Low-energy electron microscopy of graphene outside UHV: electron-induced removal of PMMA residues used for graphene transfer

Two-dimensional materials, such as graphene, are usually prepared by chemical vapor deposition (CVD) on selected substrates, and their transfer is completed with a supporting layer, mostly polymethyl methacrylate (PMMA). Indeed, the PMMA has to be removed precisely to obtain the predicted superior properties of graphene after the transfer process. We demonstrate a new and effective technique to achieve a polymer-free CVD graphene - by utilizing low-energy electron irradiation in a scanning low-energy electron microscope (SLEEM). The influence of electron-landing energy on cleaning efficiency and graphene quality was observed by SLEEM, Raman spectroscopy (the presence of disorder D peak) and XPS (the deconvolution of the C 1s peak). After removing the absorbed molecules and polymer residues from the graphene surface with slow electrons, the individual graphene layers can also be distinguished outside ultra-high vacuum conditions in both the reflected and transmitted modes of a scanning low-energy (transmission) electron microscope

Voluntary disclosure of corporate strategy: determinants and outcomes. An empirical study into the risks and payoffs of communicating corporate strategy.

Business leaders increasingly face pressure from stakeholders to be transparent. There appears however little consensus on the risks and payoffs of disclosing vital information such as corporate strategy. To fill this gap, this study analyzes firm-specific determinants and organisational outcomes of voluntary disclosure of corporate strategy. Stakeholder theory and agency theory help to understand whether companies serve their interest to engage with stakeholders and overcome information asymmetries. I connect these theories and propose a comprehensive approach to measure voluntary disclosure of corporate strategy. Hypotheses from the theoretical framework are empirically tested through panel regression of data on identified determinants and outcomes and of disclosed strategy through annual reports, corporate social responsibility reports, corporate websites and corporate press releases by the 70 largest publicly listed companies in the Netherlands from 2003 through 2008. I found that industry, profitability, dual-listing status, national ranking status and listing age have significant effects on voluntary disclosure of corporate strategy. No significant effects are found for size, leverage and ownership concentration. On outcomes, I found that liquidity of stock and corporate reputation are significantly influenced by voluntary disclosure of corporate strategy. No significant effect is found for volatility of stock. My contributions to theory, methodology and empirics offers a stepping-stone for further research into understanding how companies can use transparency to manage stakeholder relations

Proton Equilibria in the Binding of Zn2+ and of Methylmercuric Iodide to Papain

The proton liberation on the binding of zinc chloride and methylmercuric iodide to the (essential) thiol group of papain has been examined as a function of pH. This was carried out by (a) direct titration of the protons on the addition of the metal compound to active papain and (b) measurement of the extent of inhibition of enzyme activity by the metal compound as a function of pH. It was found that in the neutral pH range the thiol group or the neighbouring imidazole group in the free enzyme carries one proton, at low pH both groups do so, whereas at high pH neither group carries a proton. The pK values of the free enzyme that govern the proton release, 4.2 and 8.5, correspond to those that govern overall activity. Both from the experiments with methylmercuric iodide and from fluorescence measurements of methylmercuric papain, it was established that the imidazole group in the latter compound exhibits a pK of 5.4. Taking recent data into account, it was considered that the ion pair of thiolate anion and imidazolium cation, proposed by Polgar, is the best approximation to describe the charge distribution in the active centre and to explain the reaction mechanism