Evaluation of a novel composite of expanded polystyrene with rGO and SEBS-g-MA.

This study displays the effect of reduced graphene oxide (rGO) nanofiller and polystyrene-b-poly(ethylene-ran-butylene)-b-polystyrene-grafted maleic anhydride (SEBS-g-MA) on the optical, thermal, and mechanical features of expanded polystyrene (EPS). First, the thin films of pristine EPS and composites were prepared using solution cast method. The prepared films were subjected to fourier-transform infrared (FTIR), SEM, UV-visible spectrophotometer, thermogravimetric analysis/differential scanning calorimetry, and universal testing machine for structural, morphological, optical, thermal, and mechanical characterizations. Optical study revealed a significant increase in refractive index and absorption of composites than EPS. Indirect band-gap energy of EPS (~4.08 eV) was reduced to ~1.61 eV for rGO composite and ~ 2.23 eV for composite composed of rGO and SEBS-g-MA. Thermal analyses presented improvement in characterization temperatures such as T10, T50, Tp, Tm, and Tg of composites, which ultimately lead to the thermal stability of prepared composites than pristine EPS. Stress-strain curves displayed higher yield strength (46.62 MPa), Young's modulus (96.29 MPa), and strain at break (0.54%) for EPS+rGO composite than pure EPS having stress at break (1.01 MPa), Young's modulus (12.44 MPa), and strain at break (0.08%). Moreover, ductility with relatively higher strain at break (0.61%) and lower Young's modulus (79.32 MPa) and yield strength (32.98 MPa) was noticed in EPS+rGO+SEBS-g-MA composite than EPS+rGO composite film. Morphological analysis revealed a change in globular morphology of EPS and inhomogeneous dispersion of rGO in EPS to homogeneously dispersed rGO in EPS matrix without globules owing to the addition of SEBS-g-MA. The increase in compatibility of EPS and rGO due to SEBS-g-MA was also observed in FTIR spectra. RESEARCH HIGHLIGHTS: Here, the solution casting approach was used to create the composite film of EPS and rGO with globules of various sizes. After adding SEBS-g-MA, the shape altered to globular free films exhibiting homogenous dispersion of rGO in EPS matrix. An optical investigation showed that composite materials had a significantly higher refractive index and absorption than EPS. The optical, thermal, and mechanical investigations suggest that the produced composites may be a great substitute for virgin EPS, allowing for a wider range of applications.

Polyimide biocomposites coated with tantalum pentoxide for stimulation of cell compatibility and enhancement of biointegration for orthopedic implant.

Orthopedic implants are an important tool in the treatment of musculoskeletal conditions and helped many patients to improve their quality of life. Various inorganic-organic biocomposites have been broadly investigated particularly in the area of load-bearing orthopedic/dental applications. Polyimide (PI) is a promising organic material and shows excellent mechanical properties, biocompatibility, bio-stability, and its elastic modulus is similar to human bone but it lacks bioactivity, which is very important for cell adhesion and ultimately for bone regeneration. In this research, tantalum pentoxide (Ta2O5) coating was prepared on the surface of PI by polydopamine (PDA) bonding. The results showed that Ta2O5 was evenly coated on the surface of PI, and with the concentration of Ta2O5 in the PDA suspension increased, the content of Ta2O5 particles on the surface of PI increased significantly. In addition, the Ta2O5 coating significantly increased the roughness and hydrophilicity of the PI matrix. Cell experiments showed that PI surface coating Ta2O5 could promote the proliferation, adhesion, and osteogenic differentiation of bone marrow-derived stromal cells (BMSCs). The results demonstrated that fabricating Ta2O5 coating on the surface of PI through PDA bonding could improve the biocompatibility as well as bioactivity of PI, and increase the application potential of PI in the field of bone repair materials.

Removal of hexavalent chromium ions using micellar modified adsorbent: isothermal and kinetic investigations.

Hexavalent chromium is a very poisonous oxyanion and has had a negative impact on human health. This study assessed the viability of removing chromium(vi) using micellar modified adsorbents. In this study, chromium(vi) was removed from locally accessible wheat bran using separate applications of anionic sodium dodecyl sulfate (SDS) and cationic cetyltrimethylammonium bromide (CTAB) surfactants. The initial chromium content (5-12 ppm), pH (2-12), adsorbent dose (1-6 g/100 mL), agitation time (15-240 min), agitation speed (50-300 rpm), and temperature (15-50 °C) were all varied in the adsorption investigation. Pseudo first-order and second-order kinetic models were utilized to analyze the kinetic investigation. To determine thermodynamic parameters, the van't Hoff relationship was used. The maximum result for chromium(vi) uptake was obtained as 87.7%, 83.5% and 98.9% for WB, SDS-mWB, and CTAB-mWB, respectively, at an agitation time of 240 min (i.e., 4 h), temperature (i.e., 25-30 °C), agitation speed (150 rpm). However, both WB and CTAB-mWB derives metal ion removal at lower pH levels (2-4), whereas SDS-mWB requires a pH between 4 and 6 for maximum percentage removal of Cr(vi). The equilibrium data of WB and SDS-mWB were modeled by the Langmuir adsorption isotherm, while the data of CTAB-mWB fitted well in the Freundlich isotherm model. The kinetic analysis of WB, SDS-mWB, and CTAB-mWB revealed that the pseudo-second-order kinetic model provides a thorough explanation for each of these adsorbents. It was found that CTAB-mWB can preferably be used for the removal of chromium(vi) due to its high affinity with adsorbate molecules and adsorption capacity.

Coumarin based thiosemicarbazones as effective chemosensors for fluoride ion detection.

Anion sensing have attained immense importance as these charged ions are prevailing in agriculture industry and in heavy industry and therefore in the environment around us, chemosensors are commencing to claim several applications as their role is being better perceived day by day. In the current study, coumarin based thiosemicarbazone R-1 (phenyl moiety) and R-2 (benzyl moiety) were synthesized. It was observed that there were variations in the sensing patterns of compound bearing benzyl group, as compared to the simple phenyl group bearing receptor. Different techniques were used to confirm the interaction of coumarin based receptors with anions. These techniques included naked-eye test, UV-visible, 1H NMR, and fluorescence spectroscopic techniques. The synthesized receptors showed selectivity for fluoride ions. Benesi-Hildebrand equation was employed for determining the detection limits and binding constants values. The synthesized receptors were employed as efficient chemosensors in real life samples and satisfactory results were obtained.

Novel surfactant stabilized PLGA cisplatin nanoparticles for drug delivery applications.

In the current study, cisplatin loaded (Poly(lactic-co-glycolicacid)) (PLGA) stabilized with 4-phenylphenacylbromide based surfactants nanoparticles were developed for drug delivery applications. For the course of this study four new 4-phenylphenacylbromide based compounds abbreviated as PA(C2)3, PA(C8)3, PAC16 and PAC18 have been synthesized by the reaction of 4-phenylphenacylbromide with various long chain amines. The new surfactants were characterized with 1H and 13C NMR and FTIR spectroscopy. The critical micelle concentration (CMC) of newly synthesized surfactants are in the range of 0.024-0.091 mM. The newly synthesized surfactants have been incorporated in PLGA based nanoparticles and are used for drug encapsulation and delivery of cisplatin. The drug encapsulation efficiency for newly fabricated nanoparticles was found to be in the range of 65 ± 1.5 to 67 ± 1.6%, the drug loading was observed in the range of 1.96 ± 0.11 to 2.31 ± 0.19%, whereas the maximum drug release was found to be 85.1 ± 1.1%.

Human Biomonitoring of Trace Elements in Scalp Hair from Healthy Population of Pakistan.

The present study deals with the assessment of essential trace and toxic elements in biological samples (scalp hair) of healthy smoker and non-smoker residents of Lahore (the second most populous city), Pakistan. Human biomonitoring of various trace elements like zinc (Zn), iron (Fe), copper (Cu), chromium (Cr), cadmium (Cd), nickel (Ni), lead (Pb), and arsenic (As) was evaluated in human hair samples of smokers and non-smokers (males and females) as per IFCC criteria. For the purpose of comparison, scalp hair samples of age- and sex-equivalent healthy persons were also analyzed. The results of this study show that the concentrations (P95 values) of As (0.17, 0.81, and 0.91 µg/g), Cd (2.80, 3.81, and 3.16 µg/g), Cr (4.1, 4.2, and 5.3 µg/g), Cu (20.0, 21.0, and 21.9 µg/g), Ni (3.9, 4.6, and 4.3 µg/g), Pb (4.0, 4.8, and 5.0 µg/g), and Fe (49.0, 49.0, and 59.3 µg/g) were significantly higher in scalp hair samples of smokers than in referents, for various age groups (16-32 years, 33-50 years, and 51-62 years), respectively. The concentrations of Zn (165, 163, and 173 µg/g various age groups, respectively) in similar age group were found lower in the scalp hair samples of smokers than referents. Exposure of high toxic metal level through smoking and deficiency of Zn could be synergistic with the risk factors associated with the use of tobacco. Correlation studies for the elements in cigarette with the elements in scalp hair of male smokers show a highly positive correlation between Cr-Cd, Cr-Ni, Cu-Fe, and Ni-Zn.

Synthesis, Characterization, and Applications of Silk/Bentonite Clay Composite for Heavy Metal Removal From Aqueous Solution.

Bentonite clay is an abundant and low-cost adsorbent and silk fibroin, a naturally occurring protein, and both have a low capacity to remove lethal heavy metal ions from aqueous solution separately. To enhance their metal adsorbing capacity, a new silk fibroin-based bentonite composite was prepared for improving water quality by eliminating heavy metal ions i.e., lead, cadmium, mercury, and chromium. The as-synthesized composite shows better metal sorption capacity than either of them alone. To analyze their structural properties and characteristic functional groups, X-ray diffraction and Fourier-transform infrared spectroscopy were used. The specific surface area for silk/bentonite composite was about 4 m2/g that is smaller than the unmodified bentonite (23 m2/g) which indicates the impregnation of bentonite onto the silk fibroins. Scanning electron microscopy results shows the changes in morphology from plate aggregates to rosette like arrangements. The XRD results of clay/composite shows an increase in basal spacing (d001, from 1.55 to 3.34 nm) in comparison to pristine clay. FTIR results show the presence of organic moiety in SF clay composite. The mechanism of adsorption based on complex formation and ion exchange were proposed briefly. Various adsorption isotherms and kinetic models were applied for the removal of Pb(II), Cd(II), Hg(II), and Cr(VI). As the kinetic study was concerned, kinetic data fitted well to pseudo second order kinetics because experimental values of qe are much closer to the calculated values. The adsorption equilibrium was best studied by Langmuir isotherm whose regression coefficient values (0.985-0.995) are best when compared to Freundlich adsorption isotherm (0.954-0.990) and are indicative of homogeneity of adsorption sites on the SF/clay composite. The monolayer adsorption capacity for Cd(II), Pb(II), Hg(II), and Cr(VI) was found to be 11.35, 11.1, 10.5, and 10.2 mg/g, respectively.