Molecular Dyads Comprising Metalloporphyrin and Alkynylplatinum(II) Polypyridine Terminal Groups for Use as a Sensitizer in Dye‐Sensitized Solar Cells

A new class of molecular dyads comprising metalloporphyrin‐linked alkynylplatinum(II) polypyridine complexes with carboxylic acids as anchoring groups has been designed and synthesized. These complexes can sensitize nanocrystalline TiO₂ in dye‐sensitized solar cell (DSSC) studies. The photophysical, electrochemical, and luminescence properties of the complexes were studied and their excited‐state properties were investigated by nanosecond transient absorption spectroscopy, with the charge‐separated [Por^.??{(C?C)Pt(tBu₃tpy)}^.+] state observed upon excitation. Excited‐state redox potentials were determined; the electrochemical data supports the capability of the complexes to inject an electron into the conduction band of TiO₂. The complexes sensitize nanocrystalline TiO₂ and exhibited photovoltaic properties, as characterized by current–voltage measurements under illumination of air mass 1.5 G sunlight (100 mWcm^?2). A DSSC based on one of the complexes showed a short‐circuit photocurrent of 10.1 mAcm^?2, an open‐circuit voltage of 0.64 V, and a fill factor of 0.52, giving an overall power conversion efficiency of 3.4 %.     

Si-based two-dimensional photonic crystals coupled to one-dimensional Bragg mirrors

Planar two-dimensional photonic crystals can be combined with a one-dimensional Bragg mirror to control the quality factor and out-of-plane coupling of optical Bloch modes. We have investigated the optical properties of such structures fabricated on silicon. The photonic crystals are fabricated in the upper Si layer deposited on top of quarter-wave thick SiO₂-polycrystalline Si layers. The optical properties are probed by the room-temperature photoluminescence of Ge/Si self-assembled islands as an internal source. We show that an enhancement of the quality factor can be obtained by controlling the thickness of the silicon upper layer in which the two-dimensional photonic crystal is etched and by controlling the air filling factor of the photonic crystal. Quality factors of 2200 around 1100 nm are obtained by this method for defect-free photonic crystals with a square lattice pattern. The experimental results are supported by three-dimensional finite-difference time-domain (FDTD) calculations of the radiated modes for the investigated structures.     

From centrality to temporary fame: Dynamic centrality in complex networks

We develop a new approach to the study of the dynamics of link utilization in complex networks using records of communication in a large social network. Counter to the perspective that nodes have particular roles, we find roles change dramatically from day to day. “Local hubs” have a power law degree distribution over time, with no characteristic degree value. Our results imply a significant reinterpretation of the concept of node centrality in complex networks, and among other conclusions suggest that interventions targeting hubs will have significantly less effect than previously thought. © 2006 Wiley Periodicals, Inc. Complexity 12: 59–63, 2006     

A chiral luminescent Au16 ring self-assembled from achiral components

A luminescent supramolecular chiral Au16 ring with 4.822 nm perimeter that self-assembled from a tetrameric array of achiral Au2 units is described. Intra- and intermolecular Au...Au interactions play an important role in directing its chiral self-assembly.     

Stimulated brillouin scattering from CO2 laser produced plasma

Preliminary observations of stimulated backscatter from CO₂ laser produced plasma are reported. The scattered radiation has been spectrally resolved and the measured shift found to be consistent with that expected from ion acoustic waves. The change in wavelength shift when helium is substituted for hydrogen is in agreement with √m_i, where m_i = ion mass.     

Discrete observer in the design of sampled-data control systems

This paper considers the problem of designing a feedback controller for sampled-data systems by using a discrete observer. Longitudinal control of an automated transit vehicle is used as an example to discuss the application of the discrete-observer design.     

Ruthenium(II) complexes in polymerised bicontinuous microemulsions

Novel polymerised bicontinuous microemulsions can provide unique microenvironments for some functional molecules of scientific interests and practical applications.     

From big data to important information

Advances in science are being sought in newly available opportunities to collect massive quantities of data about complex systems. While key advances are being made in detailed mapping of systems, how to relate these data to solving many of the challenges facing humanity is unclear. The questions we often wish to address require identifying the impact of interventions on the system and that impact is not apparent in the detailed data that is available. Here, we review key concepts and motivate a general framework for building larger scale views of complex systems and for characterizing the importance of information in physical, biological, and social systems. We provide examples of its application to evolutionary biology with relevance to ecology, biodiversity, pandemics, and human lifespan, and in the context of social systems with relevance to ethnic violence, global food prices, and stock market panic. Framing scientific inquiry as an effort to determine what is important and unimportant is a means for advancing our understanding and addressing many practical concerns, such as economic development or treating disease. © 2016 Wiley Periodicals, Inc. Complexity 21: 73–98, 2016     

Photochromic Dithienylethene‐Containing Triarylborane Derivatives: Facile Approach to Modulate Photochromic Properties with Multi‐addressable Functions

A series of dithienylethene‐containing triarylboranes has been designed, synthesized, and characterized. The electrochemistry, photophysics, and photochromic behavior have also been studied. The photophysical and photochromic properties could be facilely tuned in this system by varying the thiophene spacers (thiophene, thienothiophene, and bithiophene) between the dithienylethene and the dimesitylboron (BMes₂) or the position of the BMes₂ substitution in the thiophene spacers. The absorption of closed form has been found to be more sensitive towards the structural modification upon incorporation of the BMes₂ unit. Moreover, multi‐addressable photochromic reactivity is obtained upon addition of Lewis base (F^?), which is due to the formation of boron–Lewis base adduct. The dependence of the photophysical and photochromic properties on the thiophene spacers and the position of the BMes₂ substitution has been further supported by computational studies.