Carbon-Supported Nanocomposite Synthesis, Characterization, and Application as an Efficient Adsorbent for Ciprofloxacin and Amoxicillin.

The existence of antibiotics in the environment has recently raised serious concerns about their possible hazards to human health and the water ecosystem. In the current study, an activated carbon-supported nanocomposite, AC-CoFe2O3, was synthesized by a coprecipitation method, characterized, and then applied to adsorb different drugs from water. The synthesized composites were characterized by using energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller plots, and scanning electron microscopy. The adsorption of both Ciprofloxacin (Cipro) and Amoxicillin (Amoxi) antibiotics on the composite followed the pseudo-second-order kinetic model (R2 = 0.9981 and 0.9974 mg g-1 min-1, respectively). Langmuir isotherm was the best-fit model showing 312.17 and 217.76 mg g-1 adsorption capacities for Ciprofloxacin and Amoxicillin, respectively, at 333 K. The negative Gibbs free energy (ΔG°) specified the spontaneity of the method. The positive change in the enthalpy (ΔH) indicated that the adsorption process was assisted by higher temperatures. The different optimized parameters were pH, contact time, adsorbent weight, concentration, and temperature. The maximum adsorption of Cipro was found to be 98.41% at pH 12, while for Amoxi, it was 89.09% at pH 2 at 333 K. The drugs were then successfully determined from natural water samples at optimized conditions using these nanocomposites.

Synthesis and Computational Study of an Optical Fluorescent Sensor for Selective Detection of Ni2+ Ions.

The presence of an abnormal amount of Ni2+ in the human body causes various health issues. Therefore, this work aimed to synthesize the curcumin-based fluorescence-on sensor P [2,6-bis((E)-4-chlorobenzylidene)-cyclohexan-1-one] that was capable of selectively responding to Ni2+ ions in aqueous solution. The structure of P was confirmed by 1H NMR and Fourier transform infrared (FTIR) spectroscopy. The Ni2+ ion sensing was based on the fluorescence enhancement of the fluorophore (P) in neutral aqueous medium. The response of the P-based sensor was highly selective toward Ni2+ ions, whereas the possible interferences from other metal cations were negligible. P had a fast response; it was selective and had a sensitive detection limit (LOD = 2 × 10-10 M) toward Ni2+ ions in neutral medium with a high association constant (K) value of 3.6 × 105 M-2 for the complex formation between the P and Ni2+ ions. Job's plot and DFT calculations proved that the binding stoichiometry of P for Ni2+ was 2:1. P was recovered using EDTA as a chelating agent after being employed as a fluorescent sensor. These characteristics ensured the potential use of P as a new class of chemosensor for environmental applications.

Rapid Detection of Cd2+ Ions in the Aqueous Medium Using a Highly Sensitive and Selective Turn-On Fluorescent Chemosensor.

Herein, a novel optical chemosensor, (CM1 = 2, 6-di((E)-benzylidene)-4-methylcyclohexan-1-one), was designed/synthesized and characterized by 1H-NMR and FT-IR spectroscopy. The experimental observations indicated that CM1 is an efficient and selective chemosensor towards Cd2+, even in the presence of other metal ions, such as Mn2+, Cu2+, Co2+, Ce3+, K+, Hg2+,, and Zn2+ in the aqueous medium. The newly synthesized chemosensor, CM1, showed a significant change in the fluorescence emission spectrum upon coordination with Cd2+. The formation of the Cd2+ complex with CM1 was confirmed from the fluorometric response. The 1:2 combination of Cd2+ with CM1 was found optimum for the desired optical properties, which was confirmed through fluorescent titration, Job's plot, and DFT calculation. Moreover, CM1 showed high sensitivity towards Cd2+ with a very low detection limit (19.25 nM). Additionally, the CM1 was recovered and recycled by the addition of EDTA solution that combines with Cd2+ ion and, hence, frees up the chemosensor.

Synthesis and Characterization of MIPs for Selective Removal of Textile Dye Acid Black-234 from Wastewater Sample.

Herein, a molecularly imprinted polymer (MIP) was prepared using bulk polymerization and applied to wastewater to aid the adsorption of targeted template molecules using ethylene glycol dimethacrylate (EGDMA), methacrylic acid (MAA), acid black-234 (AB-234), 2,2'-azobisisobutyronitrile (AIBN), and methanol as a cross linker, functional monomer, template, initiator, and porogenic solvent, respectively. For a non-molecularly imprinted polymer (NIP), the same procedure was followed but without adding a template. Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and a surface area analyzer were used to determine the surface functional groups, morphology and specific surface area of the MIP and NIP. At pH 5, the AB-234 adsorption capability of the MIP was higher (94%) than the NIP (31%). The adsorption isotherm data of the MIP correlated very well with the Langmuir adsorption model with Qm 82, 83 and 100 mg/g at 283 K, 298 K, and 313 K, respectively. The adsorption process followed pseudo-second-order kinetics. The imprinted factor (IF) and Kd value of the MIP were 5.13 and 0.53, respectively. Thermodynamic studies show that AB-234 dye adsorption on the MIP and NIP was spontaneous and endothermic. The MIP proved to be the best selective adsorbent for AB-234, even in the presence of dyes with similar and different structures than the NIP.

Selective Removal of the Emerging Dye Basic Blue 3 via Molecularly Imprinting Technique.

A molecularly imprinting polymer (MIP) was synthesized for Basic Blue 3 dye and applied to wastewater for the adsorption of a target template. The MIPs were synthesized by bulk polymerization using methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA). Basic Blue 3 dye (BB-3), 2,2'-azobisisobutyronitrile (AIBN) and methanol were used as a functional monomer, cross linker, template, initiator and porogenic solvent, respectively, while non-imprinting polymers (NIP) were synthesized by the same procedure but without template molecules. The contact time was 25 min for the adsorption of BB-3 dye from 10 mL of spiked solution using 25 mg polymer. The adsorption of dye (BB-3) on the MIP followed the pseudo-second order kinetic (k2 = 0.0079 mg·g-1·min-1), and it was according to the Langmuir isotherm, with maximum adsorption capacities of 78.13, 85.4 and 99.0 mg·g-1 of the MIP at 283 K, 298 K and 313 K, respectively and 7 mg·g-1 for the NIP. The negative values of ΔG° indicate that the removal of dye by the molecularly imprinting polymer and non-imprinting polymer is spontaneous, and the positive values of ΔH° and ΔS° indicate that the process is endothermic and occurred with the increase of randomness. The selectivity of the MIP for BB-3 dye was investigated in the presence of structurally similar as well as different dyes, but the MIP showed higher selectivity than the NIP. The imprinted polymer showed 96% rebinding capacity at 313 K towards the template, and the calculated imprinted factor and Kd value were 10.73 and 2.62, respectively. In this work, the MIP showed a greater potential of selectivity for the template from wastewater relative to the closely similar compounds.

2,6-bis(E)-4-methylbenzylidine)-cyclohexan-1-one as a Fluorescent-on Sensor for Ultra Selective Detection of Chromium Ion in Aqueous Media.

The ligand 2,6-bis(E)-4-methylbenzylidine)-cyclohexan-1-one sensor has been synthesized as a fluorescence-on sensor/probe for the trace level detection of chromium III ion. The synthesized ligand was characterized by FTIR, 1H-NMR spectroscopy, and fluorimetery. The sensor exhibited an ultra-selective response to chromium among the tested heavy metal ions. Different parameters were optimized like pH, effect of concentration of sensor C, metal ion and contact time. The binding stoichiometry of C:Cr3+ was calculated to be 2:1 (Job's plot) with a significantly low detection limit of 2.3 × 10- 9 M. Sensor C were practically employed for detection of chromium in spiked water samples.

Particle packed mixed-mode chromatographic stationary phase for the separation of peptide in liquid chromatography.

A particle-based stationary phase has been prepared for the separation of five synthetic peptides and a mixture containing tryptic digest of cytochrome C in liquid chromatography. Particles originating from silica monolith were differentially sedimented to obtain 1-2 µm particles. A stationary phase was achieved by the coating of poly(styrene-methacrylic acid-N-phenylacrylamide) copolymer onto the particles via reversible addition-fragmentation chain transfer polymerization reaction. Stainless steel column (30 cm long and 1 mm internal diameter) was packed with stationary phase. Very high separation efficiency (ca. 351 000 plates/m) was achieved for five commercial peptides with a percent relative standard deviation of less than 1%. Protocol for the synthesis and modification of silica monolith particles has been well optimized with a good reproducibility both in particle and pore size. The column resolved about 21 peptide components from a mixture containing tryptic digest of cytochrome C, under the elution conditions of acetonitrile/15 mM ammonium format (65/35 v/v%) with a flow rate of 28 µL/min.

Synthesis and Evaluation of a Schiff-Based Fluorescent Chemosensors for the Selective and Sensitive Detection of Cu2+ in Aqueous Media with Fluorescence Off-On Responses.

Copper being an essential nutrient; also pose a risk for human health in excessive amount. A simple and convenient method for the detection of trace amount of copper was employed using an optical probe R1 based on Schiff base. The probe was synthesized by Schiff base condensation of benzyl amine and 2-hydroxy-1-napthaldehyde and characterized by single X-ray diffraction, 1H NMR and FTIR. By screening its fluorescence response in a mixture of DMSO and H2O (20:80, v/v) R1 displayed a pronounced enhancement in fluorescence only upon treatment with copper. Other examined metal ions such as alkali, alkaline and transition had no influence. Within a wide pH range 5-12 R1 could selectively detect copper by interrupting ICT mechanism that results in CHEF. From Job's plot analysis a 2:1 binding stoichiometry was revealed. The fluorescence response was linear in the range 1-10 × 10-9 M with detection limit 30 × 10-9 M. Association constant was determined as 1 × 1011 M-2 by Benesi-Hilderbrand plot. As a fast responsive probe it possesses good reproducibility and was employed for detection of copper in different water samples.