Hydroxylated graphene quantum dots as fluorescent probes for sensitive detection of metal ions

Highly sensitive methods are important for monitoring the concentration of metal ions in industrial wastewater.Here,we developed a new probe for the determination of metal ions by fluorescence quenching.The probe consists of hydroxylated graphene quantum dots(H-GQDs),prepared from GQDs by electrochemical method followed by surface hydroxylation.It is a non-reactive indicator with high sensitivity and detection limits of 0.01μM for Cu2+,0.005μM for Al3+,0.04μM for Fe3+,and 0.02μM for Cr3+.In addition,the low biotoxicity and excellent solubility of H-GQDs make them promising for application in wastewater metal ion detection.

A portable and low-cost parallel-plate capacitor sensor for alkali and heavy metal ions detection

A portable and low-cost design of parallel-plate capacitor sensor is proposed and investigated for detection of heavy and alkali metal ions concentration in liquid solution.The application of a thin and long-sided parallel PCB plate allows one to measure the dielectric response of each sample through capacitive sensing technique.The measurements were based on the peak output voltage corresponding to the capacitance of the output measured by an oscilloscope with metal ions concentration of the solution varying from 0 to 10 ppm and input frequency ranging from 1 kHz to 10 MHz.The ICF of Li,Na and K in chloride solution was 2.4,2.1 and 1.9 MHz,respectively.The ICF of Na and K in hydroxide solution was 1.5 MHz and 1.1 MHz,respectively,while the ICF of Pb(NO_(3))_(2)was 490 kHz.The detected ICF was applied to further construct the portable sensor system,which is simple in design,low-cost in fabrication and easy to operate.The finding of ICF of each chemical element is necessary to solve the selectivity challenge of the capacitance-based sensor,which will be appropriate for chemical,environmental and engineering applications.

Magnetic-optical dual functional Janus particles for the detection of metal ions assisted by machine learning

Functional polymer microspheres have broad application prospects in various fields,such as metal ion detection,adsorption,separation,and controlled drug release.However,integrating different functions in a single microsphere system is a significant challenge in this field.In this work,we prepared multicompartmental emulsion droplets utilizing microfluidic technology.Fe3O4 magnetic nanoparticles were added to one of the compartments of the emulsion droplets as functional particles,and Janus microspheres were obtained after curing.Fluorescent probes enter the two compartments of the Janus microspheres by diffusion.The fluorescence changes of the microspheres were observed in situ and captured through a fluorescence microscope.The images are processed by image recognition software and a Python program.The“fingerprint”of the detected metal ions is obtained by dimensionality reduction of the data through Principal Component Analysis.We employ different algorithms to build Machine Learning models for predicting the metal ion species and concentration.The variation of fluorescence intensity of the three fluorescent probes and the corresponding R,G,and B channel values and time are used as descriptors.The results show that the Random Forest,K-neighborhood(KNN),and Neural Network models demonstrated a better predicted effect with a variance(R2)greater than 0.9 and a smaller root mean square error;among them,the KNN model predicted the most accurate results.

Review of Cellulose Nanocrystal-based Fluorophore Materials and Their Application in Metal Ion Detection

Cellulose nanocrystals （CNCs）, a unique and promising natural material extracted from native cellulose, have attracted considerable attention owing to their physical properties and special surface chemistry. This review focuses on chemical conjugation strategies that can be used for preparation of ？uorescent-molecule labeled CNCs and the development of biomaterials. Furthermore, their application in the detection of metal ions and future development prospects are discussed. We hope to provide a clear view of the strategies for surface fluorescent modifcation of CNCs and their application in detection of metal ions.

Sign Response Mechanism of TCA Self-assembled Fluorescence Probe for Cu^2＋ Detection： FRET Evidence by DFT

A new type of self-assembled molecule ON-OFF fluorescence probe for toxic transition metal ions, made up of thiacalix[4]arene, micelle and fluorescence group, has been studied by DFT/TDDFT method combined with experiment spectra. Since the mechanism of the optical quenching signal response of such self-assembled micelle probe has always been a controversial issue of uncertainty, the spatial construction and geometric structures of the functional units of probe in the Cu2＋ ion detecting process were calculated and the mechanism was investigated by the molecular transition orbital pairs method to explore the origination of ON-OFF fluorescence sign response. The results presented that the signal response mechanism of the micelle probe is ascribed to F？rster resonance energy transfer（FRET） which provides new sights different from most of the conclusions by the related research work reported.

Nanopore-Based Metal Ion Detection and Metal Ion-Mediated Nanopore Sensing

With the continuous development of nanotechnology,single-molecule nanopore detection has become a popular research topic.In this review,we summarize the application of biological nanopores for metal ions detection as well as overview the function of metal ions in the ion-mediated nanopore detection of different analytes in recent decades.According to the previous reports,biological nanopores utilize two strategies to detect metal ions.First,the specific binding sites are engineered in the nanopore to slow down the translocation rate of metal ions,resulting in the diverse specific current blockage signals.Secondly,the external molecule probes are added in the detection system to interact with metal ions,leading to the characteristic changes in the signals.At the same time,the external addition of metal ions into the nanopore detection systems enhances the sensitivity and selectivity through the changes of pore charges,the coordination with analytes or indirect detection.This review provides a summary on the role of metal ions in the application of nanopore detection technology.

Synthesis of β-cyclodextrin functionalized gold nanoparticles for the selective detection of Pb2＋ ions from aqueous solution

In the present study we carried out the synthesis of β-cyclodextrin （β-CD） functionalized gold nanoparticles （AuNPs） using a microwave assisted heating method in alkaline media. Stable dispersion of β-CD stabilized AuNPs was obtained at an optimized pH of 10,5. At this pH value the deprotonated secondary hydroxyl group of β-CD shows the highest chelating affinity toward Pb2＋ ions thereby inducing AuNP aggregation. The Pb2＋ induced aggregation in β-CD-AuNP solution is monitored by both colorimetric response and UV-Vis spectroscopy. TEM, DLS and FTIR analyses were carried out to confirm the Pb2＋ ion induced aggregation behaviour of β-CD-AuNPs under alkaline conditions. Furthermore at the experimental pH the response of the β-CD-AuNP system towards Pb2＋ ions is selective when compared with other interfering metal cations.

Promising graphdiyne-based nanomaterials for environmental pollutant control

ABSTRACT Environmental pollutants,including gas phase pollutants,liquid organic pollutants,heavy metal ions,and pathogenic bacteria,pose a serious threat to our ecological environment and human health.Effectively addressing these pollutants has become one of the most urgent issues.Graphdiyne(GDY),as an emerging carbon material for environmental remediation,has unique acetylene bonds and abundant pore structures.The unique carbon atomic structure of sp/sp2 hybrid endows it with tunable electronic structure and outstanding physical and chemical properties.This review summarizes the practical applications of GDY-based nanomaterials in the context of environmental pollution control,including carbon monoxide(CO)oxidation,ozone(O_(3))decomposition,heavy metal ion detection and adsorption,organic pollutant degradation,and bacterial inactivation.Furthermore,the structure-performance relationship of GDYbased nanomaterials is analyzed,and the issues and challenges in the field of environmental remediation of GDY-based materials are indicated.

A green path to extract carbon quantum dots by coconut water:Another fluorescent probe towards Fe^(3+) ions

In recent years,carbon quantum dots(CQDs)have been of great enthrallment in the fluorescent probe field.Carbon precursors with interesting physicochemical properties may be derived from natural sources.In this research,for the first time,coconut water has been used as a source of carbon to prepare blue fluorescent CQDs without any modification and functionalization.The preparation of CQDs is very simple and cost-effective,when compared with other conventional techniques.The reaction parameters temperature and pH were varied to obtain monodispersed spherical CQDs with an average grain size of ∼5 nm.The CQDs exhibit blue emission with a wavelength of 487 nm with an excitation wavelength of 390 nm and are used for Fe^(3+) ions detection.Fe^(3+) ions have been observed to quench the fluorescence intensity of the CQDs than other heavy metals.In the presence of Fe^(3+) ions,the fluorescent CQDs are quenched due to the interaction of CQDs and Fe^(3+) ions.A spectroscopic result shows that Fe^(3+) ions can be observed within a concentration of 0-700μM,as well as the detection limit is 0.30μM.The CQDs provide a unique pathway for potential application in the environmental monitoring of heavy metal ions.

Formation mechanism and application potential of carbon dots synthesized from palm kernel shell via microwave assisted method

The present study systematically investigated the influence of synthesis conditions(duration,reaction medium,and doping concentration)and formation mechanism of carbon dots(CDs)derived from low-cost and abundant biomass palm kernel shell(PKS).Surprisingly,the dopant(urea)did not enhance the photoluminescence of CDs as expected,which could be attributed to the low reactivity between the dopant and PKS macromolecules.Variation of synthesis duration from 30 to 120 s clearly indicated the formation mechanism of CDs,involving the stages of dehydration,carbonization,and nucleation.The CDs with the highest photoluminescent intensity and quantum yield was obtained at synthesis duration of 90 s,aligned well with the perfect spherical shape of CDs and the synergistic effects of both surface and carbogenic core conditions.Understanding the formation mechanism could be used to optimize the synthesis of CDs,and hence linked to quantum yield and fluorescent intensity.In terms of application potential,the CDs illuminated well as fluorescent ink and in bacteria cells imaging.The potential of CDs as sensing material has also been proven with the quenching of fluorescence in the presence of metal ions.The linear range for detection of Cu2+ions was 0.1–0.5 mM with a detection limit as low as 0.05 mM.This signifies the potential of CDs fabricated from PKS as a low-cost and easily available material for Cu2+ions detection in aqueous solution.The CDs possessed reasonable photo stability as indicated by its consistent fluorescence level even after exposure to UV radiation for a prolonged period of 180 minutes.Overall,a simple,straightforward,and fast method is developed to synthesis strong blue emissive CDs from green PKS that are potentially suitable for Cu2+ions sensing in real application.