Selective Detection Of Cr Research Articles

Synthesis of Intrinsically-Fluorescent Aliphatic Tautomeric Polymers for Proton-Conductivity, Dual-State Emission, and Sensing/Oxidation-Reduction of Metal Ions.

Herein, fluorescent conducting tautomeric polymers (FCTPs) are developed by polymerizing 2-methylprop-2-enoic acid (MPEA), methyl-2-methylpropenoate (MMP), N-(propan-2-yl)prop-2-enamide (PPE), and in situ-anchored 3-(N-(propan-2-yl)prop-2-enamido)-2-methylpropanoic acid (PPEMPA). Among as-synthesized FCTPs, the most promising characteristics in FCTP3 are confirmed by NMR and Fourier transform infrared (FTIR) spectroscopies, luminescence enhancements, and computational studies. In FCTP3, ─C(═O)NH─, -C(═O)N<, ─C(═O)OH, and ─C(═O)OCH3 subluminophores are identified by theoretical calculations and experimental analyses. These subluminophores facilitate redox characteristics, solid state emissions, aggregation-enhanced emissions (AEEs), excited-state intramolecular proton transfer (ESIPT), and conductivities in FCTP3. The ESIPT-associated dual emission/AEEs of FCTP3 are elucidated by time correlated single photon counting (TCSPC) investigation, solvent polarity effects, concentration-dependent emissions, dynamic light scattering (DLS) measurements, field emission scanning electron microscopy images, and computational calculations. The cyclic voltammetry measurements of FCTP3 indicate cumulative redox efficacy of ─C(═O)OH, ─C(═O)NH─/-C(═O)N<, ─C(─O─)═NH+─/─C(─O─)═N+, and ─C(═N)OH functionalities. In FCTP3, ESIPT-associated dual-emission enable in the selective detection of Cr(III)/Cu(II) at λem1/λem2 with the limit of detection of 0.0343/0.079 ppb. The preferential interaction of Cr(III)/Cu(II) with FCTP3 (amide)/FCTP3 (imidol) and oxidation/reduction of Cr(III)/Cu(II) to Cr(VI)/Cu(I) are further supported by NMR-titration; FTIR and X-ray photoelectron spectroscopy analyses; TCSPC/electrochemical/DLS measurement; alongside theoretical calculations. The proton conductivity of FCTP3 is explored by electrochemical impedance spectroscopy and I-V measurements.

Eu3+ Complex-Based Superhydrophobic Fluorescence Sensor for Cr(VI) Detection in Water.

Cr(VI) compounds are bioaccumulative and highly toxic pollutants, and there is a need for simple and fast detection methods to monitor their trace levels. In this work, we developed a Eu3+ complex-based fluorescence sensor to easily detect Cr(VI) in water droplets. Our sensor consists of a nanofibrous membrane electrospun with a blend of polyvinylidene fluoride (PVDF), silica particles, and Eu3+ complex. Upon modifying the membrane surface with fluoroalkyl chemistry, the sensor displayed superhydrophobicity. When a water droplet with Cr(VI) was placed on such a superhydrophobic fluorescence sensor, the overlapping absorption of Cr(VI) and Eu3+ complex facilitated the inner filter effect, allowing the selective detection of Cr(VI) down to 0.44 µM (i.e., 45.76 µg L-1). We proposed and designed of new inexpensive and fast sensor for the detection of Cr(VI).

Iron‐Porphyrin‐Based Covalent Assembly with Peroxidase‐Like Activity and High Efficiency for Cr(VI) Colorimetric Detection

AbstractEfficient synthesis of functional nanomaterials for simple, sensitive, and accurate colorimetric detection of chromate [Cr(VI)] has attracted great interest due to the toxicity of Cr(VI). Here, novel covalently assembled iron porphyrins (CAIPs) are fabricated through covalently cross‐linking reaction between iron‐tetra‐(4‐hydroxy‐phenyl) porphyrin and three different cross‐linkers based on 3,3´‐dithiodipropionic acid. The results show that CAIPs have a spherical vesicle framework with favorable dimensional structure and enzymatic activity. In the presence of H2O2, CAIPs exhibit high peroxidase‐like activity toward 3,3´,5,5´‐tetramethylbenzidine. Based on these findings, CAIPs are used as an efficient colorimetric catalyst for the sensitive and selective detection of Cr(VI) with a detection limit about 23 nm. The feasibility of this method for real‐water samples is verified by a standard addition experiment. This system further facilitates the developments of nanomaterial, and its application in colorimetric detection fields.

Facile fabrication of an Au/Cu bimetallic nanocluster-based fluorescent composite film for sensitive and selective detection of Cr(VI).

To overcome the disadvantage of simple bimetallic nanocluster solutions being difficult to store and utilize, we prepared and obtained a novel gold and copper bimetallic nanocluster-doped chitosan fluorescent composite film. In this study, gold and copper bimetallic nanoclusters emitting strong red fluorescence were first synthesized by a chemical reduction method. Subsequently, a novel gold and copper bimetallic nanocluster-doped chitosan fluorescent composite film was successfully prepared by a solution casting method. After 60 minutes of UV light irradiation or 30 days at room temperature, the relative fluorescence intensity values of the composite film decreased by 0.9% and 1.2%, respectively. This indicates that its optical properties are stable and that it can be stored for a long time. The composite film has strong and bright red fluorescence and can be used as a fluorescent probe to achieve real-time detection of Cr(VI). It also has a low detection limit for Cr(VI) (0.26 ppb), so it can be applied to the detection of Cr(VI) in actual water samples and get satisfactory detection results. Due to its portability, high selectivity, and high sensitivity, it can also be extended to chemical and food detection.

Non-toxic carbon dots fluorescence sensor based on chitosan for sensitive and selective detection of Cr (VI) in water

A novel fluorescence carbon dots (CS-CDs) were prepared via a one-step hydrothermal approach using chitosan and urea as precursors. CS-CDs exhibited good selectivity and sensitivity of fluorescence response to Cr (VI) in a wide range with a detection limit of 0.59 μM. More interestingly, CS-CDs-based fluorescent hydrogel sensors were further developed for quantitative detection of Cr (VI) in water. The fluorescence signals of the composite were recorded by a smartphone and converted to grayscale parameters linearly related to concentration of Cr (VI) by Image J software. This composite showed a broad linear range of 10–300 μM and a low detection limit of 2.83 μM. All results demonstrate the great potential for the portable, low-cost and green detection of Cr (VI) in practical application.

N, P Co-Doped Carbon Dots as Multifunctional Fluorescence Nano-Sensor for Sensitive and Selective Detection of Cr(VI) and Ascorbic Acid

N, P Co-Doped Carbon Dots as Multifunctional Fluorescence Nano-Sensor for Sensitive and Selective Detection of Cr(VI) and Ascorbic Acid

A Magnetic Sensor Based on Poly(γ-Glutamic Acid)-Functionalized Iron Oxide Nanoparticles for Cr3+ Detection

Background: The highly sensitive and selective detection of Cr3+ is critical. Objective: We report the development of poly(γ-glutamic acid) (γ-PGA)-functionalized iron oxide nanoparticles (γ-PGA-Fe3O4 NPs) as a magnetic nanosensor for magnetic resonance (MR) detection of trivalent chromium (Cr3+) in aqueous solution. Methods: The γ-PGA-Fe3O4 NPs with a mean particle size of 7.3 nm, good colloidal stability and ultrahigh r2 relaxivity (326.8 mM−1s−1) were synthesized via a facile mild reduction approach in the presence of γ-PGA, and used for MR detection of Cr3+. Results: Upon exposure to Cr3+, the γ-PGA-Fe3O4 NPs aggregated into nanoclusters as verified by dynamic light scattering due to the coordination of Cr3+ with γ-PGA side chain carboxyl groups, resulting in the decrease in their transverse relaxation time. This MR signal change enables detection of Cr3+ in a concentration range of 0.4-1 nM. We also show that the γ-PGA-Fe3O4 NPs have an excellent selectivity toward Cr3+ and a high recovery percentage of 83.8% or above. Conclusion: This study thus demonstrates that the developed γ-PGA-Fe3O4 NPs may be used as a nanoprobe for MR sensing of Cr3+ in water environment.

PEGylated silicon oxide nanocomposites with blue photoluminescence prepared by a rapid electron-beam irradiation approach: Applications in IFE-based Cr (VI) sensing and cell-imaging

Blue photoluminescent silicon oxide nanocomposites (SiONCs) with simultaneous in situ PEGylation were prepared in few seconds by an electron beam-assisted approach. Thermogravimetric analysis (TGA) revealed the formation of a dense PEG coating on nanocomposites. Various characterization studies such as XPS, FTIR, and EDX indicated the formation of silicon oxide nanocomposites (SiOx<2). XRD pattern showed their amorphous nature. The average size of nanocomposites determined by TEM measurements was ~ 103 nm. The UV-Vis absorption spectra of SiONCs showed an onset and a shoulder peak at ~380 and 300 nm, respectively. Interestingly, the nanocomposites exhibited excitation-wavelength-dependent photoluminescence (PL) spectra (maximum quantum efficiency ~49%), which could be attributed to the presence of multiple emission centers (ECs). The nature of ECs was analyzed by various complementary studies, such as pH- and temperature-dependent PL, fluorescence excitation spectrum, and time-resolved PL studies. Considering the low cytotoxicity, strong PL, and stable colloidal properties, various prospective applications of the as-prepared nanocomposites were explored. Cell-imaging experiments demonstrated the internalization of nanocomposites within tumor cells, as evidenced by the bright fluorescence images from the cytoplasmic region. In addition, these nanocomposites showed highly sensitive and selective detection of Cr (VI) (detection limit = 0.74 μM). Mechanistic investigations revealed inner filter effect (IFE) based PL quenching. Meanwhile, paper kits were prepared using PEGylated SiONCs, and samples (containing different ions) were tested to check their practicality for real-time detection of Cr (VI).

Non-Toxic Carbon Dot Fluorescence Sensor Based on Chitosan for Sensitive and Selective Detection of Cr (Vi) in Water

Non-Toxic Carbon Dot Fluorescence Sensor Based on Chitosan for Sensitive and Selective Detection of Cr (Vi) in Water

Dual-excitation red-emissive carbon dots excited by ultraviolet light for the mitochondria-targetable imaging and monitoring of biological process in living cells

The bifunctional carbon dots (CA-p-CDs) with truly red-emission under short-wavelength light excitation (such as ultraviolet light, blue light or cyan light) were easily and successfully fabricated by attaching citric acid (CA) molecules onto the pristine p-CDs using an ultrasonic-triggered surface re-engineering approach under room conditions. Especially, the CA-p-CDs show truly red emission and excitation-wavelength-independent properties when excited by ultraviolet-light with a wavelength in the range of 360–400 nm or excited by progressively longer excitation wavelengths in the range of 440–500 nm. The CA-p-CDs were verified to be very low cytotoxicity. Importantly, the CA-p-CDs were further used for the targeted mitochondria imaging or direct evaluation on the intracellular biological process in living cells through variable PL emission colors with the gradually depletion of attached CA molecules. Furthermore, the strongest PL peaks of CA-p-CDs showed fluorescence enhancement response toward Cr3+ ions. The CA-p-CDs were also used for the highly sensitive and selective detection of Cr3+ ions in tap water with a limit of detection as low as 12 nM. This work presented designable fabrication of bifunctional CDs by linking molecules as an excellent nanoprobes for the mitochondria-targetable imaging and chemical sensing of heavy metal ions in water.

Polymeric carbon dot/boehmite nanocomposite made portable sensing device (Kavach) for non-invasive and selective detection of Cr(VI) in wastewater and living cells

This work reports a handheld fluorometric probe, namely ‘Kavach’ for monitoring hexavalent chromium in industrial wastewater and living systems. Kavach is capable to detect chromium contamination in a rapid and facile way. The device is made of a thin layer (~1 mm) of carbon dot decorated boehmite nanostructure (BH@CD) incorporated in a layer of poly vinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) membrane. The doped membrane has an excellent blue fluorescence upon UV excitation (355 nm) and alters its fluorescence level when exposed to Cr(VI). In reality, tiny carbon dots leach out from the nano-matrices to produce secondary contamination. Incorporation of the BH@CD into the polymeric matrix of PVDF-HFP significantly reduces such contamination and makes this material a potential sensing probe. This photoinduced electron transfer (PET) based sensor is tremendously selective and sensitive (LOD ~66 nM) towards aqueous chromium. The performance of the probe remains unaltered in different pH and water qualities. Additionally, this material can sense chromium in living cells, which has been validated theoretically using molecular docking and observed experimentally using fluorescence microscopy. Kavach is truly a handheld, reusable and non-invasive sensing probe against Cr(VI), which can be employed for on-site low-cost detection.

A luminescent Zn-MOF exhibiting high water stability: selective detection of Cr(VI) ion and treatment activity on sepsis

ABSTRACT A fresh metal-organic framework (MOF) based on the Zn ions as the metal ions has been prepared via the solvothermal method, and its chemical formula is [Zn(byia)(DMF)]·1.5DMF·7H2O (1, byia = 5-(benzimidazol-2-yl) isophthalic acid). It is worth noting that the compound 1 has excellent water stability (which can be maintained in the water for at least a month). Most fascinating, in water, the compound 1 exhibits the strong blue luminescence, which can only be selectively quenched via the contaminant of the Cr2O7 2– ion. The selective luminescence quenching with low limits of detection and high values of K sv proved its better sensing property, which can be compared with the contemporary materials. To development new strategy for the sepsis treatment, the biological activity and mechanism of the compound was explored. Firstly, the ELIA detection was performed in this experiment to assess the inhibition of compound against inflammatory factor storm during sepsis. Then, the inflammatory response in the immune cells was assessed by real time RT-PCR.

Facile synthesis of carboxymethyl cellulose sulfur quantum dots for live cell imaging and sensitive detection of Cr(VI) and ascorbic acid

Nowadays the synthesis of stable fluorescent sulfur quantum dots (SQDs) remains a big challenge. Herein, the utilization of carboxymethyl cellulose (CMC) to synthesis of SQDs is reported. Benefiting from the unique composition and structure of CMC macromolecule, the resulted CMC-SQDs simultaneously show high aqueous dispersibility and stability, tunable emission, stable fluorescence and low cytotoxicity, which make them promising for working as a fluorescent probe. Fluorescence detection experiments suggested that the CMC-SQDs could serve as a fluorescence on-off-on switch to sensitive and selective detection of Cr(VI) and ascorbic acid (AA) based on the inner filter effect (IFE). The limit of detection towards Cr(VI) and AA can reach 0.024 and 0.18 μM with linear range of 0.5−225 and 1−300 μM, respectively, which compares favorably to other reported fluorescent probes. In addition, the employment of fluorescent CMC-SQDs for practical detection of Cr(VI) and AA was also studied.

Ingenious aspartic acid-functionalized gold nanoparticles by one-pot protocol for the sensitive detection of chromium (III) ions

In this work, we report an effective one-pot strategy for synthesizing aspartic acid-functionalized gold nanoparticles (Asp-AuNPs) and constructing chromium (III) ion (Cr3+) colorimetric sensing system. Aspartic acid, acting as a reductant and stabilizer, was used directly to synthesize functionalized AuNPs without additional surface modification procedure. The Asp-AuNPs possesses the same good stability and optical properties as citrate-stabilized AuNPs, which become a new option for preparing AuNPs. More importantly, aspartic acid exhibits superior performance than citrate and other succinic acid derivatives because of its Cr3+identifying property. The Asp-AuNPs was used for the sensitive and selective detection of Cr3+ based on the aggregation-induced color change of AuNPs from wine red to blue-gray. Under optimal conditions, the absorbance ratios (A660 nm/A520 nm) show good linearity with Cr3+ concentrations with a limit of detection of 0.6 nM. Furthermore, the proposed method was applied for the analysis of Cr3+ in environmental water samples successfully with a reliable recovery of 95.4%-105.1%. Besides, the scanometric analysis model based on three primary colors change was established to deal with the requirement for the rapid quantitative determination of Cr3+ inenvironmental emergencies.

Three water-stable luminescent two-dimensional CdII-based coordination polymers as sensors for highly sensitive and selective detection of Cr2O72− and CrO42− anions

Three 2D CdII-CPs with different topologies were prepared, in which 1 and 3 are rare examples which display excellent sensitivity, selectivity, recyclability and structural stabilities for the detection of Cr2O72−/CrO42−.

Amine functionalized NaY/GdF4:Yb,Er upconversion-silver nanoparticles system as fluorescent turn-off probe for sensitive detection of Cr(III)

In this work, a label-free fluorimetric method for sensitive and selective detection of Cr(III) was developed by utilizing NaY/GdF4:Yb,Er upconversion nanoparticles (UCNPs) and citrate-modified silver nanoparticles (Cit-AgNPs) mixed system. The photophysical and morphological properties of the prepared UCNPs were characterized by various spectroscopic and microscopic techniques. The fluorescence of amino-modified UCNPs can be quenched due to the Cr(III) induced aggregation of Cit-AgNPs by means of inner filter effect. The observed quenching in the fluorescence intensity of the UCNPs is found to be dependent on the concentration of Cr(III). The fluorescence decreases linearly within the investigated concentration of 0.5–40 μM Cr(III) with a limit of detection 34 nM. The practical applicability of the present sensing method is ascertained by detecting Cr(III) in spiked tap water and instant tea samples.

One-step synthesized fluorescent nitrogen doped carbon dots from thymidine for Cr (VI) detection in water

A novel, simple and low-cost nitrogen doped carbon dots (N-CDs) fluorescent sensor for sensitive detection of Cr (VI) was developed via one-step hydrothermal method using thymidine as carbon source. As-prepared N-CDs exhibited the ability of sensitive and selective detection of Cr (VI) through the inner filter effect (IFE). The performances of N-CDs were investigated with the characterization methods of transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Under the optimized conditions, a good logarithm correlation between the fluorescence intensity of N-CDS and the concentration of Cr (VI) was obtained ranging from 0.1 μM to 430 μM (R2 = 0.992), with a low detection limit (LOD; S/N = 3) of 1.26 nM. The fluorescent sensor showed good repeatability, reproducibility and stability. Furthermore, N-CDs fluorescent sensor had a good applicability for Cr (VI) detection in real water samples with acceptable recoveries, and the detection results were consistent with the inductively coupled plasma mass spectrometry (ICP-MS) results, indicating this fluorescent sensor has a great potential for the environmental monitoring.

Highly sensitive and selective fluorescent sensor based on a multi-responsive ultrastable amino-functionalized Zn(II)-MOF for hazardous chemicals

A microscale amino-functionalized Zn(II)-MOF, namely [Zn(NH2-bdc)(4,4’-bpy)] (1) (NH2-H2bdc = 2-amino-1,4-benzenedicarboxylic acid and 4,4’-bpy = 4,4’-bipyridine), has been successfully synthesized, structurally characterized and further utilized as multi-responsive fluorescent sensor for highly sensitive and selective detection of Cr(VI) and 2,4,6-trinitrophenol (TNP). Compound 1 features non-porous 5-fold interpenetrated 3D framework with the Lewis basic sites including the uncoordinated amino and carboxylate groups on the framework for anchoring and recognizing the guest. 1 exhibits not only excellent water and thermal stability but also tolerance to acidic and basic media over an extensive pH range of 2–12. This ultrastable material can sensitively and selectively detect Cr2O72− and CrO42− in water based on the luminescent quenching with relatively low limits of detection (2.21 μM for CrO42− and 1.30 μM for Cr2O72−). Moreover, the unprecedented solvent-dependent luminescent response of 1 as a fluorescent probe for high-efficiency TNP detection was observed. Significantly, 1 not only displays high sensitive fluorescent enhancement upon TNP binding in ethanol but also exhibits fluorescent quenching toward TNP in water with very low limits of detection of 4.47 nM and 0.32 μM in ethanol and water, respectively. This work reports the first example of the utilization of MOF as a sensor for the detection of TNP based on dual responsive luminescence. Importantly, 1 can be simply and rapidly regenerated, displaying excellent recyclability after the sensing experiments.

Switchable fluorescence of MoS2 quantum dots: a multifunctional probe for sensing of chromium(VI), ascorbic acid, and alkaline phosphatase activity.

A simple strategy for modulating the fluorescence of MoS2 quantum dots (QDs) is described. The fluorescence of MoS2 QDs was firstly switched off by the addition of Cr(VI), and the quenched fluorescence was further switched on by introducing ascorbic acid (AA) into the mixture. The fluorescence quenching of MoS2 QDs by Cr(VI) was attributed to the fluorescence inner filter effect. After the addition of AA, Cr(VI) was reduced to Cr(III), and the fluorescence was restored. This finding has been applied for the fluorescent sensing of Cr(VI) in drinking water and AA in serum samples. In addition, the present method has been extended for turn-on sensing of an important biomarker alkaline phosphatase (ALP). There is a linear relationship between the fluorescence intensity and the concentrations of ALP in the range from 2.5 to 50U/L, and the limit of detection is 0.34U/L. The results showed MoS2 QDs hold great potential as a multifunctional fluorescent probe for the detection of metal ions, biological small molecules, and proteins. Graphical abstract The fluorescence of MoS2 QDs can be switched off by Cr(VI), and the quenched fluorescence can be further switched on by the addition of ascorbic acid or enzymatically generated ascorbic acid. This allows the selective detection of Cr(VI), ascorbic acid, and alkaline phosphatase based on the fluorescence of MoS2 QDs.

A highly sensitive and selective detection of Cr(VI) and ascorbic acid based on nitrogen-doped carbon dots

A highly sensitive and selective detection of hexavalent chromium (Cr(VI)) and ascorbic acid (AA) was proposed using nitrogen-doped carbon dots (N-CDs). In the absence of AA, the quantitative detection of Cr(VI) was realized through Cr(VI) acting as a quencher to quench the fluorescence of N-CDs by inner filter effect (IFE) and static quenching effect. Under the optimal conditions, the linear range for Cr(VI) detection was from 0.01 to 250μM with a detection limit of 5nM (S/N = 3). In the presence of AA, the fluorescence intensity could be rapidly enhanced compared with the fluorescence of N-CDs/Cr(VI) system since Cr(VI) can be reduced into trivalent chromium (Cr(III)) by AA. And a wide linear range for AA detection was obtained from 1 to 750μM. The detection limit was 0.3μM (S/N = 3). More importantly, this method can be successfully applied to the detection of Cr(VI) in real water samples, and AA in vitamins C tablets and human serum sample.