A non-doped microporous titanosilicate for bimodal adsorption-photocatalysis based removal of organic water pollutants

Access to clean drinking water is limited for millions around the world and lead to dire health and economic ramifications, particularly in developing nations. This study explores a recyclable, low-cost, non-doped, microporous titanosilicate for effective removal of organic water pollutants. Rhodamine B was utilized as a modal pollutant to explore and optimize the activity of the titanosilicate, which evidently occurred via an adsorption and subsequent photocatalytic degradation based bimodal mechanism. The novel titanosilicate has high surface area (SBET of 468 m2/g), is microporous (∼1.3 nm pore diameter), achieved via a surfactant templating technique. Its’ physicochemical properties were characterised using FTIR, Raman, BET, SEM, PXRD and XPS. The photocatalytic activity of the material was studied under a solar simulator via time dependent UV–vis absorption measurements. The material showed 97% removal of Rhodamine B (5 mg/L) within 3 h, and outperformed nanosized titanium dioxide (anatase:rutile 4:1), the most conventionally used photocatalyst in tertiary water treatment. Interestingly, the titanosilicate displayed a dual mechanism of pollutant removal: an initial rapid removal of 59% due to adsorption during a 30 min equilibrating step in the dark, followed by near complete removal within 3 h. Additionally, a >90% efficiency of Rhodamine B removal by the titanosilicate catalyst was achieved consistently throughout 4 cycles, demonstrating its ability for regeneration and reusability. Such activity has not been previously reported in non-doped or non-composite titanosilicates, and opens up pathways to efficient, low-cost water treatment materials, consisting only of environmentally benign raw materials and synthetic procedures

Plasmachemical Functionalisation for Modification of Surfaces with Biomolecules and Metals

Plasmachemical functionalisation offers a versatile route to surface functionalisation, allowing a wide variety of functional groups to be deposited in a substrate independent process. This thesis presents the application of pulsed plasmachemical functionalisation in two areas. Firstly, the construction of covalently tethered DNA or protein arrays is examined, and novel routes are presented based on the introduction of aldehyde and bromine functions onto substrates such as glass, silicon, polystyrene beads and carbon nanotubes. Secondly, the use of plasmachemical layers for the tethering of metal centres is also presented, with aldehyde and vinylpyridine functional surfaces presented, and their use in the metallization of substrates such as carbon nanotubes demonstrated. The functionalisation and reaction of plasmachemical surfaces is monitored by a variety of surface sensitive methods including XPS, FT-IR, contact angles, and reflectometry

An insight into the air stability of the benchmark polymer:Fullerene photovoltaic films and devices: A comparative study

In this study, a comparative analysis of the instabilities and degradation routes of organic solar cell (OSCs) employing the three benchmarked donor polymers namely poly(3-hexylthiophene) (P3HT), poly[N-900- hepta-decanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazole)] (PCDTBT) and Poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2- b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2 ethylhexyl)carbonyl] thieno[3,4-b]thiophenediyl]] (PTB7) along with [6,6]-phenylC71 butyric acid methyl-ester (PC71BM) acceptor have been conducted using the extracted photovoltaic parameters in conjunction with the X-ray photoelectron spectroscopy (XPS), optical and morphological analysis. During the 14 days air stability test, the power conversion efficiency (PCE) decreased by 78.85%, 65.83% and 83.36% for P3HT:PC71BM, PCDTBT:PC71BM and PTB7:PC71BM based devices, respectively. However, the degradation study of the bulk heterojunction (BHJ) films was prolonged to 28 days in order to further elucidate the degradation factors affecting the device performance. XPS, optical and morphological studies enabled detailed information on the device degradation mechanisms and confirmed the oxidation of photoactive layer after ageing, morphological deterioration and fall in absorbance, particularly, the PTB7:PC71BM blend that showed the rapid degradation among all three. The results obtained in the current study advance the understanding of the stability/degradation mechanisms pertaining to the three most commonly used BHJ materials and hence, will help to improve the OSCs for longer lifetime

Role of Smart-Release Pigments in Preventing Corrosion Driven Cathodic Disbondment of Organically Coated Hot Dip Galvanised Steel

The role of smart-release corrosion inhibitive pigments in preventing cathodic delamination of organically coated hot-dip galvanized steel (HDG) is investigated. The pigments consisted of hydrotalcite (HT) exchanged with a range of inorganic and organic anionic species and were dispersed in a model PVB coating. A scanning Kelvin probe (SKP) technique was used to determine cathodic delamination rates, and the inhibition efficiencies obtained for inorganic ions increased in the order ${{{\rm{CO}}}_{3}}^{2-}$ < ${{{\rm{MoO}}}_{4}}^{2-}$ < ${{{\rm{NO}}}_{3}}^{-}$ < ${{{\rm{VO}}}_{4}}^{3-}$ < ${{{\rm{WO}}}_{4}}^{2-}$ < ${{{\rm{PO}}}_{4}}^{3-}$ < ${{{\rm{CrO}}}_{4}}^{2-}.$ The inhibition efficiencies for organic-based pigments increased in the order triazole <phenylphosphonate <trans-cinnamate <benzoate <salicylate <benzotriazole. The inhibition efficiency afforded by the best performing organic inhibitor, benzotriazole (BTA), rivalled that of HT containing stored chromate anions. Findings are consistent with HT-BTA acting to sequester anions from the underfilm electrolyte, releasing BTA− which subsequently strongly adsorbs on the underfilm metal surface but can also form an insoluble Zn-BTA precipitate at the coating-defect boundary

The effects of vacuum annealing on the conduction characteristics of ZnO nanorods

Optimised ZnO nanorods characteristics are essential for novel devices to operate efficiently. The effects of vacuum annealing on the electrical transport properties and defect chemistry of ZnO nanorods have been studied. Annealing to 500 °C removed surface contamination causing reduced resistance while annealing to 600 °C created acceptor defects, changing the contact type from ohmic to rectifying. At 700 °C donor defects reduced leading to increased resistance while annealing to 800 °C caused a reduction in all defects and decreased resistance. This suggests that contact resistance is the major contributor to the system’s resistance rather than the inherent material resistance alone. The results indicate that contact type can be controlled by manipulating the defect chemistry via controlled annealing

Enhanced Electrical Conductivity and Seebeck Coefficient in PEDOT:PSS via a Two-Step Ionic liquid and NaBH4 Treatment for Organic Thermoelectrics

A two-step approach of improving the thermoelectric properties of Poly(3,4-ethylenedioxythiophene)poly(4-styrenesulfonate) (PEDOT:PSS) via the addition of the ionic liquid, 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM:TFSI) and subsequent reduction with NaBH4 is presented. The addition of 2.5 v/v% of EMIM:TFSI to PEDOT:PSS increases the electrical conductivity from 3 S·cm−1 to 1439 S·cm−1 at 40 °C. An additional post treatment using the reducing agent, NaBH4, increases the Seebeck coefficient of the film from 11 µV·K−1 to 30 µV·K−1 at 40 °C. The combined treatment gives an overall improvement in power factor increase from 0.04 µW·m−1·K−2 to 33 µW·m−1·K−2 below 140 °C. Raman and XPS measurements show that the increase in PEDOT:PSS conductivity is due to PSS separation from PEDOT and a conformational change of the PEDOT chains from the benzoid to quinoid molecular orientation. The improved Seebeck coefficient is due to a reduction of charge carriers which is evidenced from the UV–VIS depicting the emergence of polarons

Improvement in liquid absorption of open-cell polymeric foam by plasma treatment for food packaging applications

Free-moving meat exudate in plastic packaging is perceived as unhygienic and unattractive by consumers. It facilitates the deterioration of meat quality and safety, increasing meat waste and loss. This work discusses an innovative approach in scavenging meat exudate within commercial plastic packaging. This involves improving the liquid absorption capabilities of open-cell polystyrene (PS) foam through the application of oxygen plasma treatment rather than chemical wetting agents. The excited plasma species diffuse into the porous foam structure introducing polar oxygen groups onto the pore walls and improves their surface hydrophilicity. Hence, the foam pores, with enhanced wettability towards water-based liquids, are proposed to have a larger sucking capillary pressure thus increasing the absorption capacity of the porous PS foam. The specific liquid absorption capacity of PS foam sheets (thickness: 5 mm) increased from 1.09 g g-1 (grams of exudate simulant liquid absorbed per gram of PS foam) to 8.78 g g-1 as a result of plasma treatment; an 8-fold increase in liquid capacity (g g-1) that persisted even 60 days post treatment. This study demonstrates the practicality of using plasma treatment as a non-chemical and efficient technology in scavenging meat and food exudates in plastic packagin

Sources of Pb(0) artefacts during XPS analysis of lead halide perovskites

X-Ray Photoelectron spectroscopy (XPS) spectra of methyl ammonium lead halide perovskite films typically show the presence of lead as Pb(II), but Pb(0) is also often observed, potentially influencing the interpretation of the device physics. In this article the reproducible evolution of Pb(0) peaks which are likely artefacts generated under typical XPS analytical conditions are demonstrated from methyl ammonium lead halide films that contain no Pb(0) initially. The evolution of Pb(0) occurs via (1) X-ray photolysis under typical analytical conditions and (2) alongside other chemical changes as a result of film aging in air. In both cases we note the presence of PbI2 as a common factor contributing to in situ reactions to generate Pb(0) artefacts. Hence the observation of Pb(0) should be treated with extreme caution and here we recommend simple precautions to ensure materials analysis of these films gives reliable information when analyzed under UHV conditions