Raffaello Papadakis

By Raffaello Papadakis, Ioanna Deligkiozi and Hu Li

Organic compounds and materials with photoconductive properties have been studied for many years because of their importance in many technological applications such as dye-sensitized solar cells, photodiodes, photoresistors, electronics, biomolecular sensing, etc. For multiple purposes, such molecules require intense protection from various factors which can decrease their durability and cause fatigue. Interlocked molecules and macromolecules involving photoconductive organic components and various types of macrocycles, such as cyclodextrins, cyclophanes, or macrocyclic ethers, are promising candidates for new photoconductivity-related applications. In this chapter, a review in this emerging research area in materials science and technology is provided. Focus is placed on photoconductive (poly)rotaxanes and (poly)catenanes. Various types of such materials and compounds are reviewed, and recent examples are provided. The relation between their structure and photoconductive behavior is discussed.

Part of the book: Advances in Photodetectors

By Raffaello Papadakis and Ioanna Deligkiozi

Today it is well-established that solvents demonstrate an important role in chemistry. Solvents are able to affect the reactivity, as well as the electronic, optical, and generally physicochemical properties of compounds in solution. Taking this into account, in this chapter we analyze the importance of solvent polarity in phenomena closely related to supramolecular systems as well as the aptitude of various supramolecules to interact with solvent molecules and thus to give rise to chromic effects such as solvatochromism. Main focus is placed on mechanically interlocked molecules, e.g., rotaxanes, catenanes, etc., exhibiting solvent-controlled shuttling movements, switching, and/or solvatochromism. The effect of solvents in various supramolecular architectures is a further focus of this chapter.

Part of the book: Solvents, Ionic Liquids and Solvent Effects

By Ioanna Deligkiozi and Raffaello Papadakis

In this work three molecules exhibiting dual sensing solvatochromic behaviors are examined in the context of solvation in binary solvent mixtures (BSMs). The compounds studied involve two functional groups with high responsiveness to solvent polarity namely pentacyanoferrate(II) (PC) and azo groups. Two of these compounds are [2]rotaxanes involving alpha- or beta- cyclodextrin (CyD) and the third is their CyD-free precursor. The dual solvatochromic behavior of these compounds is investigated in water/ethlylene glycol (EG) mixtures and their dual solvatochromic responses are assessed in terms of the intensity of solvatochromism and the extent of preferential solvation. To achieve this the linear solvation model by Kamlet, Abboud and Taft [J. Organomet. Chem. 1983, 48, 2877–2887] and the two-phase model of solvation by Bagchi and coworkers [J. Phys. Chem. 1991, 95, 3311–3314] are employed. The influence of the presence or lack of CyD (alpha- or beta-) on these dual solvatochromic sensors is analyzed.

Part of the book: Dyes and Pigments

By Raffaello Papadakis

Part of the book: Dyes and Pigments

By Hu Li and Raffaello Papadakis

Graphene is a two-dimensional allotrope of carbon with a range of highly attractive physicochemical properties suitable for a wide variety of applications. In the context of fluorescence imaging graphene and its derivatives have recently started to gain more attention since they could assist in the enhancement of imaging of cells, tissue, or other biologically relevant samples such as cell organoids for example mitochondria as well as in the imaging of cancer cells, tumors, and various pathogens. This chapter attempts to cover the most relevant, recent advances in this growing research field. Some basic information on the physical and (photo)chemical properties of important members of the graphene family is provided. Additionally, novel approaches involving graphene-based materials (GBMs) in cellular and tissue imaging systems are reviewed. Important examples of contemporary applications of GBMs in cancer detection using fluorescence imaging are also presented. The specific role of graphene (or other GBMs) in each case is explained and analyzed. Finally, future perspectives and novel applications of fluorescent imaging techniques involving GBMs are discussed.

Part of the book: Fluorescence Imaging