Molecular photonic switch

Figure 5.14 shows an example of a molecular photonic switch in which a Ru complex and an Os complex are bridged by an azobipyridine ligand. The emission of this complex changes depending on the redox state of the... 

New natural polymers based on synthesis from renewable resources, improved recyclability based on retrosynthesis to reusable precursors, and molecular suicide switches to initiate biodegradation on demand are the exciting areas in polymer science. In the area of biomolecular materials, new materials for implants with improved durability and biocompatibility, light-harvesting materials based on biomimicry of photosynthetic systems, and biosensors for analysis and artificial enzymes for bioremediation will present the breakthrough opportunities. Finally, in the field of electronics and photonics, the new challenges are molecular switches, transistors, and other electronic components molecular photoad-dressable memory devices and ferroelectrics and ferromagnets based on nonmetals. 

The area of molecular nonlinear optics has been rejuvenated by efforts to investigate three-dimensional multipolar systems, functionalized polymers as optoelectronic materials, near infrared optical parametric oscillators and related aspects.71 There have been some advances in chromophore design for second-order nonlinear optical materials 72 these include onedimensional CT molecules, octopolar compounds and organometallics. Some of the polydiacetylenes and poly(/>-phenylenevinylene)s appear to possess the required properties for use as third-order nonlinear optical materials for photonic switching.73... 

Substantial progress has been accomplished in the fabrication of molecular and biomolecular optoelectronic devices. Light-activated molecular and bio-molecular systems have been integrated with electronic transducers, and the optical switching of the systems has been electronically transduced to the macroscopic environment. In particular, the photonic switching of an electron-transfer cascade has allowed the amplified electronic transduction of an input... 

A current challenge is the development of efficient strategies for the design of switchable nonlinear optical (NLO) materials. The ability to switch the NLO activity of a molecule on and off is of relevance for the development of molecular photonic devices, as those properties can be... 

Porphyrins and metalloporphyrins represent a highly advantageous class of building blocks for the construction of large functional supramolecular architectures. These architectures have potential applications as new photonic materials, molecular wires, switches, photon funnels. 

A clever choice of molecular components and their assembly in suitable sequences enable the design of very interesting molecular-level photonic switches for photoin-duced energy and electron transfer processes. 

In this chapter we have described various types of diarylethene derivatives with different functionalities. The characteristic features of the photochromic reactions, such as switch of Ji-conjugation length, geometrical structure changes, and electric as well as vibrational structure changes, can find applications in various molecular photonics devices. 

From a different perspective, the lumophore appended receptor represents a molecular-scale light switch, which is triggered by a chemical species (whether or not it is of biological or technological consequence). Thus, photonic signals can be chemically generated with spatial, temporal, colour... 

Such a stationary minimum on the distribution curve has tentatively been ascribed by Kurbatov et al. to a pre-ionization process from a high excited molecular level, situated near the first-excited leyel of the ion. The neutral excited molecule M could switch, during its lifetime, to the state M+ + e (process 3 in Section III). This suggestion is, however, doubtful, since it implies that the excitation of the molecule to a higher state decreases the probability of the direct transitions to the ionized state. For benzene, o-, m-xylene, mesitylene, and durene, when the photons exceed Ip by 2.3-2.6 e.v., new sharp maxima of slow electrons appear. 

The substrate carries information defined by its molecular recognition features and constitutes a signal that may be modulated by the switching process. The stimulus to which the switch responds and the substrate on which it operates may both be either of photonic, electronic, ionic, magnetic, thermal or mechanical nature. Thus, a whole set of switches based on (substrate-stimulus) pairs, is defined by the combination of the various types opto-photo, opto-electro, electro-photo, etc. 

In general, optically, electrically or chemically triggered switches would seem to be preferable to mechanically activated ones, as are photo-, electro- and chemo devices with respect to mechano devices and electronic or photonic computing with respect to mechanical computing. The ultimate in (nano)mechanical manipulation of a molecular device is represented by the realization of a bistable switch based on the motion of a single atom by means of the scanning tunnelling microscope [8.295] (see also Section 9.9). 

The formation of photonic, electronic, ionic switching devices from molecular components and their incorporation into well-defined organized assemblies represents the next step towards the development of circuitry and functional materials at... 

The situation changes sharply the moment the receptor module within the molecular system captures the chosen analyte (which is a cation for the purposes of illustration). Again, if we consider excitation of the lumophore module, we find the analyte influences the transferring electron. At the simplest level, this is due to electrostatic charge attraction between the jumping electron and the captured analyte. So the photoinduced electron transfer is arrested and the unused energy of the excited state is dumped as a luminescence photon. This is how the analyte population is visualized. Now we have the on state of the molecular switch. 

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