput testing, and onsite environmental assessments.

A novel molecular imprinted polymer grafted on N, S Co-doped carbon quantum dots-based fluorescence sensor for chloramphenicol in food and clinical samples

Globally, antibiotic consumption surpasses thousands of tons on every year and even during this alarming state, the abundant traces of antibiotics have been found in the environment especially on water bodies and food producing creatures. The high accumulation of Chloramphenicol (CPL) may cause microbial resistance and lowering the general immunity. All these finding urges to develop a sensitive detection system for CPL. The present work describes the fabrication of Molecular Imprinted Polymer (MIP) grafted on Nitrogen and Sulfur doped Carbon Quantum Dots (N, S-CQDs) as a probe for the nanomolar level detection of CPL in food and clinical samples by using fluorescence technique. The developed N, S-CQDs based MIP sensor exhibits a bright fluorescence response and high recognition capability on CPL. The proposed sensor system has shown the detection limit of 7.65 nM and the linearity range was found between 0.24 μM and 26.1 μM. The real time consistency of the proposed sensor system has been verified by applying on clinical and food samples. Interestingly, we have received an excellent recovery varies from 97 % to 103 %. All these research outcomes further boost up the novel strategy to develop MIP based fluorescence probe for the detection of CPL.

Ultra-selective pyrene-based fluorescent sensor for detection of Fe+3 in neat aqueous medium

Transition metals, particularly Fe+3, play vital roles in biological and environmental systems, yet their chronic elevation can lead to severe diseases. Early detection of Fe+3 is crucial for diagnosing associated ailments. While traditional detection methods have drawbacks, fluorescent sensors offer promising alternatives due to their ease of use, cost-effectiveness, and real-time monitoring capability. Pyrene-based sensors have demonstrated notable sensitivity and selectivity for Fe+3, but challenges remain in achieving applicability in neat aqueous systems. We present two novel turn-off pyrene-based sensors, APTS (sodium 8-aminopyrene-1,3,6-trisulfonate) and APSS (sodium (E)-4-hydroxy-3-((pyren-1-ylimino)methyl)benzenesulfonate), incorporating sulfonate groups to enable their use in pure water samples and achieve nanomolar-level detection limits. Through meticulous experimental and characterization efforts, we elucidate the significance of the imine linkage in enhancing selectivity towards Fe+3 ions. Our sensors exhibit exceptional selectivity and sensitivity, with LODs of 45.6 nM and 45.9 nM for APTS and APSS, respectively, surpassing environmental protection guidelines. Additionally, binding stoichiometry studies reveal insights into the interaction mechanisms, supported by fluorescence lifetime analysis and DFT studies. APSS particularly stands out for its lack of interference from other metal ions, notably Cu2+ as well as Fe2+, offering promising potential for real-time applications and development of paper strip tests. The practical applicability of our sensors is demonstrated through successful Fe+3 detection in various water samples with recoveries ranging from 94 % to 104 %. Overall, our study highlights the effectiveness of APTS and APSS as robust fluorescent probes, with implications for environmental monitoring and biomedical diagnostics.

Subtle structural variation of antipyrine derivatives for ESIPT based fluorescence recognition of Al3+ and Zn2+ ions

Three imine derivatives containing antipyrine moiety viz. A1, A2 and A3 have been synthesized and characterized by SC-XRD analysis. The molecules are weakly fluorescent due to ESIPT process. The A1 and A2 have high affinity as well as selectivity for Al3+ that allow its nano-molar level detection. On the other hand, A3 interacts with both Al3+ and Zn2+ as reflected from the change of emission profiles at two different wavelengths. Such distinctive photo-physical interaction of A3 over A1 and A2 may be elucidated through hard-soft interaction concept. Various spectroscopic techniques have been used to explain the sensing mechanism. DFT studies have been performed to explain and justify experimental findings. The interaction of A3 towards Al3+ and Zn2+ has been utilized to construct a logic gate. Moreover, real water analysis has also been performed.

Synthesis and characterization of a xanthene-based molecular probe to detect triphosgene in solution and vapor phases

The ability of a detection approach to direct a visible and easy-to-monitor characteristic is an important aspect of molecular-level detection. From this viewpoint, we developed the molecular probe Xanth-Py, which allows us to visually detect triphosgene (TPG) by modulating the probe's photophysical characteristics. Since Xanth-Py exhibits a strong fluorescence, its interaction with TPG causes the non-radiative decay of the probe. As TPG concentrations increase, the fluorescence intensity decreases linearly, leading to a nanomolar level detection limit. The interaction of Xanth-Py with TPG accompanied a color change from pink to blue, enabling a visible detection protocol. Probe-coated paper strips have been used as an inexpensive detection tool for vapor-phase TPG detection, revealing the potential of the Xanth-Py. Further, triphosgene has been detected using a smartphone-assisted RGB analysis tool in conjunction with a portable UV-light source device.

Functional Group-Assisted Fluorescence Sensing Platform for Nanomolar-Level Detection of an Antineoplastic Drug and a Neurotransmitter from Environmental Water and Human Biofluids.

A fast, sensitive, selective, and biocompatible dual sensor of an antineoplastic medication (methotrexate) and a neurotransmitter (adrenaline) is still being searched by present-day scientists. To overcome this issue, we have designed a functionalized, robust, bio-friendly luminescent MOF for the sensitive, selective, and rapid monitoring of methotrexate and adrenaline. This probe is the first ever reported MOF-based fluorescence sensor of methotrexate and second only for adrenaline. This fluorescence probe has a very low limit of detection (LOD) of 0.34 and 11.2 nM for adrenaline and methotrexate, respectively. The sensor can detect both the targeted analytes rapidly within 5 s. It can also detect adrenaline and methotrexate from human blood serum and urine accurately and precisely. This reusable sensor is equally efficient in detecting methotrexate from environmental water specimens. Biocompatible, user-friendly, and inexpensive chitosan@MOF@cotton composites were fabricated for the detection of adrenaline and methotrexate from the nanomolar to the micromolar range by the naked eye under a fluorescence lamp. This probe displayed high reproducibility, precision, and accuracy in sensing methotrexate and adrenaline. Fluorescence resonance energy transfer (FRET) and the inner filter effect (IFE) are the possible mechanisms for adrenaline and methotrexate sensing, respectively. The possible mechanism was supported by using required instrumental techniques and theoretical simulations.

Unique Reaction-Based Polynorbornene Sensing Probes for Ultrasensitive Detection of Hydrazine in Both Environmental and Biological Systems.

Hydrazine-mediated formation of 1,4-phthalazinedione analogues from phthalimide-like components has been utilized to formulate fluorescent probe NorTh. A turn-on fluorescent process has been evaluated to detect hydrazine in a highly selective manner by a small molecular probe NorTh and its homopolymer Poly-NorTh. Both these probes have been evaluated as excellent candidates for nanomolar level detection of hydrazine with a time frame of <15 min, which is rapid in terms of real application. Due to the reaction-based detection process, we have achieved high selectivity for our probes toward the identification of hydrazine in the presence of metal ions, anions, amino acids, and various amines. Limit of detection values are 16 and 35 nM for NorTh and Poly-NorTh, respectively, which are well below the permissible limit given by WHO and EPA. Poly-NorTh has been utilized to detect hydrazine in environmental water samples, soil samples, and biological samples to establish the applicability of our probes in real-field scenarios. We introduce an easy-to-synthesize, cheap, and small molecular probe and its polymer for ultrafast, highly selective, and sensitive detection of hydrazine in all possible mediums to counter the hydrazine toxicity through fluorescence turn-on signal output.

Naphthalimide functionalized metal-organic framework for rapid and nanomolar level detection of hydrazine and anti-hypertensive drug nicardipine.

The increasing utilization of hydrazine and its derivatives across diverse sectors highlights the pressing need for efficient detection methods to safeguard human health and the environment. Likewise, nicardipine, a widely used medication for heart diseases, necessitates accurate sensing techniques for clinical research and therapeutic monitoring. Here, we propose a novel approach using a naphthalimide-functionalized Zr-MOF as a fluorometric probe capable of detecting both hydrazine and nicardipine in aqueous medium. Our designed probe exhibited a significant 31-fold increase in fluorescence intensity upon interaction with hydrazine. At the same time, nicardipine induced 86% fluorescence quenching with an exceptionally rapid response time (100 s for hydrazine and 5 s for nicardipine). The designed probe has the ability to detect both analytes at nanomolar concentrations (LOD for hydrazine is 1.11 nM while that for nicardipine is 9.6 nM). Investigation across various wastewater samples and pH conditions further validated its practical utility. The mechanism behind fluorometric sensing of nicardipine was thoroughly investigated using modern instrumentation. Our study presents a versatile and effective approach for detecting hydrazine and nicardipine, addressing crucial needs in both industrial and biomedical contexts.

Sustainable synthesis of carbon dots from Ananas Comosus as renewable biomass: nanomolar level detection of glutathione

The adoption of green alternatives has become critically important for ensuring a sustainable environment in light of the state of our ecosystem.

Binary metal oxide (NiO/SnO2) composite with electrochemical bifunction: Detection of neuro transmitting drug and catalysis for hydrogen evolution reaction

The synergetic effect between dual oxides in binary metal oxides (BMO) makes them promising electrode materials for the detection of toxic chemicals, and biological compounds. In addition, the interaction between the cations and anions of diverse metals in BMO tends to create more oxygen vacancies which are beneficial for energy storage devices. However, specifically targeted synthesis of BMO is still arduous. In this work, we prepared a nickel oxide/tin oxide composite (NiO/SnO2) through a simple solvothermal technique. The crystallinity, specific surface area, and morphology were fully characterized. The synthesized BMO is used as a bifunctional electrocatalyst for the electrochemical detection of dopamine (DPA) and for the hydrogen evolution reaction (HER). As expected, the active metals in the NiO/SnO2 composite afforded a higher redox current at a reduced redox potential with a nanomolar level detection limit (4 nm) and excellent selectivity. Moreover, a better recovery rate is achieved in the real-time detection of DPA in human urine and DPA injection solution. Compared to other metal oxides, NiO/SnO2 composite afforded lower overpotential (157 mV @10 mA cm−2), Tafel slope (155 mV dec−1), and long-term durability, with a minimum retention rate. These studies conclude that NiO/SnO2 composite can act as a suitable electrode modifier for electrochemical sensing and the HER.

Robust Optical Detection of Ga3+ by a Rhodamine- and Coumarin-Based Proficient Probe: Theoretical Investigations and Biological Applications.

The present investigation highlights a rhodamine-B- and coumarin-based efficient probe that selectively detects Ga3+ over other metal ions. The active pocket of the ligand for trapping the metal ions and the binding stoichiometry of its Ga3+ complex were discovered by single-crystal X-ray diffraction (SC-XRD) analysis. This binding stoichiometry was further confirmed in the solution state by mass spectrometry and Job's plot. The detection limit was found to be at the nanomolar level. Pyrophosphate being a well-known quencher could easily quench the fluorescence intensity of the RC in the presence of Ga3+ and reversibly recognize Ga3+ in the solution. The spiro ring opening of the ligand after Ga3+ insertion is proposed to be the principal mechanism for the turn-on fluorescence response. This ring opening was confirmed by SC-XRD data and nuclear magnetic resonance (NMR) titration experiments. Both ground- and excited-state calculations of the ligand and complex have been carried out to obtain information about their energy levels and to obtain the theoretical electronic spectra. Furthermore, the live-cell imaging of the probe only and the probe after the addition of Ga3+ have been carried out in HaCaT cells and satisfactory responses were observed. Interestingly, with the help of this probe, Ga3+ can be tracked inside the intracellular organelle such as lysosomes along with other regions of the cell. The article highlights a rhodamine-coumarin-based probe for the detection of Ga3+ over other metal ions with a nanomolar level detection limit. Structural characterization of the ligand and its Ga3+ complex was investigated by SC-XRD. Density functional theory (DFT) and time-dependent DFT (TD-DFT) studies were carried out to explore the excited-state energies and electronic spectra. The application of the probe for the detection of Ga3+ in live cells has been explored, and positive responses were observed.

Detection of multiple metal ions exclusively at bilayer interface: Does the nature of the membranous aggregates affect the sensitivity?

A pyrenylated fluorogenic probe has been designed that can detect heavy metal pollutants exclusively at the bilayer interface. The compound, due to extensive self-aggregation, showed no interaction with metal ions in the bulk solution phase. However, effective, nanomolar level detection of multiple metal ions, such as Cu2+, Hg2+, and Ni2+, etc. was achieved exclusively in vesicular aggregates. The optical response towards metal ions, including selectivity and sensitivity, largely depends on the microenvironment around the probe molecules, governed by the nature of the bilayer membrane (polarity, order, interfacial hydration, etc). In zwitterionic membranes, like DPPC, Hg2+-induced fluorescence quenching was witnessed along with red-shifted emission maxima. On the contrary, turn-off responses along with blue-shifted in maxima were noted upon addition of both Cu2+ and Ni2+ ions in the anionic phospholipid vesicle, DPPA. Moreover, an improvement in sensitivity was witnessed when the probe was embedded into phospholipid vesicles with a fluid-like liquid crystalline phase. The larger mobility of the probe molecules on the bilayer membrane, resulting in ease of reorganization, might be the probable reason for this.

Hf-Based MOF for Rapid and Selective Sensing of a Nerve Agent Simulant and an Aminophenol: Insights from Experiments and Theory.

The metal-organic framework (MOF) Hf-DUT-52 was prepared with diamino functionality by the solvothermal method. This material displayed fluorometric sensing ability toward a nerve agent simulant (diethyl chlorophosphate (DCP)) and 3-diethylaminophenol (3-DEAP). It is the first-ever reported fluorescent MOF sensor for DCP and 3-DEAP. Apart from a fast response (<5 s), the sensor had a very low detection limit for both DCP and DEAP (limit of detection (LOD) values for DCP and 3-DEAP sensing were 9 and 125 nM, respectively). The obtained detection limit is the second lowest among all of the reported optical sensors for DCP. The sensor also displayed its capability to identify the presence of trace amount of DCP in various natural water specimens with good selectivity. Moreover, MOF@cotton composites were developed for visual, on-site, nanomolar-level detection of both targeted analytes. Furthermore, a MOF@PVA thin film was fabricated and successfully utilized for the detection of highly volatile and deadly poisonous DCP in the vapor phase. The sensor was also recyclable for up to five cycles without losing appreciable efficiency. Density functional theory (DFT)-based periodic and cluster calculations were performed to shed light on the sensing ability of the MOF by studying the interactions of DCP and DEAP with the MOF. Our theoretical results reveal the importance of linker defects and water chemisorption on the adsorption/complexation of the analytes at uncoordinated Hf sites.

Alendronate-Functionalized Graphene Quantum Dots as an Effective Fluorescent Sensing Platform for Arsenic Ion Detection.

Alendronate-functionalized graphene quantum dots (ALEN-GQDs) with a quantum yield of 57% were synthesized via a two-step route: preparation of graphene quantum dots (GQDs) by pyrolysis method using citric acid as the carbon source and post functionalization of GQDs via a hydrothermal method with alendronate sodium. After careful characterization of the obtained ALEN-GQDs, they were successfully employed as sensing materials with superior selectivity and sensitivity for the detection of nanomolar levels of arsenic ions (As(III)). According to the mechanistic investigation, arsenic ions can quench the fluorescence intensity of ALEN-GQDs through metal-ligand interaction between the As(III) ions and the surface functional groups of the fluorescent probe. This probe provided a rapid method to monitor As(III) with a wide detection range (44nM-1.30µM) and a low detection limit of 13nM. Finally, to validate the applicability, this novel fluorescent probe was successfully applied for the quantitative determination of As(III) in rice and water samples.

Easily synthesizable molecular probe for the nanomolar level detection of Cd2+ in near aqueous media: Theoretical investigations and live cell imaging

The present investigation highlights a quinoline-based small molecule probe (DEQ) for the detection of Cd2+ among other metal ions in near-aqueous media. The probe DEQ and its Cd2+ complex (DEQ-Cd) have been synthesized and characterized by all possible spectroscopic methods. The weakly emissive DEQ showed its strong emission in the presence of Cd2+, which is attributed to the photoinduced electron transfer (PET) along with the chelation-enhanced fluorescence (CHEF) mechanism. The 1:1 binding mode between ligand and Cd2+ is confirmed by single crystal XRD analysis, which is further supported by Job’s plot and HRMS. The detection limit of the probe to recognize Cd2+ was found to be as low as 89 nM. Furthermore, DEQ can act as a reversible fluorescence probe with the off-on-off mechanism by the alternative addition of Cd2+ and EDTA. DFT and TD-DFT studies exposed the proposed mechanism after Cd2+ insertion and the obtained results for electronic spectra are in line with the experimental results. The response towards pH was quite interesting and allowed us to study its application in live cell imaging. With all the positive results, the proposed ligand DEQ can be used as a potential probe for the detection of Cd2+ in real-life applications.

Development of low-cost copper nanoclusters for highly selective “turn-on” sensing of Hg2+ ions

The development of low-cost earth abundant metal based fluorescent sensors for a rapid and selective nanomolar level detection of Hg2+ is essential due to the increasing world-wide concern of its detrimental effect on humans as well as the environment. Herein, we present a perylene tetracarboxylic acid functionalized copper nanoclusters (CuNCs) based “turn-on” fluorescence probe for highly selective detection of toxic Hg2+ ions. The fabricated CuNCs exhibited high photostability with emission maximum centered at 532 nm (λex = 480 nm). The fluorescence intensity of CuNCs was remarkably enhanced upon the addition of Hg2+ over other competing ions and neutral analytes. Notably, the ‘turn-on’ fluorescence response exhibits highly sensitive detection limit as low as 15.9 nM (S/N ∼ 3). The time resolved fluorescence spectroscopy suggested the energy transfer between CuNCs and Hg2+ ions following either inhibited fluorescence resonance energy transfer (FRET) or surface modification of CuNCs during Hg2+ sensing. This study offers the systematic design and development of new fluorescent ‘turn-on’ nanoprobes for rapid and selective recognition of heavy metal ions.

A portable electrochemical sensor based on binary transition metal oxide (CoO/ZnO) for the evaluation of eugenol in real-time samples

We report a one-step hydrothermal synthesis route of synthesizing the binary transition metal oxide-based composite using zinc acetate and cobalt acetate precursors. A synthesized binary transition metal oxide-based composite is characterized to understand features of crystalline and structural arrangements, functionality, chemical composition, and surface morphologies using the XRD, FT-IR, XPS, FESEM, & HR-TEM techniques. The composite materials tend to show excellent morphology with spherical morphology. Owing to this, the synthesized binary transition metal oxide composite is then modified over the surface of the glassy carbon electrode (GCE) towards the electrochemical sensing of Eugenol (EUG). In this regard, the CoO/ZnO/GCE composite delivers much more improved electrocatalytic activity because of the synergistic features offered by the binary transition metal oxides due to their unique structural morphology, high surface area, and increased active sites which afford rapid electron transfer rate to the CoO/ZnO/GCE when compared to other electrodes. CoO/ZnO/GCE sensor of determining the (EUG) with a wider linear range of 0.049 – 179.8 µM possessed nanomolar level detection (LOD) of under DPV & LSV is calculated to be 4 nM & 7 nM along with sensitivity found to be 1.366 µA µM−1 cm−2 & 1.01 µA µM−1 cm−2. The proposed CoO/ZnO/GCE has better selectivity over interference studies, with practical feasibility features of repeatability, reproducibility, and storage stability. Real-time sample practical applicability with exceptional recoveries of 99 % for the clove sample and urine samples.

Dye-surfactant co-assembly as the chromogenic indicator for nanomolar level detection of Cu(I) ions via a color-changing response.

Polyaromatic amphiphilic probes have been developed, that can be involved in chromogenic detection of Cu+ ions in anionic micelles. A rapid change in solution color from yellow to orange was observed in the presence of Cu+ ions. The detection limit was found at the nanomolar range. To the best of our knowledge, this is the first report of the visible detection of Cu+ ions in aqueous medium using anionic micelles as a stabilizing agent. Interestingly, the compound can also detect Cu+ ions, generated in situ from physiological redox processes. The mechanistic investigation suggests that the probe molecule forms a diamagnetic tetrahedral complex with the Cu+ ion, coordinating through a pyridyl ketone unit. In addition, we have also followed the interaction with Cu+ on a bilayer surface made of anionic phospholipids. Further, a Cu2+-probe ensemble is used to assay the reducing ability of different biogenic thiols depending upon the pKa of their sulfhydryl (-SH) group. This allows us to determine the amount of reducing thiols present in human urine samples. Considering the high sensitivity of the present system, we screened water samples collected from different natural sources for Cu+ ions. Nearly 100% recovery values with considerably small relative standard deviations (<5%) indicate that the present system is indeed suitable for real-life sample analysis. Finally, low-cost, reusable, chemically-modified paper strips have been developed for rapid, on-location detection of Cu+ ions.

Divalent Metal Cation Optical Sensing Using Single-Walled Carbon Nanotube Corona Phase Molecular Recognition.

Colloidal single-walled carbon nanotubes (SWCNTs) offer a promising platform for the nanoscale engineering of molecular recognition. Optical sensors have been recently designed through the modification of noncovalent corona phases (CPs) of SWCNTs through a phenomenon known as corona phase molecular recognition (CoPhMoRe). In CoPhMoRe constructs, DNA CPs are of great interest due to the breadth of the design space and our ability to control these molecules with sequence specificity at scale. Utilizing these constructs for metal ion sensing is a natural extension of this technology due to DNA's well-known coordination chemistry. Additionally, understanding metal ion interactions of these constructs allows for improved sensor design for use in complex aqueous environments. In this work, we study the interactions between a panel of 9 dilute divalent metal cations and 35 DNA CPs under the most controlled experimental conditions for SWCNT optical sensing to date. We found that best practices for the study of colloidal SWCNT analyte responses involve mitigating the effects of ionic strength, dilution kinetics, laser power, and analyte response kinetics. We also discover that SWCNT with DNA CPs generally offers two unique sensing states at pH 6 and 8. The combined set of sensors in this work allowed for the differentiation of Hg2+, Pb2+, Cr2+, and Mn2+. Finally, we implemented Hg2+ sensing in the context of portable detection within fish tissue extract, demonstrating nanomolar level detection.