Synthesis and characterization of a nanostructure conductive copolymer based on polyaniline and polylactic acid as an effective substrate in proteins impedimetric biosensing

Despite of all the developments in DNA microarray technology, there is not sufficient knowledge about protein abundance or their function in processes such as proteolysis, phosphorylation. Therefore, there is a significant need for direct detection and quantification of proteins, especially in processes such as proteomics, drug design and disease prediction. The present work introduce the new generation of polymeric substrate based on polyaniline and, polylactic acid, which it was used for impedimetric sensor in detection of proteins in particular for bovine serum albumin (BSA). In this copolymerization, the polylactic acid-block-polyaniline copolymer (PLA-b-PANI) was synthesized to attach polylactic acid and polyaniline using epichlorohydrin as a coupling agent. The structure of synthesized compounds in all steps, were confirmed by FT-IR and, 1H-NMR. The thermal properties and, morphology were analyzed by DSC, TGA, and, SEM. Also the electrochemical characteristics of fabricated PLA-b-PANI electrode were investigated by Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV). The results demonstrated that morphology of the PLA-b-PANI is sphere shape nanoparticles with dimension less than 100 nanometer diameters and, reasonable thermal properties. PLA-b-PANI was used to modify a screen-printed carbon electrode (SPCE) to fabricate a BSA impedimetric sensor. In order to increase the performance of the proposed impedimetric sensor, optimization of incubation time, pH and amount of PLA-b-PANI were investigated. The results show that the impedimetric sensor has the highest response when the electrode surface is covered with 5 microliters of PLA-b-PANI, and is incubated in BSA solution with pH 6.5 for 5 min. Impedimetric results showed that the PLA-b-PANI has excellent properties in reducing the charge transfer resistance and increasing the electron charge transfer rate. The final impedimetric sensor exhibited good repeatability, reproducibility, and chemical stability within the linear concentration range of 0.1-20 μg L-1 of BSA, and a detection limit of 0.05 μg L-1.

Physicochemical Properties and Atomic-Scale Interactions in Polyaniline (Emeraldine Base)/Starch Bio-Based Composites: Experimental and Computational Investigations

The processability of conductive polymers still represents a challenge. The use of potato starch as a steric stabilizer for the preparation of stable dispersions of polyaniline (emeraldine base, EB) is described in this paper. Biocomposites are obtained by oxidative polymerization of aniline in aqueous solutions containing different ratios of aniline and starch (% w/w). PANI-EB/Starch biocomposites are subjected to structural analysis (UV-Visible, RAMAN, ATR, XRD), thermal analysis (TGA, DSC), morphological analysis (SEM, Laser Granulometry), and electrochemical analysis using cyclic voltammetry. The samples were also tested for their solubility using various organic solvents. The results showed that, with respect to starch particles, PANI/starch biocomposites exhibit an overall decrease in particles size, which improves both their aqueous dispersion and solubility in organic solvents. Although X-ray diffraction and DSC analyses indicated a loss of crystallinity in biocomposites, the cyclic voltammetry tests revealed that all PANI-EB/Starch biocomposites possess improved redox exchange properties. Finally, the weak interactions at the atomic-level interactions between amylopectin–aniline and amylopectin–PANI were disclosed by the computational studies using DFT, COSMO-RS, and AIM methods.

Polypyrrole-based adsorbents for Cr(VI) ions remediation from aqueous solution: a review

Anthropogenic activities are principally responsible for the manifestation of toxic and carcinogenic hexavalent chromium (Cr(VI)) triggering water pollution that threatens the environment and human health. The World Health Organisation (WHO) restricts Cr(VI) ion concentration to 0.1 and 0.05 mg/L in inland surface water and drinking water, respectively. The available technologies for Cr(VI) ion removal from water were highlighted with an emphasis on the adsorption technology. Furthermore, the characteristics of several polypyrrole-based adsorbents were scrutinized including amino-containing compounds, biosorbents, graphene/graphene oxide, clay materials and many other additives with reported effective Cr(VI) ion uptake. This efficiency in Cr(VI) ions adsorption is attributed to enhanced redox properties, increased number of functional groups as well as the synergistic behaviour of the materials making up the composites. The Langmuir isotherm best described the adsorption processes with maximum adsorption capacities ranging from 3.40-961.50 mg/g. The regeneration of Cr(VI) ion-laden adsorbents was studied. Ion exchange, electrostatic attractions, complexation, chelation reactions with protonated sites and reduction were the mechanisms of adsorption. Nevertheless, there are limited details on comprehensive adsorbent regeneration studies to prolong robustness in adsorption-desorption cycles and utilization of the Cr(VI) ion-laden adsorbent in other areas of research to limit the threat of secondary pollution.

Application of polypyrrole-based adsorbents in the removal of fluoride: a review

When fluoride levels in water exceed permitted limits (>1.5 mg L−1), water pollution becomes a major concern to humans.

Biodegradable polymers and their nano-composites for the removal of endocrine-disrupting chemicals (EDCs) from wastewater: A review

Endocrine-disrupting chemicals (EDCs) target the endocrine system by interfering with the natural hormones in the body leading to adverse effects on human and animal health. These chemicals have been identified as major polluting agents in wastewater effluents. Pharmaceuticals, personal care products, industrial compounds, pesticides, dyes, and heavy metals are examples of substances that could be considered endocrine active chemicals. In humans, these chemicals could cause obesity, cancer, Alzheimer's disease, autism, reproductive abnormalities, and thyroid problems. While in wildlife, dysfunctional gene expression could lead to the feminization of some aquatic organisms, metabolic diseases, cardiovascular risk, and problems in the reproductive system as well as its levels of hatchability and vitellogenin. EDCs could be effectively removed from wastewater using advanced technologies such as reverse osmosis, membrane treatment, ozonation, advanced oxidation, filtration, and biodegradation. However, adsorption has been proposed as a more promising and sustainable method for water treatment than any other reported technique. Increased attention has been paid to biodegradable polymers and their nano-composites as promising adsorbents for the removal of EDCs from wastewater. These polymers could be either natural, synthetic, or a combination of both. This review presents a summary of the most relevant cases where natural and synthetic biodegradable polymers have been used for the successful removal of EDCs from wastewater. It demonstrates the effectiveness of these polymers as favorable adsorbents for novel wastewater treatment technologies. Hitherto, very limited work has been published on the use of both natural and synthetic biodegradable polymers to remove EDCs from wastewater, as most of the studies focused on the utilization of only one type, either natural or synthetic. Therefore, this review could pave the way for future exploration of biodegradable polymers as promising and sustainable adsorbents for the removal of various types of pollutants from wastewater.

Synthesis of Magnetic Short-Channel Mesoporous Silica SBA-15 Modified with a Polypyrrole/Polyaniline Copolymer for the Removal of Mercury Ions from Aqueous Solution

A novel magnetic short-channel mesoporous silica SBA-15 composite adsorbent was prepared by the copolymerization of pyrrole and aniline. The prepared novel nanoadsorbent polypyrrole-polyaniline/CoFe2O4-SBA-15 (PPy-PANI/M-SBA-15) has a significant adsorption effect on heavy metal mercury ions. The batch adsorption experiment was carried out to study the effects of various parameters including solution pH, initial concentration (C 0), adsorbent dose (dosage), temperature (T), and contact time on the adsorption effect. The analysis results of the response surface method (RSM) and central composite design (CCD) show that the importance for adsorption factors is pH > C 0 > T > dosage, and the maximum capacity of PPy-PANI/M-SBA-15 is 346.2 mg/g under the optimal conditions of pH = 6.7, T = 310 K, C 0 = 29.5 mg/L, and a dosage of 0.044 g/L. The pseudo-second-order kinetic model and the Langmuir isotherm model simulate the adsorption behavior of mercury ions. In addition, thermodynamic parameters indicate self-heating and reversible adsorption processes. A covalent bond is formed between the nitrogen-containing functional group and the mercury ions. Excellent magnetic properties and high reproducibility indicate that PPy-PANI/M-SBA-15 has excellent recyclability and environmentally friendly properties and can become a potential heavy metal ion adsorbent in practical applications.

Removal of heavy metals and radionuclides from water using nanomaterials: current scenario and future prospects

There is an increase in concern about the hazardous effects of radioactivity due to the presence of undesirable radioactive substances in our vicinity. Nuclear accidents such as Chernobyl (1986) and Fukushima (2011) have further raised concerns towards such incidents which have led to contamination of water bodies. Conventional methods of water purification are less efficient in decontamination of radioisotopes. They are usually neither cost-effective nor environmentally friendly. However, nanotechnology can play a vital role in providing practical solutions to this problem. Nano-engineered materials like metal oxides, metallic organic frameworks, and nanoparticle-impregnated membranes have proven to be highly efficient in treating contaminated water. Their unique characteristics such as high adsorption capacity, large specific surface area, high tensile strength, and excellent biocompatibility properties make them useful in the field of water purification. This review explores the present status and future prospects of nanomaterials as the next-generation water purification systems that can play an important role in the removal of heavy metals and radioactive contaminants from aqueous solutions.

Cyclic Sequential Removal of Alizarin Red S Dye and Cr(VI) Ions Using Wool as a Low-Cost Adsorbent

Alizarin red S (ARS) removal from wastewater using sheep wool as adsorbent was investigated. The influence of contact time, pH, adsorbent dosage, initial ARS concentration and temperature was studied. Optimum values were: pH = 2.0, contact time = 90 min, adsorbent dosage = 8.0 g/L. Removal of ARS under these conditions was 93.2%. Adsorption data at 25.0 °C and 90 min contact time were fitted to the Freundlich and Langmuir isotherms. R2 values were 0.9943 and 0.9662, respectively. Raising the temperature to 50.0 °C had no effect on ARS removal. Free wool and wool loaded with ARS were characterized by Fourier Transform Infrared Spectroscopy (FTIR). ARS loaded wool was used as adsorbent for removal of Cr(VI) from industrial wastewater. ARS adsorbed on wool underwent oxidation, accompanied by a simultaneous reduction of Cr(VI) to Cr(III). The results hold promise for wool as adsorbent of organic pollutants from wastewater, in addition to substantial self-regeneration through reduction of toxic Cr(VI) to Cr(III). Sequential batch reactor studies involving three cycles showed no significant decline in removal efficiencies of both chromium and ARS.

Functional rGO aerogel as a potential adsorbent for removing hazardous hexavalent chromium: adsorption performance and mechanism

A novel functional rGO aerogel was synthesized by a facile hydrothermal method. In this process, graphene oxide (GO) was used as the precursor and oxidant to synthesize the aerogels. Ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) and pyrrole monomer (reducing agent) were selected to use as hole scavenger and nitrogen sources. The obtained EDTA-2Na/polypyrrole (Ppy)/rGO aerogel (EPGA) has a high adsorption capacity for Cr(VI) anions, and the maximum adsorption capacity reached 361 mg/g at 298 K at pH of 2. In addition, EPGA exhibited a good ability to selectively remove Cr(VI) anions under the effect of coexisting ions (Cl^-, NO₃^-, SO₄^2-, PO₄^3-, Ni⁺, Cu²⁺, Zn²⁺, and Cd²⁺) and good regeneration ability. The kinetics process and adsorption isotherm can be fitted well with the pseudo-second-order kinetic model and Freundlich isotherm model, respectively. The removal mechanism involved electrostatic interaction, reduction, ion exchange, and chelation process. This work provides a simple and environmentally friendly synthetic route for EPGA, which will be a potential candidate for efficient removal Cr(VI) anions from industrial wastewater.

Comparative Study of the Adsorption of Acid Blue 40 on Polyaniline, Magnetic Oxide and Their Composites: Synthesis, Characterization and Application

Conducting polymers (CPs), especially polyaniline (PANI) based hybrid materials have emerged as very interesting materials for the adsorption of heavy metals and dyes from an aqueous environment due to their electrical transport properties, fascinating doping/de-doping chemistry and porous surface texture. Acid Blue 40 (AB40) is one of the common dyes present in the industrial effluents. We have performed a comparative study on the removal of AB40 from water through the application of PANI, magnetic oxide (Fe₃O₄) and their composites. Prior to this study, PANI and its composites with magnetic oxide were synthesized through our previously reported chemical oxidative synthesis route. The adsorption of AB40 on the synthesized materials was investigated with UV-Vis spectroscopy and resulting data were analyzed by fitting into Tempkin, Freundlich, Dubinin-Radushkevich (D-R) and Langmuir isotherm models. The Freundlich isotherm model fits more closely to the adsorptions data with R² values of 0.933, 0.971 and 0.941 for Fe₃O₄, PANI and composites, respectively. The maximum adsorption capacity of Fe₃O₄, PANI and composites was, respectively, 130.5, 264.9 and 216.9 mg g^-1. Comparatively good adsorption capability of PANI in the present case is attributed to electrostatic interactions and a greater number of H-bonding. Effect of pH of solution, temperature, initial concentration of AB40, contact time, ionic strength and dose of adsorbent were also investigated. Adsorption followed pseudo-second-order kinetics. The activation energy of adsorption of AB40 on Fe₃O₄, PANI and composites were 30.12, 22.09 and 26.13 kJmol^-1 respectively. Enthalpy change, entropy change and Gibbs free energy changes are -6.077, -0.026 and -11.93 kJ mol^-1 for adsorption of AB40 on Fe₃O₄. These values are -8.993, -0.032 and -19.87 kJ mol^-1 for PANI and -10.62, -0.054 and -19.75 kJ mol^-1 for adsorption of AB40 on PANI/Fe₃O₄ composites. The negative sign of entropy, enthalpy and Gibbs free energy changes indicate spontaneous and exothermic nature of adsorption.

Graphene oxide-based materials for efficient removal of heavy metal ions from aqueous solution: A review

Graphene with atomic layer of sp²-hybridized carbon atoms in a hexagonal structure has attracted multidisciplinary attention since its discovery. Due to the inherent advantages of large specific surface area and abundant functional groups, its derivative graphene oxide (GO) nanomaterials have achieved large-scale development in effective pollution treatment. In the past few years, novel GO-based nanomaterials through coupling with other nanomaterials have been synthesized with significant process and applied for efficient elimination of different kinds of pollutants. This paper aims to summarize recent research results on the excellent removal ability of GO-based nanomaterials for various heavy metal ions in aqueous solutions. The synthesis, adsorption process characteristics and interaction mechanism of the adsorbent are emphasized and discussed. The effects of various environmental conditions are outlined. At last, a brief summary, perspective and outlook are presented. This review is intended to provide some thrilling information for the design and manufacture of GO-based nanomaterials for the elimination of heavy metal ions from wastewater in environmental pollution management.

Parametric Analysis of Electrical Conductivity of Polymer-Composites

The problem associated with mixtures of fillers and polymers is that they result in mechanical degradation of the material (polymer) as the filler content increases. This problem will increase the weight of the material and manufacturing cost. For this reason, experimentation on the electrical conductivities of the polymer-composites (PCs) is not enough to research their electrical properties; models have to be adopted to solve the encountered challenges. Hitherto, several models by previous researchers have been developed and proposed, with each utilizing different design parameters. It is imperative to carry out analysis on these models so that the suitable one is identified. This paper indeed carried out a comprehensive parametric analysis on the existing electrical conductivity models for polymer composites. The analysis involves identification of the parameters that best predict the electrical conductivity of polymer composites for energy storage, viz: (batteries and capacitor), sensors, electronic device components, fuel cell electrodes, automotive, medical instrumentation, cathode scanners, solar cell, and military surveillance gadgets applications. The analysis showed that the existing models lack sufficient parametric ability to determine accurately the electrical conductivity of polymer-composites.

Adsorption mechanism of Cr(VI) onto GO/PAMAMs composites

Graphene oxide/polyamidoamine dendrimers (GO/PAMAMs) composites were used to remove Cr(VI) from simulated effluents, the adsorption kinetics and thermodynamics of Cr(VI) onto GO/PAMAMs were systematically investigated. The results showed that the optimum pH value was 2.5, the removal percentage reached 90.7% for 30 mg/L of Cr(VI) within 120 min. The adsorption process was well described by pseudo-second-order kinetic model. The maximum adsorption capacities of Cr(VI) onto GO/PAMAMs were found to be 131.58, 183.82 and 211.42 mg/g at 293.15, 303.15 and 313.15 K, respectively, which were calculated from the Langmuir model equation. The adsorption thermodynamic parameters indicate that the adsorption of Cr(VI) onto GO/PAMAMs is a spontaneous endothermic process. The XPS analysis reveals the adsorption and removal mechanism of Cr(VI) on GO/PAMAMs that first the Cr(VI) binds to the protonated amine of GO/PAMAMs, then Cr(VI) be reduced to Cr(III) with the assistance of π-electrons on the carbocyclic six-membered ring of GO in GO/PAMAMs, and then Cr(III) was released into solution under the electrostatic repulsion between the Cr(III) and the protonated amine groups.

The development of a ternary nanocomposite for the removal of Cr(vi) ions from aqueous solutions

The aim of this study is to develop a ternary nanocomposite (NC) of polyaniline (PANI)/2-acrylamido-2-methylpropanesulfonic acid (AMPSA)-capped silver nanoparticles (NPs)/graphene oxide quantum dots (PANI/Ag (AMPSA)/GO QDs) as an efficient adsorbent for the removal of the highly toxic hexavalent chromium (Cr(vi)) from polluted water. PANI/Ag (AMPSA)/GO QDs NC was synthesized via in situ oxidative polymerization. The effects of pH, adsorbent dose, initial concentration, temperature, contact time, ionic strength and co-existing ions on the removal of Cr(vi) by PANI/Ag (AMPSA)/GO QDs were investigated. The PANI/Ag (AMPSA)/GO QDs NC (25.0 mg) removed 99.9% of Cr(vi) from an aqueous solution containing 60 mg L⁻¹ Cr(vi) ions at pH 2. Energy dispersive X-ray (EDX) and inductively coupled plasma spectrometry (ICP) studies confirmed the adsorption of Cr(vi) and that some of the adsorbed Cr(vi) was reduced to Cr(iii). Cr(vi) removal by the PANI/Ag (AMPSA)/GO QDs NC followed the pseudo-second order kinetic model, and the removal was highly selective for Cr(vi) in the presence of other co-existing ions. In summary, the PANI/Ag (AMPSA)/GO QDs NC has potential as a novel adsorbent for Cr(vi).

The aim is to develop a ternary nanocomposite of polyaniline/2-acrylamido-2-methylpropanesulfonic acid-capped silver nanoparticles/graphene oxide quantum dots as an efficient adsorbent for the removal of the highly toxic hexavalent chromium (Cr(vi)) from polluted water.

Dynamic filtration and static adsorption of lead ions in aqueous solution by use of blended polysulfone membranes with nano size MCM-41 particles coated by polyaniline

MCM-41 mesopore was prepared by hydrothermal method and used for synthesis of polyaniline/MCM-41 nanocomposite via in situ polymerization. The nanocomposite was blended with polysulfone to prepare mixed matrix membrane in different content of nanocomposite by phase inversion method. Structural and surface properties of the samples were characterized by SEM, XRD, FTIR, AFM, TGA, BET, and zeta potential measurements. Effect of the nanocomposite content on the hydrophilicity, porosity, and permeability of the membrane was determined. Membrane performance was evaluated for removal of lead ions in dynamic filtration and static adsorption. The membranes were found as effective adsorptive filters for removal of lead ions via interactions between active sites of nanocomposite in membrane structure and lead ions during filtration. Results of batch experiments proved adsorptive mechanism of membranes for removal of lead ions with the maximum adsorption capacity of 19.6 mg/g.

Nanoadsorbents based on conducting polymer nanocomposites with main focus on polyaniline and its derivatives for removal of heavy metal ions/dyes: A review

Water contamination by toxic heavy metal ions and dyes remains a serious public health problem for humans, so attention on specific methods and technologies to remove heavy metal ions and dyes from wastewaters/aqueous solutions are desired. Numerous adsorbents have been reported for the removal of heavy metal ions/dyes from wastewaters/aqueous solutions. Polyaniline (PANI) and its derivatives, as conducting polymers, are good adsorbents to remove various kinds of heavy metal ions and dyes from wastewaters/aqueous solutions. The nanoadsorbents based on PANI and its derivatives have received much consideration, and are extensively reported in literature. This review focuses on the PANI and its derivatives based on nanoadsorbents for water purification. Various types of these nanoadsorbents used for the removal of heavy metal ions/dyes from wastewaters/aqueous solutions are also briefly compared in this review.

Efficient removal of anti-inflammatory phenylbutazone from an aqueous solution employing a composite material based on poly(aniline-co-pyrrole)/multi-walled carbon nanotubes

Poly(Ani-co-Py)/MWCNT was synthesized by chemical oxidation in a triple-phase interface system and presented a high capacity for the removal of PBZ from wastewater.

Polymer-based nanocomposites for heavy metal ions removal from aqueous solution: a review

A review of versatile polymer-based composites containing different functional organic and/or inorganic counterparts for the removal of hazardous metal ions from wastewater solutions.

Selective removal of toxic Cr(VI) from aqueous solution by adsorption combined with reduction at a magnetic nanocomposite surface

The adsorption of toxic hexavalent chromium (Cr(VI)) and its reduction to trivalent chromium (Cr(III)) are important processes for the treatment of industrial wastewater. Conducting polymers can adsorb and reduce Cr(VI) to less toxic Cr(III) but have low adsorption capacities due to agglomeration of particles and are difficult to separate from treated water. In this study, magnetic polypyrrole (PPy)-polyaniline (PANI)/iron oxide (Fe₃O₄) nanocomposite was synthesized for the selective removal of Cr(VI) in aqueous solution. PPy-PANI/Fe₃O₄ nanocomposite was characterized using various techniques including ATR-FTIR, FE-SEM, HR-TEM, EDX, TGA, XRD, VSM and XPS analyses. PPy-PANI/Fe₃O₄ nanocomposite (0.05g) removed 99% of Cr(VI) from aqueous solution (100mg/L, pH 2). Speciation studies confirmed Cr(VI) adsorption and reduction to Cr(III) by the PPy-PANI/Fe₃O₄ nanocomposite in solutions with initial pH of 2 and 3 and that no Cr(VI) reduction occurred at pH values of 4 and above. The Langmuir maximum adsorption capacity for Cr(VI) removal by PPy-PANI/Fe₃O₄ nanocomposite at pH 2 was 303mg/g at 25°C. PPy-PANI/Fe₃O₄ nanocomposite was highly selective for Cr(VI) removal and could be used for three consecutive treatment cycles without loss of adsorption capacity. Moreover, the magnetic nanocomposite could be separated from the reaction fluid using an external magnet. PPy-PANI/Fe₃O₄ nanocomposite is therefore a promising magnetic adsorbent for the treatment of industrial wastewater.

Conjugated Polyelectrolyte Based Sensitive Detection and Removal of Antibiotics Tetracycline from Water

A new conjugated polyelectrolyte poly[5,5'-(((2-phenyl-9H-fluorene-9,9-diyl)bis(hexane-6,1-diyl))bis(oxy))diisophthalate] sodium (PFPT) was synthesized via the palladium-catalyzed Suzuki cross-coupling polymerization method and successfully applied for the rapid, real time, and highly sensitive detection of antibiotics tetracycline (Tc) in 100% aqueous media via photoinduced electron transfer with detection limit in the ppb level. Remarkably, PFPT could also be applied for the trace analysis of Tc in serum samples having recoveries well in the range 92-97% with relative standard deviations (RSD) of 1.01-1.14%, confirming reliability of the present method for the analysis of Tc. Additionally, PFPT was blended with the abundant natural polysaccharide chitosan to form CS-PFPT composite films and developed as a biopolymer based membrane for the removal of Tc from water samples with a good adsorption capacity of 3.12 mg g^-1, thus finding vital application in the treatment of antibiotic infested wastewater.

Applications of Gold Nanoparticles in Biosensors

Gold nanoparticles (AuNPs) as one of the most stable metal nanoparticles have demonstrated extensive applications in recent years. This paper will give a focus on the AuNPs as biosensors, due to their inertness, unique optical properties, high surface area, and various surface functionalization methods. Synthesis of AuNps and the surface functionalization will be discussed in the first part. The size, shape, and stability can be controlled by different synthetic methods, while reductant usually needed. By surface functionalization with different molecules such as polymers, nucleic acids, and proteins, AuNPs will aggregate when specified molecule linkages showing up enables selective detections. The application in biosensing to detect proteins, oligonucleotide, glucose, and heavy metals will be exemplified, followed by the summary and future perspective part in the conclusion.