Colorimetric Detection of Copper in Water Samples Using Dopamine Dithiocarbamate-Functionalized Au Nanoparticles

Valorised polypropylene waste based reversible sensor for copper ion detection in blood and water

Heavy metals and plastic pollutants are the two most disastrous challenges to the environment requiring immediate actions. In this work, a techno-commercially feasible approach to address both challenges is presented, where a waste polypropylene (PP) based reversible sensor is produced to selectively detect copper ions (Cu2+) in blood and water from different sources. The waste PP-based sensor was fabricated in the form of an emulsion-templated porous scaffold decorated with benzothiazolinium spiropyran (BTS), which produced a reddish colour upon exposure to Cu2+. The presence of Cu2+ was checked by naked eye, UV-Vis spectroscopy, and DC (Direct Current) probe station by measuring the current where the sensor's performance remained unaffected while analysing blood, water from different sources, and acidic or basic environment. The sensor exhibited 1.3 ppm as the limit of detection value in agreement with the WHO recommendations. The reversible nature of the sensor was determined by cyclic exposure of the sensor towards visible light turning it from coloured to colourless within 5 min and regenerated the sensor for the subsequent analysis. The reversibility of the sensor through exchange between Cu2+- Cu+ was confirmed by XPS analysis. A resettable and multi-readout INHIBIT logic gate was proposed for the sensor using Cu2+ and visible light as the inputs and colour change, reflectance band and current as the output. The cost-effective sensor enabled rapid detection of the presence of Cu2+ in both water and complex biological samples such as blood. While the approach developed in this study provides a unique opportunity to address the environmental burden of plastic waste management, it also allows for the possible valorization of plastics for use in enormous value-added applications.

Ultrahigh-sensitivity multi-parameter tacrolimus solution detection based on an anchor planar millifluidic microwave biosensor

To detect drug concentration in tacrolimus solution, an anchor planar millifluidic microwave (APMM) biosensor is proposed. The millifluidic system integrated with the sensor enables accurate and efficient detection while eliminating interference caused by the fluidity of the tacrolimus sample. Different concentrations (10-500 ng mL^-1) of the tacrolimus analyte were introduced into the millifluidic channel, where it completely interacts with the radio frequency patch electromagnetic field, thereby effectively and sensitively modifying the resonant frequency and amplitude of the transmission coefficient. Experimental results indicate that the sensor has an extremely low limit of detection (LoD) of 0.12 pg mL^-1 and a frequency detection resolution (FDR) of 1.59 (MHz (ng mL^-1)). The greater the FDR and the lower the LoD, the more the feasibility of a label-free biosensing method. Regression analysis revealed a strong linear correlation (R² = 0.992) between the concentration of tacrolimus and the frequency difference of the two resonant peaks of APMM. In addition, the difference in the reflection coefficient between the two formants was measured and calculated, and a strong linear correlation (R² = 0.998) was found between the difference and tacrolimus concentration. Five measurements were performed on each individual sample of tacrolimus to validate the biosensor's high repeatability. Consequently, the proposed biosensor is a potential candidate for the early detection of tacrolimus drug concentration levels in organ transplant recipients. This study presents a simple method for constructing microwave biosensors with high sensitivity and rapid response.

Hybrid photoluminescent material from lanthanide fluoride and graphene oxide with strong luminescence intensity as a chemical sensor for mercury ions

In this work, we employed NaxLiyGdF4:Tb3+@PMA@Phen@GO nanocomposite as chemical sensor for selective and sensitive luminescence sensing of toxic Hg2+ metal ion.

Nanoremediation technologies for sustainable remediation of contaminated environments: Recent advances and challenges

A major and growing concern within society is the lack of innovative and effective solutions to mitigate the challenge of environmental pollution. Uncontrolled release of pollutants into the environment as a result of urbanisation and industrialisation is a staggering problem of global concern. Although, the eco-toxicity of nanotechnology is still an issue of debate, however, nanoremediation is a promising emerging technology to tackle environmental contamination, especially dealing with recalcitrant contaminants. Nanoremediation represents an innovative approach for safe and sustainable remediation of persistent organic compounds such as pesticides, chlorinated solvents, brominated or halogenated chemicals, perfluoroalkyl and polyfluoroalkyl substances (PFAS), and heavy metals. This comprehensive review article provides a critical outlook on the recent advances and future perspectives of nanoremediation technologies such as photocatalysis, nano-sensing etc., applied for environmental decontamination. Moreover, sustainability assessment of nanoremediation technologies was taken into consideration for tackling legacy contamination with special focus on health and environmental impacts. The review further outlines the ecological implications of nanotechnology and provides consensus recommendations on the use of nanotechnology for a better present and sustainable future.

Asparagine modified downconversion NaGdF4:Dy3+/Tb3+ nanophosphor for selective and sensitive detection of Cu(ii) ion

Pure NaGdF4, NaGdF4:Dy3+, and Dy3+/Tb3+ co-doped NaGdF4 nanoparticles with different concentrations of Tb3+ (ranging from 3 to 20 mol%) were prepared via hydrothermal method.

A dual signal on-off fluorescent nanosensor for the simultaneous detection of copper and creatinine

The transition of conventional medicine to personalized medicine has paved the way for sensing new biomolecules. Consequently, this field attracted wide interest due to its capability to provide information on point of care basis. Multi-analyte sensors that emerged recently can perform quick and affordable analysis with minimum quantity of blood samples compared to traditional sensing of individual analytes. The present study focuses on the development of a quantum dot (Qd) based nanosensor for the simultaneous detection of copper and creatinine; two biologically relevant molecules. The sensor was designed by forming a complex of Qd with 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and picric acid through carboxylic bond formation of Qd-EDC with picric acid. The dual independent emissions of the Qd-EDC complex was used for the simultaneous detection of creatinine and copper by a turn on/turn off method and was successfully demonstrated with a sensitivity of nanomolar to millimolar, and micromolar to millimolar range respectively. The multianalyte sensor thus developed has quick response and works well under normal conditions of temperature and pH. It is also shown to work in cellular environment and blood serum. A simple image based detection of creatinine using the sensor strips has also been attempted by means of a mobile camera and validated with human blood samples.

Triggered drug release from hybrid thermoresponsive nanoparticles using near infrared light

Aim: Developing hybrid poly(N-isopropylacrylamide)-based nanogels decorated with plasmonic hollow gold nanoparticles for on-demand drug delivery and their physico-chemical characterization, bupivacaine loading and release ability upon light irradiation, and in vitro cell viability. Materials & methods: Hollow gold nanoparticles were prepared by galvanic replacement reaction; poly(N-isopropylacrylamide)-based nanogels were synthesized via precipitation polymerization and their electrostatic coupling was accomplished using poly(allylamine hydrochloride) as cationic polyelectrolyte linker. Results & conclusion: Colloidal stability of the resulted hybrid nanovectors was demonstrated under physiological conditions together with their fast response and excellent heating efficiency after light stimulation, indicating their potential use as triggered drug-delivery vectors. Moreover, their influence on cell metabolism and cell cycle under subcytotoxic doses were studied showing excellent cytocompatibility.

Self-assembled gold nanoparticles and amphiphile peptides: a colorimetric probe for copper(ii) ion detection

We show that arginine/phenylalanine based peptides can be used to control the aggregation of gold nanoparticles in different ways. The arrangement provides a colorimetric approach to detect Cu²⁺ ions in water.

Influence of doping ion, capping agent and pH on the fluorescence properties of zinc sulfide quantum dots: Sensing of Cu2+ and Hg2+ ions and their biocompatibility with cancer and fungal cells

Herein, a facile one-pot synthetic method was explored for the fabrication of glutathione capped Mn²⁺ doped‑zinc sulphide quantum dots (GSH-Mn²⁺-ZnS QDs) for both fluorescent detection of Cu²⁺ and Hg²⁺ ions and for fluorescence imaging of two cancer (RIN5F and MDAMB231) and fungal (Rhizopus oryzae) cells. Particularly, doping of Mn²⁺ into ZnS QDs nanocrystal structure resulted a great improvement in the fluorescence properties of ZnS QDs. The emission peak of undoped ZnS QDs was found at 447 nm, which is due to the large number of surface defects in the ZnS QDs nanostructures. Under identical conditions, there is a good linear relationship between the quenching of fluorescence intensity and analytes (Cu²⁺ and Hg²⁺ ions) concentration in the range of 0.005 to 0.2 mM and of 0.025 to 0.4 mM for Cu²⁺ and Hg²⁺ ions, respectively. The GSH-Mn²⁺-ZnS QDs exhibit least cytotoxicity against RIN5F and MDAMB231 cells, demonstrating the multifunctional applications in sensing of metal ions and biocompatibility towards cancer (RIN5F and MDAMB231) and fungal (Rhizopus oryzae) cells.

'Green' synthesis of metals and their oxide nanoparticles: applications for environmental remediation

In materials science, “green” synthesis has gained extensive attention as a reliable, sustainable, and eco-friendly protocol for synthesizing a wide range of materials/nanomaterials including metal/metal oxides nanomaterials, hybrid materials, and bioinspired materials. As such, green synthesis is regarded as an important tool to reduce the destructive effects associated with the traditional methods of synthesis for nanoparticles commonly utilized in laboratory and industry. In this review, we summarized the fundamental processes and mechanisms of “green” synthesis approaches, especially for metal and metal oxide [e.g., gold (Au), silver (Ag), copper oxide (CuO), and zinc oxide (ZnO)] nanoparticles using natural extracts. Importantly, we explored the role of biological components, essential phytochemicals (e.g., flavonoids, alkaloids, terpenoids, amides, and aldehydes) as reducing agents and solvent systems. The stability/toxicity of nanoparticles and the associated surface engineering techniques for achieving biocompatibility are also discussed. Finally, we covered applications of such synthesized products to environmental remediation in terms of antimicrobial activity, catalytic activity, removal of pollutants dyes, and heavy metal ion sensing.

Colorimetric detection of Cu2+ based on the formation of peptide-copper complexes on silver nanoparticle surfaces

We developed a colorimetric method for the rapid detection of copper ions (Cu2+) in aqueous solution. The detection of Cu2+ is based on coordination reactions of Cu2+ with casein peptide-functionalized silver nanoparticles (AgNPs), leading to a distinct color change of the solution from yellow to red. The developed method has a good detection limit of about 0.16 µM Cu2+ using 0.05 mL of AgNPs stock solution and a linearity in the range of 0.08-1.44 µM Cu2+ with a correlation coefficient of R2 = 0.973. The developed method is a useful tool for the detection of Cu2+ ions. Furthermore, it can be used for monitoring Cu2+ in water at concentrations below the safe limit for drinking water set by the World Health Organization.

Enhanced Sensitivity to Detection Nanomolar Level of Cu2+ Compared to Spectrophotometry Method by Functionalized Gold Nanoparticles: Design of Sensor Assisted by Exploiting First-order Data with Chemometrics

A simple, sensitive and efficient colorimetric assay platform for the determination of Cu²⁺ was proposed with the aim of developing sensitive detection based on the aggregation of AuNPs in presence of a histamine H2-receptor antagonist (famotidine, FAM) as recognition site. This study is the first to demonstrate that the molar extinction coefficients of the complexes formed by FAM and Cu²⁺ are very low (by analyzing the chemometrics methods on the first order data arising from different metal to ligand ratio method), leading to the undesirable sensitivity of FAM-based assays. To resolve the problem of low sensitivity, the colorimetry method based on the Cu²⁺-induced aggregation of AuNPs functionalized with FAM was introduced. This procedure is accompanied by a color change from bright red to blue which can be observed with the naked eyes. Detection sensitivity obtained by the developed method increased about 100 fold compared with the spectrophotometry method. This sensor exhibited a good linear relation between the absorbance ratios at 670 to 520nm (A₆₇₀/₅₂₀) and the concentration in the range 2-110nM with LOD=0.76nM. The satisfactory analytical performance of the proposed sensor facilitates the development of simple and affordable UV-Vis chemosensors for environmental applications.

π-Conjugated thiolate amplified spectrophotometry nitrite assay with improved sensitivity and accuracy

π-Conjugated thiolate amplified sensitive nitrite detection based on the π-conjugation enhanced molar absorption coefficient and the corresponding absorbance is presented.

Interaction between Diethyldithiocarbamate and Cu(II) on Gold in Non-Cyanide Wastewater

A surface-enhanced Raman scattering (SERS) detection method for environmental copper ions (Cu2+) was developed according to the vibrational spectral change of diethyldithiocarbamate (DDTC) on gold nanoparticles (AuNPs). The ultraviolet-visible (UV-Vis) absorption spectra indicated that DDTC formed a complex with Cu2+, showing a prominent peak at ~450 nm. We found Raman spectral changes in DDTC from ~1490 cm-1 to ~1504 cm-1 on AuNPs at a high concentration of Cu2+ above 1 μM. The other ions of Zn2+, Pb2+, Ni2+, NH₄⁺, Mn2+, Mg2+, K⁺, Hg2+, Fe2+, Fe3+, Cr3+, Co2+, Cd2+, and Ca2+ did not produce such spectral changes, even after they reacted with DDTC. The electroplating industrial wastewater samples were tested under the interference of highly concentrated ions of Fe3+, Ni2+, and Zn2+. The Raman spectroscopy-based quantification of Cu2+ ions was able to be achieved for the wastewater after treatment with alkaline chlorination, whereas the cyanide-containing water did not show any spectral changes, due to the complexation of the cyanide with the Cu2+ ions. A micromolar range detection limit of Cu2+ ions could be achieved by analyzing the Raman spectra of DDTC in the cyanide-removed water.

Green Synthesis of Silver Nanoparticles Stabilized with Mussel-Inspired Protein and Colorimetric Sensing of Lead(II) and Copper(II) Ions

This articles reports a simple and green method for preparing uniform silver nanoparticles (AgNPs), for which self-polymerized 3,4-dihydroxy-l-phenylalanine (polyDOPA) is used as the reducing and stabilizing agent in aqueous media. The AgNPs functionalized by polyDOPA were analyzed by UV-Vis spectroscopy, high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), Raman spectrophotometry, and X-ray diffraction (XRD) techniques. The results revealed that the polyDOPA-AgNPs with diameters of 25 nm were well dispersed due to the polyDOPA. It was noted that the polyDOPA-AgNPs showed selectivity for Pb²⁺ and Cu²⁺ detection with the detection limits for the two ions as low as 9.4 × 10^-5 and 8.1 × 10^-5 μM, respectively. Therefore, the polyDOPA-AgNPs can be applied to both Pb²⁺ and Cu²⁺ detection in real water samples. The proposed method will be useful for colorimetric detection of heavy metal ions in aqueous media.

Greener synthesis and characterization, antimicrobial and cytotoxicity studies of gold nanoparticles of novel shapes and sizes

We hereby present a novel approach for the synthesis of gold nanoparticles (AuNPs) using water soluble, naturally-derived flavonoids.

Transport, fate, and stimulating impact of silver nanoparticles on the removal of Cd(II) by Phanerochaete chrysosporium in aqueous solutions

Despite the knowledge about increasing discharge of silver nanoparticles (AgNPs) into wastewater and its potential toxicity to microorganisms, the interaction of AgNPs with heavy metals in the biological removal process remains poorly understood. This study focused on the effect of AgNPs (hydrodynamic diameter about 24.3±0.37 nm) on the removal of cadmium (Cd(II)) by using a model white rot fungus species, Phanerochaete chrysosporium. Results showed that the biological removal capacity of Cd(II) increased with the concentration of AgNPs increasing from 0.1 mg/L to 1 mg/L. The maximum removal capacity (4.67 mg/g) was located at 1 mg/L AgNPs, and then decreased with further increasing AgNPs concentration, suggesting that an appropriate concentration of AgNPs has a stimulating effect on the removal of Cd(II) by P. chrysosporium instead of an inhibitory effect. Results of Ag(+) and total Ag concentrations in the solutions together with those of SEM and XRD demonstrated that added AgNPs had undergone oxidative dissolution and transported from the solution to the surface of fungal mycelia (up to 94%). FTIR spectra confirmed that amino, carboxyl, hydroxyl, and other reducing functional groups were involved in Cd(II) removal, AgNPs transportation, and the reduction of Ag(+) to AgNPs.

Colorimetric determination of copper(ii) ions using gold nanoparticles as a probe

A colorimetric method for the fast, sensitive and selective detection of Cu²⁺ using gold nanoparticles was developed.

Dicoumarol assisted synthesis of water dispersible gold nanoparticles for colorimetric sensing of cysteine and lysozyme in biofluids

A schematic representation of the mechanism for the colorimetric sensing of Cys and Lys using DIC–Au NPs as a probe.

Malonamide dithiocarbamate functionalized gold nanoparticles for colorimetric sensing of Cu2+ and Hg2+ ions

In this study, a colorimetric probe was developed based on malonamide dithiocarbamate functionalized gold nanoparticles (MA–DTC–Au NPs) for the simultaneous colorimetric detection of Cu²⁺ and Hg²⁺ ions.

Sensitive and selective colorimetric detection of Cu(2+) in aqueous medium via aggregation of thiomalic acid functionalized Ag nanoparticles

A simple and effective colorimetric method for determination of Cu(2+) in real samples was developed. In this method, thiomalic acid functionalized silver nanoparticles (TMA-AgNPs) were prepared and changes in solution color, induced by the aggregation of TMA-AgNPs in the presence of Cu(2+), were employed for quantitative analysis. The surface plasmon resonance (SPR) band of our synthesized TMA-AgNPs was located at 392 nm and shifted to a longer wavelength after aggregation due to the interactions between carboxylate and Cu(2+). A band intensity ratio of A455/(A392-A455) was constructed and used to correlate with the concentration of Cu(2+). A linear relationship was found with a linear response up to 50 nM of Cu(2+). Due to the formation of a stable carboxylate Cu(2+) complex, highly sensitive detection of Cu(2+) was achieved with the estimated detection limit approaching 1 nM. Moreover, the formation of the stable complex leads to high selectivity in the detection of Cu(2+), which was verified by examination of 12 other metal ions. In the detection of Cu(2+) in real samples, results indicated that our proposed method is simple, sensitive and selective for application in such measurements.

Sensitive and selective colorimetric sensing of Fe3+ion by using p-amino salicylic acid dithiocarbamate functionalized gold nanoparticles

DTC-PAS-Au NPs successfully acted as probes for the selective and sensitive colorimetric sensing of Fe³⁺ions in biological samples.