Eu3+-ion doped strontium molybdate perovskite quantum dots as a turn-off-on fluorescent sensor for simultaneous detection of hypoxanthine biomarker and Fe3+ ions

A fluorescence "turn-off-on" nanoprobe is designed by using europium-doped strontium molybdate perovskite quantum dots (Eu3+:SMO PQDs) for the sequential detection of hypoxanthine (Hx) and Fe3+. The Eu3+:SMO PQDs were prepared by the sol-gel method using Sr(NO3)2, (NH4)6Mo7O24.4H2O, and Eu(OCOCH3)3 as precursors. The green fluorescence of Eu3+:SMO PQDs was efficiently reduced (turn-off) in the presence of Hx, then it was restored (turn-on) gradually by introducing Fe3+ due to the competitive formation of Hx@Fe3+, which results to the release of Eu3+:SMO PQDs. In addition, the fluorescent probe exhibits excellent selectivity and sensitivity. Under the optimized experimental conditions, linear ranges and detection limits were 0.25-25 μM and 12.30 nM for Hx and 0.025-50 μM and 10.44 nM for Fe3+ , respectively. Furthermore, the fluorescence method was successfully explored to detect Hx and Fe3+ in plasma and urine samples.

Ag@CDs nanohybrid: Fabrication, design of a multi-mode chemosensory probe for selective Fe3+ detection and logic gate operation

In this study, we propose a unique use of silver-carbon dot nanohybrid (Ag@CDs) with an average size of 16 nm as a multi-mode sensor for the selective detection of Fe³⁺ and the construction of logic gates based on these unique detection properties. The Ag NPs exhibit colourimetric sensing and fluorescence quenching in response to Fe³⁺ in the concentration range of 10-100 ppm, with the carbon dots acting as the fluorescent entity. Surprisingly, the nanohybrid was shown to have excellent sensitivity to Fe³⁺, resulting in aggregation and formation of yellowish-brown clumps. When the reaction mixture was treated with Fe³⁺, there was a discernible change in the colour of the assay mixture and fluorescence quenching. That is, the Ag@CDs acted as a calorimetric and fluorescence multi-mode sensor. Even in interfering groups in the natural river water sample, the produced nanohybrid displayed good selectivity towards Fe³⁺, with a minimum LOD of 0.76 ppm. Further, we constructed an advanced logic system, IMP-OR gate, by using additional inputs - ascorbic acid and urea.

Rapid and efficient colorimetric sensing of clindamycin and Fe3+ using controllable phyto-synthesized silver/silver chloride nanoparticles by Syzygium cumini fruit extract

Abstract

The first evidence of a green, single-step, and additive-free process for the fabrication of silver/silver chloride nanoparticles (Ag/AgCl NPs) by fruit extract of Syzygium cumini (S. cumini) without the usage of any stabilizer and halide source was provided. The formation of nanoparticles was optimized to control the shape, size, and stability via various pHs of the reaction mixture, the quantity of fruit extract, temperature, concentrations of silver ion, and reaction time. The optimal conditions were determined: pH = 7.0, the quantity of the leaf extract = 3.0 mL, silver ion concentration = 1.0 mM, temperature = 60 °C, and incubation time = 40 min. As an application in colorimetric sensing, the ability of the prepared Ag/AgCl NPs to sense clindamycin and Fe3+ ion in an aqueous medium was investigated. The SPR band and color of the solution of Ag/AgCl NPs undergo dramatic changes in exposure to clindamycin with new SPR peaks appearing at 500 nm, accompanied by a color change from yellow to pink due to the aggregation of NPs. Under the optimized pH of 3.0, this sensor was shown a linear dynamic range from 10.0 to 100.0 µM with a LOD of 1.2 µM and good linear relationships (R2 = 0.99) for clindamycin. On the other hand, the quenching of the SPR peak at 412 nm was used to monitor the Fe3+ ions with wide linear ranges of 10.0–350.0 µM under the optimized pH (pH = 9) with a LOD of 5.6 µM. In addition, the proposed sensor displayed applicability in the real sample containing clindamycin (in capsules and injection ampoules) and Fe3+ ions (in water samples) detection.

Graphical Abstract

The Versatility in the Applications of Dithiocarbamates

Dithiocarbamate ligands have the ability to form stable complexes with transition metals, and this chelating ability has been utilized in numerous applications. The complexes have also been used to synthesize other useful compounds. Here, the up-to-date applications of dithiocarbamate ligands and complexes are extensively discussed. Some of these are their use as enzyme inhibitor and treatment of HIV and other diseases. The application as anticancer, antimicrobial, medical imaging and anti-inflammatory agents is examined. Moreover, the application in the industry as vulcanization accelerator, froth flotation collector, antifouling, coatings, lubricant additives and sensors is discussed. The various ways in which they have been employed in synthesis of other compounds are highlighted. Finally, the agricultural uses and remediation of heavy metals via dithiocarbamate compounds are comprehensively discussed.

Highly selective, sensitive and simpler colorimetric sensor for Fe2+ detection based on biosynthesized gold nanoparticles

Herein, we describe the fabrication of green bell pepper, Capsicum annuum L. extract capped gold nanoparticles (CA-AuNPs) in aqueous medium using tetrachloroaurate (HAuCl₄·3H₂O) as precursor salt and sodium hydroxide (NaOH) solution as accelerator as well as pH adjuster. Formation of CA-AuNPs was verified via colour change from yellowish to ruby red with further confirmation through surface plasmon resonance (SPR) band at 519 nm using ultraviolet violet-visible (UV-Vis) spectroscopy. Other characterizations techniques include, Fourier transform infra-red (FTIR) spectroscopy, atomic force microscopy (AFM), dynamic light scattering (DLS) with Zeta-potential analysis (ZPA) and X-ray diffraction (XRD) method. The resulting AuNPs were efficaciously implemented as highly sensitive colorimetric sensor for selective detection of Fe²⁺ in the presence of several interfering cations including Fe³⁺. Importantly, the fabricated CA-AuNPs based colorimetric sensor functioned linearly in the range of 0.3-7.0 ppb Fe²⁺, based on increasing absorption intensity with R² value of 0.9938 using UV-Vis spectrometry. The limit of detection (LOD) and limit of quantification (LOQ) for Fe²⁺ were estimated as 0.036 and 0.12 ppb, respectively. Finally, the sensor was effectively tested for determination of Fe²⁺ in some locally collected real water samples.

Selective colorimetric sensing of deferoxamine with 4-mercaptophenol- and mercaptoacetic acid-functionalized gold nanoparticles via Fe(iii) chelation

The multidentate deferoxamine ligand can selectively aggregate the Fe(iii)-attached AuNPs@(4MP–MAA) colorimetric nanoprobe, whereas other bidentate iron chelators cannot bridge the nanoparticles.

Distinctive detection of Fe2+ and Fe3+ by biosurfactant capped silver nanoparticles via naked eye colorimetric sensing

Distinctive detection of Fe²⁺ and Fe³⁺via naked eye colorimetic sensing.

Carbon dots derived from lychee waste: Application for Fe3+ ions sensing in real water and multicolor cell imaging of skin melanoma cells

Exploit of biomass as an inexhaustible resource has accepted much more curiosity to the present research world. Herein, a simple, one-step solvothermal action has been used to synthesize an ascendable amount of fluorescent carbon dots (CDs) with an average size of~3.13 nm, from Low-reasonable and green source lychee waste. The excitation/emission maxima of CDs have 365/443 nm with high quantum yield (23.5%). The present ingredient predominantly contained carboxylic acid and hydroxyl group that acted as a passive agent for stabilizing the CDs. The structural and optical properties were evaluated through HRTEM, FTIR, UV-vis, zeta potential, XPS, fluorescence, and fluorescence lifetime experiments. We investigated the manoeuvre of our synthesized CDs as a probe for detection of Fe³⁺ ions in water bodies; This sensing approach showed impressive selectivity and sensitivity towards Fe³⁺ions with LOD 23.6 nM. The sensing mechanism took place through static quenching which was entrenched through fluorescence lifetime measurements. Fe³⁺ ions detection was basically carried out with efficacy in real water. For its lofty Photo-stability, low cytotoxicity and cell viability the probe were substantially applied for bio-imaging experiment i.e. intracellular multi-color cell imaging in skin melanoma cells (A375 cells) with and without Fe³⁺ ions exemplifying its real applications in living cells.

Low-temperature phyto-synthesis of copper oxide nanosheets: Its catalytic effect and application for colorimetric sensing

The last decade has seen a remarkable detonation in modifying chemical processes for nanomaterial synthesis to make them 'green'. Owing to the unique properties of nanomaterial and with regard to environmental issues, in this study, a new alternative and fast eco-friendly approach for the synthesis of copper oxide nanosheets (CuO-NSs) using Terminalia catappa (Indian almond) leaf extract as a renewable and non-toxic reducing agent and efficient stabilizer was reported. It is noteworthy to mention that the present fabrication process can open up the possibility of fast, low cost and high efficiency synthesis of CuO nanostructures with an interesting morphology of nanosheets at ambient temperature and pressure. Optimization of important factors such as pH, the quantity of leaf extract, copper precursor concentration, incubation time and temperature on the formation of CuO-NSs were investigated. The formation of bioreduced CuO-NSs was certified by UV-Vis spectroscopy, XRD, TEM analysis and FT-IR spectroscopy. Due to good stability, and excellent catalytic activity of the synthesized CuO-NSs, they are exerted to degrade of MB dye in water as a model color pollutant in the presence of NaBH₄ at room temperature. Furthermore, color properties of CuO nanostructures aid us to apply these biosynthesized nanomaterials in the design of optical sensors for detection of Fe²⁺ and Fe³⁺ ions. In view of many advantages of the current optical sensors based on CuO-NSs, such as eco-friendly, cost-effective, and straightforward design, the sensing system presents a potential application in environmental science.

Ficus retusa-stabilized gold and silver nanoparticles: Controlled synthesis, spectroscopic characterization, and sensing properties

Ficus retusa was used as reducing and stabilizing agent in the green synthesis of silver and gold nanoparticles with high dispersion stability and controllable size and shape. The controlling of reaction conditions i.e. contact time, extract quantity, metal concentration, and pH value enables the tuning of the particle size and size distribution of the metal nanoparticles. UV-visible spectroscopy was used to follow the spectral profile changes of the surface plasmon resonance of the metal nanoparticles due to different treatments. The surface plasmon resonance varies between 400 and 432 nm and between 522 and 554 nm for silver and gold nanoparticles, respectively, depending on the different reaction parameters. Atomic force and transmission electron microscopy results confirmed the success of preparation of spherical silver (15 nm) and gold (10-25 nm) nanoparticles with narrow size-distribution. Fourier transform infrared spectroscopy suggested the phenolic compounds play the key role in the reduction and stabilizing of metal ions. The colorimetric sensitivity of silver and gold nanoparticles to detect the presence of heavy metals in water was studied.

Well-Aligned TiO2 Nanotube Arrays with Ag Nanoparticles for Highly Efficient Detection of Fe3+ Ion

Nowadays, determination of the iron ions with high sensitivity and selectivity with novel methods becomes a matter of urgency for monitoring healthy body and environment. In this paper, for the first time, we present a set of high-performance TiO₂ nanotube arrays which are quite sensitive to iron ions. Firstly, the anodic oxidation method was adopted to prepare ordered TiO₂ nanotube arrays, followed by functionalized Ag nanoparticle deposition with the enhancement ability in iron ion sensing. Besides, the spectrum of the TiO₂ nanotube with/without the Ag nanoparticles was analyzed with an X-ray photoelectron spectrometer, which shows that Ag nanoparticles can effectively reduce the recombination rate of electrons and holes, and increase the conductivity and the charge transfer rate of the electrodes. Further, when functionalized Ag nanoparticles on well-ordered TiO₂ nanotube arrays were used, iron ion sensing performed with the anodic stripping voltammetry method was investigated to validate the great potential of TiO₂ nanotube arrays with a sensitivity of approximately 30 μA/ug/L in becoming Fe³⁺ sensors. This method creates new possibilities for developing sensors for monitoring of Fe³⁺ in biological samples without any sample pretreatment procedure.

Pyrazinium thioacetate capped gold nanoparticles as Fe(III) sensor and Fe(III) marked anti-proliferating agent in human neuroblastoma cells

Gold nanoparticles (AuNPs) stabilized by new cationic 1‑(3‑(acetylthio)propyl)pyrazin‑1‑ium ligand (PPTA) were synthesized. AuNPs stabilized by PPTA (PPTA-AuNPs) were found to be spherical and polydispersed with the average size of 60 nm. Human neuroblastoma (SHSY-5Y) cells permeability of PPTA-AuNPs was found to be a key feature to study the intracellular quenching of Fe(III) proliferative activity. In vitro MTT assay revealed non-cytotoxicity of PPTA and PPTA-AuNPs at 100 μM concentration, while treatment of 100 μM of Fe(III) with SHSY-5Y cells resulted into higher cells viability. Contrary, a mixture of 1:1 Fe(III) with PPTA-AuNPs showed no change in the viability of cells at same concentration which suggests the intracellular complexation and recognition of Fe(III) by PPTA-AuNPs. AFM morphological analysis of SHSY-5Y cells also supported the MTT assay results, and it is safe to conclude that PPTA-AuNPs can be used as Fe(III) probes in living cells. In addition, Fe(III) caused a significant decrease in the absorbance of surface plasmon resonance (SPR) band of PPTA-AuNPs in a wide range of concentration and pH, with limit of detection 4.3 μM. Moreover, the specific response of PPTA-AuNPs towards Fe(III) was unaffected by the interference of other metals and components of real samples of tap water.

Highly Sensitive Colorimetric Assay for Determining Fe3+ Based on Gold Nanoparticles Conjugated with Glycol Chitosan

A highly sensitive and simple colorimetric assay for the detection of Fe³⁺ ions was developed using gold nanoparticles (AuNPs) conjugated with glycol chitosan (GC). The Fe³⁺ ion coordinates with the oxygen atoms of GC in a hexadentate manner (O-Fe³⁺-O), decreasing the interparticle distance and inducing aggregation. Time-of-flight secondary ion mass spectrometry showed that the bound Fe³⁺ was coordinated to the oxygen atoms of the ethylene glycol in GC, which resulted in a significant color change from light red to dark midnight blue due to aggregation. Using this GC-AuNP probe, the quantitative determination of Fe³⁺ in biological, environmental, and pharmaceutical samples could be achieved by the naked eye and spectrophotometric methods. Sensitive response and pronounced color change of the GC-AuNPs in the presence of Fe³⁺ were optimized at pH 6, 70°C, and 300 mM NaCl concentration. The absorption intensity ratio (A₇₀₀/A₅₁₀) linearly correlated to the Fe³⁺ concentration in the linear range of 0-180 μM. The limits of detection were 11.3, 29.2, and 46.0 nM for tap water, pond water, and iron supplement tablets, respectively. Owing to its facile and sensitive nature, this assay method for Fe³⁺ ions can be applied to the analysis of drinking water and pharmaceutical samples.

Fluorescent oligomer as a chemosensor for the label-free detection of Fe(3+) and dopamine with selectivity and sensitivity

In this article, a sensitive and selective turn-off fluorescence chemosensor, Tyloxapol (one kind of water soluble oligomer), was developed for the label-free detection of Fe(3+) ions in aqueous solution. Fluorescence (FL) experiments demonstrated that Tyloxapol was a sensitive and selective fluorescence sensor for the detection of Fe(3+) directly in water over a wide range of metal cations including Na(+), K(+), Ag(+), Hg(2+), Cd(2+), Co(2+), Cu(2+), Cr(3+), Mn(2+), Ba(2+), Zn(2+), Ni(2+), Mg(2+), Ca(2+), and Pb(2+). Moreover, the fluorescence intensity of Tyloxapol has shown a linear response to Fe(3+) in the concentration range of 0-100 μmol L(-1) with a detection limit of 2.2 μmol L(-1) in aqueous solution. Next, based on a competition mechanism, another turn-on sensing application of the Tyloxapol/Fe(3+) platform to probe dopamine (DA) against various other biological molecules such as other neurotransmitters or amino acids (norepinephrine bitartrate, acetylcholine chloride, alanine, valine, phenylalanine, tyrosine, leucine, glycine, histidine) were also investigated. It is expected that our strategy may offer a new approach for developing simple, cost-effective, rapid and sensitive sensors in biological and environmental applications.

Selective sensing of submicromolar iron(III) with 3,3',5,5'-tetramethylbenzidine as a chromogenic probe

The development of highly selective and sensitive method for iron(III) detection is of great importance both from human health as well as environmental point of view. We herein reported a simple, selective and sensitive colorimetric method for the detection of Fe(III) at submicromolar level with 3,3,'5,5'-tetramethylbenzidine (TMB) as a chromogenic probe. It was observed that Fe(III) could directly oxidize TMB to form a blue solution without adding any extra oxidants. The reaction has a stoichiometric ratio of 1:1 (Fe(III)/TMB) as determined by a molar ratio method. The resultant color change can be perceived by the naked eye or monitored the absorbance change at 652 nm. The method allowed the measurement of Fe(III) in the range 1.0×10(-7)-1.5×10(-4) mol L(-1) with a detection limit of 5.5×10(-8) mol L(-1). The relative standard deviation was 0.9% for eleven replicate measurements of 2.5×10(-5) mol L(-1) Fe(III) solution. The chemistry showed high selectivity for Fe(III) in contrast to other common cation ions. The practically of the method was evaluated by the determination of Fe in milk samples; good consistency was obtained between the results of this method and atomic absorption spectrophotometry as indicated by statistical analysis.

2,3,4-Trihydroxy benzophenone as a novel reducing agent for one-step synthesis of size-optimized gold nanoparticles and their application in colorimetric sensing of adenine at nanomolar concentration

2,3,4-trihydroxy benzophenone acts as a novel reducing and stabilizing agent for one-step synthesis of size-optimized Au NPs and used as a probe for colorimetric sensing of adenine.

Optical sensor: a promising strategy for environmental and biomedical monitoring of ionic species

In this review, we cover the recent developments in fluorogenic and chromogenic sensors for Cu²⁺, Fe²⁺/Fe³⁺, Zn²⁺and Hg²⁺.

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.

Simultaneous colorimetric detection of four drugs in their pharmaceutical formulations using unmodified gold nanoparticles as a probe

Schematic representation for the aggregation of unmodified Au NPs induced by four drugs (venlafaxine, imipramine, amlodipine, and alfuzosin).

Siderophore-inspired nanoparticle-based biosensor for the selective detection of Fe3+

Au nanoparticles modified with catechol-functionalised polymers provide a strong optical response which is highly specific to Fe³⁺ ions at physiologically relevant concentrations.

Fluorescent, MRI, and colorimetric chemical sensors for the first-row d-block metal ions

Transition metals (d-blocks) are recognized as playing critical roles in biology, and they most often act as cofactors in diverse enzymes; however, improper regulation of transition metal stores is also connected to serious disorders. Therefore, the monitoring and imaging of transition metals are significant for biological research as well as clinical diagnosis. In this article, efforts have been made to review the chemical sensors that have been developed for the detection of the first-row d-block metals (except Cu and Zn): Cr, Mn, Fe, Co, and Ni. We focus on the development of fluorescent sensors (fall into three classes: "turn-off", "turn-on", and ratiometric), colorimetric sensors, and responsive MRI contrast agents for these transition metals (242 references). Future work will be likely to fill in the blanks: (1) sensors for Sc, Ti, and V; (2) MRI sensors for Cr, Mn, Co, Ni; (3) ratiometric fluorescent sensors for Cr(6+), Mn(2+), and Ni(2+), explore new ways of sensing Fe(3+) or Cr(3+) without the proton interference, as well as extend applications of MRI sensors to living systems.