Critical Evaluation of Published Algorithms for Determining Environmental and Hazard Impact Green Metrics of Chemical Reactions and Synthesis Plans

In this paper, we analyze six published algorithms that evaluate environmental and hazard impact green metrics. The methods are compared and contrasted on a common set of chemical reactions and synthesis plans. The relative greenness of four reaction procedures to prepare iron­(II)­oxalate dihydrate and three industrial preparations of aniline are examined. We also examine the organic syntheses preparations of 2,2-diethoxy-1-isocyanoethane, thiete 1,1-dioxide, and ethyl phenylcyanopyruvate that we previously evaluated by material efficiency. We discuss the merits and limitations of all algorithms with respect to quality of calculation outputs, visualization, and ease of use

European journal of cell biology : EJCB

A detailed investigation examines how the size of allylbenzene-capped silicon nanocrystals (ncSi:AB) affects their chemical reactivity with gaseous O₂, H₂O, and O₂/H₂O as probed by in situ luminescence spectroscopy. Specifically, changes in the photoluminescence (PL) of size-separated ncSi:AB are monitored through alterations of their PL absolute quantum yield (AQY) as well as the wavelength and intensity of their PL spectra over time. These experiments, conducted under both continuous and intermittent illumination, help elucidate the roles of O₂, H₂O, and mixtures of O₂/H₂O, with respect to oxidation of ncSi:AB as a function of their size, providing vital information for any perceived application in advanced materials and biomedical devices

Switching-on quantum size effects in silicon nanocrystals

The size-dependence of the absolute luminescence quantum yield of size-separated silicon nanocrystals reveals a volcano behavior, which switches on around 5 nm, peaks at near 3.7-3.9 nm, and decreases thereafter. These three regions respectively define: i) the transition from bulk to strongly quantum confined emissive silicon, ii) increasing confinement enhancing radiative recombination, and iii) increasing contributions favoring non-radiative recombination

Non-wettable, oxidation-stable, brightly luminescent, perfluorodecyl-capped silicon nanocrystal film

Here we describe for the first time the synthesis of colloidally stable, brightly luminescent perfluorodecyl-capped silicon nanocrystals and compare the properties of solutions and films made from them with those of their perhydrodecyl-capped relatives. The perfluorodecyl capping group compared to the perhydrodecyl capping group yields superior hydrophobicity and much greater resistance to air oxidation, the enhanced electron-withdrawing character induces blue shifts in the wavelength of photoluminescence, and the lower-frequency carbon-fluorine stretching modes disfavor non-radiative relaxation pathways and boost the absolute photoluminescence quantum yield. Together these attributes bode well for advanced materials and biomedical applications founded upon perfluorodecyl-protected silicon nanocrystals

Size-Dependent Absolute Quantum Yields for Size-Separated Colloidally-Stable Silicon Nanocrystals

Size-selective precipitation was used to successfully separate colloidally stable allylbenzene-capped silicon nanocrystals into several visible emitting monodisperse fractions traversing the quantum size effect range of 1–5 nm. This enabled the measurement of the absolute quantum yield and lifetime of photoluminescence of allylbenzene-capped silicon nanocrystals as a function of size. The absolute quantum yield and lifetime are found to monotonically decrease with decreasing nanocrystal size, which implies that nonradiative vibrational and surface defect effects overwhelm spatial confinement effects that favor radiative relaxation. Visible emission absolute quantum yields as high as 43% speak well for the development of “green” silicon nanocrystal color-tunable light emitting diodes that can potentially match the performance of their toxic heavy metal chalcogenide counterparts

The Green Chemistry Initiative’s contributions to education at the University of Toronto and beyond

The Green Chemistry Initiative (GCI) is a student-led group founded in 2012 with the primary mission of promoting green chemistry education at the University of Toronto. In order to achieve this, the GCI’s activities have included undergraduate curriculum development, arrangement of an external speaker seminar series, and organization of an annual three-day symposium along with biweekly trivia challenges. To broaden education beyond the Department of Chemistry, a successful YouTube video campaign articulating the Twelve Principles of Green Chemistry in an accessible manner has also been undertaken (acquiring over 40,000 views), in addition to monthly blog posts and conference/outreach presentations. Descriptions of these activities are discussed in this paper, along with the resulting impact they have had. Through such efforts, undergraduate and graduate students are showing a growing understanding of the relevance of green chemistry in today’s world, with the GCI serving as a platform for similar groups to build upon across Canada

Non-wettable, Oxidation-Stable, Brightly Luminescent, Perfluorodecyl-Capped Silicon Nanocrystal Film

Here we describe for the first time the synthesis of colloidally stable, brightly luminescent per­fluoro­decyl-capped silicon nano­crystals and compare the properties of solutions and films made from them with those of their per­hydro­decyl-capped relatives. The per­fluoro­decyl capping group compared to the per­hydro­decyl capping group yields superior hydro­phobicity and much greater resistance to air oxidation, the enhanced electron-withdrawing character induces blue shifts in the wavelength of photo­lumin­escence, and the lower-frequency carbon–fluorine stretching modes disfavor non-radiative relaxation pathways and boost the absolute photo­lumin­escence quantum yield. Together these attributes bode well for advanced materials and biomedical applications founded upon per­fluoro­decyl-protected silicon nanocrystals