Combined spectroscopic and theoretical analysis of the binding of a water-soluble perylene diimide to DNA/RNA polynucleotides and G-quadruplexes

We present here a combined spectroscopic and theoretical analysis of the binding of N,N'-bis(2-(1-piperazino)ethyl)-3,4,9,10-perylenetetracarboxylic acid diimide dichloride (PZPERY) to different biosubstrates. Absorbance titrations and circular dichroism experiments, melting studies and isothermal calorimetry (ITC) titrations reveal a picture where the binding to natural double-stranded DNA is very different from that to double and triple-stranded RNAs (poly(A)∙poly(U) and poly(U)∙poly(A)⁎poly(U)). As confirmed also by the structural and energetic details clarified by density functional theory (DFT) calculations, intercalation occurs for DNA, with a process driven by the combination of aggregates disruption and monomers intercalation. Oppositely, for RNAs, no intercalation but groove binding with the formation of supramolecular aggregates is observed. Among all the tested biosubstrates, the affinity of PZPERY towards DNA G-quadruplexes (G4) is the greatest one with a preference for human telomeric G4s. Focusing on hybrid G4 forms, either sitting-atop ("tetrad-parallel") or lateral ("groove-parallel") binding modes were considered in the discussion of the experimental results and molecular dynamics (MD) simulations. Both turned out to be possible concurrently, in agreement also with the experimental binding stoichiometries higher than 2:1.

Chemical and Temperature Sensors Based on Functionalized Reduced Graphene Oxide

In this work, we investigated the functionalization of reduced graphene oxide (rGO) with 2-(dodecen-1-yl) succinic anhydride (TPSA) to increase the rGO effective interactions with organic solvents both in liquid and vapor phases. Thermogravimetric analysis, STEM, XPS, FTIR-ATR, and Raman spectroscopy confirmed the effective functionalization of rGO with about the 30 wt% of grafted TPSA without affecting the structural characteristics of graphene but successfully enhancing its dispersibility in the selected solvent except for the apolar hexane. Solid TPSA-rGO dispersions displayed a reproducible semiconducting (activated) electrical transport with decreased resistance when heated from 20 °C to 60 °C and with a negative temperature coefficient of 10−3 K−1, i.e., comparable in absolute value with temperature coefficient in metals. It is worth noting that the same solid dispersions showed electrical resistance variation upon exposure to vapors with a detection limit in the order of 10 ppm and sensitivity α of about 10−4 ppm−1.

Electrically-Conductive Polyketone Nanocomposites Based on Reduced Graphene Oxide

In this work, we investigated the functionalization of polyketone 30 (PK30) with glycyl-glycine (Gly-Gly) via the Paal-Knorr reaction with the aim of homogenously dispersing two types of reduced graphene oxide (rGO, i.e., lrGO and hrGO, the former characterized by a lower degree of reduction in comparison to the latter) by non-covalent interactions. The functional PK30-Gly-Gly polymer was effective in preparing composites with homogeneously distributed rGO characterized by an effective percolation threshold at 5 wt. %. All the composites showed a typical semiconductive behavior and stable electrical response after several heating/cooling cycles from 30 to 115 °C. Composites made by hrGO displayed the same resistive behaviour even if flanked by a considerable improvement on conductivity, in agreement with the more reduced rGO content. Interestingly, no permanent percolative network was shown by the composite with 4 wt. % of lrGO at temperatures higher than 45 °C. This material can be used as an ON-OFF temperature sensor and could find interesting applications as sensing material in soft robotics applications.

Effect of the Polyketone Aromatic Pendent Groups on the Electrical Conductivity of the Derived MWCNTs-Based Nanocomposites

Electrically conductive plastics with a stable electric response within a wide temperature range are promising substitutes of conventional inorganic conductive materials. This study examines the preparation of thermoplastic polyketones (PK30) functionalized by the Paal⁻Knorr process with phenyl (PEA), thiophene (TMA), and pyrene (PMA) pendent groups with the aim of optimizing the non-covalent functionalization of multiwalled carbon nanotubes (MWCNTs) through π⁻π interactions. Among all the aromatic functionalities grafted to the PK30 backbone, the extended aromatic nuclei of PMA were found to be particularly effective in preparing well exfoliated and undamaged MWCNTs dispersions with a well-defined conductive percolative network above the 2 wt % of loading and in freshly prepared nanocomposites as well. The efficient and superior π⁻π interactions between PK30PMA and MWCNTs consistently supported the formation of nanocomposites with a highly stable electrical response after thermal solicitations such as temperature annealing at the softening point, IR radiation exposure, as well as several heating/cooling cycles from room temperature to 75 °C.

An easy synthetic way to exfoliate and stabilize MWCNTs in a thermoplastic pyrrole-containing matrix assisted by hydrogen bonds

MWCNTs were dispersed in a thermoplastic polymer containing pyrrole units in the main chain and hydroxyl pendant groups, affording a well-distributed percolative network. The resulting soft nanocomposite shows stable conductive behavior.

Key role of the linker in pyrene-linker-carboxylate surfactants for the efficient aqueous dispersion of multiwalled carbon nanotubes

This study establishes that the structure of the linker group between the hydrophobic and hydrophilic units in the new surfactants 1–13 plays an important role in the dispersibility of multiwalled carbon nanotubes (MWNTs) in water.