A Gelation-Induced Enhanced Emission Active Stimuli Responsive and Superhydrophobic Organogelator: “Turn-On” Fluorogenic Detection of Cyanide and Dual-Channel Sensing of Nitroexplosives on Multiple Platforms

A pyrene-based highly emissive low-molecular-weight organogelator, [2-(4-fluorophenyl)-3-(pyren-1-yl)acrylonitrile] (F1), is presented, which divulges thixotropic and thermochromic fluorescence switching via reversible gel-to-sol transition and tremendous superhydrophobicity (mean contact angles: 149–160°), devoid of any gelling and/or hydrophobic units. The rationale for the design strategy reveals that the restricted intramolecular rotation (RIR) in J-type self-assembly promotes F1 for the prolific effects of aggregation- and gelation-induced enhanced emission (AIEE and GIEE). Meanwhile, hindrance in charge transfer via the nucleophilic reaction of cyanide (CN–) on the CC unit in F1 facilitates the selective fluorescence “turn-on” response in both solution [9:1 (v/v) DMSO/water] and solid state [paper kits] with significantly lower detection limits (DLs) of 37.23 nM and 13.4 pg/cm2, respectively. Subsequently, F1 discloses CN– modulated colorimetric and fluorescence “turn-off” dual-channel response for aqueous 2,4,6-trinitrophenol (PA) and 2,4-dinitrophenol (DNP) in both solution (DL = 49.98 and 44.1 nM) and solid state (DL = 114.5 and 92.05 fg/cm2). Furthermore, the fluorescent nanoaggregates of F1 in water and its xerogel films permit a rapid dual-channel “on-site” detection of PA and DNP, where the DLs ranged from nanomolar (nM) to sub-femtogram (fg) levels. Mechanistic insights reveal that the ground-state electron transfer from the fluorescent [F1-CN] ensemble to the analytes is responsible for anion driven sensory response, whereas the unusual inner filter effect (IFE) driven photoinduced electron transfer (PET) was responsible for self-assembled F1 response toward desired analytes. Additionally, the nanoaggregates and xerogel films also detect PA and DNP in their vapor phase with reasonable percentage of recovery from the soil and river water samples. Therefore, the elegant multifunctionality from a single luminogenic framework allows F1 to provide a smart pathway for achieving environmentally benign real-world applications on multiple platforms

Photochemical Structural Transformation of a Linear 1D Coordination Polymer Impacts the Electrical Conductivity

A pair of 4-(1-naphthylvinyl)­pyridine (4-nvp) ligands has been successfully aligned in head-to-tail fashion in a one-dimensional (1D) double chain ladder polymer [Cd­(adc)­(4-nvp)₂(H₂O)]_<i>n</i> (<b>1</b>; H₂adc = acetylenedicarboxylic acid) that undergoes a photochemical [2 + 2] cycloaddition reaction accompanied by single-crystal to single-crystal (SCSC) structural transformation from a 1D chain to a 2D layer structure. These structural changes have a significant impact on the conductivity and Schottky nature of the compound

Aminoisophthalate Bridged Cd(II)-2D Coordination Polymer: Structure Description, Selective Detection of Pd²⁺ in Aqueous Medium, and Fabrication of Schottky Diode

Photoluminescence activity of coordination polymers (CPs) has evoked intricate applications in the field of materials science, especially sensing of ions/molecules. In the present study, 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) and 5-aminoisophthalate (HAIPA–) coordinated to Cd(II) to architect a coordination polymer, {[Cd(HAIPA)(tppz)(OH)]·3H2O}n (CP1) which unveils blue emission in an aqueous acetonitrile (98% aqueous) suspension. The emission is selectively quenched by Pd2+ only without interference in the presence of as many as 16 other cations. The structure of CP1 shows the presence of a free –COOH group, and the interlayer (–CO)O(2)···O(7) (OC–) distance, 4.242 Å, along with the π···π interactions (3.990, 3.927 Å), may make a cavity which suitably accommodates only Pd2+ (van der Waal’s radius, 1.7 Å) through the Pd(II)-carboxylato (–COO–Pd) coordination. The stability of the composite, [CP1 + Pd2+] may be assessed from the fluorescence quenching experiment, and the Stern–Volmer constant (KSV) is 7.2 × 104 M–1. Therefore, the compound, CP1, is a promising sensor for Pd(II) in a selective manner with limit of detection (LOD), 0.08 μM. The XPS spectra of CP1 and [CP1 + Pd2+] have proven the presence of Pd2+ in the host and the existence of a coordinated –COO–Pd bond. Interestingly, inclusion of Pd2+ in CP1 decreases the band gap from 3.61 eV (CP1) to 3.05 eV ([CP1 + Pd2+]) which lies in the semiconducting region and has exhibited improved electrical conductivity from 7.42 × 10–5 (CP1) to 1.20 × 10–4 S m–1 ([CP1 + Pd2+]). Upon light irradiation, the electrical conductivities are enhanced to 1.45 × 10–4 S m–1 (CP1) and 3.81 × 10–4 S m–1 ([CP1 + Pd2+]); which validates the highly desired photoresponsive device applications. Therefore, such type of materials may serve as SDG-army (sustainable development goal) to battle against the environmental issues and energy crisis

Self-Poled Transparent and Flexible UV Light-Emitting Cerium Complex–PVDF Composite: A High-Performance Nanogenerator

Cerium­(III)-<i>N</i>,<i>N</i>-dimethylformamide-bisulfate [Ce­(DMF)­(HSO₄)₃] complex is doped into poly­(vinylidene fluoride) (PVDF) to induce a higher yield (99%) of the electroactive phases (β- and γ-phases) of PVDF. A remarkable enhancement of the output voltage (∼32 V) of a nanogenerator (NG) based on a nonelectrically poled cerium­(III) complex containing PVDF composite film is achieved by simple repeated human finger imparting, whereas neat PVDF does not show this kind of behavior. This high electrical output resembles the generation of self-poled electroactive β-phase in PVDF due to the electrostatic interactions between the fluoride of PVDF and the surface-active positive charge cloud of the cerium complex via H-bonding and/or bipolar interaction among the opposite poles of cerium complex and PVDF, respectively. The capacitor charging capability of the flexible NG promises its applicability as piezoelectric-based energy harvester. The cerium­(III) complex doped PVDF composite film exhibit an intense photoluminescence in the UV region, which might be due to a participation of electron cloud from negative pole of bipolarized PVDF. This fact may open a new area for prospective development of high-performance energy-saving flexible solid-state UV light emitters

Succinato-bridged Cd(II)-nicotinylhydrazone 3D coordination polymer: structure, photoconductivity and computational studies

Strategies for clean energy are important components of the United Nation’s Sustainable Development Goals (SDGs). To this end, we have studied the conductivity of a Cd(II)-based 3D coordination polymer, [Cd(succ)(pcih)(H2O)]n (1) (H2succ = succinic acid; pcih = pyridine-4-carboxaldehyde iso-nicotinoyl hydrazone). Compound 1 was structurally characterized by single-crystal X-ray diffraction. The bridging groups, succ2− and pcih, self-assembled via H-bonding and π∙∙∙π interactions. The optical band gap calculated from a Tauc’s plot was determined to be 3.71 eV which is consistent with semiconducting behavior. The experimental barrier height, 0.71 eV (dark phase); 0.49 eV (light phase) and series resistance, 358.48 Ω (dark); 133.73 Ω (light), also support the photoinduced enhancement of conductivity. The non-ohmic relation, I α V2, showed an enhancement of conductivity by 2.5 times upon light irradiation [3.36 × 10−6 S m−1 (dark) and 8.37 × 10−6 S m−1 (light)]. DFT computations employing the crystallographic parameters of 1 indicated a HOMO/LUMO energy gap of 4.06 eV, within the range of semiconducting materials. The optical stability of 1 was examined by fluorescence measurements and lifetime data.</p

Intercatenated Coordination Polymers (ICPs) of Carboxylato Bridged Zn(II)-Isoniazid and Their Electrical Conductivity

Three new coordination polymers (CPs) of coordinated isoniazid (INH) to Zn­(II) with succinic acid (H₂succ), fumaric acid (H₂fum), and terephthalic acid (H₂bdc) as organic linker, [Zn­(INH)­(succ)]_<i>n</i> (<b>1</b>), [Zn­(INH)­(fum)]_<i>n</i> (<b>2</b>), and [Zn­(INH)­(bdc)]_<i>n</i> (<b>3</b>), respectively, have been characterized. The structure determination by the single crystal X-ray diffraction technique shows a ZnN₂O₄ distorted octahedral geometry, and the 1D chain is constituted via the INH and carboxylate coordination along with the hydrogen bonding (N–H···O) which comprises a 2D structure. The CPs, <b>1</b> and <b>2</b>, are isostructural and fabricate supramolecular networks by inclined intercatenation of two 2D layers, while <b>3</b> shows parallel intercatenation. The electrical conductivity and Schottky barrier diode behavior have been established by the charge transport mechanism of the compounds at the quasi-Fermi level state. The analysis indicates that the compound <b>1</b> has the highest mobility (2.53 × 10 ^–10 m² V^–1 s^–1) than <b>2</b> (1.86 × 10^–10 m² V^–1 s^–1) and <b>3</b> (1.89 × 10^–10 m² V^–1 s^–1) and the highest electrical conductivity (2.26 × 10^–4 S m^–1) than the others (1.12 × 10^–4 S m^–1 (<b>2</b>) and 1.25 × 10^–4 S m^–1 (<b>3</b>)). DFT computation of the structural motif of CPs has calculated the band gap (Δ<i>E</i>: 3.93 eV (<b>1</b>), 4.45 eV (<b>2</b>), 4.26 eV (<b>3</b>)), which supports the progression of conductivity