Three novel electron donor–acceptor conjugated polymers ( P1 – P3 ) bearing various imidazole pendants have been synthesized. Their excellent photophysical and electrochemical properties make them suitable transduction materials for chemosensing applications. Indeed, polymers P1 – P3 have been found to show remarkable sensing capabilities towards H+ and Fe2+ in semi‐aqueous solutions. Upon titration with H+, polymers P1 and P2 showed hypsochromic shifts of their absorptions and photoluminescence (PL) maxima with enhanced fluorescence intensities. However, P3 showed diminished absorption and fluorescence intensities under similar conditions due to static quenching. The anomalous behavior of P3 compared with P1 and P2 has been clarified in terms of electronic distributions through computational analysis. Furthermore, P3 (KSV=1.03×107) showed a superior sensing ability towards Fe2+ compared with P1 (KSV=2.01×106) and P2 (KSV=4.12×106) due to its improved molecular wire effect. Correspondingly, the fluorescence lifetime of P3 was greatly decreased (almost 11‐fold) compared to those of polymers P1 (4.6‐fold) and P2 (6.2‐fold) in the presence of Fe2+. By means of a fluorescence on‐off‐on approach, chemosensing reversibilities in protonation–deprotonation and metallation–demetallation have been achieved by employing triethylamine (TEA) and the disodium salt of ethylenediaminetetraacetic acid (Na2‐EDTA)/phenanthroline, respectively, as suitable counter ligands. 1H NMR titrations have revealed the unique behavior of P3 compared with P1 and P2 . To the best of our knowledge, there have been no previous reports of Fe2+ sensors based on single imidazole receptors conjugated to a main‐chain polymer showing such a diverse sensitivity pattern depending on their attached substituents. 相似文献
The practical application of polyaniline-poly(sodium 4-styrenesulfonate) (PANI-PSS) composite particles has been held back by the low stability of their dispersed state in water. In this work, we present a general oxidation approach to prepare PANI-PSS composite nanoparticles that can form highly stable colloids in water or buffer over a wide range of pH from 1 to 11. We demonstrate that the size of the PANI-PSS composite particles can be controlled by the acidity of precursor solutions. It is hypothesized that the number of negatively charged sites on PSS, which can be affected by the acidity of the precursor solutions, plays an important role in determining the size of the PANI-PSS composite particles and the stability of corresponding colloids in water. 相似文献
Attachment of the redox-active C(60)(H)PPh(2) group modulates the electronic structure of the Fe(2) core in [(μ-bdt)Fe(2)(CO)(5)(C(60)(H)PPh(2))]. The neutral complex is characterized by X-ray crystallography, IR, NMR spectroscopy, and cyclic voltammetry. When it is reduced by one electron, the spectroscopic and density functional theory results indicate that the Fe(2) core is partially spin-populated. In the doubly reduced species, extensive electron communication occurs between the reduced fullerene unit and the Fe(2) centers as displayed in the spin-density plot. The results suggest that the [4Fe4S] cluster within the H cluster provides an essential role in terms of the electronic factor. 相似文献
Reactive polymer coatings were synthesized via chemical vapor deposition (CVD) polymerization process. These coatings decouple surface design from bulk properties of underlying materials and provide a facile and general route to support thiol‐ene and thiol‐yne reactions on a variety of substrate materials. Through the reported technique, surface functions can be activated through a simple design of thiol‐terminated molecules such as polyethylene glycols (PEGs) or peptides (GRGDYC), and the according biological functions were demonstrated in controlled and low‐fouling protein adsorptions as well as accurately manipulated cell attachments. 相似文献
The capillary viscometer is used to measure the shear stress-shear rate relationship of a wide range of purely viscous fluids.
It is however not considered as an appropriate instrument for obtaining the yield stress and the post-yield behaviour of fluids
that have a yield stress. This is partly because conventional methods of processing the capillary viscometry data of purely
viscous fluids cannot be applied to similar data of fluids with yield stress. The unavoidable experimental noise in the capillary
data, particularly at low shear rates, also makes it difficult to obtain a reliable estimate of the yield stress from capillary
data. In this investigation the problem of converting the capillary viscometry data of yield stress fluids into a shear stress-shear
rate curve and a yield stress is formulated as a Volterra integral equation of the first kind. This is an ill-posed problem
i.e. noise in the data will be amplified by inappropriate methods of data processing. A method, based on Tikhonov regularisation
that takes into account the ill-posed nature of the problem, is then developed to solve this problem for fluids with yield
stress. The performance of this method is assessed by applying it to a set of “synthetic” capillary viscometry data with added
random noise and to a set of experimental data for a concentrated suspension of TiO2 taken from the literature. In both cases Tikhonov regularisation was able to extract the complete shear properties of these
fluids from capillary viscometry data alone.
Received: 22 November 1999/Accepted: 17 December 1999 相似文献
Summary: A highly hydrophobic surface with a water contact angle of 148.0° has been constructed by depositing salicylic acid‐doped polyaniline (PANI‐SA) spheres on a glass substrate using a template‐free method. The hydrophobicity originates from the contribution of the air trapped in the inter‐space of a rough surface aggregated by micro‐ and nanospheres. Moreover, the deposition time strongly affects the hydrophobicity of the PANI‐SA spheres deposited on the substrate. The formation mechanism and hydrophobic origin of the PANI‐SA spheres deposited on the substrate are discussed.
The PANI films prepared at 60 min polymerization time is composed of co‐existing nano‐ and microspheres (left). The ability of the layers to trap large amounts of air makes the surface highly hydrophobic and results in a water contact angle of 148.0° (right). 相似文献
A novel approach has been explored to prepare brain‐like polyaniline (PANI) nanostructures with many convolutions (140–170 nm in average diameter) using aniline/citric acid (CA) salt as the template and chlorine gas as the oxidant by a gas/solid reaction for the first time. The method provided here differs significantly from the traditional one in which the polymerization of PANI is usually carried out in acidic solution.
Summary: A controlled fabrication of rod‐like nanostructures of cadmium sulfide (CdS) incorporated into polymer fiber matrices has been developed by an electrospinning method. Here, poly(vinyl pyrrolidone) (PVP) was used as a polymer capping reagent, utilizing the interactions of cadmium ions with the carbonyl groups in the PVP molecules. The formation of CdS nanorods inside the PVP was carried out via the reaction of Cd2+ with H2S. SEM images showed that the electrospun films of PVP/CdS are composed of fibers with a diameter between 100 and 900 nm. TEM proved that most of the CdS nanorods are incorporated in the PVP fibrous film. The diameter of the rod is about 50 nm and the length is from 100 to 300 nm.
TEM image of the CdS nanorods formed in the PVP fibrous film. 相似文献