A near-infrared dye for dye-sensitized solar cell: Catecholate-functionalized zinc phthalocyanine

The design and synthesis of an asymmetrical zinc phthalocyanine sensitizer modified with a catechol anchoring group is reported. The performance of this sensitizer was evaluated in a dye-sensitized solar cell. A strong interaction between the catechol dye and TiO₂ (with the formation of a five-membered charge-transfer complex) was evidenced by a strong shift in the Q-band of the ZnPc-Cat from 680 nm in solution to 750 nm on TiO₂, along with an appreciable absorption tail extending to ∼1000 nm. The fabricated solar cell containing the phthalocyanine sensitizer showed relatively high light-to-electron conversion efficiency (η = 0.92%), considering that few catechol dyes exceed η = 0.7% in dye-sensitized solar cells. Values of I_sc = 2.53 mA cm⁻² and V_oc = 540 mV were obtained, referring to a standard N719 cell (η = 6.46%). A comparison of zinc phthalocyanine sensitizers bearing different anchoring groups affirmed the superiority of carboxylate groups relative to those bearing catechol groups in terms of cell performance.     

A partial binary tree DEA-DA cyclic classification model for decision makers in complex multi-attribute large-group interval-valued intuitionistic fuzzy decision-making problems

This paper proposes the idea of combining “interest groups” with the practical decision information to classify the decision makers (DMs) in complex multi-attribute large-group decision-making (CMALGDM) problems in interval-valued intuitionistic fuzzy (IVIF) environment. It constructs a partial binary tree DEA-DA cyclic classification model to achieve the multiple groups’ classification of DMs. Not only does this method provide references for the classification of DMs when the decision information is known, but it also lays foundations for DMs’ effective weight determination and the aggregation of decision information. First, this paper normalizes all of the cost attributes into benefit attributes to avoid the wrong decision result. Second, it employs the C-OWA operator to transform IVIF number (IVIFN) samples into single-valued samples. With respect to this transformation, this paper provides the corresponding BUM functions of DMs according to their risk attitudes; therefore, the preference information of DMs can be more objectively aggregated. Third, this paper adopts the partial binary tree DEA-DA cyclic classification model to present an accurate classification of DMs. Thus, for each interest group, group members with different interest preferences can be distinguished and distributed to the appropriate groups. Finally, to show the feasibility and validity of the model, we give an illustrative example.     

The role of tutors in peer led teaching

Problem based learning can impact not only on students’ academic performance but also their social interactions within their peer group, and many institutions have embedded such teaching within their core curriculum. This paper looks at the interactions within a first year undergraduate engineering cohort that uses peers to tutor small groups through problem based learning at a Scottish Higher Education Institution. Most significantly, this work focusses on the impact that these interactions have on the students engaged as tutors within the programme, bridging the gap left by previous studies and providing an insight into how tutors are affected by their experiences. It was found that the recruitment of tutors requires careful consideration of their social as well as academic qualities, and that they should receive training and guidance within their adopted roles that takes account of social factors, questioning the traditional practice of employing individuals purely on the basis that they have studied the class previously themselves. The dynamic of tutor position with regard to the presence of senior staff is also explored, and suggests mechanisms for further student development.     

Classification into homogeneous groups using combined cluster and discriminant analysis

The classification of observations into groups is a general procedure in modern research. However, when searching for homogeneous groups the difficulty of deciding whether further division of a classification is necessary or not to obtain the desired homogeneous groups arises. The presented method, Combined cluster and discriminant analysis (CCDA), aims to facilitate this decision.CCDA consists of three main steps: (I) a basic grouping procedure; (II) a core cycle where the goodness of preconceived and random classifications is determined; and (III) an evaluation step where a decision has to be made regarding division into sub-groups. These steps of the proposed method were implemented in R in a package, under the name of ccda.To present the applicability of the method, a case study on the water quality samples of Neusiedler See is presented, in which CCDA classified the 33 original sampling locations into 17 homogeneous groups, which could provide a starting point for a later recalibration of the lake's monitoring network.     

Degradation behavior of polymer blend of isotactic polypropylenes with and without unsaturated chain end group

Abstract

In this work, the relationship between the unsaturated chain end group content and the thermal oxidative degradation rate was systematically studied with binary polymer blends of isotactic polypropylene (iPP) with and without the unsaturated chain end group. The iPPs with and without the unsaturated chain end group were synthesized by a metallocene catalyst in the absence of hydrogen and by a Ziegler catalyst in the presence of one, respectively. The thermal oxidative degradation rate of the binary iPP blends was estimated from the molecular weight and the apparent activation energy (ΔE), which were obtained through size exclusion chromatography (SEC) and thermogravimetric analysis (TGA) measurements, respectively. These values exhibited a negative correlation against the mole content of the unsaturated chain end group. The thermal oxidative degradation rate apparently depends on the content of the unsaturated chain end group. This tendency suggests that the unsaturated chain end acts as a radical initiator of the iPP degradation reaction.     

Aerodynamic forces on two stationary and oscillating square prisms in tandem and side by side arrangements

Abstract

In order to gain further understanding of aerodynamic forces and their effects on groups of high‐rise buildings, this study used wind‐tunnel experiments. Two square prisms were arranged both in tandem and side‐by‐side arrangement with different spacings in between. Similar experiments were carried out to study the interactions of aerodynamics between the two prisms when both were stationary, when only one prism oscillated, and finally, when both prisms oscillated.

The results showed that the aerodynamic responses were either enhanced or suppressed by the spacing ratios, the oscillating frequencies, and the mutual influences of the two square prisms in various arrangements. The aerodynamics also changed due to the occurrences of different flow patterns, such as channel flow, deflected flow, pulsating flow, and so on. Obviously, the aerodynamics of the flow patterns of the two square prisms in tandem and side‐by‐side arrangements proved to be more complex than those of a single square prism.     

The effects of individual innovativeness on users’ adoption of Internet content filtering software and attitudes toward children’s Internet use

The introduction of Internet content filtering software (ICFS) has led to intense debate among civil liberties groups. This paper explores the relationship between membership in five previously established adopter categories and users’ adoption of ICFS. The study also investigates how membership in the five adopter categories (innovators, early adopters, early majority adopters, late majority adopters, and laggards) affects user perceptions of and satisfaction with the software as well as parental attitudes towards their children’s Internet use.     

Influence of support’s oxygen functionalization on the activity of Pt/carbon xerogels catalysts for methanol electro-oxidation

Highly mesoporous carbon xerogels (CXs) were synthesized using two different resorcinol to catalyst, R/C, molar ratios and functionalized with different oxidation treatments. The synthesized carbon materials were used as supports for Pt particles, deposited by impregnation and reduction in formic acid. Both carbon supports and the catalysts prepared were characterized by means of N₂ physisorption, scanning and transmission electron microscopy, temperature programmed desorption and X-ray diffraction. The electrochemical activity of the catalysts towards the oxidation of carbon monoxide and methanol was assayed by means of cyclic voltammetry and chronoamperometry. Textural characterization of the materials prepared evidenced more developed and mesopore-enriched porous structure for the carbon xerogel prepared using the highest R/C molar ratio. Enhanced textural properties of this material led to the preparation of highly active Pt-catalysts, which showed increased tolerance to CO and higher activity in methanol electro-oxidation, in comparison to Pt-E-TEK and the catalysts prepared in an analogous way using Vulcan XC-72R carbon black as support. Functionalization treatments resulted in enhanced dispersion, lower Pt crystal size and improved catalytic performance in the case of the catalysts prepared using the carbon xerogel possessing a less developed porous structure. Pt agglomeration was found to strongly determine the activity of the catalysts prepared. At high potentials, i.e. 1 V vs. RHE, the catalyst prepared using the carbon xerogel submitted to the most stringent oxidation treatment showed the highest specific peak activity towards methanol electro-oxidation, probably due to the positive influence of the presence of oxygen surface groups in Pt-carbon interaction, in spite of the higher agglomeration extent confirmed by TEM. On the other hand, at 0.60 V vs. RHE, highest activity towards methanol electro-oxidation was determined for the catalysts prepared using the non-functionalized carbon xerogel which can be explained in terms of enhanced reactant/product diffusion together with intrinsic higher catalytic activity due to lower Pt crystal size. In any case, the activity of this catalyst prepared using a carbon xerogel as support was found to be more than 2 times higher than the one determined for Pt/E-TEK, confirming the considerable improvement of the electrocatalytic system by means of optimization of the carbon support employed.     

Electronic Structure and Ground State Properties of PMMA Polymer: II. Protection of PMMA Against Gamma Irradiation Damage

ABSTRACT

The equilibrium ground state geometric parameters of N,N,N′,N′,-tetraoxaloylsulphanilamide (Ligand I), N,N-dioxaloylbenzenesulpony-N′,N′,-dioxaloylthiocarbazide (Ligand II) and p-N,N-dioxaloylaminobenzene-N′,N′-dioxaloylbenzenesulphonyloxamide (Ligand III) as polyfunctional ligands were investigated theoretically using AM1-MO method. The expected biradicals formed after gamma radiolysis for each ligand can be detected. The radiation protection of the PMMA matrix from gamma rays, using the biradicals formed of ligands (I), (II), and (III), can be considered theoretically. The structure of the protected chains formed after recombination of two symmetric chains with biradical are theoretically modelled, because in the reaction medium the chain of PMMA formed is asymmetric. All interpretations concerning the ground state properties of the protected chains are qualitative. The thionyl, phenyl, and benzenesulphonyl biradicals are more efficient than carbonyl, thioamides, and sulphonyl biradicals as indicated from the MO-results, molecular weight investigation, and infrared spectroscopy. The protection of PMMA by the formed biradicals is confrmed by proton NMR spectroscopy.     

Peculiarities of the Thermal Degradation of Chlorosulphonated Polyethylenes

Abstract

A kinetic study is made of the thermal degradation of chlorosulphonated polyethylenes containing 3–40 wt% of Cl and 1.4–2.2 wt% of sulphur. It is concluded that the instability of these polymers is principally due to activation of the CHCl structures in the β-position to the [sbnd]CH₂[sbnd]SO₂Cl groups.