Tailored fluorophore design: Enhancing selectivity for cyanide ion sensing in water and food samples, and innovative device development.

A rigid fluorophore unit of Julolidine/coumarin fused with an indolium-conjugated system was built for the immediate and effective recognition of cyanide ions in a 90 % aq. DMSO solution. The probes are capable of displaying better sensitivity/selectivity for the cyanide ion over a wide range of other interfering ions. The probe JI showed an instant colorimetric variation, whereas the modified probe JCI showed both colorimetric and fluorimetric variation with cyanide ion. The observed detection limit values indicated excellent sensitivity of the probe to the cyanide ion. HRMS and 1H NMR studies confirmed that the mechanism of detection of CN- is via the nucleophilic attack on the electron-deficient indolium moiety of the molecule. Moreover, the probes are well proficient in selective recognition of cyanide in various real time applications (test strips, electronic sensor kit, food and water sample analysis).

Optimizing cyanine dye properties for enhanced dyeing and inkjet printing on diverse Substrates: Photophysical and colorimetric investigations.

Cyanine-based cationic dyes with different substituents in the donor unit were easily synthesized using readily available starting materials. The prepared dye molecules were spectroscopically characterized by NMR, FT-IR, and HR-Mass, and their thermal stability was measured by TGA, DSC, and XRD. Based on the TGA and DSC measurements, it was concluded that all the dyes are thermally stable up to 200 °C. Also, powder XRD was studied for all dyes to identify the explicit crystallinity and morphological nature of the dyes. A dye dispersion solution was prepared for the proper dyeing of modacrylic fabric and the dyed fabric showed good color strength K/S for dyes R1, R2, and R6 and fragile color strength for R3, R4,and R5. These dyes are also used for printing on substrates like paper and fabric using ink-jet printing. These dyes were also used for transferability printing applications on various fabrics.

An ICT-based highly fluorescent isoquinoline scaffold for selective Hg(II) detection in real-water samples: Development of a smart, low-cost RGB-Arduino electronic platform.

Selective detection and quantification of Hg2+ ions is crucial to minimize health and environmental risks. Fluorescent organic small-molecule probes have been expeditiously utilized owing to their unique set of improved properties. However, isoquinoline core has not been extensively explored as a fluorescence platform partly due to synthetic challenges. Herein, a serendipitously discovered synthetic route to access a small yet highly functionalized novel isoquinoline-based probe, IQ is reported. The synthesis is achieved through the in-situ generation of ammonia, followed by intermolecular [5C + 1 N] aza-annulation reaction with a ketendithioacetal-based precursor, P-IQ. IQ displayed excellent recognition ability towards Hg2+ ions in H2O:ACN (99:1, v/v) via ICT-off fluorescent quenching behavior. Comparative FT-IR, 1H/13C NMR, mass spectral studies, and DFT analyses were carried out to validate the suggested mechanisms. Reversible studies confirm the secondary recognition effect of in-situ generated (IQ + Hg2+) complex on cysteine. The binding constant and LOD were estimated to be 3.7 × 104 M-1 and 0.86 µM, respectively. Further, IQ was utilized to evaluate the mercury ion content in real water samples demonstrating its effectiveness in water quality monitoring. The practical utility of IQ was further explored by developing TLC strips, Whatman filter-paper strips, and a low-cost, portable Arduino-based platform. Arduino microcontroller is interfaced with an RGB sensor to detect color changes and quantify mercury concentration w.r.t. RGB values.

A novel fluorophore with multichromic effect and its application in LED light for the volatile vapor detection.

Successfully designed and synthesized diaryl maleimide DAM, and their structure was confirmed by mass spectroscopy and NMR techniques. They investigated their photophysical properties, such as solvatochromic and the aggregation effect of AIE/ACQ on the water/DMF ratio, and other studies of solid-state mechanofluorochromic, such as grinding, exposure to solvent fumes, hydrostatic pressures, and vapochromic. Interestingly, the solvent methods gave very similar results in both the dissolving phase and the vapor phase. For the solution state from hexane to CH2Cl2, a greenish-yellow to orange emission was observed. From hexane to dichloromethane, naked-eye colorimetric changes (from yellow to orange in a solid state) were observed. Very interesting results were obtained, the yellow solid was ground for 1 min, it turned into an orange color, and its wavelengths were red-shifted in both absorption and emission. Subsequently, the ground sample was exposed to diethyl ether vapors, which returned to the original green-yellow emission and absorption. The applied hydrostatic pressures (0-4Mpa) in DAM gave excellent red-shifted emission, and then their hydrostatic pressures were increased to 4-16 Mpa, and the red-shifted emission gradually decreased.

Highly emissions of TPA-linear based pyrazine derivatives with different mechanochromic luminosity.

We designed the TPA-based linear pyrazine derivatives of PP-1 and PP-2, synthesized using the conventional Suzuki cross-linking reaction. It was followed by photophysical studies such as aprotic solvent (Haxene to DMF). A red-shift was observed from the non-polar aprotic solvent to the polar aprotic solvent, and the emission intensity was gradually decreased. In addition, the Aggregation-induced emission (AIE) effect has been studied against the DMF/water addition of linear pyrazine compounds. It showed a classic aggregation-caused quenching effect (ACQ) and red-shifted at an increase of (fw) 0 to 40%. After this case, when the water fraction in these studies was increased by (fw) 50 to 90%, a blue shift and a mild AIE effect has occurred. And also, was investigated acidochromic effect of compounds PP-1 and PP-2 using TFA acid. Absorption and emission intensity were gradually reduced as the acid concentration increased for these studies, while the new peaks appeared red-shifted in the absorption spectrum. They were examined before and after exposure to UV light irradiation in the synthesized dye compounds.

Effects of Xanthene Fluorophore on Light Physical Properties and their Dyeing Performance on Modacrylic Fabrics.

We designed the new xanthene dyes by introducing the donor and acceptor group of electrons in the 5' position of the carboxyphenyl ring. These synthesized dye molecules were identified using spectroscopy. And the photophysical studies, such as solvent optimization, were further explored before and after photodegradation of all synthesized dye compounds in both states (solution and solid). The resulting dyed modacrylic fabrics and measured their K/S values, reflectance (%), solid UV absorbance, and photoluminescence. All compounds are plotted on a chromaticity map in the pink region. During photodegradation, the stability of the molecule depends on the effect of the functional groups (donor to acceptor). In this case, ln[C/C0] (%) became the decreasing sequence from an electron donor to acceptor, as the electrons followed from the donation function group to the carboxylic function group. Therefore, the electron-accepting group dyes decompose rapidly during ultraviolet radiation.

A Pyrene-Tetrazole Fused Fluorescent Probe for Effective Real Time Detection Towards Aluminium Ion.

We constructed a novel-binding site for metal ion detection using a fused tetrazole ring conjugated with aminopyrene (R). The designed structure of the molecule was successfully synthesized and determined the probe's selectivity by testing various metal ions and found that the probe effectively detects Al3+ ion visually. Checked the sensing ability of the probe with different approaches (fluorimetric and colorimetric), and the effectiveness is double confirmed. The added Al3+ ion to R procured a rapid change in color from yellowish orange to colorless. Under the UV lamp, a turn-on blue fluorescence was observed after adding aluminium ion, whereas the probe was non-fluorescent before detecting aluminium ion. The probable interface of the probe with aluminium ion has also been expected from HRMS spectral analysis results. The probe's utility in real-time monitoring of Al3+ ion in water is confirmed by a simple test kit prepared using filter paper. The kit showed a possible naked-eye detection with a notable color change, and when checked, the aluminium ion detected test kit under a UV lamp showed blue fluorescence.

A novel class of xanthene dyes with chemically linked UV absorber molecule and their photophysical properties.

In this paper, we prepared a new class of chemically linked UV absorber XU2 & XU3, and their photophysical, chemical properties and substrate durability were investigated. Spectroscopic behavior at various solvent and pH levels for this dye solution has been evaluated. Successfully designed an open ring form of xanthene moiety, linked a UV absorber to it, and made XU2 & XU3 that have shown good absorbance and emission band maxima at all solvents and pH mediums. Further, the found UV-Vis absorbance band maxima (λmax), PL emission maxima (λem), molar extinction coefficient (εmax) and Stokes shifts (ΔνST) when compared to commercially available dye 1. The synthesised XU2 & XU3 have shown brilliant results from exposed UV light at irradiation processing time, due to the light energy passes through the molecule by keto-enol tautomerisation between phenolic hydrogen and carbonyl carbon like a six-member ring. So it can be acted as radioless behaviour in the visible region, and it can relax the energy without any assistance. Hence, the UV absorber has protected the compound like a UV Resistance.

Simple easy to make xanthene based optical probe for solid and liquid state Hg2+ ion detection.

An easy to make xanthene based optical probe synthesized, precise recognition towards mercury ion been achieved by the probe RP and can detect Hg2+ effectively in both for solid and liquid state with a vivid color change. The other tested ion showed no interference, visual and instrumental methods confirms the probe selectivity. Stoichiometry (1:1) confirmed by job's plot, plausible binding of Hg2+ ion with the probe confirmed by mass and NMR studies. Test strip prepared for the prompt onsite detection in aqueous medium with outstanding color variation in daylight.

Do HOMO-LUMO Energy Levels and Band Gaps Provide Sufficient Understanding of Dye-Sensitizer Activity Trends for Water Purification?

A dye-sensitized solar cell assembly can be used to harvest solar energy, while suitable dye sensitizers can be used to purify water. Here, we characterized the activity trends of four dye sensitizers, namely, PORPC-1, PORPC-2, PORPC-3, and PORPC-4, for water purification applications using density functional theory (DFT) with the Perdew-Burke-Ernzerhof (PBE), B3LYP, and PBE0 functionals, ΔSCF, time-dependent DFT (TD-DFT), and quasiparticle Green's function (GW) methods. The energy levels of the highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) were calculated using gas-phase and aqueous-phase methods in order to understand charge-injection abilities and the dye regeneration processes. PBE, B3LYP, PBE0, and TD-DFT methods failed to predict PORPC-4 to be the best sensitizer, while PORPC-2 and PORPC-4 were predicted to be the best sensitizers using ΔSCF coupled with the implicit solvation method, and HOMO-LUMO energies were corrected for the aqueous environment in the GW calculations. However, none of these methods accurately predicted the performance trend of all four dye sensitizers. Consequently, we used the aggregation assembly patterns of the dye molecules in an aqueous environment to further probe the activity trends and found that PORPC-3 and PORPC-4 prefer J-aggregated assembly patterns, whereas PROPC-1 and PORPC-2 prefer to be H-aggregated. Therefore, the performance of these dye molecules can be determined by combining HOMO-LUMO energy levels with aggregate-assembly patterns, with the activity trend predicted to be PORPC-4 > PORPC-2 > PORPC-3 > PORPC-1, which is in good agreement with experimental findings.

Robust Photodegradation of Methylene Blue with the Biphenyl-Porphyrin/TiO2 Photocatalyst Under Visible Light Condition.

Herewith, we approached a synthesis of new biphenyl porphyrin derivative and confirmed its structure with 1H-NMR and 13C-NMR studies, FT-IR and mass analytical methods. The porphyrin derivative grafted with TiO2 and the composite (PORBP-TiO2) was further confirmed with different analytical techniques like diffuse reflectance spectra, XRD, FT-IR, XPS, SEM analysis. PORBP-TiO2 was checked for photodegradation of methylene blue in visible light condition and degradation results were compared with bare TiO2. Our newly synthesized photocatalyst showed a very fast and efficient photocatalytical activity in comparison with bare TiO2. Fluoresence life time results also supported the strong photocatalytic activity of PORBP-TiO2. The reusability studies also showed that PORBP-TiO2 is having very good stability upto 10 cycles also. Finally we proposed a suitable catalytic diagram for PORBP-TiO2 photocatalysis.

Synthesis of Novel Oxazolidines and Study of Its Naked Eye CO2 Detecting Properties.

Herewith, we synthesized the new oxazolidines (SP-1, SP-2 and SP-3) by without using any withdrawing or donating substitution, and for these molecules we demonstrated CO2 sensing properties in naked eye condition with different colors (yellow and magenta). All the dyes showed different colors in the presence and absence of CO2 in ethanol solution with the concept of ring closing and opening. In UV-visible absorption spectrum all the compounds showed visible light absorptions after purging of CO2. To confirm this mechanism for SP-1 molecule case, we approached the 1H-NMR and 13C-NMR techniques deuterated methanol as a solvent and we clearly identified. The stability of the SP-1 molecule in ethanol for CO2 purging case, we studied repeatability test up to ten cycles and we confirmed that there is no any decrease in sensing ability.

Electrochemical, Photophysical and Theoretical Studies of Novel Zinc Phthalocyanines.

In this research, we successfully synthesized three novel zinc phthalocyanines and applied for electrochemical and photo physical properties. These phthalocyanines are naphthoxy derivatives with methyl, benzyl and butyl-benzyl, with halo substitution (PCME, PCBN and PCBBN) and poses very good solubility in all industrial solvents. To check the preliminary results of LCD green color filter properties of these molecules, we taken the UV-Visible absorption and transmittance studies in Propylene glycol monomethyl ether acetate and achieved around 90% of transmittance in the region of 400-550 nm. Further understand the solubility of our phthalocyanines, we checked the aggregation property in PGMEA and we observed no any aggregation. All compounds showed very nice electro chemical properties with nice oxidation and reduction peaks. These phthalocyanines are fit for LCD color filter applications. Finally to get insights of the electronic and UV-Visible properties of the new dyes, the DFT calculations were performed.

Spontaneous optical response towards cyanide ion in water by a reactive binding site probe.

Indolium derivatives bearing diphenyl amine (R1) and dibenzylamine (R2) linked through benzene was designed, synthesized, characterized and its cyanide recognizing abilities are studied in 100% water. The probes were exhibited dual channel properties i.e. both colorimetric and fluorimetric changes for the effective sensing of cyanide ion. The discrete color variation of probes with cyanide ion makes possible as colorimetric sensor and which was seen easily through naked eye. The recognition of cyanide ion is accomplished via the attachment of cyanide ion at the C atom of indolium CN group through nucleophilic addition. Also, the found detection limits of probes (nM range) were much lower than the WHO limit. Besides, the probes were effectively applied to determine cyanide ion in real water samples and thus was confirmed with HPLC method.

A diaminomaleonitrile-appended BODIPY chemosensor for the selective detection of Cu2+ via oxidative cyclization and imaging in SiHa cells and zebrafish.

A specific Cu2+ sensor, 2-amino-3-(BODIPYmethyleneamino)maleonitrile (BDM), was established by a simple dehydration between BODIPY and diaminomaleonitrile. Cu2+ could be recognized by BDM over other competing metal ions in acetonitrile with distinct fluorescence emission signal response. Upon the addition of Cu2+ to BDM in acetonitrile, the maximum absorption at approximately 530 nm on the longer wavelength side was quenched, and the emission at 530 nm was ignited simultaneously. The fluorescence intensity enhancement could reach a maximum of 204 times the intensity of the BDM blank solution. The fluorescence "off-on" effect is established according to the Cu2+-induced fast intramolecular oxidative cyclization reaction, which could be deduced from the formation of an imidazole ring appended to the cyclization product (2-BODIPY-1H-imidazole-4,5-dicarbonitrile, BMC). Single-crystal structure analysis of the sensor BDM and cyclization product BMC further demonstrated this oxidative cyclization. Finally, the Cu2+ recognition property of BDM was validated in SiHa cells and living zebrafish. Additionally, the blood-brain barrier of the zebrafish can be penetrated by the BDM dye and the neuron cells in the brain were stained.

Ultrasonic synthesis of α-MnO2 nanorods: An efficient catalytic conversion of refractory pollutant, methylene blue.

In this work, uniform α-MnO2 nanorods were synthesized via a simple hydrothermal followed by ultrasonication method using ultrasonic bath (20 kHz, 100 W) without using any surfactant and template. The crystallographic phases and surface morphology were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transition electron microscopy (TEM) analysis, respectively. Functional group identification and chemical states of α-MnO2 nanorods were confirmed by Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The as-synthesized uniform nanorods of α-MnO2 exhibit excellent catalytic conversion of toxic organic contaminant (methylene blue (MB)) in the presence of NaBH4 as reductant. The α-MnO2 exhibits excellent stability up to four repeated catalytic cycles with nearly 92% conversion. The kinetic rate constant (k), and turnover frequency (TOF) were 0.736 min-1 and 0.02 mmol mg-1 min-1, respectively. In addition, the fast electron transfer mechanism were investigated and discussed. These results open a new avenue for developing various metal oxide catalysts, which are expected to be very useful catalytic conversions.

A Chromone Based Fluorescent Probe for the Effective Detection of Aluminium Ion.

A new chromone moiety fused with phenyl hydrazine carboxamide as a binding site for metal ion was designed and synthesized as a colorimetric/fluorimetric probe for selective sensing of Al3+ ion. The absorption and fluorescence spectral results showed selective and sensitive recognition of Al3+ with no significant interference from other competitive metal ions. The addition of Al3+ to R brought a prompt color change from colorless to yellow and the turn-on fluorescence response with Al3+ among different cations was studied. The visible color change and turn-on fluorescence Al3+ ion with R was attributed to the intra molecular charge transfer transition. The plausible binding nature of the receptor with Al3+ has also been anticipated by the results of 1H NMR and mass spectral analysis. For the practical effectiveness, test strip prepared using probe R was successfully applied to monitor the presence of Al3+ ion in aqueous medium.

Dye Clicked Thermoplastic Polyurethane as a Generic Platform toward Chromic-Polymer Applications.

Chromic dyes responding against external stimuli are useful in various field of applications especially to colorimetric sensors. However, there have been several limitations in generic application because of its cost, stability and reliability. Here, we introduced highly functionalizable polymeric materials as a supporter covalently modified with controlled amount of chromic dyes. The photochromic organic dye (spiropyran) and highly functional thermoplastic polyurethanes (TPU) have been adopted as a representative example. Conventional polymeric solution processes such as film processing, wet-spinning, electrospinning and ink-writing are readily applicable because dye-TPU maintains its own solubility in various organic solvents. Additionally, since the concentration of dye on TPU are precisely controllable, these dye-TPU solution can be adopted in broad range of specific applications, such as secret coding, smart fabric, and chromic polymeric film layer.

Ultrasound-assisted method to improve the structure of CeO2@polyprrole core-shell nanosphere and its photocatalytic reduction of hazardous Cr6.

In this work, the CeO2@polypyrrole (CeO2@PPy) core-shell nanosphere has been synthesized via an ultra-sonication method using bath type (WUC-D22H, Daihan Scientific, Korea) and they are utilized for the photo-reduction of hazardous Cr6+ to benign Cr3+. The ultrasonic frequency and power were 20 kHz and 100 W, respectively. The PPy shielded CeO2 in aqueous solution could prevent the dissolution of CeO2 and to improve the photocatalytic ability of CeO2. X-ray diffraction was used to confirm the crystalline structure of as prepared CeO2@PPy core-shell and FT-IR was used to identify the functional groups. The uniform sized core of PPy and shell of CeO2 were observed by transition electron microscopy. The ultrasonic assisted synthesized CeO2@PPy core-shell exhibits a narrow bandgap (UV-DRS) and good reduction efficiency with higher reusability and stability compared to pure CeO2, PPy and mechanical mixing of CeO2@PPy. Moreover, the synergistic effect of CeO2 and PPy core-shell structure facilitate a higher electron transfer rate and prolong lifetime of photogenerated electron-hole pairs which can achieve good reduction rate of 98.6% within 30 min. In particular, the pH, catalyst, and Cr6+ concentration effects were optimized in photocatalytic reduction reactions. Meanwhile, this photocatalysis with fast and effective electron transfer mechanism for the Cr6+ reduction was elucidated. This method opens a new window for simple fabrication of conducting polymers-based metal oxide nanocomposite towards wastewater remediation and beyond.

Investigating Polaron Formation in Anatase and Brookite TiO2 by Density Functional Theory with Hybrid-Functional and DFT + U Methods.

Anatase and brookite are robust materials with enhanced photocatalytic properties. In this study, we used density functional theory (DFT) with a hybrid functional and the Hubbard on-site potential methods to determine electron- and hole-polaron geometries for anatase and brookite and their energetics. Localized electron and hole polarons were predicted not to form in anatase using DFT with hybrid functionals. In contrast, brookite formed both electron and hole polarons. The brookite electron-polaronic solution exhibits coexisting localized and delocalized states, with hole polarons mainly dispersed on two-coordinated oxygen ions. Hubbard on-site potential testing over the wide 4.0-10 eV range revealed that brookite polarons are formed at U = 6 eV, while anatase polarons are formed at U = 8 eV. The brookite electron polaron was always localized on a single titanium ion under the Hubbard model, whereas the hole polaron was dispersed over four oxygen atoms, consistent with the hybrid DFT studies. The anatase electron polarons were dispersed at lower on-site potentials but were more localized at higher potentials. Both methods predict that brookite has a higher driving force for the formation of polarons than anatase.