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The construction of buildings has a very important impact on the environment, and the process of manufacturing and transporting of building materials, and installing and constructing of buildings consumes great energy and emits large quantity of greenhouse gas (GHG). The present paper defines four sources of GHG emissions in building construction, which are: manufacture and transportation of building materials; energy consumption of construction equipment; energy consumption for processing resources; and disposal of construction waste, and then establishes the calculation method of GHG emissions. This paper presents a case study of GHG emissions in building construction in Hong Kong.The results show that 82-87% of the total GHG emissions are from the embodied GHG emissions of building materials, 6-8% are from the transportation of building materials, and 6-9% are due to the energy consumption of construction equipment. The results also indicate that embodied GHG emissions of concrete and reinforced steel account for 94-95% of those of all building materials, and thus the use of This is the Pre-Published Version.-2 -recycled building materials, especially reinforced steel, would decrease the GHG emissions by a considerable amount.

Capping or functionalization of semiconductor quantum dots (QDs) is unavoidable for their photostability in practical use including sensitizer and biological tagging agents. However, the efficiency of the electron/hole transport from the photoexcited QDs to the external environments across the capping shell is not well-understood. In this study we report on the femtosecond carrier dynamics of core−shell type CdSe−ZnS semiconductor QDs of various sizes. Steady-state spectroscopic studies followed by picosecond-resolved time correlated single photon counting (TCSPC) experiments on the complexation of the QDs with a well-known electron acceptor, benzoquinone (BQ), reveal that the complex is essentially static in nature. Femtosecond-resolved fluorescence upconversion experiments on the complex explore the dynamics of electron transport from core CdSe to BQ via ZnS shell. The dependence of the electron transport dynamics on the core size of the QDs has also been explored. We have also studied the dynamics of electron transport from the core CdSe of various sizes to another TiO2 nanoparticle as an electron acceptor across the shell. Our studies support the relevance of core shell type semiconducting quantum dots in light harvesting devices.

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