Spontaneously formed conjugated polymer nanoparticles (CPNs) or polymer dots displayed remarkable fluorescence response toward nitroexplosive-picric acid (PA) in multiple environments including 100% aqueous media, solid support using portable paper strips and vapor phase detection via two terminal device. This new cationic conjugated polyelectrolyte (CPE) poly(3,3'-((2-phenyl-9H-fluorene-9,9-diyl)bis(hexane-6,1-diyl))bis(1-methyl-1H-imidazol-3-ium)bromide) (PFMI) was synthesized by Suzuki coupling polymerization followed by post functionalization method without employing any hectic purification technique. Highest quenching constant value (K(sv)) of 1.12 × 10(8) M(-1) and a very low detection limit of 30.9 pM/7.07 ppt were obtained exclusively for PA in 100% aqueous environment which is rare and unique for any CPE/CPNs. Contact mode detection of PA was also performed using simple, cost-effective and portable fluorescent paper strips for achieving on-site detection. Furthermore, the two terminal sensor device fabricated with nanoparticles of PFMI (PFMI-NPs) provides an exceptional and unprecedented platform for the vapor mode detection of PA under ambient conditions. The mechanism for the ultrasensitivity of PFMI-NPs probe to detect PA is attributed to the "molecular-wire effect", electrostatic interaction, photoinduced electron transfer (PET), and possible resonance energy transfer (RET).

The development of highly efficient latent fingerprint (LFP) technology remains extremely vital for forensic and criminal investigations. In this contribution, a straightforward, rapid, and cost-effective method has been established for the quick development of well-preserved latent fingerprint on multiple substrates, including plastic, glass, aluminum foil, metallic surfaces, and so forth, without any additional treatment, based on aggregation-induced enhanced emission-active conjugated polyelectrolyte (CPE) 3,3'-((2-(4-(1,2-diphenyl-2-(p-tolyl)vinyl)phenyl)-7-(7-methylbenzo[c][1,2,5]thiadiazol-4-yl)-9H-fluorene-9,9-diyl)bis(hexane-6,1-diyl))bis(1-methyl-1H-imidazol-3-ium) bromide, revealing clearly the third-level details (ridges, bifurcations, and pores) with high selectivity, high contrast, and no background interference even by blood stains, confirming the ability of the proposed technique for LFP detection with high resolution. The LFP development process was accomplished simply by immersing fingerprint-loaded substrate into the CPE solution for ∼1 min, followed by shaking off the residual polymer solution and then air drying. The CPE was readily transferred to the LFPs because of the strong electrostatic and hydrophobic interaction between the CPE molecules and the fingerprint components revealing distinct fluorescent images on various smooth nonporous surfaces.

A two terminal sensor device based on PDI-HIS was developed for room temperature vapor phase detection of ammonia at very low sub-ppm levels under ambient conditions.

The influence of structural ordering of methyl cyclohexane appended naphthalene diimide (NMeCy2) thin films and their correlation with enhanced device performances are presented here. The vacuum-deposited thin-film microstructure and morphology of NMeCy2 have been investigated using thin-film X-ray diffraction (XRD), atomic force microscopy (AFM), and field emission scanning electron microscopy (FESEM) and were comparable with the bulk-phase crystalline structure and packing of NMeCy2. The organic field-effect transistor (OFET) fabricated on a glass substrate consists of a bilayer polymer dielectric poly(methyl methacrylate) (PMMA) over poly(vinyl alcohol) (PVA) and an inorganic high-k dielectric Al 2 O 3 as the third layer. NMeCy2 thermally deposited at an optimized substrate temperature (T sub ) of 60°C displayed excellent molecular packing over a large area that resulted in the improved field-effect performance with electron mobility (μ e ) value of 0.6 cm 2 V −1 s −1 and current on/off ratio (I on/off ) of 10 6 via modifications in dielectric configuration. Furthermore, the device afforded an unprecedented threshold voltage (V Th ) of 5.23 V with this material. We have been successful in developing a facile, reliable, and cheap method to tune the dielectric features which can culminate in improved field-effect transport properties. ■ INTRODUCTIONElectronic devices based on small organic molecules and polymers have received considerable attention in recent years due to their low cost and milder operating conditions. Particularly, small molecule based organic semiconductors (OSCs) are versatile, inexpensive, reliable, easily functionalized, and used as active materials in organic light-emitting devices (OLEDs), 1 organic photovoltaics (OPVs), 2 and organic fieldeffect transistors (OFETs). 3 The key problems of these molecules are the low mobility and low environmental stability. High mobility in OFETs is a prerequisite for fast response in high speed device applications. On the other hand, OFETs impose serious limitations to their practical applications due to the high operating voltage and high threshold voltage. Serious efforts have been devoted by researchers to improve these factors. This can be achieved by designing molecules with superior properties, device engineering, controlling the roughness and morphology of the dielectric, and OSC layers. The growth of OSCs and the alignment of crystalline layers on the dielectric surfaces are the key requirements for achieving high mobility. 4 Generally, the hydrophobic surface is more favorable for the growth of OSCs than hydrophilic surfaces. Highly compact well-organized molecular packing among adjacent molecules with significant π-orbital overlap and the absence of grain boundaries facilitate efficient charge transport enabling high mobility. 5 The low operating voltage is one of the main criteria for the integrated digital circuits and biosensor applications. The reduction in the threshold voltage and operating voltage can be achieved by using high-k dielectri...

A new derivative of naphthalene diimide (NDMI) was synthesized that displayed optical, electrical, and visual changes exclusively for the most widespread nitroexplosive and highly water-soluble toxicant picric acid (PA) due to strong π-π interactions, dipole-charge interaction, and a favorable ground state electron transfer process facilitated by Coulombic attraction. The sensing mechanism and interaction between NDMI with PA is demonstrated via X-ray diffraction analysis, (1)H NMR studies, cyclic voltammetry, UV-visible/fluorescence spectroscopy, and lifetime measurements. Single crystal X-ray structure of NDMI revealed the formation of self-assembled crystalline network assisted by noncovalent C-H···I interactions that get disrupted upon introducing PA as a result of anion exchange and strong π-π stacking between NDMI and PA. Morphological studies of NDMI displayed large numbers of single crystalline microrods along with some three-dimensional (3D) daisy-like structures which were fabricated on Al-coated glass substrate to construct a low-cost two terminal sensor device for realizing vapor mode detection of PA at room temperature and under ambient conditions. Furthermore, an economical and portable electronic prototype was developed for visual and on-site detection of PA vapors under exceptionally realistic conditions.