Occurrence, distribution and provenance of micro plastics: A large scale quantitative analysis of beach sediments from southeastern coast of South Africa.

Microplastics (MPs) existence, identification and source were investigated by studying a total of 2539 particles in 349 sediment samples from nine different tourist beaches [(Sodwana & Richard Bays; Ballito, Mtunzini, Tugela, Zinkwazi, Ballito (north & south) and Durban north & south)] of southeastern coast of South Africa. They are more abundant in the beaches of the Durban city, followed by the Sodwana & Richards Bays, Ballito and Mtunzini. The black particles prevailed over the blue, white, pink, brown, red and green MPs. Supremacy of MPs in the Durban city is mainly due to the longshore coastal Agulhas current in the South eastern side of African coast aiding the degradation of primary plastics coming both from continent and sea. SEM images provided the evidences of weathering/degrading process through grooves, cracks, deep fissures, sharp edges and layered degradation showing signs of oxidation due to long term exposure in the coastal environment. EDS results suggested presence of elements (i.e. C, -O, Si, Al, Fe, Ca, Mg, Na, K, S, Ti, Cu and Zn introduced during the production of plastics as additives. FTIR spectral matches identified from all samples infer polypropylene (PP) (62%), rayon (RY) (17.2%), polycarbonate (PC) (29.8%), nylon (NY) (18.92%), polyester (PES) (31.2%), polyacrylonitrile (PAN) (11.21%) and polystyrene (PS) as well as low (28.9%) & high (36.1%) polyethylene terephthalate (PET). Higher abundance of MPs in the beaches of South Africa in comparison with studies around the world emphasizes the need of dispersal monitoring and use of plastic materials/polymers.

Electronic and optical competence of TiO2/BiVO4 nanocomposites in the photocatalytic processes.

Nanocomposites with different ratios of titanium dioxide and bismuth vanadate [TiO2]/[BiVO4] give rise to compatible electronic band structure alignment at their interfaces to ensure enhanced photoactivated charge transfer under visible light. The sol-gel method and suitable post-synthesis thermal treatments were used to synthesize different compositions with stabilized anatase phase of TiO2 and monoclinic scheelite polymorph BiVO4. Structural, electronic and optical characterizations were performed and the results were analysed as a function of the stoichiometry, in which both crystalline structures show a clear junction formation among their characteristic stacking planes. Photocatalytic and (photo) electrochemical responses of the nanocomposites were investigated and tested for the degradation of azo dyes (Acid Blue-113, AB-113) (~ 99%) under visible light radiation. The nanocomposite with a mass ratio of (1:10) shows the highest photocatalytic efficiency compared to the other compositions. HRTEM images showed marked regions in which both crystalline structures form a clear junction and their characteristic planes. However, the increase of BiVO4 content in the network overcomes the photocatalytic activity due to the decrease in the reduction potential of the photo-generated electrons with high recombination rates.

Properties of mechanochemically synthesized ZnS nanoparticles.

The bulk and surface properties of mechanochemically synthesized ZnS nanoparticles were studied. XRD, SEM, TEM (HRTEM), AFM, UV-VIS, low temperature nitrogen sorption as well as TPR characterization methods have been applied. Cubic ZnS nanocrystals (2-4 nm) with characteristic blue shift have been obtained by high-energy milling. There is an evidence of the nanocrystal aggregates formation in products of milling. The surface uniformity, homogeneity as well as enhanced uptake of hydrogen have been documented.

Solution based synthesis of Cu(In,Ga)Se2 microcrystals and thin films.

Herein, for the first time, we report the synthesis of quaternary Cu(In,Ga)Se2 microcrystals (CIGSe MCs) using a facile and economical one-pot heating-up method. The most important parameters such as reaction temperature and time were varied to study their influences on the structural, morphological, compositional and optical properties of the MCs. Based on the results, the formation of CIGSe was initiated from binary ß-CuSe and then converted into pure phase CIGSe by gradual incorporation of In3+ and Ga3+ ions into the ß-CuSe crystal lattice. As the reaction time increases, the band gap energy was increased from 1.10 to 1.28 eV, whereas the size of the crystals increased from 0.9 to 3.1 µm. Besides, large-scale synthesis of CIGSe MCs exhibited a high reaction yield of 90%. Furthermore, the CIGSe MCs dispersed in the ethanol was coated as thin films by a drop casting method, which showed the optimum carrier concentration, high mobility and low resistivity. Moreover, the photoconductivity of the CIGSe MC thin film was enhanced by three order magnitude in comparison with CIGSe NC thin films. The solar cells fabricated with CIGSe MCs showed the PCE of 0.59% which is 14.75 times higher than CIGSe NCs. These preliminary results confirmed the potential of CIGSe MCs as an active absorber layer in low-cost thin film solar cells.

Gold-Iron oxide yolk-shell nanoparticles (YSNPs) as magnetic probe for fluorescence-based detection of 3 base mismatch DNA.

Seed-mediated Gold-Iron oxide yolk-shell nanoparticles (YSNPs) were synthesized and functionalized with cy5 attached- thiolated single strand DNA probe for the detection of mutated DNA. The optimum concentration of thiolated DNA determined from a bathochromic shift of surface plasmon resonance (SPR) peak, was 0.177µM. The effect of pH (2-10), temperature (4, 37, 60 and 100 °C), and ionic strengths (1 M to 4 M) on the stability of ssDNA probe tethered YSNPs, studied with the assistance of flocculation parameter. The detection of mutation in DNA was possible using such ssDNA probe functionalized and stabilized nanoparticles. The hybridization of the oligonucleotide probe with the complementary, non-complementary and mutated DNA strands are determined via their respective intensities of the fluorescence of cy5, an efficient fluorescent marker. The intensities help in the comprehension of the specificity of the system. The report predicts controlled efficiency of hybridization with the aid of Hamaker constant, which is determined as 1.15 × 10-20 J for DNA functionalized YSNPs. The minimum concentration of target DNA detected using this methodology was 1.2 × 10-11 mol/L.

Cu2ZnSn(S,Se)4 thin-films prepared from selenized nanocrystals ink.

For the first time, CZTS ink was formulated using low-temperature heating up synthesis of NCs. Besides, the influence of powder concentration on the properties of the films was examined. Subsequently, the CZTS films were annealed under a selenium (Se)/argon (Ar) atmosphere at different temperatures to enhance their properties. The influence of selenization temperature on the properties of CZTS films was examined in detail. Structural analysis showed a peak shift towards lower 2θ values for CZTSSe films because of Se incorporation, resulting in larger lattice parameters for CZTSSe than CZTS. As the selenization temperature increases, an increment in the grain size was observed and the band gap was decreased from 1.52 to 1.05 eV. Hall Effect studies revealed a significant improvement in the mobility and carrier concentration with respect to selenization temperatures. Moreover, film selenized at 550 °C exhibited higher photoconductivity as compared to other films, indicating their potential application in the field of low-cost thin-film solar cells.

Structural and morphological data of RF-Sputtered BiVO4 thin films.

Structural and morphological modulation of rf-sputtered BiVO4 thin films deposited using mechanochemical synthesis prepared BiVO4 nano-powders as sintered target are included in this data article. The crystalline nature of as-prepared films, namely amorphous and crystalline was acquired with time and temperature dependent in-situ high temperature X-ray diffraction (HT-XRD), at a time interval of 1 h. Typical Fourier transform infrared (FT-IR) spectra of annealed thin film of monoclinic BiVO4 structure is given. Furthermore, correlation between morphologies of various substrate temperature fabricated BiVO4 thin films are presented.

Design and evaluation of surface functionalized superparamagneto-plasmonic nanoparticles for cancer therapeutics.

Designing a multifunctional nanomaterial is always considered as a biggest concern in the field of nanomedicine which aims to promote versatile action in a single use from tracking to therapeutics. Therefore, metallic nanoparticles are well exploited as a major platform with the assemblage of surface modifications which can be effectively engaged for plenty of applications. Here, in this work, we have successfully amalgamated gold coated magnetite core-shell nanoparticles along with bio-functionalization of folic acid and doxorubicin to explore its possibility as a distinct nanocargo for cancer nanotheranostics. This unique combination of both magnetic and optical properties makes its function to be more precise. For example, in case of in-vitro drug-release studies more than 75% of drug moieties are released at acidic pH 5.4 and exactly fitting in first order rate kinetics. As gold shell retains the superparamagnetic nature of the core it exhibited high r2 values, and because of large relaxivities (r2/r1) ratio, they are confirmed as T2-weighted contrast agent by MRI. Finally, under microwave of 2.45GHz exhibited enough heat which can induce both apoptosis & necrosis leading to cell death. Thus, we conclude that our nanoparticle can be a multitool for diagnosis and therapeutics for various human diseases.

Camphor-mediated synthesis of carbon nanoparticles, graphitic shell encapsulated carbon nanocubes and carbon dots for bioimaging.

A green method for an efficient synthesis of water-soluble carbon nanoparticles (CNPs), graphitic shell encapsulated carbon nanocubes (CNCs), Carbon dots (CDs) using Camphor (Cinnamomum camphora) is demonstrated. Here, we describe a competent molecular fusion and fission route for step-wise synthesis of CDs. Camphor on acidification and carbonization forms CNPs, which on alkaline hydrolysis form CNCs that are encapsulated by thick graphitic layers and on further reduction by sodium borohydride yielded CDs. Though excitation wavelength dependent photoluminescence is observed in all the three carbon nanostructures, CDs possess enhanced photoluminescent properties due to more defective carbonaceous structures. The surface hydroxyl and carboxyl functional groups make them water soluble in nature. They possess excellent photostability, higher quantum yield, increased absorption, decreased cytotoxicity and hence can be utilized as a proficient bio imaging agent.

Plasmonic/Magnetic Multifunctional nanoplatform for Cancer Theranostics.

A multifunctional magneto-plasmonic CoFe2O4@Au core-shell nanoparticle was developed by iterative-seeding based method. This nanocargo consists of a cobalt ferrite kernel as a core (Nk) and multiple layers of gold as a functionalizable active stratum, (named as Nk@A after fifth iteration). Nk@A helps in augmenting the physiological stability and enhancing surface plasmon resonance (SPR) property. The targeted delivery of Doxorubicin using Nk@A as a nanopayload is demonstrated in this report. The drug release profile followed first order rate kinetics optimally at pH 5.4, which is considered as an endosomal pH of cells. The cellular MR imaging showed that Nk@A is an efficient T2 contrast agent for both L6 (r2-118.08 mM-1s-1) and Hep2 (r2-217.24 mM-1s-1) cells. Microwave based magnetic hyperthermia studies exhibited an augmentation in the temperature due to the transformation of radiation energy into heat at 2.45 GHz. There was an enhancement in cancer cell cytotoxicity when hyperthermia combined with chemotherapy. Hence, this single nanoplatform can deliver 3-pronged theranostic applications viz., targeted drug-delivery, T2 MR imaging and hyperthermia.

Microplastics in tourist beaches of Huatulco Bay, Pacific coast of southern Mexico.

The presence and impacts of plastic marine debris (PMD) have been documented in the oceans worldwide, and they deserve special attention. This study is the first to report the presence of microplastics in tourist beaches located in Huatulco Bay, southern Mexico. A total of 70 beach sediment samples (for 2 distinct seasons) were collected from Huatulco Bay in April 2013 and December 2014. The samples were subsequently extracted by scanning electron microscopy (SEM) to identify the fibrous microplastics (diameter<5mm). The maximum number of fibrous materials was found in April 2013 and December 2014 in the Rincón Sabroso beach (48/30g sediment) and the Cuatunalco beach (69/30g sediment), respectively. Overall, a high amount of microplastics is present in the Conejos, Tangolunda, Santa Cruz, and San Agustin beaches. The microplastics are mainly derived from tourism-based activities and effluents discharged from the hotels and restaurants located along the beaches.

Synthesis and Characterization of Bimetallic Ni50Pt50 Catalyst Supported on SiO2 for N2O Decomposition.

Nanometallic and bimetallic catalyst of Ni, Pt and Ni50Pt50 were studied by the decompositions of N2O. The catalyst were prepared by incipient wetness impregnation of the silica with low superficial area of 50 m2/g supported with aqueous solution of the metal precursors, for Pt H2Pt Cl6 x 6H2O was used and for Ni, Ni(NO3)2 was used to a total metal loading of 1% wt. Catalyst were oxidized for 2 hours at 400 degrees C with O2, then the samples were reduced for 30 minutes with N2 and 2 hours with H2, all at the same temperature. The catalyst was characterized by Transmission Electron Microscopy (TEM), High Angular Annular Dark Field (HAADF), High Resolution Transmission Electron Microscopy (HR-TEM) and Termoprogramed Reduction (TPR). The mean particle sizes obtained by TEM and HAADF were about 12.5 nm for Ni/SiO2, 2.8 nm for Pt/SiO2 and 3.5 nm Ni50Pt50/SiO2 catalysts respectability. HR-TEM and HAADF analysis showed differences between Ni and Pt catalysts displaying mainly cuboctahedral shapes. Stepped surface defects were found in the Ni50Pt50/SiO2 catalyst. Finally Ni50Pt50/SiO2 was more active than Pt/SiO2 and Ni/SiO2 catalysts for the decomposition of N2O.

Synthesis of Culn(1-x)Ga(x)Se2 Nanoparticles by Thermal Decomposition Method with Tunable Ga Content.

Chalcopyrite Culn(1-x)Ga(x)Se2 (CIGS) nanoparticles were synthesized by mixing copper (I) chloride (CuCl), Indium (III) chloride (InCl3), gallium (III) chloride (GaCl3) and selenium (Se) in oleylamine (OLA) at 260 degrees C for 4 h under nitrogen atmosphere. The Ga/(In+ Ga) ratio was tuned across the entire stoichiometric range from 0 to 1. X-ray diffraction analysis (XRD) revealed chalcopyrite crystal structure for samples prepared with x = 0, 0.3, 0.5, 0.7 and 1. The lattice parameters a and c decreased linearly with increasing Ga concentration which is consistent with Vegard's law. Raman spectra exhibited A, optical phonon vibrational mode for synthesized nanoparticles which gradually shifted to higher wavenumber with increasing Ga content. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images showed irregular as well as hexagonal plate like morphologies in the size range of 100 to 400 nm. High-resolution transmission electron microscopy (HR-TEM) images showed well-defined lattice fringes and d-spacing correspond to (112) plane which gradually decreases with increasing Ga content. The material compositions of synthesized CIGS nanoparticles with x = 0, 0.3, 0.5, 0.7 and 1 were very close to the desired stoichiometry which was confirmed by energy dispersive X-ray analysis (EDAX). Ultraviolet visible near infrared (UV-VIS-NIR) absorption spectra of the synthesized CIGS nanoparticles revealed that the bandgap could be tuned over the range 1 to 1.7 eV by varying the Ga/(In+Ga) ratio.

Synthesis and Characterization of Cadmium Sulfide Nanoparticles by Chemical Precipitation Method.

Cadmium sulfide (CdS) nanoparticles were synthesized by chemical precipitation method using cadmium chloride (CdCl2), sodium sulfide (Na2S) and water as a solvent by varying temperatures from 20-80 degrees C. The nanoparticles were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), High-resolution transmission electron microscopy (HR-TEM) and UV-Visible spectroscopy. XRD pattern revealed cubic crystal structure for all the synthesized CdS nanoparticles. Raman spectra showed first and second order longitudinal optical (LO) phonon vibrational modes of CdS. The size of CdS nanoparticles was found to be in the range of 15-80 nm by FE-SEM analysis, in all cases. The atomic percentage of cadmium and sulfur was confirmed to be 1:1 from EDS analysis. TEM micrograph depicts the spherical shape of the particles and the size is in the range of 15-85 nm while HR-TEM images of CdS nanoparticles exhibit well-resolved lattice fringes of the cubic structure of CdS. The optical properties of CdS were examined by UV-Visible spectroscopy which showed variation in absorption band from 460-480 nm. The band gap was calculated from the absorption edge and found to be in the range of 3.2-3.5 eV which is greater than the bulk CdS.

Study of low resistivity and high work function ITO films prepared by oxygen flow rates and N2O plasma treatment for amorphous/crystalline silicon heterojunction solar cells.

Pulsed DC magnetron sputtered indium tin oxide (ITO) films deposited on glass substrates with lowest resistivity of 2.62 x 10(-4) Ω x cm and high transmittance of about 89% in the visible wavelength region. We report the enhancement of ITO work function (Φ(ITO)) by the variation of oxygen (O2) flow rate and N2O surface plasma treatment. The Φ(ITO) increased from 4.43 to 4.56 eV with the increase in O2 flow rate from 0 to 4 sccm while surface treatment of N2O plasma further enhanced the ITO work function to 4.65 eV. The crystallinity of the ITO films improved with increasing O2 flow rate, as revealed by XRD analysis. The ITO work function was increased by the interfacial dipole resulting from the surface rich in O- ions and by the dipole moment formed at the ITO surface during N2O plasma treatment. The ITO films with high work functions can be used to modify the front barrier height in heterojunction with intrinsic thin layer (HIT) solar cells.