Bright molecules with sense, logic, numeracy and utility

Abstract

Using cartoons as an organizational aid, we illustrate how the 'fluorophore-spacer-receptor' format of fluorescent PET (photoinduced electron transfer) sensors and switches can be logically extended in many different directions. These include emissive sensors for various chemical species and properties, and exploit various kinds of emission. Common sensing issues such as dynamic range, internal referencing, selectivity, mapping and space resolution are addressed. The sensory output function is also developed into more complex forms, molecular logic/computation being one such example. Molecular logic leads to molecular arithmetic. Real-life applications to physiological monitoring, medical diagnostics and molecular computational identification of small objects are included.

Functionalization of single-walled carbon nanotubes with optically switchable spiropyrans

“…Already in his early work Hirshberg envisaged the suitability of such compounds as photochemical erasable memory [14]. Furthermore, optical molecular switches have attracted much attention as a result of their potential use in optical data storage and digital processing [9], sensing [15] and photoregenerable surface modifications [13]. The preparation of integrated nanomaterials where switchable molecular units are coupled to SWCNTs has received some interest recently [16][17][18][19], with Haddon and co-workers initially demonstrating the possibility of photo-inducing electronic transitions in semiconducting nanotubes [16].…”

Information gathering and processing with fluorescent molecules

“…The pKa value of the indicator, which determines the position of the input/output characteristic on the pH axis, should be adjustable by electrostatic repulsion between the receptor-bound proton and another cation held closeby. Modifying the 'fluorophore-spacer-receptor' structure to a 'fluorophore-spacer1-receptor1-spacer2-receptor2' system, 34 where the second receptor is not capable of engaging in any major interactions with the fluorophore, achieves this purpose. Of course, the receptor1 should target only protons and receptor2 should interact with cations other than protons.…”

Taking baby steps in molecular logic-based computation

“…60 However, this characteristic function is tunable with a third variable. Similar tuning of the sigmoidal intensity-pH profile can be arranged by employing a 'fluorophore-spacer1-receptor1-spacer2-receptor2' system, 53 where the second receptor is not capable of engaging in any major 70 interactions with the fluorophore (Figure 4). Now, the pKa value of the sensor becomes adjustable by electrostatic repulsion between the receptor1-bound H + and another cation held by receptor2 provided that the two receptors actions are orthogonal.…”