Nickel ion detection by imidazole modified carbon dots

Absorption-based colorimetric detection of nickel(II) ion by phase separation of thermoresponsive magnetic nanoparticles under microflow

Therma-Max™ LSA Streptavidin is a thermoresponsive magnetic nanoparticle (TMNP). It can be introduced conveniently to molecular recognition groups by avidin-biotin interaction. In this study, we demonstrated the detection of nickel(II) ions by the magnetic separation of TMNP induced by their phase transition under microflow. The NTA-tagged TMNP solution mixed with a Ni2+ sample was introduced into a microchannel with a well structure. Moreover, the sample was heated to induce the thermally induced aggregation of TMNP. The Ni-capturing TMNP were trapped in the well by magnetic fields. The supernatant was removed from the outlet, and a dimethylglyoxime (DMG) solution was introduced into the device for colorimetric detection in the well. Because DMG has a higher stability constant with Ni2+, sensitive colorimetric detection of Ni2+ can be achieved in devices where the sample volume, e.g., optical pathlength, is short. To demonstrate the feasibility of the proposed method, a recovery test was conducted using a commercially available cosmetic sample. Therein, complete collection was achieved.

Synthesis, properties and potential applications of photoluminescent carbon nanoparticles: A review

Photoluminescent-carbon nanoparticles (PL-CNPs) are a new class of materials that received immense interest among researchers due to their distinct characteristics, including photoluminescence, high surface-to-volume ratio, low cost, ease of synthesis, high quantum yield, and biocompatibility. By exploiting these outstanding properties, many studies have been reported on its utility as sensors, photocatalysts, probes for bio-imaging, and optoelectronics applications. From clinical applications to point-of-care test devices, drug loading to tracking of drug delivery, and other research innovations demonstrated PL-CNPs as an emerging material that could substitute conventional approaches. However, some of the PL-CNPs have poor PL properties and selectivity due to the presence of impurities (e.g., molecular fluorophores) and unfavourable surface charges by the passivation molecules, which impede their applications in many fields. To address these issues, many researchers have been paying great attention to developing new PL-CNPs with different composite combinations to achieve high PL properties and selectivity. Herein, we thoroughly discussed the recent development of various synthetic strategies employed to prepare PL-CNPs, doping effects, photostability, biocompatibility, and applications in sensing, bioimaging, and drug delivery fields. Moreover, the review discussed the limitations, future direction, and perspectives of PL-CNPs in possible potential applications.

A two-step strategy for simultaneous dual-mode detection of methyl-paraoxon and Ni (Ⅱ)

Exogenous pollution of Chinese medicinal materials by pesticide residues and heavy metal ions has attracted great attention. Relying on the rapid development of nanotechnology and multidisciplinary fields, fluorescent techniques have been widely applied in contaminant detection and pollution monitoring due to their advantages of simple preparation, low cost, high throughput and others. Most importantly, synchronous detection of multi-targets has always been pursued as one of the major goals in the design of fluorescent probes. Herein, we firstly develop a simultaneous sensing method for methyl-paraoxon (MP) and Nickel ion (Ni, Ⅱ) by using carbon based fluorescent nanocomposite with ratiometric signal readout and nanozyme. Notably, the designed system showed excellent effectiveness even when the two pollutants co-exist. Under the optimum conditions, this method provides low limits of detection of 1.25 µM for methyl-paraoxon and 0.01 µM for Ni (Ⅱ). To further verify the reliability, recovery studies of these two analytes were performed on ginseng radix et rhizoma, nelumbinis semen, and water samples. In addition, smartphone-based visual analysis has been introduced to expand its applicability in point of care detection. This work not only expands the application of the dual-mode approach to pollutant detection, but also provides insights into the analysis of multiple pollutants in a single assay.

Design of metalloenzyme mimics based on self-assembled peptides for organophosphorus pesticides detection

Organophosphorus pesticides (OPs) detection has attracted considerable attention because of the extensive application of OPs. In this research, non-toxic and high-performance metalloenzyme mimics of Zn²⁺-bonding peptides were developed by obtaining inspiration from phosphotriesterase (PTE) and nanofiber formation. Furthermore, based on the electrochemical activity of p-nitrophenol (PNP), the electrochemical sensor of metalloenzyme mimics was developed. By examining the effect of the active sites of peptides and fibril formation on the degradation of OPs, the optimal metalloenzyme mimic was selected. Furthermore, optimal metalloenzyme mimics were combined with NiCo₂O₄ to develop an electrochemical sensor of OPs. By monitoring square wave voltammetry (SWV) signals of PNP degraded from OPs, the amounts of OPs in actual samples could be determined in 15 min. We discovered that both the active sites of α metal and β metal were required for metalloenzyme mimics; Zn²⁺ promoted peptide fibrosis and especially acted as a cofactor for degrading OPs. Compared to traditional methods, the electrochemical sensor of metalloenzyme mimics was sensitive, reliable, and non-toxic; furthermore, the detection limit of methyl paraoxon was as low as 0.08 µM. The metalloenzyme mimics will be a promising material for detecting OPs in the food industry and environment fields.

Carbon Quantum Dots’ Synthesis with a Strong Chemical Claw for Five Transition Metal Sensing in the Irving–Williams Series

Carbon quantum dots (CQDs) are an excellent eco-friendly fluorescence material, ideal for various ecological testing systems. Herein, we establish uniform microwave synthesis of the group of carbon quantum dots with specific functionalization of ethylenediamine, diethylenetriamine, and three types of Trilon (A, B and C) with chelate claws -C-NH3. CQDs’ properties were studied and applied in order to sense metal cations in an aquatic environment. The results provide the determination of the fluorescence quench in dots by pollutant salts, which dissociate into double-charged ions. In particular, the chemical interactions with CQDs’ surface in the Irving–Williams series (IWs) via functionalization of the negatively charged surface were ascribed. CQD-En and CQD-Dien demonstrated linear fluorescence quenching in high metal cation concentrations. Further, the formation of claws from Trilon A, Trilon B, and C effectively caught the copper and nickel cations from the solution due to the complexation on CQDs’ surface. Moreover, CQD-Trilon C presented chelating properties of the surface and detected five cations (Cu2+, Ni2+, Ca2+, Mg2+, Zn2+) from 0.5 mg/mL to 1 × 10−7 mg/mL in the Irving–William’s series. Dependence was mathematically attributed as an equation (ML regression model) based on the constant of complex formation. The reliability of the data was 0.993 for the training database.

A novel symmetrical imidazole-containing framework as a fluorescence sensor for selectively detecting silver ions

In this study, a novel and highly efficient "turn-off" fluorescence imidazole-based sensor (BIB) with a symmetric structure was synthesized by a four-step reaction, from o-phenylenediamine, 6-bromo-2-pyridinecarboxaldehyde, and 1-bromohexane. The sensing mechanism was confirmed via fluorescence titration, HRMS, and ¹HNMR techiniques. The results showed that the binding ratio of BIB and Ag⁺ was 1 : 1 in a DMF-HEPES (pH 7.4) solution (9 : 1, v/v). The fluorescence response of BIB exhibited a good linear response within the Ag⁺ concentration ranging from 2 × 10^-7 to 8 × 10^-6 mol L^-1, and the limit of detection was calculated to be 4.591 × 10^-8 mol L^-1. BIB was successfully applied to the detection of Ag⁺ in water samples with recoveries of 97.25-109.50% and relative standard deviations (RSD) of 1.14-2.45%. In addition, BIB can successfully be applied to qualitatively and quantitatively identify Ag⁺ in water by test paper strips of BIB, which is fast and convenient. This provides a possible potential for the rapid monitoring of metal ions by sensors in environmental research.

Ultratrace Detection of Nickel(II) Ions in Water Samples Using Dimethylglyoxime-Doped GQDs as the Induced Metal Complex Nanoparticles by a Resonance Light Scattering Sensor

This study aimed to synthesize dimethylglyoxime (DMG) (N-source)-doped graphene quantum dots (N-GQDs) via simultaneous pyrolysis of citric acid and 1.0% (w/v) DMG. The maximum excitation wavelength (λmax, ex = 380 nm) of the N-GQD solution (49% quantum yield (QY)) was a red shift with respect to that of bare GQDs (λmax, ex = 365 nm) (46% QY); at the same maximum emission wavelength (λmax, em = 460 nm), their resonance light scattering (RLS) intensity peak was observed at λmax, ex/em = 530/533 nm. FTIR, X-ray photoelectron spectroscopy, XRD, energy-dispersive X-ray spectroscopy, and transmission electron microscopy analyses were performed to examine the synthesized materials. The selective and sensitive detection of Ni2+ using the RLS intensity was performed at 533 nm under the optimum conditions consisting of both 25 mg L-1 N-GQDs and 2.5 mg L-1 DMG in the ammonium buffer solution of pH 9.0. The linearity of Ni2+ was 50.0-200.0 μg L-1 with a regression line, y = 5.031x - 190.4 (r 2 = 0.9948). The limit of detection (LOD) and the limit of quantitation (LOQ) were determined to be 20.0 and 60.0 μg L-1, respectively. The method precision expressed as % RSDs was 4.90 for intraday (n = 3 × 3) and 7.65 for interday (n = 5 × 3). This developed method afforded good recoveries of Ni2+ in a range of 85-108% when spiked with real water samples. Overall, this innovative method illustrated the identification and detection of Ni2+ as a DMG complex with N-GQDs, and the detection was highly sensitive and selective.

An Overview of the Recent Developments in Carbon Quantum Dots—Promising Nanomaterials for Metal Ion Detection and (Bio)Molecule Sensing

The fluorescent carbon quantum dots (CQDs) represent an emerging subset of carbonaceous nanomaterials, recently becoming a powerful tool for biosensing, bioimaging, and drug and gene delivery. In general, carbon dots are defined as zero-dimensional (0D), spherical-like nanoparticles with <10 nm in size. Their unique chemical, optical, and electronic properties make CQDs versatile materials for a wide spectrum of applications, mainly for the sensing and biomedical purposes. Due to their good biocompatibility, water solubility, and relatively facile modification, these novel materials have attracted tremendous interest in recent years, which is especially important for nanotechnology and nanoscience expertise. The preparation of the biomass-derived CQDs has attracted growing interest recently due to their low-cost, renewable, and green biomass resources, presenting also the variability of possible modification for the enhancement of CQDs’ properties. This review is primarily focused on the recent developments in carbon dots and their application in the sensing of different chemical species within the last five years. Furthermore, special emphasis has been made regarding the green approaches for obtaining CQDs and nanomaterial characterization toward better understanding the mechanisms of photoluminescent behavior and sensing performance. In addition, some of the challenges and future outlooks in CQDs research have been briefly outlined.

Cellulose and Vanadium Plasmonic Sensor to Measure Ni2+ Ions

A novel vanadium–cellulose composite thin film-based on angular interrogation surface plasmon resonance (SPR) sensor for ppb-level detection of Ni(II) ion was developed. Experimental results show that the sensor has a linear response to the Ni(II) ion concentrations in the range of 2–50 ppb with a determination coefficient (R2) of 0.9910. This SPR sensor can attain a maximum sensitivity (0.068° ppb−1), binding affinity constant (1.819 × 106 M−1), detection accuracy (0.3034 degree−1), and signal-to-noise-ratio (0.0276) for Ni(II) ion detection. The optical properties of thin-film targeting Ni(II) ions in different concentrations were obtained by fitting the SPR reflectance curves using the WinSpall program. All in all, the proposed Au/MPA/V–CNCs–CTA thin-film-based surface plasmon resonance sensor exhibits better sensing performance than the previous film-based sensor and demonstrates a wide and promising technology candidate for environmental monitoring applications in the future.

Contemporary Progress in the Synthetic Strategies of Imidazole and its Biological Activities

Heterocyclic compounds are pervasive in many areas of life and one of the heterocycles, imidazole is a unique heterocyclic five-membered aromatic compound having two sp2 hybridized nitrogen atoms. Its integral name is 1, 3 diazole and previously, it was known as glyoxalin. This moiety has achieved a considerable place among scientists in recent years by reason of its divergent synthetic strategies and uncommon biological and pharmacological activities, for example, anti-convulsant, anti-microbial, anti-cancer, anti-inflammatory, anti-tumor, anti-viral, anti-ulcer, analgesic, etc. Due to distinct therapeutic actions, it is still an engrossed area of research. Researchers currently are inventing new greener methods to synthesize its derivatives and to improve its pharmacological activities. The purpose of this review is to study the literature that can help researchers to explore this area, its prevailing program for synthesis in environmentally friendly conditions and biological profile throughout past decades.

Mito-targeted "turn-on" fluorescent probe for nickel (II) detection

In this paper, we unveil a new highly selective and sensitive mito-tracker (NiP) for Ni²⁺ detection. NiP itself held very weak fluorescence and exhibited a high selectivity (≥160-fold) toward Ni²⁺ over other metal ions, with a limit of detection of 21.6 nmol. We demonstrate the practicality of NiP for the rapid determination of Ni²⁺ levels in mitochondria of living cells. This approach offers advantages by being fast, simple and low cost.

Fluorescence Characteristics of Aqueous Synthesized Tin Oxide Quantum Dots for the Detection of Heavy Metal Ions in Contaminated Water

Tin oxide quantum dots were synthesized in aqueous solution via a simple hydrolysis and oxidation process. The morphology observation showed that the quantum dots had an average grain size of 2.23 nm. The rutile phase SnO₂ was confirmed by the structural and compositional characterization. The fluorescence spectroscopy of quantum dots was used to detect the heavy metal ions of Cd²⁺, Fe³⁺, Ni²⁺ and Pb²⁺, which caused the quenching effect of photoluminescence. The quantum dots showed the response of 2.48 to 100 ppm Ni²⁺. The prepared SnO₂ quantum dots exhibited prospective in the detection of heavy metal ions in contaminated water, including deionized water, deionized water with Fe³⁺, reclaimed water and sea water. The limit of detection was as low as 0.01 ppm for Ni²⁺ detection. The first principle calculation based on the density function theory demonstrated the dependence of fluorescence response on the adsorption energy of heavy metal ions as well as ion radius. The mechanism of fluorescence response was discussed based on the interaction between Sn vacancies and Ni²⁺ ions. A linear correlation of fluorescence emission intensity against Ni²⁺ concentration was obtained in the logarithmic coordinates. The density of active Sn vacancies was the crucial factor that determined fluorescence response of SnO₂ QDs to heavy metal ions.

Facile synthesis of fluorescent carbon dots from Prunus cerasifera fruits for fluorescent ink, Fe3+ ion detection and cell imaging

Carbon dots (CDs) synthesized from natural products have drawn numerous attentions due to some unique properties. Here, Prunus cerasifera fruits were used as carbon source to synthesize high luminescent CDs by hydrothermal method. The obtained CDs were characterized by TEM, FTIR and XPS methods, founding the CDs were near-spherical and contained abundant nitrogen element. The CDs aqueous solution exhibited bright blue fluorescence under ultraviolet illumination, with the maximum emission at 450 nm. They could be potentially used as invisible fluorescent ink by written on the paper and irradiated by UV light, due to their fluorescent properties. Moreover, the CDs were found being selectively quenched by Fe³⁺ ion. The quench of CDs was linearly related to the concentration of Fe³⁺ ion in the range of 0-0.5 mM, meaning they could be developed as fluorescent probe of Fe³⁺ ion. At last, the CDs were used for cell imaging, founding they were low toxicity to HepG2 cells and exhibited blue and green fluorescence under a fluorescence microscope. In summary, the CDs prepared from Prunus cerasifera fruits exhibited excellent fluorescence properties, and could be potentially applied in the field of fluorescent ink, Fe³⁺ ion detection and cell imaging.