Harnessing electron transfer from the perchlorotriphenylmethide anion to Y@C82(C(2v)) to engineer an endometallofullerene-based salt.

We show that electron transfer from the perchlorotriphenylmethide anion (PTM(-)) to Y@C82(C2v) is an instantaneous process, suggesting potential applications for using PTM(-) to perform redox titrations of numerous endohedral metallofullerenes. The first representative of a Y@C82-based salt containing the complex cation was prepared by treating Y@C82(C2v) with the [K(+)([18]crown-6)]PTM(-) salt. The synthesis developed involves the use of the [K(+)([18]crown-6)]PTM(-) salt as a provider of both a complex cation and an electron-donating anion that is able to reduce Y@C82 C2v). For the first time, the molar absorption coefficients for neutral and anionic forms of the pure isomer of Y@C82(C2v) were determined in organic solvents with significantly different polarities.

Emergent Insulator-Metal Transition with Tunable Optical and Electrical Gap in Thin Films of a Molecular Conducting Composite.

Composites exhibit unique synergistic properties emerging when components with different properties are combined. The tuning of the energy bandgap in the electronic structure of the material allows designing tailor-made systems with desirable mechanical, electrical, optical, and/or thermal properties. Here, we study an emergent insulator-metal transition at room temperature in bilayered (BL) thin-films comprised of polycarbonate/molecular-metal composites. Temperature-dependent resistance measurements allow monitoring of the electrical bandgap, which is in agreement with the optical bandgap extracted by optical absorption spectroscopy. The semiconductor-like properties of BL films, made with bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF or ET) α-ET2I3 (nano)microcrystals as two-dimensional molecular conductor on one side and insulator polycarbonate as a second ingredient, are attributed to an emergent phenomenon equivalent to the transition from an insulator to a metal. This made it possible to obtain semiconducting BL films with tunable electrical/optical bandgaps ranging from 0 to 2.9 eV. A remarkable aspect is the similarity close to room temperature of the thermal and mechanical properties of both composite components, making these materials ideal candidates to fabricate flexible and soft sensors for stress, pressure, and temperature aiming at applications in wearable human health care and bioelectronics.

Functionalization of polyacrylamide for nanotrapping positively charged biomolecules.

Engineering new materials which are capable of trapping biomolecules in nanoscale quantities, is crucial in order to achieve earlier diagnostics in different diseases. This article demonstrates that using free radical copolymerization, polyacrylamide can be successfully functionalized with specific synthons for nanotrapping positively charged molecules, such as numerous proteins, through electrostatic interactions due to their negative charge. Specifically, two functional random copolymers, acrylamide/acrylic acid (1) and acrylamide/acrylic acid/N-(pyridin-4-yl-methyl)acrylamide (2), whose negative net charges differ in their water solutions, were synthetized and their ability to trap positively charged proteins was studied using myoglobin as a proof-of-concept example. In aqueous solutions, copolymer 1, whose net charge for a 100 chain fragment (Q pH 6/M) is -1.323 × 10-3, interacted with myoglobin forming a stable monodisperse nanosuspension. In contrast, copolymer 2, whose value of Q pH 6/M equals -0.361 × 10-3, was not able to form stable particles with myoglobin. Nevertheless, thin films of both copolymers were grown using a dewetting process, which exhibited nanoscale cavities capable of trapping different amounts of myoglobin, as demonstrated by bimodal AFM imaging. The simple procedures used to build protein traps make this engineering approach promising for the development of new materials for biomedical applications where trapping biomolecules is required.

Harnessing ICl reduction processes for synthesis of different BEDT-TTF-based molecular conductors.

Both calculations and experimental data, showing the possibility of formation of I3-, I2Cl-, and ICl2- anions through ICl reduction processes, are described in detail. The above processes were used successfully for the preparation of different molecular conductors based on trihalide anions and bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF). The reaction between ICl and BEDT-TTF occurring in a strong polar reaction media (epsilon > or = 34.8 D) results in the formation of novel molecular conductors containing different sets of the I3-, I2Cl-, and ICl2- anions: beta-(BEDT-TTF)2[(I3)0.4(I2Cl)0.6], beta'BEDT-TTF)2[(I2Cl)0.2(ICl2)0.8], and beta' '-('-(BEDT-TTF)2[(I3)0.075(I2Cl)0.150(ICl2). These molecular conductors reveal semiconducting (beta'-phase) as well as metallic (beta- and beta' '-phases) transport properties. It is also shown that in the reaction media with polarity less than 18.4 D only the I3- anion is incorporated in the BEDT-TTF-based molecular crystals. This fact is an unexpected outcome of our study.

Prototype of a nanostructured sensing contact lens for noninvasive intraocular pressure monitoring.

PURPOSE: To present the application of a new sensor based on a flexible, highly piezoresistive, nanocomposite, all-organic bilayer (BL) adapted to a contact lens (CL) for non-invasive monitoring intraocular pressure (IOP). METHODS: A prototype of a sensing CL, adapted to a pig eyeball, was tested on different enucleated pig eyes. A rigid, gas-permeable CL was designed as a doughnut shape with a 3-mm hole, where the BL film-based sensor was incorporated. The sensor was a polycarbonate film coated with a polycrystalline layer of the highly piezoresistive molecular conductor ß-(ET)2I3, which can detect deformations caused by pressure changes of 1 mm Hg. The pig eyeballs were subjected to controlled-pressure variations (low-pressure transducer) to register the electrical resistance response of the CL sensor to pressure changes. Similarly, a CL sensor was designed according to the anatomic characteristics of the eye of a volunteer on the research team. RESULTS: A good correlation (r² = 0.99) was demonstrated between the sensing CL electrical response, and IOP (mm Hg) changes in pig eyes, with a sensitivity of 0.4 Ω/mm Hg. A human eye test also showed the high potential of this new sensor (IOP variations caused by eye massage, blinking, and eye movements were registered). CONCLUSIONS: A new nanostructured sensing CL for continuous monitoring of IOP was validated in an in vitro model (porcine eyeball) and in a human eye. This prototype has adequate sensitivity to continuously monitor IOP. This device will be useful for glaucoma diagnosis and treatment.

Linked crystallites in the conducting topmost layer of polymer bilayer films controlled by temperature: from micro- to nanocrystallites.

Temperature has great impact on the structure and size of the linked crystallites of the conducting topmost layer formed at the surface of a polycarbonate film via the reaction BEDT-TTF+IBr [BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene]. We show that fine temperature control permits formation of a semiconducting topmost layer of alpha'-(BEDT-TTF)(2)(I(x)Br(1-x))(3) crystallites with either micro- or nanometre size, a result that opens a route to miniaturized conducting plastic materials.

Multistability in a BEDT-TTF based molecular conductor.

The low dimensional organic conductor (BEDT-TTF)(2)Br(1.3)I(1.1)Cl(0.6) [BEDT-TTF = bis(ethylenedithio)tertathiafulvalene] is shown to be a unique molecular solid that exists in three crystalline polymorphic forms (alpha'-, alpha' "-, beta' '-phase) and, surprisingly, is able to adopt the same metal-like beta' '-phase at both low (T < 185 K) and high (T > 395 K) temperatures. Several crystals of the alpha'- and alpha' "-phases have been studied using three different techniques: dc-conductivity measurements, ESR spectroscopy, and X-ray diffraction analysis. All these techniques show the existence of the reversible semiconductor <--> metal (alpha' " <--> beta' ') phase transition at both high and low temperatures as well as the alpha' <--> alpha' " phase transition at high temperatures. The phase transitions of these polymorphs are characterized by huge hysteresis and dramatic changes in the transport and magnetic properties. Based on ab initio calculations, it is suggested that dipole-dipole interactions can play a key role in the rich polymorphism of this molecular solid.