Sensor In Aqueous Solution Research Articles

PVC plasticized membranes modified with Fe3O4 nanoparticles for potentiometric sensing of sulfate

Potentiometric sensing is one of the most wide spread platforms for analysis of aqueous solutions. The development of potentiometric sensors for hydrophilic anions such as sulfate, phosphate and bicarbonate is a challenging problem, since their high hydration energy results in a low affinity for non-polar polymer membranes – a standard material for potentiometric sensor production.In this study we propose a new type of polymeric sensor membranes for ion-selective sensors with pronounced selectivity to hydrophilic anions. The membranes are based on inorganic Fe3O4 nanoparticles (NP) embedded into plasticized poly(vinyl chloride). Six different formulations of membranes with various combinations of Fe3O4 nanoparticles and other membrane-active components were synthesized and characterized with a wide range of physico-chemical methods. Contact angle measurements, FTIR spectra, SEM and AFM imaging, magnetization hysteresis curves, ZFC/FC studies were performed. The obtained results proved the formation of nanocomposites and demonstrated a structure with “cavities” in membranes with embedded nanoparticles. Potentiometric sensitivity and selectivity of the developed sensors in aqueous solutions of SO42−, HPO42−, HCO3−, H2PO4−, NO3− and Cl−anions were studied. The developed sensors showed high sensitivity to sulfate ion (-22 mV/dec in the concentration range from 10−5 to 10−3 M) and low sensitivity to the typical interfering anions – chloride and nitrate (-14 mV/dec). The optimized sensor membrane composition demonstrated sulfate selectivity higher than that of commercially available ion-selective sensor formulations. The novel sensors were tested for quantification of SO42− in real samples of natural mineral water and the obtained content of sulfate was in a good agreement with the reference data (relative error < 3 %)

A Simple Fluorescence Sensor Based on Merocyanine 540-MnO2 System to Detect Hypochlorite

Merocyanine 540 (MC540)- Manganese oxide (MnO2) system-based fluorescence sensor is reported as an anion sensor in aqueous solution. MnO2 was synthesized in the presence of Potassium permanganate (KMnO4) and Cetyltrimethylammonium bromide (CTAB) using 3-(N-morpholino) propane sulfonic acid (MOPS) buffer. The formation of MnO2 was first confirmed by a color change and characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Ultraviolet–Visible (UV–Vis). absorption spectroscopy techniques. Next, the interaction of MC540 with MnO2 in aqueous solution was investigated at various conditions by UV–Vis. absorption and fluorescence spectroscopy. The sensing ability of the MC540-MnO2 was tested to detect hypochlorite (ClO-) ion as a “Turn-off” fluorescent sensor. The MC540-MnO2 revealed to be high selectivity and sensitivity to detect hypochlorite (ClO-) ion without being affected by the other thirteen anions. The detection limits for ClO- were evaluated in two different concentration ranges and calculated to be 0.14 μM at 0.33-4.46 μM and 0.38 μM at 5.06-14.30 μM, respectively.

Synthesis of Yellow Fluorescence Carbon Dots for the Applications of Vitamin B12Detection and Cell Imaging.

In this work, bright yellow fluorescent and multifunctional carbon dots (N-CDs) were prepared by hydrothermal method from O-phenylenediamine and 4-aminobenzoic acid. The fluorescence characterization showed that the N-CDs possessed good optical properties (QY = 32%) and excitation dependent multi-color emission. By exciting with 390nm, the strong selective interaction of VB12 with N-CDs could result in a sharp decrease in the luminescence of N-CDs at 567nm. An efficient fluorescence sensor in aqueous solution was constructed which could linearly respond VB12 in wide concentration ranges of 0-90μM and 140-250μM. The linear correlation coefficients of N-CDs and VB12 were 0.9950 and 0.9968, respectively, and the detection limit was 0.119μM. N-CDs were performed for sensitive determination of VB12 in real samples. Moreover, the N-CDs were exploited to image cell.This N-CDs was a sensitive fluorescence probe to monitor VB12 and presented prospective potential in living cells imaging. Schematic diagram of the synthesis process and application research of N-CDs.

Fabrication of the CNTs/NiAl–LDH nanocomposite as a carrier of a luminescent sensor for DNA detection

Since the 21st century, nanocomposites based on layered double hydroxide (LDH) and carbon nanotubes (CNTs) are extensively employed as heat stabilizers, supercapacitors and electrocatalysts, due to their high conductivity, outstanding stability and environmental friendliness. Herein, CNTs/NiAl–LDH composite were obtained by one-step hydrothermal method and used as a platform for Ru(phen)3Cl2 (tris(1,10-phenanthroline)ruthenium (II) dichloride) sensor to selectively detect CT DNA (Calf thymus DNA). It was found that CNTs/NiAl–LDH composite could effectively quench the emission of the Ru(phen)3Cl2 sensor in aqueous solution. After adding a certain amount of CT DNA to the above system, the Ru(phen)3Cl2 interacted with CT DNA immediately and released from the CNTs/NiAl–LDH, resulting in the fluorescence recovery. In the concentration range of 4.4–26.3 μg/mL, the increase of luminescence was linearly proportional to the amount of CT DNA added, and the correlation coefficient was 0.9967. The detection limit was 6.09 × 10−8 g/mL.

Mimicking the light harvesting system for sensitive pattern recognition of monosaccharides

Boronate affinity-based indicator displacement assay is a promising approach to develop high performance saccharide sensors. However, it is difficult to improve the sensitivity of saccharide sensors in aqueous solutions due to the highly hydrophilic and hydromimetic nature of saccharides. Inspired by the fact that the natural photosynthesis system uses densely packed dyes with a high energy donor to acceptor ratio to improve the light harvesting efficiency, an enhanced FRET complex named 4Esculetin-BAAP was designed with four coumarin units as the energy donor and one porphyrin moiety as the acceptor. The desired sensor array 4EBSA was then readily constructed by simple dissolving complex 4Esculetin-BAAP in PBS solutions with three different pH values. With this light harvesting mimic strategy, sensor array 4EBSA was determined to be accurate and sensitive for pattern recognition of 7 kinds of monosaccharides in a wide concentration range in both PBS and even 10% serum. Moreover, 4EBSA was successfully applied for distinguishing glucose and its phosphorylated product in mixed form in serum samples with a sensitivity of 0.01 mM and visualized identification of unknown monosaccharide samples.

2-Nitroterephthalato-based uranyl coordination polymers: Selective luminescent sensing for vitamin B5 and Cr2O72–

Under solvothermal conditions, a series of new uranyl coordination polymers based on 2-nitroterephthalic acid (H2ntp) and additional auxiliary ligands were successfully synthesized, which can be denoted as (UO2)(ntp)(dm-phen) (1), (Hphen)2∙[(UO2)(ntp)1.5]2 (2), (Hphen)2∙[(UO2)2(ntp)3]∙(H2O)2 (3), and (Hphen)2∙[(UO2)2(ntp)2.5]2∙(H2O)2 (4) (dm-phen = 4,7-dimethyl-1,10-phenanthroline, phen = 4,7-phenanthroline). The characteristics of as-prepared compounds were revealed by single crystal and powder X-ray diffraction, thermogravimetry, infrared spectroscopy and luminescent measurement. Furthermore, Compound 2 presents excellent sensitivity and selectivity to sense vitamin B5 (VB5) and Cr2O72− anion as a dual-functional luminescent sensor in aqueous solution. 2 is the first turn-on luminescent sensor for detecting VB5 with a low detection limit (LOD) of 1.39 μM, and the experimental detection range was 10–90 μM. In addition, in the linear range of 50–450 μM, 2 also exhibits obvious luminescence quenching effect for Cr2O72− anion with the LOD value of 7.27 μM. This work possesses potential application in detecting VB5 in newborn calf serum and Cr2O72− in river water samples.

SARS-CoV-2 Surveillance in Indoor Air Using Electrochemical Sensor for Continuous Monitoring and Real-Time Alerts.

The severe acute respiratory syndrome related coronavirus 2 (SARS-CoV-2) has spread globally and there is still a lack of rapid detection techniques for SARS-CoV-2 surveillance in indoor air. In this work, two test rigs were developed that enable continuous air monitoring for the detection of SARS-CoV-2 by sample collection and testing. The collected samples from simulated SARS-CoV-2 contaminated air were analyzed using an ultra-fast COVID-19 diagnostic sensor (UFC-19). The test rigs utilized two air sampling methods: cyclone-based collection and internal impaction. The former achieved a limit of detection (LoD) of 0.004 cp/L in the air (which translates to 0.5 cp/mL when tested in aqueous solution), lower than the latter with a limit of 0.029 cp/L in the air. The LoD of 0.5 cp/mL using the UFC-19 sensor in aqueous solution is significantly lower than the best-in-class assays (100 cp/mL) and FDA EUA RT-PCR test (6250 cp/mL). In addition, the developed test rig provides an ultra-fast method to detect airborne SARS-CoV-2. The required time to test 250 L air is less than 5 min. While most of the time is consumed by the air collection process, the sensing is completed in less than 2 s using the UFC-19 sensor. This method is much faster than both the rapid antigen (<20 min) and RT-PCR test (<90 min).

Multisensory Systems Based on Perfluorosulfonic Acid Membranes Modified with Polyaniline and PEDOT for Multicomponent Analysis of Sulfacetamide Pharmaceuticals.

The degradation of sulfacetamide with the formation of sulfanilamide leads to a deterioration in the quality of pharmaceuticals. In this work, potentiometric sensors for the simultaneous determination of sulfanilamide, sulfacetamide and inorganic ions, and for assessing the degradation of pharmaceuticals were developed. A multisensory approach was used for this purpose. The sensor cross-sensitivity to related analytes was achieved using perfluorosulfonic acid membranes with poly(3,4-ethylenedioxythiophene) or polyaniline as dopants. The composite membranes were prepared by oxidative polymerization and characterized using FTIR and UV-Vis spectroscopy, and SEM. The influence of the preparation procedure and the dopant concentration on the membrane hydrophilicity, ion-exchange capacity, water uptake, and transport properties was investigated. The characteristics of the potentiometric sensors in aqueous solutions containing sulfanilamide, sulfacetamide and alkali metals ions in a wide pH range were established. The introduction of proton-acceptor groups and π-conjugated moieties into the perfluorosulfonic acid membranes increased the sensor sensitivity to organic analytes. The relative errors of sulfacetamide and sulfanilamide determination in the UV-degraded eye drops were 1.2 to 1.4 and 1.7 to 4%, respectively, at relative standard deviation of 6 to 9%.

The detection of selectivity and sensitivity towards TNP by a new Zn(II)-coordination polymer as luminescent sensor in aqueous solution

Nitroaromatic compounds (NACs) can lead to various environmental pollution healh problems. In order to effectively recognize and sense NACs, a novel coordination polymers (CPs) with fluorescent characteristic [Zn3(btc)2(tpt)(H2O)2]·4H2O (1) (tpt = tris(4-pyridyl)triazine, H3btc = 1,3,5-benzenetricarboxylic acid) has been triumphantly prepared as an fluorescence probe by solvothermal method. 1 possesses remarkable PH stability ranging from 2.0 to 12.0 and is also stable in different pure organic solvents. It should be noted that 1 manifests a fluorescence quenching response against the detection of selectivity and sensitivity towards 2,4,6-trinitrophenol (TNP) in aqueous solution. It also makes analysis on the limit of detection towards TNP, which is as low as 0.94 µM compared with most reported CPs sensors for TNP. Therefore, 1 can become a satisfactory sensor for TNP detection with remarkable selectivity, strong anti-interference and favorable recyclability. In addition, the quenching mechanisms were also discussed. It was supposed that the mechanisms of photoinduced electron transfer (PET) as well as resonance energy transfer (RET) might be the main influencing factors.

Влияние природы активных компонентов и модификаторов на электроаналитические свойства планарных цефалексин-селективных сенсоров

The 1st generation cefalexine-cephalosporine antibiotic is used in the treatment of various infectious diseases. Spectrophotometry, kinetic spectrophotometry, spectrofluorimetry are proposed to determination of cefalexine in medicine and biological environment. Planar screenprinted sensors allow analyzing the micro-volumes of samples, which is important for the analysis of biological objects without preliminary samplepreparation. Depending on the active material and modifiers, you can create planar sensors for the determination of different organic compounds. In this work we have studied the influence of the nature of electroactive compounds and modifiers on the electroanalytic properties of planar cefalexine-selective sensors. Associates of tetradecylammonium and dimethyldistearylammonium with complex compounds silver (1) – cefalexine (Ceas = 1–3%), polyaniline modifiers and cupric oxide nanoparticles have been used as active components, the ratio EAS: modifier is 1:1. The main electroanalytic and operational characteristics of cefalexine-selective sensors in aqueous solutions and on the background of oral fluid are determined. Advantage of tetradecylammonium in active components of cefalexine-selective sensors is shown. For cefalexine- sensors, the optimal is: linearity interval 1·10-2 – 1·10-4, response time 20–25 seconds, for unmodified: 10–15 sec, for modified in 1·10-2 M solutions of cefalexine, service life – 1 month. Modifiers approximate angular coefficients of electrode functions to theoretical values for single-charge ions, reduce response time and drift of potential, reduce the detection limit of cefalexine. Sensors are used for the determination of cephalexine in model aqueous solutions and oral fluid with added antibiotic additives, in expired cephalexine preparations.

Synthesis of a New Amino-Furopyridine-Based Compound as a Novel Fluorescent pH Sensor in Aqueous Solution.

Development of new fluorescent molecules, especially pH-sensitive fluorescent dyes, is always in high demand due to their wide applications in various fields and the limited number of common chromophores. In this work, a family of 3-amino-N-phenylfuro[2,3-b]pyridine-2-carboxamides (AFP) was synthesized as novel fluorescent compounds. Besides fluorescence in an organic solvent, AFP 1 and AFP 2 exhibit good fluorescence properties in both acidic and basic aqueous solution, which could be explained by protonation or different conformations formed in solution. Density functional theory (DFT) calculations on the highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO-LUMO) of various conformations were performed for further support.

Inducing proton tunnelling to increase the reactivity of boronic acids towards diols: A quantum biology study

Designing an efficient saccharide sensor in aqueous solution is an ongoing endeavour. Even though using hydrogen bonding groups on the sensor sounds like an efficient way for targeting the saccharides, it might lack accuracy due to the possibility of interaction with the solvent molecules. Boronic acid based sensors on the other hand, covalently and reversibly bind to saccharides with high sensitivity in aqueous medium. Many attempts are done to understand the mechanism of boronic acid’s reaction with diols. However, the binding affinity of fructose cannot be clearly identified in such attempts. This study employs a novel computational approach to increase both reactivity and selectivity of boronic acid towards diols. Using DFT, five different electronegative R-groups are simulated to calculate boronic acid’s reactivity towards diol by adding the tunnelling effect to the calculations, where higher electronegative R-groups reduce the proton donor-acceptor distance that induces proton tunnelling and increases the reaction rate.

Modified planar sensors for determination of some cephalosporin antibiotics in biological and medicinal media

Pluripotential cephalosporin antibiotics of different generations active against Gram-negative bacteria are used when treating urinary tract infections, mild and moderate pyelonephritis, acute otitis in children, etc. Rapid determination of cephalosporin antibiotics in the biological fluids is important to evaluate physiological and biochemical processes resulting from their metabolism in a human organism. Planar potentiometric sensors of different types — unmodified and modified with polyaniline (0.3 – 1%), NiZnFeO nanoparticles, and their binary mixes — are developed on the basis of associates of tetradecylammonium (TDA) with complex compounds silver (I) — β -lactam [Ag (I) – ( β -lac) 2 ] which are sensitive to some cephalosporin antibiotics, i.e., cefazoline (Cef), cefuroksime (Cefur) and ceftriaksone (Ceftr). In the sensors of type I, electrode-active components (EAC) and modifiers were added to carbon-containing ink, whereas in type II sensors the polyvinylchloride plasticized unmodified and modified membranes based on [Ag 2 (Ceftr) 2 ] 2 · 2TDA were used. Electroanalytic and operational characteristics of unmodified and modified planar sensors in aqueous solutions of cefazoline, cefuroxime, ceftriaxone and against the background of oral fluid were estimated. It is shown that introduction of the modifiers into sensor membranes leads to stabilization of their potential, increases angular coefficients of electrode functions, decreases the antibiotic detection limit to 1.7 Ч 10 –5 M, reduces the response time and potential drift. Nanoparticles of NiZnFeO appeared to be the most effective modifier. For the sensors of type II linearity of electrode functions is observed in the range of ceftriaxone concentrations of 3.1 Ч 10 –5 – 0.1 Ч 10 –1 M. Depending on the content of the electrode active components in the membrane phase of the unmodified planar sensors, the values of the angular coefficients of the electrode functions vary within 25 – 27 mV/p C and correspond to the values of the non-static value for doubly-charged ions. The linearity intervals of sensor electrode functions are identical at all EAC concentrations under study; as Ceas increases, potential drift and response time decreases. The developed planar sensors were used for determination of cephalosporin antibiotics in model aqueous solutions, medicinal preparations and oral fluid.

Potentiometric multisensory system based on perfluorosulfonic acid membranes and carbon nanotubes for sulfacetamide determination in pharmaceuticals

Abstract Hybrid materials based on perfluorinated sulfonic acid (PFSA) Nafion®-type membranes with homogeneous and with a gradient distribution of multiwalled carbon nanotubes (CNTs) along the sample were obtained. The studies of water uptake, ionic conductivity, and diffusion permeability of the materials were performed. Hybrid membranes were used to create potentiometric Donnan potential (DP) sensors. The influence of the CNTs concentration on the performance of the sensors in aqueous solutions containing sulfacetamide anions and alkali metal cations was studied. The dependences of the cross-sensitivity of DP sensors to anions and cations on the diffusion permeability of the hybrid membranes were established. A potentiometric multisensory system was developed for the simultaneous determination of sulfacetamide anions and potassium (or sodium) cations at concentrations range from 1.0·10−4 to 1.0·10−2 M and рН from 5 to 8. The advantages of the system are the following: the response time of the system is less than 1 min, the analysis does not require sample preparation, and the characteristics of the sensors persist for at least 1 year. An array of cross-sensitive DP-sensors based on PFSA Nafion®-type membranes, containing 1.0 and 1.5 wt% CNTs, was used to determine the active component in the drug “Sulfacyl sodium (Albucide)” (eye drops). The accuracy of the determination is 94–95%.

Construction of Ln3+-Substituted Arsenotungstates Modified by 2,5-Thiophenedicarboxylic Acid and Application in Selective Fluorescence Detection of Ba2+ in Aqueous Solution.

Developing organic-inorganic hybrid lanthanide(Ln)-functionalized polyoxometalates (POMs) has long been a main research topic. In this article, two novel hexameric Ln-containing arsenotungstates modified by 2,5-thiophenedicarboxylic acid (H2tpdc) [H2N(CH3)2]21Na13{Ln6W14O40(H2O)18(Htpdc)2}[B-α-AsW9O33]6·nH2O [Ln = Eu3+, n = 94 (1Eu); Ln = Gd3+, n = 114 (2Gd)] were successfully obtained, and the sulfur-heterocyclic carboxylic acid ligand was for the first time introduced to the POM system. Both polyoxoanion skeleton structures can be regarded as an aggregation of six trivacant Keggin [B-α-AsW9O33]9- entities linked by a S-shaped [Ln6W14O40(H2O)18(Htpdc)2]20- cluster. More surprisingly, two carboxyl O atoms in Htpdc- groups directly coordinate with two W atoms other than Ln atoms, which is rarely seen in tungsten-oxo clusters. Fluorescence properties of 1Eu in solid state and aqueous solution have been systematically investigated. Also, 1Eu as a fluorescence sensor in aqueous solution toward the detection of the Ba2+ ion has been explored. As expected, 1Eu may be a promising fluorescence probe for the Ba2+ detection in the absence of Ca2+ or Sr2+ ions in aqueous environment with high sensitivity, good selectivity, and low detection limit (1.19 × 10-3 mM). This work not only first introduces the S-heterocyclic carboxylic acid ligand into the POM system and enriches the types of organic ligands which can be used in POM chemistry but also broadens the POMs' application in fluorescence detection.

Surface plasmon resonance based biomimetic sensor for urinary tract infections

Tailor-made Escherichia coli (E. coli) receptors were created with microcontact imprinted technique and binding events of E. coli were carried out by a surface plasmon resonance (SPR) sensor in aqueous solution and in urine mimic in real time and label-free. N-methacryloyl-(l)-histidine methyl ester (MAH) was selected as a functional monomer to design tailor-made E. coli receptors on the polymeric film and during the formation of the polymeric film on a chip surface, Ag nanoparticles (AgNPs) were entrapped into the polymer mixture in order to lower the detection limit of biomimetic SPR based sensor. The polymeric film was characterized with atomic force microscopy (AFM), scanning electron microscopy (SEM), ellipsometer and contact angle measurements. Limit of detection (LOD) was found 0.57 CFU/mL and feasibility of the biomimetic sensor was investigated in urine mimic.

Modified solid-contact sensors for determination of cefuroxime and cefalexin in medicines and oral fluid

Cefuroxime, cefuroxime axetil and cefalexin are broad-spectrum pluripotential cephalosporin antibiotics. Their determination in various objects suggests using expensive spectroscopic, chromatographic, electrochemical equipment and organic solvents. Potentiometric sensors can provide rapid detection of cephalosporin antibiotics in a small sample volume without a preliminary sample preparation. The study is aimed at the developing of modified solid-contact potentiometric sensors for determination of cefuroxime and cefalexin in aqueous, biological media, and pharmaceuticals. The electroanalytical characteristics of unmodified and modified polyaniline and copper oxide nanoparticle sensors are evaluated. Tetradecylammonium(TDA) with a silver (I) – cefuroxime complex are used as the active membrane components, whereas polyaniline and copper oxide nanoparticles are used as modifiers. The main electroanalytic and operational characteristics of the studied sensors in aqueous solutions of antibiotics and against the background of oral fluid (LRP) are determined. The results of comparative evaluation of the electroanalytical properties of unmodified and modified solid-contact sensors in aqueous media of some â-lactam antibiotics and against the background of oral fluid are presented. The sensors based on Ag (Cefur)2TDA are characterized by a short response time: for modified polyaniline (PAN) and copper oxide nanoparticles within 5 – 10 sec, for unmodified — 10 – 20 sec. The linear range of the electrode functions for unmodified and modified sensors is 1 × 10–4 – 1 × 10–1 M, the detection limit is 7.4 × 10–5 M for unmodified and 6.3 × 10–5 M for modified sensors, respectively. The potential drift is 6 – 12 and 4 – 6 mV/day, service life is 1.5 and 2 months for unmodified and modified sensors, respectively. The modifiers stabilize the electrode potential, perform the function of the electron transfer mediator thus enhancing the electroanalytical characteristics of the sensors. The effect of the redox agents on the sensor properties is revealed: 1 × 10–3 – 1 × 10–4 MK 2Cr2O7 and FeCl3 solutions reduce the linearity intervals of the electrode functions, KI and Mohr’s salt do not affect the characteristics of the sensors in cefuroxime and cephalexin solutions. The coefficients of potentiometric selectivity of cefuroxime-selective sensors (modified with CuO nanoparticles) with respect to cefazolin, cefotaxime, and cefalexin are close to unity; Kijpot with respect to inorganic anions being part of the oral fluid (, Cl Br,I,HCO3 ,H PO 24 ,HPO4 2) are n × 10–2 – n × 10–3. This indicates the possibility of using sensors for detecting individual cephalosporin antibiotics or their total content in the presence of 100 – 1000 fold excesses of inorganic ions in medicinal and biological environments, small sample volumes, which is important when studying the pharmacokinetics of antibiotics and in determination of the maximum therapeutic dose when adjusting the treatment process.

Computational and spectroscopic investigations on boronic acid based fluorescent carbohydrate sensor in aqueous solution at physiological pH 7.5

In this study, the structural and photophysical properties of 2-ethoxy-4-fluoro phenyl boronic acid (BA1) fluorescent compound was analysed using experimental spectroscopy, single crystal X-ray diffraction techniques and theoretical calculations were implemented using DFT and TD-DFT methods. The complete vibrational assignments of wave numbers were made on the basis of potential energy distribution (PED). The calculated HOMO-LUMO energies shows charge transfer within the molecule and the transitions were predicted to be as п-п∗. Besides, frontier molecular orbitals (FMO), molecular electrostatic potential (MEP), UV–Vis absorption spectra and Non-linear optical properties were also studied using the same method and basis set. The BA1 compound has been tested for sugar sensing applications by absorption and emission spectroscopic analysis, to understand BA1 with sugars (D-glucose and D-fructose) complexes. The fluorescence measurements of BA1 at physiological pH 7.5, demonstrated a phenomenal quenching response to fructose and glucose molecules by having a decrease in fluorescence intensity with 3.5 fold and 1.3 fold for 0 M–0.5 M concentration of fructose and glucose, respectively, which shows strong sugar binding affinity. The association and dissociation constants were calculated by employing Stern-Volmer equation. The Job's plot and the mass spectroscopic analysis was carried to know the stoichiometry ratio of binding. The counterpoise correction method was implemented to calculate the complexation energy of the BA1-sugar complexes. The fluorescence life time of the molecule was measured in the presence and absence of sugars. The obtained lifetimes were in comparison with the theoretically calculated lifetimeusing PhotochemCAD. All these results showed that, BA1 can readily bind with sugars and could play an important role in carbohydrate sensing applications.

Graphene Nanobuds: A New Second-Generation Phosgene Sensor with Ultralow Detection Limit in Aqueous Solution.

Selective and sensitive detection of highly toxic chemicals by a suitable, fast, inexpensive, and trustworthy method is vital due to its serious health threats to humankind and breach of public security caused by unexpected terrorist attacks and industrial accidents. Phosgene or carbonyl dichloride is widely employed in many chemical industries and pharmaceuticals, and in pesticide production, which is extremely toxic by severe (short-term) inhalation exposure. Because of the non-existence of a phosgene sensor in aqueous solution and the immense emphasis gained by nanomaterials, especially carbonaceous materials, augmented attention has been given to the development of a fluorophore-functionalized carbon-based method to detect this noxious substance. In this study, surfactant free 1,8-diaminonaphthalene (DAN)-functionalized graphene quantum dots (DAN-GQDs) were prepared to detect phosgene in aqueous solution. The FESEM (field emission scanning electron microscopy) and HRTEM (high-resolution transmission electron microscopy) analyses confirm the as-prepared DAN-GQD morphology as nanobuds (NBs) with an average diameter of ca. 35-40 nm. The crystalline nature, elemental composition, and chemical state of DAN-GQDs were analyzed by standard physiochemical techniques. The edge-termination at the carboxyl functional group of GQDs with DAN was examined by XPS, Raman, FT-IR, and 1H NMR spectroscopy analyses. The aqueous solution of DAN-GQDs (4.89 × 10-9 M) exhibits a strong emission peak at 423 nm upon excitation at 328 nm. The addition of the phosgene molecule (0 → 88 μL) quenches the initial fluorescence intensity of DAN-GQDs (ΦF 53.6 → 34.6%) through the formation of a stable six-membered cyclized product. The DAN-GQDs displayed excellent selectivity and sensitivity for phosgene ( Ka = 3.84 × 102 M-1 and LoD (limit of detection) = 2.26 ppb) over other competing toxic pollutants in water. The time-resolved fluorescence analysis confirms that the quenching of DAN-GQDs follows nonradiative relaxation of excited electrons. Furthermore, bioimaging experiments of phosgene in living human breast cancer (HeLa) cells and cell viability test successfully demonstrated the practicability of DAN-GQDs.

Analysis of the Outputs and Corrosion Rates of ACM Sensors in Aqueous Solutions with Different Salt Concentrations

ぬれ環境下における腐食速度検討のため，各種濃度のNaCl水溶液中にFe/Ag対ACM（Atmospheric Corrosion Monitoring）センサを浸漬して出力電流測定およびFe-Ag間電位差測定を行った．また，RCM（Resistmetry Corrosion Monitor）センサによって実腐食量を求め，ACMセンサの出力と比較した．その結果，実腐食量とACMセンサ出力には明らかな相関が認められ，ACMセンサの出力電流に比べてFe-Ag間電位差の方が優れていることがわかった．従って，雨が直接かからない環境下では従来の出力電流値を用い，ぬれ環境下ではFe-Ag間電位差を用いることで精度の高い腐食速度推定が可能と考えられる．また，この方法はACMセンサの長寿命化にも寄与できると考えられる．