Nanomolar Level Detection Research Articles

Influence of mineralizer in the preparation of Bi2CuO4 sensor for the electrochemical evaluation of chlorogenic acid in various real-time samples

Bismuth copper oxide (Bi2CuO4) has been prepared with varied morphologies and explored as an electrode modifier for chlorogenic acid (CGA) electrochemical sensors. The mineralizer agents such as NaOH, KOH, and NH4OH served as a chemical agent and pH stabilizer in attaining variations in the morphology. The variation in the morphology attributes to the effect of viscosity of the corresponding mineralizer. The attained variation between the prepared Bi2CuO4 was revealed by different physicochemical characterization and electrochemical techniques. Bi2CuO4–KOH modified glassy carbon electrode (GCE) exemplifies an excellent redox performance, due to the higher ionic mobility and conductivity of KOH. The Bi2CuO4–KOH modified GCE was implemented towards the electrochemical sensing of CGA with the aid of differential pulse voltammetry (DPV). Further, it demonstrates exquisite electroanalytical performance including a wide linear range (0.05–556 μM) and nanomolar level detection (4.8 nM) with appraisable sensitivity of 0.22 μA/μM cm−2 for oxidation. In addition, the proposed sensor exemplifies higher selectivity with excellent repeatability, reproducibility, and stability. Moreover, the practical feasibility analysis with various real samples displays excellent recovery results for the electrochemical sensing of CGA.

Electrochemical Evaluation of Vitamin B2 through a Portable Electrochemical Sensor Based on Binary Transition Metal Oxide in Various Biological and Vegetable Samples

Fabrication & electrochemical evaluation of Vitamin B2-riboflavin (RF) sensor based on binary transition metal oxide (ZnO-MnO) core–shell nanocomposites (CSNs) on the surface of the glassy carbon electrode (GCE). Firstly, ZnO-MnO core–shell nanocomposites are attained through a one-step hydrothermal synthesis route using zinc acetate and manganese acetate as precursors where ZnO act as a core and MnO formed as a shell. As synthesized binary transition metal oxide-based composite is scrutinized through various physicochemical techniques thereby demonstrating excellent physiochemical features. ZnO-MnO/GCE composite delivers synergistic features of improving the electrochemical properties towards detection of Riboflavin (RF) at an operational voltage of 0.42 V, with the increased active sites because of its structural morphology along with high surface areas. ZnO-MnO/GCE is examined through electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), differential pulse voltammetry (DPV), and linear sweep voltammetry (LSV). Furthermore, ZnO-MnO/GCE shows a remarkable kinetic transfer rate and superior electron transfer rate over other modified electrodes. It also exemplifies a wider linear range (0.05–1102 μM), with Nanomolar level detection (LOD) of 13 nM aided with a sensitivity of 0.3746 μA μM−1 cm−2, respectively. The proposed ZnO-MnO/GCE sensor demonstrates excellent selectivity over the presence of co-interfering species exquisite repeatability, reproducibility, and stability. Further, the real-time monitoring analysis exemplifies excellent recovery percentages from 96.95–99.61% for various biological and vegetable samples.

Graphene quantum dots-based nanocomposite for electrocatalytic application of L-cysteine in whole blood and live cells

Driven by the urgent need to detect amino acids in live cells at trace levels, as they are an important biomarker for various diseases. For this purpose, we have developed a nanomolar level detection of l-cysteine (L-Cys) and real-time cellular quantification from live cells based on graphene quantum dots (GQDs)-AuNPs-metal-free organic framework (MFOF). Different analytical and microscopic techniques were used to confirm the synthesized nanocomposite. The sensitive electrochemical sensing system of l-Cys-was detected synergistically with GQDs-AuNPs-MFOF/GCE by voltammetry and amperometric i-t curve. The electrocatalytic oxidation signal of l-Cys-at Epa = none, +0.45, +0.36 and +0.21 V (vs. Ag/AgCl) with enhanced current responses were observed at control GCE, MFOF, GQDs-MFOF, and GQDs-AuNPs-MFOF/GCEs by DPV. The nanocomposite modified sensor probe showed a wide linear range concentration from 1 nM to 0.5 mM with LOD of 0.124 nM (S/N = 3), LOQ of 0.863 nM (S/N = 10) and sensitivity of 2.364 μA μM−1 cm−2. Subsequently, the selective detection of l-Cys-in the presence of possible other interfering biothiols. amino acids, and metal ions were achieved. The practical application was demonstrated in human whole blood and bio-fluid samples. Finally, the endogenous real-time detection of cellular cysteine in live cells was demonstrated.

Ultrasensitive Electrochemical Detection and Plasmon-Enhanced Photocatalytic Degradation of Rhodamine B Based on Dual-Functional, 3D, Hierarchical Ag/ZnO Nanoflowers.

The sensitive detection and degradation of synthetic dyes are pivotal to maintain safety owing to the adverse side effects they impart on living beings. In this work, we developed a sensitive electrochemical sensor for the nanomolar-level detection of rhodamine B (RhB) using a dual-functional, silver-decorated zinc oxide (Ag/ZnO) composite-modified, screen-printed carbon electrode. The plasmon-enhanced photocatalytic degradation of organic pollutant RhB was also performed using this nanocomposite prepared by embedding different weight percentages (1, 3, and 5 wt%) of Ag nanoparticles on the surface of a three-dimensional (3D), hierarchical ZnO nanostructure based on the photoreduction approach. The structure and morphology of an Ag/ZnO nanocomposite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental mapping, ultraviolet-visible (UV-vis) spectroscopy, and X-ray diffraction (XRD). The electrochemical sensor exhibited a very high sensitivity of 151.44 µAµM−1cm−2 and low detection limit of 0.8 nM towards RhB detection. The selectivity, stability, repeatability, reproducibility, and practical feasibility were also analyzed to prove their reliability. Furthermore, the photocatalysis results revealed that 3 wt% of the Ag/ZnO hybrid nanostructure acquired immense photostability, reusability, and 90.5% degradation efficiency under visible light. Additionally, the pseudo-first-order rate constant of Ag-3/ZnO is 2.186 min−1 suggested promising activity in visible light photocatalysis.

Efficient Tb3+-to-Eu3+ energy transfer for colorimetric luminescence sensing

State-of-the-art Tb-to-Eu energy transfer (TEET) efficiency (>90%) under ultralow Eu3+ proportion (<6%) has been achieved in Eu/Tb bimetallic lanthanide coordination polymers (LnCPs). The yellow-light-emitting sample as sensor exhibits micromolar l-phenylalanine (l-Phe) in water and serum via obvious yellow-to-green luminometric behavior, meanwhile nanomolar-level detection limits are determined in terms of an updated Stern-Volmer equation with high selectivity and competitiveness. Excited-state inter-ligand photon transfer (ESILPT) greatly contributes to superior TEET property and outstanding luminometric behavior. This work opens a window for developing sensitive and stable visualization sensing, being of values on monitoring biochemical markers.

NiO/ZnO binary metal oxide based electrochemical sensor for the evaluation of hazardous flavonoid in biological and vegetable samples

Fabrication of binary transition metal oxide-based composite over the active surface area of glassy carbon electrode (GCE) stimulates the electrochemical activity due to their morphology, and higher active surface area, etc. The successful formation of (NiO/ZnO) composite has been scrutinized through various microscopic and spectroscopic techniques. Further, NiO/ZnO/GCE tends to exemplify exquisite kinetic performance with a higher electron transfer rate and charge transfer resistance (Rct) of 404 Ω. The electrochemical detection of Rutin (RT) on NiO/ZnO/GCE exemplifies a spacious linear range of 0.049 – 742.5 µM in linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV). Moreover, the proposed NiO/ZnO/GCE sensor symbolizes Nanomolar level detection of RT (11.0 & 13.6 nM) in DPV and LSV with an appraisable sensitivity of 2.52 µA µM−1 cm−2 and 0.62 µA µM−1 cm−2, respectively. The practical feasibility analysis of the proposed NiO/ZnO/GCE sensor features exemplary selectivity, repeatability, reproducibility, and storage stability. On top of that, the real-time monitoring analysis demonstrates exquisite recovery results in blood and orange samples.

Highly selective fluorescent detection platform based on isoquinoline Schiff base ligand monitors glutathione in biological systems

Aberrant levels of intracellular glutathione (GSH) have been held responsible for various disease and pathological processes, and existing evidence underscores the significance of GSH detection in biological systems. The recognition, discrimination, and precise detection of GSH in the cellular matrix and living organisms can revolutionize our understanding of the physiological and pathological processes of GSH. Herein, we reported a new isoquinoline Schiff base fluorescence probe, N'-((7-(diethylamino)-2-oxo-2H-chromene)methylene) isoquinoline-3-carbohydrazide (NCMC), which can selectively recognize GSH by its ensemble complex NCMC-Cu2+ with a low nanomolar level detection limit (4.16 × 10−8 M) in the aqueous environment. Moreover, the binding behavior and “ON-OFF-ON” fluorescence probing pattern were illustrated in detail by UV–vis titration, ESI-MS spectroscopy, and density functional theory calculations. Notably, the nontoxic NCMC-Cu2+ ensemble platform showed great potential for detecting GSH distribution in cells and zebrafish larvae, and can also be applied in differentiating endogenous GSH in both cancer cells and normal cells, which may represent a promising GSH fluorescence probe in bioimaging and disease diagnosis.

An efficient PET-based probe for detection and discrimination of Zn2+ and Cd2+ in near-aqueous media and live-cell imaging

A newly designed and synthesized quinoline-based chemosensor (DDTQ) is reported for the detection of Zn2+ and Cd2+. The ligand is characterized by all possible spectroscopic techniques. From a pool of different metal ions in aqueous medium, Zn2+ and Cd2+ ions are simultaneously detected by the probe, giving an excellent enhancement in the fluorescence intensity at 445 nm. The fluorescence intensity of DDTQ-Cd is higher than that of DDTQ-Zn. Cd2+ and Zn2+ can be distinguished by using Cu2+ as a tool for sequential quenching where, DDTQ-Zn is responsive towards Cu2+ while DDTQ-Cd is not. It is noteworthy that the novel probe has shown a nanomolar level detection limit of 154 and 126 nM for Zn2+ and Cd2+ respectively. The binding modes of the complexes are also verified by HRMS, Job’s analysis, and by single crystal-XRD analysis. Fluorescence lifetime measurements of the complexes show lifetime values of 28 ns and 26 ns for DDTQ-Zn and DDTQ-Cd complexes respectively. Photoinduced electron transfer (PET) and chelation enhanced fluorescence (CHEF) mechanisms are proposed to be responsible for the enhancement of the fluorescence intensity. The fluorescence intensity of DDTQ in presence of Zn2+ or Cd2+ is stable in the physiological pH range and this prompted us to explore the bioimaging applications in live Vero cells to demonstrate its potential for real-life applications.

Silver-capped selenium explored as an electro-catalyst for simultaneous detection of nitro-aromatic drugs in different aqueous samples

Herein, we have fabricated silver (Ag) over selenium (Se) to explore its enriched electrochemical performance towards the simultaneous detection of nitro-aromatic drugs (nitrofurantoin (NFT) and P-nitrophenol (P-NP)). Due to its synergistic effect, Ag/Se modified GCE showed excellent electro-catalytic activity compared to other electrodes. Well-defined and divergent reduction peaks were obtained at −0.49 V (NFT) and −0.85 V (P-NP) with a detection range of 0.9 V at Ag/Se/GCE. It withholds an extensive linear range of 0.1 to 210 µM for NFT and 0.1 to 150 µM for P-NP with a nanomolar level detection limit of 23.87 nM L−1 & 7.82 nM L−1; an appraisable sensitivity of 1.138 µA µM−1 cm−2 & 2.86 µA µM−1 cm−2 for NFT and P-NP, respectively. Interestingly, the electrode possesses a high selectivity in the presence of biomolecules, nitro drugs, and metal ions. Examination of nitro-aromatic drug contamination on water sources shows a massive peril to human life and marine environs due to its adverse hazardous effects. Further, the fabricated Ag/Se-based electrochemical sensor was exposed to various environmental aqueous samples to detect NFT& P-NP which has demonstrated an exquisite recovery results in practical feasibility. Thereby confirms that Ag/Se-based electrochemical sensors have boundless potential for ecological investigations and sensing applications.

A facile chemiluminescence strategy for copper(ii) ion detection utilizing azothiacalix[4]arene-functionalized carboxymethylcellulose polymeric ligand

The design and characterization of azothiacalix[4]arene-functionalized carboxymethylcellulose, used for the detection of nanomolar levels of Cu2+via a chemiluminescence method.

Synthesis and application of a 0D/2D nanocomposite for the nanomolar level detection of an antiandrogen drug

Schematic representation of fabrication and detection of Flutamide on graphite electrode.

A fluorescent zirconium organic framework displaying rapid and nanomolar level detection of Hg(ii) and nitroantibiotics

A new Zr(iv)-based MOF named IITG-5 showed fast (response time = 1 min), highly selective and nanomolar level detection limits for Hg2+(5 nM) and nitroantibiotics (NFZ = 156.7 nm and NFT = 96.3 nM) in water and methanol, respectively.

Unveiling of a smartphone-mediated ratiometric chemosensor towards the nanomolar level detection of lethal CN-: combined experimental and theoretical validation with the proposition of a molecular logic circuitry.

A promising naphthalene-functionalized ratiometric chemosensor (E)-1-((naphthalen-5-yl) methylene)-2-(2,4-dinitrophenyl) hydrazine (DNMH) is unveiled in the present work. DNMH demonstrates brisk discernible colorimetric response from yellow to red in the presence of CN−, a lethal environmental contaminant, in a near-perfect aqueous medium with a LOD of 278 nM. The “key role marker” controlling the electrochemical and non-covalent H-bonding interaction between DNMH and CN− is through the commendable role of acidic –NH functionalities. Kinetic studies reveal a pseudo second order reaction rate and the formation of an unprecedented photostable adduct. The negative value of ΔG as evaluated from ITC substantiates the spontaneity of the DNMH⋯CN− interaction. The sensing mechanism was further reinforced with state-of-the-art theoretical investigations, namely DFT, TDDFT and Fukui indices (FIs). Moreover, the proposition of a reversible multi-component logic circuitry implementing Boolean functions in molecular electronics has also been triggered by the turn-over spectrophotometric response of the ditopic ions CN− and Cd2+. The cytotoxicity of DNMH towards Bacillus thuringiensis and Escherichia coli is successfully investigated via the MTT assay. Impressively, “dip stick” and “easy to prepare” test paper device and silica gel-based solid-phase CN− recognition validate the on-site analytical application of DNMH. Furthermore, the involvement of a synergistic approach between ‘chemistry beyond the molecule’ and ‘engineering’ via an exquisitely implemented smartphone-assisted colorimetric sensory prototype makes this work unprecedented among its congeners and introduces a new frontier in multitudinous material-based functional product development.

A pyrene-based ratiometric probe for nanomolar level detection of glyphosate in food and environmental samples and its application for live-cell imaging

An in situ formed copper(ii)-complex is involved in analyzing glyphosate in real-life samples, such as crops, soil, water and biological fluids.

Two birds with one arrow: a functionalized Al(iii) MOF acts as a fluorometric sensor of dopamine in bio-fluids and a recyclable catalyst for the Biginelli reaction

A new Al(iii) MOF showed an ultra-fast response, high selectivity and a nanomolar level detection limit for the fluorometric sensing of dopamine. It also displayed great catalytic activity in the Biginelli reaction.

Barium titanate nanoparticle-based disposable sensor for nanomolar level detection of the haematotoxic pollutant quinol in aquatic systems

Barium titanate nanoparticles synthesized by a simple co-precipitation method and applied for the electrochemical detection of quinol.

Histidine Functionalized Gold Nanoparticles for Screening Aminoglycosides and Nanomolar Level Detection of Streptomycin in Water, Milk, and Whey

Aminoglycoside (AMG) antibiotics are being applied to treat infections caused by Gram-negative bacteria, mainly in livestock, and are prescribed only in severe cases because of their adverse impacts on human health and the environment. Monitoring antibiotic residues in dairy products relies on the accessibility of portable and efficient analytical techniques. Presently, high-throughput screening techniques have been proposed to detect several antimicrobial drugs having identical structural and functional features. The L-histidine functionalized gold nanoparticles (His@AuNPs) do not form a complex with other tested antibiotic classes but show high selectivity for AMG antibiotics. We used ligand-induced aggregation of His@AuNPs as a rapid and sensitive localized surface plasmon resonance (LSPR) assay for AMG antibiotics, producing longitudinal extinction shifts at 660 nm. Herein, we explore the practical application of His@AuNPs to detect streptomycin spiked in water, milk, and whey fraction of milk with nanomolar level sensitivity. The ability of the analytical method to recognize target analytes sensitively and rapidly is of great significance to perform monitoring, thus would certainly reassure widespread use of AMG antibiotics. The biosynthesis of hybrid organic–inorganic metal nanoparticles like His@AuNPs with desired size distribution, stability, and specific host–guest recognition proficiency, would further facilitate applications in various other fields.

Bi-functional renewable biopolymer wrapped CNFs/Ag doped spinel cobalt oxide as a sensitive platform for highly toxic nitroaromatic compound detection and degradation

Nanomolar-level detection of priority toxic pollutant 4-nitrophenol (4-NP) in environment using a novel ternary nanocomposite based electrochemical sensor and its photocatalytic degradation is reported in this paper. A non-toxic and renewable natural biopolymer, chitosan wrapped carbon nanofibers was embedded with Ag doped spinel Co3O4 to prepare the bi-functional ternary nanocomposite. Economical and ecofriendly sonochemical method was employed in preparation of this porous nanocomposite. We used one-pot aqueous solution approach to synthesize Ag–Co3O4 nanoflowers and ultrasound-assisted method was utilized to prepare CS-CNFs. Morphological and structural properties of synthesized materials were analyzed using different characterization techniques. Electrochemical investigations using cyclic voltammetry and differential pulse voltammetry carried out with prepared ternary nanocomposite modified carbon electrode revealed its outstanding electrocatalytic activity in 4-NP quantification. The developed 4-NP sensor showcased excellent sensitivity of 55.98 μAμM−1cm−2 and nanomolar detection limit of 0.4 nM. Moreover, reproducibility, repeatability, stability, and selectivity were evaluated to confirm reliability of developed sensor. Further, real sample analyses were conducted using domestic sewage, underground water, and tomato to affirm the practical feasibility of 4-NP detection using the proposed sensor.

Morphological evolution of nanosheets-stacked spherical ZnO for preparation of GO-Zn/ZnO ternary nanocomposite: A novel electrochemical platform for nanomolar detection of antihistamine promethazine hydrochloride

This work focuses on the nanomolar-level detection of the antihistamine, promethazine hydrochloride (PMTZ), based on a novel ternary nanocomposite sonochemically prepared using a zinc-graphene oxide (GO-Zn) complex and a nanosheets-stacked spherical ZnO. The efficient detection of PMTZ is very important because of its critical side effects when overdosed and its high toxicity to aquatic life. Morphologically varied ZnO nanostructures (spindle-like, nanosheets-stacked spherical, nanoplates-based spherical, and rod-flower) were synthesized using a new aqueous solution approach by regulating the concentration of base in the reaction mixture. Characterization techniques including SEM, TEM, elemental mapping, XRD, Raman spectroscopy, and XPS were utilized for analyzing the properties of synthesized materials. Electrochemical investigations employing cyclic voltammetry and differential pulse voltammetry techniques showcased outstanding electrocatalytic activity of the proposed ternary nanocomposite-modified screen-printed carbon electrode towards PMTZ detection. The PMTZ sensor attained ultra-low detection limit of 0.3 nM, broad linear range from 0.05 to 177.45 µM, and a sensitivity of 5.29µAµM−1cm−2. Furthermore, good operational stability, anti-interference, repeatability, and reproducibility was exhibited by the developed sensor. The real sample analysis provided excellent recovery results indicating outstanding practicability of PMTZ detection.

A rhodamine based nanosensor platform for Hg2+ sensing in near–perfect aqueous medium: Smartphone, test strip and real sample applications

Herein, a rhodamine based nanosensor platform (RHD–NPs) was designed and prepared for the sensing of Hg2+ in the near–perfect aqueous medium (v/v, 0.01/99.99, acetone/water). The structure, aqueous stability, surface charge and particle size of RHD–NPs were analyzed by using zeta particle sizer, scanning electron microscopy (SEM) and UV–Vis spectrophotometry. The spherical shaped morphology ofRHD–NPshas 61.4 nm particule size. The interaction ability of RHD–NPstowards various heavy metal ions was evaluated with UV–Vis and fluorescence spectroscopies. After the transferring of Hg2+ to RHD–NPs, a new absorption band at 562 nm was observed due to the ring–opening mechanism of rhodamine structure. The remarkable emission enhancement at 582 nm was observed through the adding of Hg2+ because of chelation–enhanced fluorescence (CHEF) and aggregation–induced enhanced emission (AIEE) phenomena. RHD–NPs nanosensor system showed good selectivity for Hg2+ monitoring with a nanomolar–level detection limit of 6.56 nM. The binding constant ofRHD–NPswith Hg2+ was determined to be 10.06 × 103 M−1 based on the Benesi–Hildebrand graph and a maximum value of Job’s graph was about 0.5 ratio (1:1) between RHD–NPs and Hg2+.The smartphone–based technique revealed an outstanding potential of the RHD–NPsplatform for the sensing of Hg2+ without further device. A visual colorimetric strip based on papers with excellent selectivity towards Hg2+ without interfering competition ions, was produced with the white–to–pink color signal change. The RHD–NPswas also employed for the quantitative determination and real–time monitoring of Hg2+ in real samples.