Metal Ion Sensors Research Articles

Luminescent carbon dots obtained from different precursors and methods and their applications as sensors for metal ions

Carbon dots (CDs) represent a rising class of nanomaterials with numerous optical and physicochemical properties that make them useful for a variety of applications. In this work, three different methods, conventional hydrothermal carbonization (CHC), microwave-assisted irradiation and heating reflux reaction technique, were used as different bottom-up approaches to obtain different CDs. The carbon nanoparticles were prepared using three different carbon precursors (maleic, fumaric and adipic acids) and one nitrogen source (ethylenediamine). The CDs were characterized using different techniques including Fourier transform infrared spectroscopy, Transmission electron microscopy, Ultraviolet-visible, Fluorescence and Zeta potential measurements. Both, the experimental method used to obtain the CDs and the different precursors, presented a considerable influence on the quantum yield values (QY), and also on the fluorescence emission curves. The molar proportion between the carbon and nitrogen source was varied to improve the QY, and one of the samples prepared by CHC method reached QY = 25.4%. The carbon nanoparticles obtained by CHC were used as nanoprobes for metal ions and exhibited great selectivity and sensitivity for Fe3+ ions, reaching a limit of detection of 35 nM, which is lower than most reported values for CD-based PL method used as probes for Fe3+ ions.

Fluorene-based polymers of intrinsic microporosity as fluorescent probes for metal ions

A portable fluorescent probe with quick response for sensing metal ions is of great demand. Here, for the first time, a novel fluorene-based polymer of intrinsic microporosity (PIM), PFLTB, was synthesized through Tröger's base reaction, which exhibits a fluorescent response for Fe3+ with high selectivity, sensitivity and rapidity. The PFLTB possesses Mn of 12,050 g mol−1, specific surface area of 453 m2 g−1, and high intrinsic fluorescence at 470 nm excited by 310 nm. It is found that the fluorescent quenching of PFLTB against Fe3+ is particularly notable as compared to other metal ions. The selectivity of PFLTB for Fe3+ was also determined by the interference experiment, and the limit of detection of PFLTB towards Fe3+ was measured to be 5.04 μmol L−1. PFLTB-based indicator film was fabricated by coating onto polyphenylene sulfide (PPS) porous non-woven, which showed the fast fluorescence quenching against Fe3+ with a response time of only 10 s. Our work offers a novel and feasible approach to fabricate efficient polymer-based sensors for metal ions, which is of great importance for diverse industrial and engineering processes.

Synthesis of carbon dots based on corn cobs as heavy metal ion sensors using the microwave method

<p class="Abstract">Carbon dots (CDots) are nanomaterials that can be applied as a heavy metal ion sensor. CDotss ware synthesized from corncobs which are abundant and underutilized. This study aims to determine the effect of variations in the concentration of corncobs on optical properties of CDots and their application as Fe<sup>3+</sup> ion sensors. CDots were synthesized with variations of corncobs’ mass 5, 10, 15, and 20 g and variations in metal ion concentrations 10<sup>-7</sup>, 10<sup>-6</sup>, 10<sup>-5</sup>, 10<sup>-4</sup>, and 10<sup>-3</sup> M. The success of CDots synthesis was indicated by luminescence green when exposed to UV light. UV-Vis characterization showed that the greater the concentration of CDots could cause a shift in the absorbance peak towards longer wavelengths and peaks at wavelengths of 290, 291, 295, 298, and 323 nm, respectively. Photoluminescence (PL) characterization showed CDots emission peaks at 511, 504, 503, and 495 nm. The greater the concentration of CDots can cause a shift in the emission peak towards a shorter wavelength and increase the intensity. The PL characterization can identify the presence of Fe<sup>3+</sup> metal ions with a wavelength shift that indicates a change in the CDots structure. The synthesis of CDots from corncobs have great potential to be applied as sensors.</p>

Fluorescent Janus ring siloxanes for detection of Au(III) and l-cysteine

Two new all-cis pyrene-substituted cyclic tetrasiloxanes (JR-01 and JR-02) are synthesized and studied as selective metal ion sensors. Both compounds exhibit solvent- and concentration-dependent excimer fluorescence emission at 482 nm. They also show highly selective fluorescence quenching by Au(III) ion with detection limits of 0.9 and 0.8 μM for JR-01 and JR-02, respectively. Data from the Stern-Volmer's plots at various temperatures, zetasizers, NMR, and UV–Vis spectroscopy indicate a plausible mechanism involving the formation of a non-emissive Au(III) complex. An application of JR-01 as Au(III) sensor in real water samples reveals a good sensing efficiency which is comparable to the analysis result from ICP-QMS. In addition, when an excess amount of l-cysteine is added to the JR-01/Au(III) mixture, the fluorescence signal is restored and the 1H NMR data suggests that JR-01 remains intact. As an extension of this study, we successfully demonstrate the detection of l-cysteine by fluorescence turn-on process using the JR-01/Au(III) mixture with a detection limit of 14.0 μM.

Green synthesized carbon quantum dot as dual sensor for Fe(II) ions and rational design of catalyst for visible light mediated abatement of pollutants

Herein we report the fabrication of carbon quantum dots through a green, cost-effective, and one-pot method from Wrightia tinctoria leaves. The CQDs are effective as fluorescent and electrochemical sensors for Fe(II) ions, with a detection limit of 2.3 nM. In the presence of Fe(II), strongly fluorescent quenching of CQDs occurred, providing the basis of Fe(II) quantification. The versatile sensing ability of CQDs in various real samples indicates the significant potential of carbon-based materials in developing sensing platforms for accurate and fast assay of different analytes. The synthesized green carbon dots and Bi4O5Br2 were fabricated on ZrO2 nanoparticles using a simple approach to create a high-efficiency ZrO2/CQD/Bi4O5Br2 photocatalyst composite to degrade contaminants. The fabricated CQD-based nanocomposite successfully degraded rhodamine B. The catalyst composition was optimized by varying Bi4O5Br2 content, and the ZrO2/CQD/Bi4O5Br2 (15 %) showed enhanced degradation efficiency and followed pseudo-first-order kinetics. More than 95 % of degradation efficiency in a short period and enhanced stability promise the nanocomposite's future industrial applications. This offers a novel approach to developing green carbon dots as a sensor for metal ions and its modified composites as visible-light-induced photocatalysts for the effective degradation of contaminants.

Real scenario of metal ion sensor: is conjugated polymer helpful to detect hazardous metal ion

Abstract Metal ions from natural and anthropogenic sources cause pollution to society and the environment is major concern in the present scenario. The deposition and contamination of metal ions in soil and water affect the biogeochemical cycles. Thus, it threatens the everyday life of living and non-living organisms. Reviews on the detection of metal ions through several techniques (Analytical methods, electrochemical techniques, and sensors) and materials (Nanoparticles, carbon dots (quantum dots), polymers, chiral molecules, metal-organic framework, carbon nanotubes, etc.) are addressed separately in the present literature. This review reveals the advantages and disadvantages of the techniques and materials for metal ion sensing with crucial factors. Furthermore, it focus on the capability of conjugated polymers (CPs) as metal ion sensors able to detect/sense hazardous metal ions from environmental samples. Six different routes can synthesize this type of CPs to get specific properties and better metal ion detecting capability in vast research areas. The metal ion detection by CP is time-independent, simple, and low cost compared to other materials/techniques. This review outlines recent literature on the conjugated polymer for cation, anion, and dual ion sensors. Over the last half decades published articles on the conjugated polymer are discussed and compared.

3D printing MOFs‐based fiber electrodes: A novel platform as electrochemical sensors for heavy metal ions

AbstractPb2+ probes play an important part in environments and human health. We developed a new free‐standing electrochemical probe by 3D printing UiO‐66‐NH2 with @rGO. This free‐standing fiber electrochemical sensor exhibited good structural stability and Pb2+ sensing performance with enhanced conductivity. This MOFs‐based hybrid probe showed an excellent sensing sensitivity for Pb2+ with a very low detection limit of 0.041 μM, significantly lower than the standard for Pb2+ in drinking water as a result of the porous structure of UiO‐66‐NH2 and the good conductivity of rGO. This study highlighted a simple strategy for MOFs‐based hybrid sensor formation and accelerated the MOFs‐based materials for Pb2+ electrochemical detection in future practical applications.

Recent Developments in G-Quadruplex Binding Ligands and Specific Beacons on Smart Fluorescent Sensor for Targeting Metal Ions and Biological Analytes.

The G-quadruplex structure is crucial in several biological processes, including DNA replication, transcription, and genomic maintenance. G-quadruplex-based fluorescent probes have recently gained popularity because of their ease of use, low cost, excellent selectivity, and sensitivity. This review summarizes the latest applications of G-quadruplex structures as detectors of genome-wide, enantioselective catalysts, disease therapeutics, promising drug targets, and smart fluorescence probes. In every section, sensing of G-quadruplex and employing G4 for the detection of other analytes were introduced, respectively. Since the discovery of the G-quadruplex structure, several studies have been conducted to investigate its conformations, biological potential, stability, reactivity, selectivity for chemical modification, and optical properties. The formation mechanism and advancements for detecting different metal ions (Na+, K+, Ag+, Tl+, Cu+/Cu2+, Hg2+, and Pb2+) and biomolecules (AMP, ATP, DNA/RNA, microRNA, thrombin, T4 PNK, RNase H, ALP, CEA, lipocalin 1, and UDG) using fluorescent sensors based on G-quadruplex modification, such as dye labels, artificial nucleobase moieties, dye complexes, intercalating dyes, and bioconjugated nanomaterials (AgNCs, GO, QDs, CDs, and MOF) is described herein. To investigate these extremely efficient responsive agents for diagnostic and therapeutic applications in medicine, fluorescence sensors based on G-quadruplexes have also been employed as a quantitative visualization technique.

Construction of Ultrastable Conjugated Microporous Polymers Containing Thiophene and Fluorene for Metal Ion Sensing and Energy Storage.

In this study, we have used the one-pot polycondensation method to prepare novel 2D conjugated microporous polymers (Th-F-CMP) containing thiophene (Th) and fluorene (Fl) moieties through the Suzuki cross-coupling reaction. The thermogravimetric analysis (TGA) data revealed that Th-F-CMP (Td10 = 418 °C, char yield: 53 wt%). Based on BET analyses, the Th-F-CMP sample displayed a BET specific surface area of 30 m2 g−1, and the pore size was 2.61 nm. Next, to show the effectiveness of our study, we utilized Th-F-CMP as a fluorescence probe for the selective detection of Fe3+ ions at neutral pH with a linear range from 2.0 to 25.0 nM (R2 = 0.9349). Furthermore, the electrochemical experimental studies showed that the Th-F-CMP framework had a superior specific capacity of 84.7 F g−1 at a current density of 0.5 A g−1 and outstanding capacitance retention (88%) over 2000 cycles.

Physical and Optical Properties of N,S-Codoped Carbon Quantum Dots Derived from Cigarette Butts for Mercury Ions Detection

The accumulation of mercury metal ion (Hg2+) in polluted river water is a problem in the emergence of various diseases in humans, because it is accumulated in drinks and food eaten every day. Therefore, the development of an accurate, sensitive, efficient and convenient method is very important to detect the content of metal mercury ions in polluted water. In this study, Carbon Quantum Dots (CQDs) was made simultaneously doped with Nitrogen (N) and Sulphur (S) atoms, so called N,-S codoped CQDs for the application of mercury metal ion sensors in polluted water. CQDs were prepared from wasted cigarette butts, which contain cellulose acetate as a source of carbon and nicotine as N-atoms source. The preparation of carbon solutions precursors were made by two ways of treatments namely put wasted cigarette filters/butts with water for 6-12 months (precursor I) and atomic S doping was done by adding sulfuric acid (H2SO4) with a volume-percentage of 0, 10% and 20% in water. The second treatment was carried out through the washing of wasted cigarette filter with sulfuric acid solution with a volume percentage of 20% sulfuric acid in water (precursor II). CQDs were prepared by use of hydrothermal method at 180°C for 6 hours. The synthesized solution was neutralized with sodium carbonate (Na2CO3). The solution was then centrifuged at 10,000 rpm for 15 minutes and filtered with a 0.22 µm microsyringe filter. The result of solution is a transparent and turns into blue when irradiated by a 365 nm UV laser, which indicates that CQDs has been formed. The FTIR results of the CQDs solution without S doping showed the presence of groups containing N atoms, namely at wave numbers 1417 cm-1 (C–N), 1540 cm-1 (CON–H), 1650 cm-1 (C=N/C=O). This means that N-doped CQDs have been formed. The C–S functional group was identified at a wave number of 1361 cm-1 in the S atom-doped CQDs. The HR-TEM images showed that the CQDs had a size less than 10 nm, and the distance between graphene crystals plane is in the range of 0.22-0.28 nm. The absorption spectra of the CQDs are ranging from 200 nm to 350 nm. S atom doping does not affect the absorbance spectrum significantly. The CQDs without S-atom doping has a PL spectrum from 300 nm to 800 nm with an emission peak of 417 nm. While, the N,-S codoped CQDs have a PL emission peak at 404 nm. The addition of doping from 10% to 20% did not change the peak emission wavelength. The CQDs sizes, optical properties and FTIR spectra of N, S-codoped CQDs show no significant difference when were prepared from precursor I and precursor II. This shows that the preparation of N, S co-doped CQDs can be produced much faster by washing cigarette butts directly with sulfuric acid prior to hydrothermal process as compared to precursor I which needs 6-12 months.

Metal Ion Complex Compound Fe(III) with Pyrazoline Derivative Ligand as Cd(II) and Zn(II) Heavy Metal Ion Sensor Based on Fluorescence

<p>The purpose of this research is to synthesize the complex compound of ion Fe<sup>3+</sup> with para-di-2-(1-phenyl-3-pyridyl-4,5-dihydro-1H-pyrazole-5-yl)benzene ligand and its potentials as the sensor of Cd<sup>2+</sup> and Zn<sup>2+</sup> heavy metal ions based on fluorescence. Complex compounds are characterized with a Fourier-Transform Infrared (FTIR) Spectrophotometer, Ultraviolet-Visible (UV-Vis) Spectrophotometer and Spectrofluorometer. Then, a complex compound fluorosensor study is conducted by adding Cd<sup>2+</sup> and Zn<sup>2+</sup> heavy metal ions using a UV-Vis Spectrophotometer and Spectrofluorometer. The results show that the synthesis of the complex compound formed by reacting Fe metal and pyrazoline derived ligands generates brown precipitate with a yield of 51.25% and a range of melting points of 252.2-253.2 . The result of characterization with FTIR (cm<sup>-1</sup>) generates 3380.20 (tertiary amine), 2922.31-2852.42 (C-H pyridine), 2360.38 (C=C aromatic), 1595.93-1451.88 (C=N), 1232.25-982.66 (C-N pyrazoline), 751.61-690.29 (C-H aromatic) and 366.54-339.44 (Fe-N). The Uv-Vis spectrophotometer study with a concentration of 5x10<sup>-5 </sup>M showed two absorption peaks at 246 nm, 354 nm, and 440 nm. The resulting fluorescence intensity of 813.1 a.u. at the wavelenght of 500 nm. The study of complex compound fluorescence shows that the addition of Cd<sup>2+</sup> heavy metal ion can be made as fluorosensor with turn-on (enhancement) type, while the complex compound in the addition of Zn<sup>2+</sup> heavy metal ion can be made as fluorosensor with turn off-on (quenching-enhancement) type.</p>

Polyaniline/carbon nanotube composites in sensor applications

Polyaniline (PA) has outstanding electronic, electrical and chemical properties. The incorporation of carbon nanotubes (CNT) into PA matrix could result in PA/CNT nanocomposites that possess enhanced properties. This review outlines the preparation methods of PA/CNT nanocomposites where they could be prepared by in situ polymerization and solution mixing. In addition, the fabrication methods of electrodes based on PA/CNT nanocomposites to be used in sensors will be investigated. In this regard, such electrodes can be fabricated through in situ synthesis of PA/CNT on electrode surface, electro-polymerization of Ani on carbon nanotube-modified electrode or casting of the prepared PA/CNT on the electrode surface. Also, the use of PA/CNT nanocomposites as sensing materials in biosensors, gas sensors, metal ion sensors, environmental pollutants sensors and pH sensors will be highlighted. The use of such nanocomposites in various types of sensors could be attributed to their remarkable chemical properties, large surface area and outstanding electrical performance.

Fully inkjet-printed paper-based Pb2+ optodes for water analysis without interference from the chloramine disinfectant.

We developed a paper-based colorimetric sensor for facile and cost-effective detection of Pb2+ in drinking and environmental water samples. The Pb2+ ion-selective optodes are fabricated by inkjet printing of ionophore, chromoionophore, and ion exchanger on cellulose paper. Pb2+ in water samples induces deprotonation of the pH chromoionophore and changes the optode color, which is acquired and analyzed by a smartphone. The paper-based optode without any plasticizer or polymer has a dynamic range and selectivity comparable to those of traditional optodes using PVC polymer and/or plasticizer. Furthermore, the response time of the plasticizer/polymer-free paper-based optode is much shorter than those of plasticized PVC-based optodes on paper and glass (5min vs. 15 and 50min). Moreover, the plasticizer/polymer-free optode preserves the water-wicking capability of porous cellulose paper, allowing for the design of pump-free microfluidic devices. Chloramine, a widely used disinfectant in drinking water, was found to be a strong and generic interference species for heavy metal ion detection via ion-selective optodes. A fully inkjet-printed lateral-flow paper-based device consisting of a sodium thiosulfate-based chloramine elimination zone and a plasticizer/polymer-free sensing zone was designed for Pb2+ detection in tap water disinfected by chloramine. The dynamic range of the Pb2+ sensor may be shifted from the current 10-6 to 10-5M to lower concentrations by using stronger ionophores, but this work lays a foundation for the design of paper-based heavy metal ion sensors without detrimental interference from disinfectants.

Luminescent carbon dots obtained from cellulose and their applications as sensors for metal ions

Carbon dots (CDs) can be obtained from different sources including wastes and green biomass materials, which, together with the method of preparation, can contribute to reduce the cost of production of these nanomaterials.In this work we have prepared different CDs from cellulose and using hydrothermal carbonization. The obtained nanocarbons were functionalized to enhance the quantum yield (QY) by two different methods: in a one pot reaction where the CDs were obtained in the presence of certain amount of ammonia or through a reaction with a oligomeric poly(ethylene glycol) diamine (PEG1500 N) after the preparation of CDs. The obtained CDs were characterized by different techniques including Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), UV-VIS spectroscopy, Fluorescence, and Potentiometric Titration. Size distribution measurements from isolated nanoparticles showed that the different obtained CDs presented a narrow size distribution, with the diameters in the range 0.7–3.0 nm. The CDs which presented high values of QY were used as probes for different metal ions, showing considerable selectivity and sensitivity for Fe3+ ions and a limit of detection of 0.15 μM in the case of CDs modified with PEG1500 N oligomers.Finally, the results presented here show the possibility to obtain CDs with a relatively low cost method, using only water as solvent and with potential applications in different areas including those as probe for metal ions.

Effects of Twisted Intramolecular Charge Transfer Behavior on Excited-State Intramolecular Proton Transfer Reactions of Methyl Benzoate Derivatives in Water Solution.

Many methyl benzoate derivatives were found to show intramolecular charge transfer (ICT), intramolecular proton transfer, and other properties, which have extensive applications in lasing media, metal ion sensors, active materials, and fluorescence probe fields. However, the intrinsic relationship and reaction mechanism between the excited-state intramolecular proton transfer (ESIPT) and ICT between methyl benzoate derivatives with different substituents have not been explained. In this paper, the density functional theory and time-dependent density functional theory methods were used to study the ESIPT and ICT behaviors of p-aminosalicylic acid methyl ester and p-dimethylaminosalicylic acid methyl ester in water and obtain the intrinsic interaction between the two behaviors. The bond parameters, infrared spectra, reduced density gradient scatter plots, and topological analyses of these two molecules in the ground state and excited state were analyzed to confirm the enhancement of the excited-state intramolecular hydrogen bonds (IHBs). The simulated absorption and fluorescence spectra of these molecules agreed well with the experimental values. Based on the optimized structure, we also plotted the natural transition orbitals, electron density difference maps, and frontier molecular orbitals (FMOs), which showed the changes of the charge distribution of these molecules intuitively upon photoexcitation. In addition, we also found that the degree of IHB enhancement with -N(CH3)2 substituents was less than that with -NH2, reflecting an inhibition effect of twisted intramolecular charge transfer (TICT) on ESIPT reaction. This conclusion was confirmed by our calculated potential energy curves. This work may better deepen the comprehension of the intrinsic relationship between ESIPT and TICT behavior and sequentially provide better theoretical guidance for the synthesis of fluorescent molecules related to these two behaviors.

Nanomaterial-based sensors and strategies for heavy metal ion detection

• Focused on the nanomaterial based sensors for heavy metal ions detection. • An overview of the nano-sensors coupled with mass spectrometry, colorimetry, electrochemistry, surface-enhanced Raman scattering and fluorescence. • Summarized the analytical performances, applications and further challenges of the metal-ion sensors. As one of the most serious toxic contaminants, heavy metal ions have severely threatened the living environment and biological system. Accurate and rapid detection of toxic metal ions is indispensable, urging the necessity of fabricating sensors with low cost, easy-to-operate, and high sensitivity. Numerous recent innovations in material science have reenergized this field and led to the emergence of well-defined nano-sensors with diverse structures and functions. Specifically, noble metal nanoparticles, porous nanomaterials, and semiconductors have been applied in sensor construction, coupled with analytical tools such as mass spectrometry, colorimetry, electrochemistry, surface-enhanced Raman scattering, and fluorescence. This review overviews the latest nanomaterials-based heavy metal ions sensors and focuses on their analytical performances, applications, and challenges.

Electrosynthesis of poly(2,5-dimercapto-1,3,4-thiadiazole) films and their composites with gold nanoparticles at a polarised liquid|liquid interface

The organosulfur compound 2,5-dimercapto-1,3,4-thiadiazole (DMcT) finds widespread applications in batteries, lubricant fluids, heavy metal ion sensors, waste-water purification and as a biocide. In this article, we demonstrate the untapped versatility inherent to using biphasic systems for electrosynthesis by showcasing several successful approaches to the electrosynthesis of poly(DMcT) films at a polarised interface between two immiscible electrolyte solutions (ITIES) by cyclic voltammetry (CV) cycling using either I 2 , Hg 2+ or O 2 as the oxidising agents. AC voltammetry is demonstrated as an effective in situ method to monitor poly(DMcT) film formation by I 2 or Hg 2+ as a function of the aqueous electrolyte anion and pH. DMcT is further shown to act as a binder molecule to promote interfacial gold nanoparticle (AuNP) assembly into floating films at an immiscible liquid|liquid (L|L) interface. Exploiting the electrocatalysis of DMcT oxidation by O 2 in the presence of adsorbed interfacial AuNPs yields AuNP/poly(DMcT) composite films. Raman spectroscopy suggests the latter were a coordination polymer of poly(DMcT) with AuNPs and surface enhanced Raman spectroscopy (SERS) active. The dielectric nature of the poly(DMcT) films suppresses the capacitance at the ITIES, yet the AuNP/poly(DMcT) films show a very high interfacial capacitance, with an ability to efficiently adsorb cations. Thus, these films open opportunities to selectively modulate the interfacial capacitance, potentially forming the basis of novel “soft” capacitors at a polarised L|L interface.

Sensing performance of metal-ion sensors based on polyfluorenes bearing N1-Alkylcytosine, oligoether, and alkylammonium side chains

π-Conjugated polyfluorenes bearing 6- N 1 -cytosinehexyl and hexaethylene glycol monomethyl ether side chains ( polymer-1 ) and 3- N 1 -cytosinepropyl and 3- N , N , N -trimethylammoniumpropyl bromide side chains ( polymer-2 ) were synthesized via the Suzuki-Miyaura coupling reactions. GPC measurements suggested that the M n values of polymers 1 and 2 were 22,900 and 8,510, whereas their M w values were 32,100 and 8,740, respectively. The metal-ion sensing behaviors of the polymers for Na + , Cu + , Cu 2+ , Fe 3+ , Pd 2+ , and Ag + , in an organic solvent and water were investigated by monitoring the decrease in the photoluminescence (PL) intensity upon the addition of a metal ion. The sensing performance of polymers depends on the polymer structure. Polymer-1 could detect Cu + , Cu 2+ , and Pd 2+ at the micro-molar level. The Benesi–Hildebrand method using PL quenching data was available to investigate the association behavior between the cytosine groups of the polymers and metal salts. The mechanism of PL quenching with polymer metal complexation was also discussed. • A Polyfluorene bearing N 1 -alkylcytosine and oligoether side chains was obtained. • The metal complexes of the polymer interacted with oligoether side chain. • Polymer photoluminescence was decreased upon the addition of metal ions. • The polymer acted as a highly sensitive sensor for metal salts.

Synthesis, physico-chemical characterization, and environmental applications of meso porous crosslinked poly (azomethine-sulfone)s

To develop innovative mesoporous crosslinked poly(azomethine- sulfone)s with environmental applications, a simple Schiff base condensation technique based on barbituric acid BA or condensed terephthaldehyde barbituric acid TBA in their structures as monomeric units are applied. Different analysis methodologies and viscosity measurements identify them as having stronger heat stability and an amorphous structure. The photophysical features of the multi stimuli response MSR phenomenon are observable, with white light emission at higher concentrations and blue light emission at lower concentrations. Their emission characteristics make them an excellent metal ions sensor through diverse charge transfer methods. They can have a better inhibition efficiency and be employed as both mixed-type and active corrosion inhibitors according to their fluorescence emission with metals, demonstrating their capacity to bind with diverse metals. The adsorption of two distinct dye molecules, Methylene blue MB cationic and sunset yellow SY anionic, on the mesoporous structures of the polymers is investigated, revealing their selectivity for MB dye adsorption. Quantum studies support these amazing discoveries, demonstrating a crab-like monomeric unit structure for the one that is heavily crosslinked.

Multi-functional carbon dots from simple precursors: An excellent heavy metal ions sensor with photocatalytic activity in aqueous environment

Carbon dots (CDs) with core and surface structures were prepared from simple precursors (ethylenediamine and ethylene glycol) by using house-hold microwave oven. The structural and optical properties were exclusively studied with HR-TEM, XRD, UV-Vis and PL techniques. The fluorescence emission of the CDs was predominantly dependent and/or independent on excitation-wavelength are owed to the existence of assorted functional groups on surface and uniform arrangement in core structure. Hence, the CDs shows better stability against photo bleaching and ionic strength. In addition, CDs are successfully used to detect heavy metal ions such as Cr6+ and Hg2+ selectively by fluorescence-based detection method through different quenching mechanisms with lower detection limit of 0.09 µM for Cr6+ and 0.16 µM for Hg2+. Similarly, we attempted rapid, simple and low cost on-field application by using two different cellulose-based filter papers for visual detection of Cr6+ and Hg2+ metal ions for quick and cheap method. Moreover, CDs were successfully employed for detoxification/degradation of Rhodamine B (RhB) dye and also 87 % degradation were achieved over the time period of 140 min under direct sunlight irradiation. At finally, the innovative CDs are superior multi-behavior material for the several environmental applications.