A porous 3D folic acid (F)-polyaniline (PANI) hybrid hydrogel (F-PANI), produced by in situ polymerization of aniline, exhibit highest compressive stress (15.1 kPa), 3D hierarchical network morphology with BET surface area 236 m2/g. Here, PANI is present in emeraldine salt (ES) state, which facilitates excellent adsorption of anionic pollutants. It exhibits an extremely high adsorption capacity for Cr­(VI) and during adsorption Cr­(VI) is reduced to Cr­(III).The electrical impedance spectra of the Cr­(VI) adsorbed xerogel, support the conversion of PANI chains from ES to pernigraniline base­(PB) making the xerogel more resistive. It also selectively adsorbs anionic dyes, the adsorption capacity increases with decrease of pH. Both the adsorption data are found to be well explained through pseudo-second-order kinetic model, and they obey Langmuir adsorption isotherm. F-PANI2 showed high adsorption capacities selectively toward anionic pollutants, for example, Cr­(VI), eosine yellow, rose bengal, methyl orange, and low adsorption capacities for Hg­(II), Pb­(II), rhodamineB, bismark brownY methylene blue, and neutral red. The removal of Cr­(VI) and anionic dyes are very much effective at neutral and acidic pH. After dye/Cr­(VI) adsorption the Nyquist plot indicate significant decrease in the capacitance of xerogels. Cyclic experiments show that, F-PANI xerogels can be effectively reused to remove Cr­(VI) from different contaminated water.

The low conductivity and poor active sites of MoS2 sheet present a huge barrier for it is exploitation of catalytic applications in the hydrogen evolution reaction (HER). To alleviate this difficulty, we have synthesized MoS2 quantum dots (QDs) having greater quantity of catalytic edge sites by breaking up the bulk MoS2 sheet using the solvent exfoliation technique. The synthesized MoS2 QDs are embedded into polyaniline (PANI)–N,N′-dibenzoyl-l-cystine (DBC) hydrogel matrix by in situ polymerization of aniline where DBC acts as a gelator, dopant, and cross-linker. The hybrid conducting aerogels (DBC-MoS2-PANI) thus produced act as an efficient electrocatalyst showing lower HER overpotential in comparison to MoS2 QDs. It exhibits an optimum overpotential value of 196 mV at 10 mA cm–2, a favorable Tafel slope of 58 mV/dec, and an excellent cyclic stability. Also, DBC-MoS2-PANI aerogel is used in photoresponding devices. The DBC-MoS2-PANI hybrid aerogel exhibits a better photoresponse compared to the DBC-PANI aerogel and MoS2 QDs upon white light illumination of 1 sun. The hybrid aerogel exhibits a maximum enhancement of photocurrent to the value of 3.95 mA at 2 V bias, and the time-dependent photoillumination shows much faster rise and decay of photocurrent compared to those of DBC-PANI aerogel and MoS2 QDs.

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Pyrene is a fluorescent polycyclic aromatic hydrocarbon, and it would be interesting to determine whether its CN-based conjugate can be used for sensing of aromatic analytes at its supramolecular aggregated state. For this purpose, we have synthesized (E)-3,4,5-tris(dodecyloxy)-N′-(pyren-1-ylmethylene)benzohydrazide (Py@B) by alkylation, substitution, and the Schiff base reaction methodology. The E-isomer of Py@B (E-Py@B) exhibits a bright fluorescence due to excimer formation in nonaromatic solvents. Upon photoirradiation with λ = 254 nm, it exhibits E-Z isomerization across the CN bond at a low concentration (10 −4 M), resulting in a quenched fluorescence intensity, and interestingly, upon photoirradiation with λ = 365 nm, the Z-isomer of Py@B returns to the E-isomer again, indicating that E-Z isomerization of Py@B is reversible in nature. The thick supramolecular aggregated morphology of E-Py@B changes to a flowery needlelike morphology after photoirradiation with λ = 254 nm. The UV−vis absorption band at 370 nm for 10 −4 M Py@B in methyl cyclohexane (MCH) is due to excimer formation for closer proximity of pyrene moieties present in E-Py@B and changes to the absorption peak at 344 nm for its Z-isomer formation. The fluorescence spectroscopy results also support the fact that the optimum concentration of the E-isomer of Py@B is 2 × 10 −4 M in MCH for excimer formation. From spectral results, it may be concluded that nonaromatic solvents assist in constructing the excimer, but aromatic solvents resist forming an excimer complex of E-Py@B. The fluorescent emission of E-Py@B in MCH is quickly quenched on addition of different aromatic analytes through both static and dynamic pathways. In the solid state, E-Py@B also senses aromatic vapors efficiently via fluorescence quenching. Absorbance spectra of a model molecule obtained using time-dependent density functional theory (TDDFT) calculations on a DFT-optimized structure indicate complex adduct formation between E-Py@B and aromatic analytes from the well-matched theoretical and experimental UV−vis spectra on addition of different analytes with E-Py@B.

Folic acid (FA), vitamin B , is a good receptor of drugs triggering cellular uptake via endocytosis. FA is sparingly soluble in water. Herein, a new approach for the formation of FA hydrogel by the hydrolysis of glucono-δ-lactone in PBS buffer under physiological conditions has been reported. The gel has a fibrillar network morphology attributable to intermolecular H-bonding and π-stacking interactions. The thixotropic property of the gel is used for the encapsulation of both hydrophilic [doxorubicin (DOX)] and hydrophobic [camptothecin (CPT)] drugs. The loading of DOX and CPT into the gel is attributed to the H-bonding interaction between FA and drugs. The release of DOX is sustainable at pH 4 and 7, and the Peppas model indicates that at pH 7 the diffusion of the drug is Fickian but it is non-Fickian at pH 4. The release of CPT is monitored by fluorescence spectroscopy, which also corroborates the combined release of both drugs. The metylthiazolyldiphenyltetrazolium bromide assay of FA hydrogel demonstrates nontoxic behavior and that the cytotoxicity of the DOX-loaded FA hydrogel is higher than that of pure DOX, with a minimal effect on normal cells.