On the Sensing Mechanisms of a Hydroresistive Flexible Film Based on an Organic Molecular Metal (original) (raw)
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Comprehensive Approach to the Interpretation of the Electrical Properties of Film-Forming Molecules
The Journal of Physical Chemistry B
This paper presents a general protocol for the interpretation of the electric surface potential of Langmuir monolayers based on a three-layer capacitor model. The measured values were correlated with the results from DFT molecular dynamics simulations, and, as a result, the local dielectric permittivities and dipole-moment components of molecules organized in the monolayer were obtained. The main advantage of the developed approach is applicability to amphiphiles of any type; irrespective of the structure of the polar head as well as the molecular organization and inclination in the surface film. The developed methodology was successively applied to an atypical surface-active compound, perfluorodecyldecane, and its derivatives containing the hydroxyl, thiol, and carboxyl moiety. The following contributions to the apparent dipole moments connected with the reorientation of water molecules and local dielectric permittivities in the vicinity of polar and apolar molecule parts, respectively, were determined: μ w /ε w = −0.85 D, ε p = 5.00, and ε a = 1.80. Moreover, the investigated perfluorodecyldecane derivatives were comprehensively characterized in terms of their surface activity, film rheology, and effective surface dissociation equilibria. The proposed methodology may be crucial for the process of the design and the preliminary characterization of molecules for sensor and material science applications.
Langmuir, 1987
The considerable activity in the area of organic thin f i i , involving very thin polymeric f i i and molecular monolayers and multilayers, led to the formation of a panel, sponsored by the Materials Sciences Division of the Department of Energy, to review this field. Its purpose was to better understand the relevant scientific topics and to suggest suitable areas of research. In particular, a number of potential applications were identified, which require further scientific advances for them to see fruition. These include nonlinear and active optical devices, chemical, biochemical, and physical sensors, protective layers (e.g., for passivation), patternable materials both for resists and for mass information storage, surface modification (e.g., wetting and electrochemical electrode properties), and synthetic biomacromolecules. Studies of these films have the added advantage that they could lead to a better scientific understanding of such subjects as the relationships between the microstructure of ordered molecular arrays and their collective properties, the tailoring of interfaces and surfaces, especially when used to model multibody interactions, and the physical and chemical reactions of films involving phase transitions and intra-and interfilm transport. The areas that appear to require the most attention include the application of new characterization techniques, such m the scanning tunneling microscope, the improvement of mechanical and thermal stability, the identification and characterization of physical and chemical defects, and the effects of internal ordering on macroscopic properties. It is further recommended that strong interdisciplinary efforts be mounted to address and solve these problems.
Defect-free diacetylene (DA) Langmuir-Blodgett films polymerized on a air/water interface have various applications in biosensors, membrane physics or low-dimensional physics. Polymerization of DA monolayers is in general way characterized by optical spectroscopy. In this study for evaluation of photopolymerization process for the first time the Maxwell displacement current (MDC) measuring technique was used. In experiment MDC flows through the metal electrode/air gap/Langmuir monolayer/water surface structure. The effect of polymerization as well as the phase transition of polymerized DA was observed. Moreover PDA domain creation and homogenization was registered.
Uniquely Shaped Double-Decker BuckyferrocenesDistinct Electron Donor−Acceptor Interactions
Journal of the American Chemical Society, 2008
Quantum chemical calculations and various photophysical techniques, ranging from steadystate absorption and steady-state as well as time-resolved fluorescence to femtosecond pump-probe experiments, were employed to examine ground-and excited-state interactions in a set of novel doubledecker buckyferrocenes (i.e., Fe 2 (C 60 Me 10 )Cp 2 ): C 2v and D 5d isomers. When compared to the individual reference systems, the intimate fullerene/ferrocene contacts reflect appreciable ground-state interactions, namely, substantial redistribution of charge density between the two electron donors (i.e., ferrocenes) and the electron acceptor (i.e., fullerene). Furthermore, an intervalence charge-transfer transition (i.e., ferrocene-ferrocenium interaction) was established, but only in the C 2v isomer. The first insight into the electron donor-acceptor interactions came from inspecting the fullerene-centered fluorescence. Relative to the reference compounds that contain no ferrocene, which exhibit quantum yields of up to 0.1, and knowing that the fluorescence of the investigated double-decker type conjugates is quenched to 10 -3 , transient absorption measurements prove unequivocally the rapid formation of the radical ion-pair states as the dominant products of excited-state deactivation in the double-decker buckyferrocenes. Despite these products having much higher lying radical ion-pair states relative to the corresponding single-decker buckyferrocene, their lifetimes, which vary between 12 and 39 ps, are slightly shorter. Guldi, D. M.; , K.; Yoshida, Y.; Luo, Ch.; Sakata, Y.; Fukuzumi, S. J. Am. Chem. Soc. 2001, 123, 6617. (d) Imahori, H.; Tamaki, K.; Araki, Y.; Sekiguchi, Y.; Ito, O.; Sakata, Y.; Fukuzumi, S. J. Am. Chem. Soc. 2002, 124, 5165. (7) (a) Guldi, D. M.; Imahori, H.; Tamaki, K.; Kashiwagi, Y.; Yamada, H.; Sakata, Y.; Fukuzumi, S. J. Phys. Chem. A 2004, 108, 541. (b) Hauke, F.; Hirsch, A.; Liu, S.-G.; Echegoyen, L.; Swartz, A.; Luo, Ch.; Guldi, D. M. ChemPhysChem 2002, 3, 195.
A New Organic Conductor and a Novel Structural Phase Transition in the BEDT-TTF Trihalide Family
Advanced Materials, 2000
decrease of transmission (absorption increase) appears. This decrease cannot be explained by the photodegradation effect and can be accounted for by the photoinduced reorientation of azo groups. The increase of the transmission from D (a minimum point in curve a) to E indicates that azo chromophores with their long axis oriented in the direction perpendicular to the pump polarization also become photodegraded. In curve b, a decrease of transmission after the initial fast jump is observed (see the inset of , which is attributed predominantly to the photoinduced orientation effects. After this decrease, photodegradation in the direction perpendicular to the pump polarization dominates and therefore the transmission increases. Compared to curve b, the fast decrease of the transmission from C to D in curve a is due to the fact that the concentration of the azo dye trans isomers with their orientation parallel to the p c pump polarization is higher due to the prior p k pump excitation.
Applied Surface Science
The developing of organic-based devices has been widely explored using ultrathin films as the transducer element, whose supramolecular architecture plays a central role in the device performance. Here, Langmuir and Langmuir-Blodgett (LB) ultrathin films were fabricated from iron phthalocyanine (FePc) solutions in chloroform (CHCl 3), dichloromethane (CH 2 Cl 2), dimethylformamide (DMF), and tetrahydrofuran (THF) to determine the influence of different solvents on the supramolecular architecture of the ultrathin films. The UV-vis absorption spectroscopy shows a strong dependence of the FePc aggregation on these solvents. As a consequence, the surface pressure vs. mean molecular area (-A) isotherms and Brewster angle microscopy (BAM) reveal a more homogeneous (surface morphology) Langmuir film at the air/water interface for FePc in DMF. The same morphological pattern observed for the Langmuir films is preserved upon LB deposition onto solid substrates. The Raman and FTIR analyses indicate the DMF-FePc interaction relies on coordination bonds between N atom (from DMF) and Fe atom (from FePc). Besides, the FePc molecular organization was also found to be affected by the DMF-FePc chemical interaction. It is interesting to note that, if the DMF-FePc leads to less aggregated FePc either in solution or ultrathin films (Langmuir and LB), with time (one week) the opposite trend is found. Taking into account the N-Fe interaction, the performance of the FePc ultrathin films with distinct supramolecular architectures composing sensing units was explored as proof-of-principle in the detection of trace amounts of atrazine herbicide in water using impedance spectroscopy. Further statistical and computational analysis reveal not only the role played by FePc supramolecular architecture but also the sensitivity of the system to detect atrazine solutions down to 10 −10 mol/L, which is sufficient to monitor the quality of drinking water even according to the most stringent international regulations.
Novel Materials for Molecular Electronics and their Characterization
Advances in Electrical and Electronic Engineering, 2006
Defect-free diacetylene (DA) Langmuir-Blodgett films polymerized on a air/water interface have various¨applications in biosensors, membrane physics or low-dimensional physics. Polymerization of DA monolayers is in general way characterized by optical spectroscopy. In this study for evaluation of photopolymerization process for the first time the Maxwell displacement current (MDC) measuring technique was used. In experiment MDC flows through the metalelectrode/air gap/Langmuir monolayer/water surface structure. The effect of polymerization as well as the phase transition of polymerized DA was observed. Moreover PDA domain creation and homogenization was registered.
RSC Adv., 2015
Three new unsymmetrical hydroxyl-functionalized donors H1-H3 closely related to hydroxymethyl-BEDT-TTF have been synthesised and characterised. Cyclic voltammetry studies showed that the compounds exhibit reversible two one-electron redox processes typical for BEDT-TTF derivatives. X-ray diffraction studies of H1 and H2 reveal p-stacking interactions between pairs of donors that are organized into distinct H-bonded square motifs and DFT calculations indicate that the HOMO is located on the central 1,3-dithiole rings. Protection of the hydroxyl group with acetyl in 13 eliminates co-facial S/S interactions between the dimers to accommodate the bulkier side chains, but short edge-to-edge S/S contacts offer an alternative pathway for electron mobility. Chemical oxidation of H1 and HMET 2 with I 2 afforded single crystals of two 1 : 1 charge transfer salts, 18 and 19. The molecules pack as dimers with close p-stacking interactions between pairs of radical cations whose crystal structures are further stabilized via an interplay of S/S and S/I contacts. Iodine-doped surface conducting polystyrene blend films of H3 deposited on a silica substrate exhibit quasiconducting properties, but afford no OFET response when fabricated into devices. Visible-NIR studies of a doped polystyrene blend film of H3 cast on a glass substrate show absorption bands at l ¼ 950 and 3000 nm, consistent with mixed valence states due to the presence of charge-transfer species on the surface of the films.