Curcumin-based fluorescent chemosensor for selective and efficient detection of picric acid

Fluorescence Quenching and Electron Transfer Dynamics of a Thiophene-Substituted 1,3,4-Oxadiazole Derivative with Nitroaromatic Compounds

This study investigates the fluorescence quenching behavior of a newly synthesized thiophene-substituted 1,3,4-oxadiazole derivative, 2-(4-(4-vinyl phenyl)phenyl)-5-(5-(4-vinyl phenyl)thiophene-2-yl)-1,3,4-oxadiazole (TSO), in the presence of various nitroaromatic compounds (NACs), including 2-nitrotoluene, 4-nitrotoluene, nitrobenzene, and picric acid (2,4,6-trinitrophenol). The interactions were examined in an ethanol medium at room temperature using steady-state and time-resolved fluorescence spectroscopy. Steady-state fluorescence analysis revealed a non-linear Stern-Volmer (SV) plot exhibiting positive deviation, while time-resolved measurements displayed a linear relationship. To interpret these findings, ground-state complex formation and the sphere-of-action static quenching models were applied. The study determined key quenching parameters, including the Stern-Volmer constant, quenching rate constant, static quenching constant, and sphere-of-action radius. Notably, fluorescence quenching efficiency increased with the number of NO2 groups in the NACs.Electrochemical analysis, complemented by Density Functional Theory (DFT) calculations, confirmed that electron transfer was the primary quenching mechanism. Furthermore, binding site analysis demonstrated a 1:1 binding stoichiometry between TSO and NACs, with picric acid exhibiting the highest binding affinity. Given the growing interest in fluorescence-based sensing approaches, these findings contribute valuable insights into the development of advanced sensors for detecting nitroaromatic pollutants and explosive residues.

Isoquinoline-Fused Benzimidazoles Based Highly Selective Fluorogenic Receptors for Detection of Cu2+, Fe3+, and Cl- Ions: Cytotoxicity and HepG2 Cancer Cell Imaging

An efficient isoquinoline-fused benzimidazole-based "turn-on" fluorescence receptor 9,10-bis(2-phenylhydrazineyl)-7H-benzo[de]imidazo[2,1-a]isoquinolin-7-one OXPH(ANQ) and "turn-off" fluorescence receptor 9,10-bis((3-(1H-imidazol-1-yl)propyl)amino)-7H-benzo[de]imidazo[2,1-a]isoquinolin-7-one OXPID(ANQ) were prepared and characterized by various spectral techniques. The sensing behavior of receptors was demonstrated by UV-vis and fluorescence experiments, and naked-eye detection exhibited prominent visual emission color change toward Cu2+/Cl- and Fe3+ over other testing cations/anions in DMSO:water (9:1, ν/v) solution. The 1:1 binding stoichiometry was confirmed by Job's plot, FT-IR, mass spectral titration, and also DFT studies with target ions as evidence for the binding nature of OXPH(ANQ)/OXPID(ANQ) with Cu2+/Cl- and Fe3+ ions, respectively. Limits of detection for OXPH(ANQ) with Cu2+/Cl- ions were of 4.50 and 4.91 μM, and OXPID(ANQ) with Fe3+ ions were of 5.06 μM. Interestingly, chemosensors OXPH(ANQ)/OXPID(ANQ) applied to intracellular image of Cu2+/Cl- and Fe3+ ions in living cells of HepG2 (Liver cancer cells) via confocal fluorescence microscopy technique at physiological environmental and also utilized for antimicrobial activity.

Curcumin-derivatives as fluorescence-electrochemical dual probe for ultrasensitive detections of picric acid in aqueous media

We are reporting the two curcumin derivatives, ferrocenyl curcumin (Fc-cur) and 4-nitro-benzylidene curcumin (NBC), as a probe through dual modalities, i.e., fluorescence and electrochemical methods, for the detection of nitro-analytes, such as picric acid (PA). The probes exhibited aggregation-induced enhanced emission (AIEE), and the addition of picric acid (PA) demonstrated good and specific fluorimetric identification of PA in the aggregated state. By using density functional theory (DFT), the mechanism of picric acid's (PA) interactions with the probes was further investigated. DFT studies shows evidence of charge transfer from curcumin derivatives probe to picric acid resulting into the formation of an adduct. The reduction of trinitrophenol (PA) to 2, 4, 6-trinitrosophenol was investigated utilizing a probe-modified glassy carbon electrode (GCE) with a good detection limit of 9.63 ± 0.001 pM and 41.01 ± 0.002 pM, respectively, for Fc-cur@GCE and NBC@GCE, taking into account the redox behavior of the probe. The applicability of the designed sensor has been utilized for real-time application in the estimation of picric acid in several water samples collected from the different source.

Pyrazoline-Based Fluorescent Probe: Synthesis, Characterization, Theoretical Simulation, and Detection of Picric Acid

2-Pyrazoline containing benzothiazole ring 2-[1-(1,3-benzothiazol-2-yl)-5-(4-methoxyphenyl)-4,5-dihydro-1H-pyrazol-3-yl]phenol (BP) have been synthesized for the effective identification of picric acid over other competing nitro compounds using fluorescence technique. The pyrazoline BP showed quenching efficiency as high as 82% comparative to other nitro aromatics. The limit of detection and limit of quantification were found to be 1.1 μM and 3.3 μM. The possible mechanism with the quenched PA detection efficiency was based on fluorescence energy transfer and photoinduced electron transfer. Moreover, the observed results were supported by the optimized structures of the compounds using the DFT/B3LYP/6-311G/LanL2DZ method. Eventually, the pyrazoline derivative BP was further utilized for natural water samples, showing recoveries in the 87.62-101.09% and RSD was less than 3%.

Alkaline n-gqds fluorescent probe for the ultrasensitive detection of creatinine

Creatinine (Crn) is an important excretory product of the human body. Medical laboratory technology has improved over years and brought many advancements in clinical diagnostics equipment, and testing techniques and made the tests more efficient. Yet, the quantitative analysis of Crn is still carried out by the classical Jaffe's reaction (using Picric acid (PA) with NaOH) method. Since PA is hazardous to human health, alternative solutions such as; nanoparticles and surface-modified nanoparticles can be used. Exploring the optoelectronic properties of carbon-based quantum dots for biomolecule sensing is of current interest among researchers. Nitrogen functionalized graphene quantum dots (Alk-NGQDs) measured featured Crn easier and reduced the time taken for the test carried out in laboratories. The synthesized Alk-NGQDs optical, structural, morphological properties, surface and compositions are studied through XPS, HRTEM, XRD, FTIR, and spectroscopic techniques. Alk-NGQDs at alkaline conditions (pH 9.5) form a stable complex with Crn through intermolecular charge transfer (ICT). The fluorescence titration method is used to sense Crn in commercial Crn samples and human blood serum. To understand the efficacy of sensing creatinine using Alk-NGQDs, working concentration, fluorescence quantum yield, the limit of detection, and quenching constant are calculated using the Stern-Volmer plot. The emission property of Alk-NGQDs is aimed to bring an alternative to the traditional colorimetric Jaffe's reaction.

Curcumin Is an Iconic Ligand for Detecting Environmental Pollutants

The rapid increase in industrial revolution and the consequent environmental contamination demands continuous monitoring and sensitive detection of the pollutants. Nanomaterial-based sensing system has proved to be proficient in sensing environmental pollutants. The development of novel ligands for enhancing the sensing efficiency of nanomaterials has always been a challenge. However, the amendment of nanostructure with molecular ligand increases the sensitivity, selectivity, and analytical performance of the resulting novel sensing platform. Organic ligands are capable of increasing the adsorption efficacy, optical properties, and electrochemical properties of nanomaterials by reducing or splitting of band gap. Curcumin (diferuloylmethane) is a natural organic ligand that exhibits inherent fluorescence and electrocatalytic property. Due to keto-enol tautomerism, it is capable of giving sensitive signals such as fluorescence, luminescence, ultraviolet absorption shifts, and electrochemical data. Curcumin probes were also reported to give enhanced meterological performances, such as low detection limit, repeatability, reproducibility, high selectivity, and high storage stability when used with nanosystem. Therefore, research on curcumin-modified nanomaterials in the detection of environmental pollution needs a special focus for prototype and product development to enable practical use. Hence, this article reviews the role of curcumin as a natural fluorophore in optical and electrochemical sensing of environmentally significant pollutants. This review clearly shows that curcumin is an ideal candidate for developing and validating nanomaterials-based sensors for the detection of environmental pollutants such as arsenic, lead, mercury, boron, cyanide, fluoride, nitrophenol, trinitrotoluene, and picric acid and toxic gases such as ammonia and hydrogen chloride. This review will afford references for future studies and enable researchers to translate the lab concepts into industrial products.

Preparation of multicolor luminescence Schiff-base compound based on solvent control and its application in the detection of pentachloronitrobenzene

Fluorescent materials with tunable optical properties are critical to their potential application. So far, the tuning of double-color luminescence has been easily achieved for many organic materials, but there are very few reports on multicolor luminescence materials. In this work, a multicolor emissions Schiff-base fluorescent compound 1,1'-{4,4'-Biphenyldiylbis[nitrilo(E)methylylidene]}di(2-naphthol) (BPDN) with an aggregation induced emission (AIE) characteristic was synthesized, and its luminescent characteristic was investigated. The BPDN molecules with low concentration in solution can emit faint light, but a new AIE phenomenon will appear when the BPDN molecules are aggregated in the solvent with low solubility or high concentration. The color and efficiency of the AIE of BPDN can be tuned by changing its aggregation state: the luminescence of the aggregate gradually redshifts (blue, green, to orange) as the solvent with poor solubility in the mixture increases or increasing the concentration of the BPDN. Based on the multicolor luminescence BPDN, a molecularly imprinted ratiometric fluorescent probe test strip (MIRF test strip) had been prepared and successfully applied to visual detection of pentachloronitrobenzene (PCNB). The color of test strip could change gradually from orange to yellow to green with the increase of the concentration of PCNB. This work shows the characteristic and application of multicolor luminescence BPDN.

Sensitive detection of picric acid in an aqueous solution using fluorescent nonconjugated polymer dots as fluorescent probes

Nonconjugated polymer dots (NPDs) were successfully used as fluorescent probes to selectively and sensitively detect picric acid (PA). The NPDs were prepared from polyethylenimine and 1,4-phthalaldehyde under mild conditions and had excitation and emission maxima of 351 and 474 nm, respectively. Fluorescence of the NPDs was efficiently quenched by PA through the inner filter effect because of the overlapping PA absorption band and NPD excitation spectrum. The NPDs allowed PA to be determined with a high degree of sensitivity. The linear range was 0-140μM and the detection limit was 0.5μM. The work involved developing a novel method for synthesizing NPDs and a promising platform for determining PA in environmental media.

Phytochemicals toward Green (Bio)sensing

Because of numerous inherent and unique characteristics of phytochemicals as bioactive compounds derived from plants, they have been widely used as one of the most interesting nature-based compounds in a myriad of fields. Moreover, a wide variety of phytochemicals offer a plethora of fascinating optical and electrochemical features that pave the way toward their development as optical and electrochemical (bio)sensors for clinical/health diagnostics, environmental monitoring, food quality control, and bioimaging. In the current review, we highlight how phytochemicals have been tailored and used for a wide variety of optical and electrochemical (bio)sensing and bioimaging applications, after classifying and introducing them according to their chemical structures. Finally, the current challenges and future directions/perspective on the optical and electrochemical (bio)sensing applications of phytochemicals are discussed with the goal of further expanding their potential applications in (bio)sensing technology. Regarding the advantageous features of phytochemicals as highly promising and potential biomaterials, we envisage that many of the existing chemical-based (bio)sensors will be replaced by phytochemical-based ones in the near future.

Molecularly imprinted ratiometric fluorescent probe for visual and fluorescent determination of aristolochic acid I based on a Schiff-base fluorescent compound

A molecularly imprinted ratiometric fluorescent probe (MIRF probe) was synthesized for the determination of aristolochic acid I (AAI) based on the Schiff-base fluorescent compound N,N'-bis(o-carboxybenzylidene)-p-4,4'-diaminobiphenyl (BDDB). The BDDB was immobilized in the silica nanoparticle (BDDB@SiO₂) as an internal standard material. The blue-emitting BDDB@SiO₂ and the yellow-emitting carbon quantum dots (y-CDs) were wrapped in the molecularly imprinted polymer (MIP) to provide a reliable reference signal at 440 nm and a fluorescent response signal at 530 nm at the excitation wavelength of 365 nm, respectively. In the preparation of the MIP of the MIRF probe, 4-vinylbenzoic acid as the functional monomer and AAI as the template molecule were used. An imprinting factor of 2.25 was obtained. Under the optimum conditions, the fluorescent response signal at 530 nm was quenched gradually by AAI in the range 1.0 to 120.0 μmol/L, while the reference signal at 440 nm remained unchanged. The limit of detection was 0.45 μmol/L, and the fluorescent color of the MIRF probe changed gradually from yellow to green to blue, which illustrated that the developed probe had a specific AAI recognition ability, a good anti-interference ability, and a sensitively visual determination ability. The probe was successfully applied to the AAI determination in traditional Chinese medicine (TCM) Asarum. The results showed that it had satisfactory recoveries (95.5-107.3%) and low relative standard deviations (2.0%). Furthermore, this method has a potential for the onsite naked eye determination of AAI in TCM samples.Graphical abstract.

Recent Developments in the Field of Explosive Trace Detection

Explosive trace detection (ETD) technologies play a vital role in maintaining national security. ETD remains an active research area with many analytical techniques in operational use. This review details the latest advances in animal olfactory, ion mobility spectrometry (IMS), and Raman and colorimetric detection methods. Developments in optical, biological, electrochemical, mass, and thermal sensors are also covered in addition to the use of nanomaterials technology. Commercially available systems are presented as examples of current detection capabilities and as benchmarks for improvement. Attention is also drawn to recent collaborative projects involving government, academia, and industry to highlight the emergence of multimodal screening approaches and applications. The objective of the review is to provide a comprehensive overview of ETD by highlighting challenges in ETD and providing an understanding of the principles, advantages, and limitations of each technology and relating this to current systems.

A stilbazolium dye-based chromogenic and red-fluorescent probe for recognition of 2,4,6-trinitrophenol in water

Probe DMAS-DP in water shows highly selective decrease in absorbance (475 nm) and fluorescence intensity (615 nm) with 2,4,6-trinitrophenol and colour change from red to yellow (visible light) and red fluorescent to black (365 nm light).

Template-directed synthesis of Sm2Ti2O7 nanoparticles: a FRET-based fluorescent chemosensor for the fast and selective determination of picric acid

Fluorescence “turn off” detection of picric acid using a Sm₂Ti₂O₇ nanoprobe.

Developed a novel sensor based on fluorescent graft conjugated polymer for the determination of aristolochic acid in traditional Chinese medicine

A novel fluorescent graft conjugated polymer (poly (2, 5-bis (Polyethylene glycol oxybutyrate)-1, 4-phenylethynylene-alt-1, 4-phenyleneethynylene, PPE-OB-PEG) has been designed and synthesized for the determination of aristolochic acid (AA). The detection conditions and detection characters of PPE-OB-PEG were systematically explored in this work. The fluorescence intensity of PPE-OB-PEG changes with the different concentration of AA. PPE-OB-PEG has a good linear range towards AA from 1.00 × 10^-7 to 8.00 × 10^-5 mol L^-1 and the limit of detection (LOD) is 3.00 × 10^-8 mol L^-1 (S/N = 3). PPE-OB-PEG have been applied to detect AA in traditional Chinese medicine samples and the results are satisfactory. The experimental results show that PPE-OB-PEG can be used as a fluorescence probe for rapid and sensitive detection of AA.

A novel and fast responsive turn-on fluorescent probe for the highly selective detection of Cd2+ based on photo-induced electron transfer

A novel, highly sensitive and fast responsive turn-on fluorescence probe ADMPA for Cd²⁺ was successfully developed based on 2,9-dimethyl-1,10-phenanthroline and o-aminophenol.