Water plays a pivotal role in structural stability of supramolecular pigment assemblies designed for natural light harvesting (for example, chlorosome antenna complex) as well as their artificial analogs. However, the dynamic role of water in the context of excite‐state relaxation has not been explored till date, which we report here. Using femtosecond transient absorption spectroscopy, we investigate the excited‐state dynamics of two types of nano‐scale assemblies of chlorophyll a with different structural motifs, rod‐shaped and micellar assemblies, that depend on the water content. We show how water participates in excess energy dissipation by vibrational cooling of the non‐thermally populated Qy band at different rates in different types of clusters but exhibits no polar solvation dynamics. For the micelles, we observe a bifurcation of stimulated emission line shape, whereas a positive‐to‐negative switching of differential absorption is observed for the rods; both these observations are correlated with their specific structural aspects. Density functional theory calculations reveal two possible stable ground state geometries of dimers, accounting for the bifurcation of line shape in micelles. Thus, our study elucidates water‐mediated structure–function relationship within these pigment assemblies.
Designing new donor-acceptor systems and probing their energy/electron transfer dynamics is essential in the context of development of biomimetic photosynthetic systems. In this work, we have designed, synthesized and characterized...
The world has witnessed a substantial upsurge in energy demand in the recent decades, which has concurrently led to increased environmental contamination due to the use of carbon-based fuels to meet this demand. The increased pollution levels across the globe combined with the rapid depletion of these carbon-based non-renewable sources of energy has forced nations to adopt cleaner sources such as solar energy, wind energy, biomass etc. for meeting energy requirements. Utilities and power transmission companies, in several countries, have begun installation and operation of large-scale solar energy projects in order to augment the present electricity generation capacity. India has a tremendous potential for solar energy as 58% of the total land area receives an average solar insolation above 5 kWh/m 2 /day, annually. However, PV installations require proper economic formulation and technical modelling of PV plants. The study presented in this paper investigates the feasibility of installing a 1 MW grid-connected PV system in the arid climatic conditions of India. Four different regions of the Thar Desert: Barmer, Jodhpur, Jaisalmer, and Kalan Ghat have been considered for the study. A comparative study has been laid out based on energy yields, losses, and degradation of various module technologies namely Mono-Si, Poly-Si, CdTe, and CIS. The performance of the PV systems has been evaluated both in the fixed-tilt and variable-tilt configurations. Simulation results show that the daily yield in winter months ranges between 5.8 and 6.9 MWh/day whereas, during summer, it ranges between 5 and 7.1 MWh/day. The study suggests that CIS module is expected to produce highest annual energy yield of 2471 MWh with a PR of 86.1%, in the variable-tilt configuration for the Jaisalmer region. Annual energy loss due to temperature is expected to be highest for Mono-Si technology (14.4%) in the variable-tilt configuration and lowest for CIS technology (9.4%) in the fixed-tilt configuation. Moreover, mismatch losses for all the four technologies lie in the range of 0.1-1.1%.
Charge‐transfer excited state (CTES) defines the ability to split photon energy into work producing redox equivalents suitable for photocatalysis. Here, we report inter‐net CTES formation within a two‐fold catenated crystalline metal–organic framework (MOF), constructed with two linkers, N,N′‐di(4‐pyridyl)‐1,4,5,8‐naphthalenetetracarboxydiimide (DPNDI) and 2,6‐dicarboxynaphthalene (NDC). The structural flexibility puts two complementary linkers from two nets in a proximal position to interact strongly. Supported by the electrochemical and steady‐state electronic spectroscopic data, this ground‐state interaction facilitates forming CTES that can be populated by direct excitation. We map the dynamics of the CTES which persists over a few nanoseconds and highlight the utilities of such relatively long‐lived CTES as enhanced conductivity of the MOF under light over that measured in dark and as a proof‐of‐the‐principle test, photo‐reduction of methyl viologen under white light.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.