Supramolecular-platform-assisted selective recognition of uric acid with high sensitivity microenvironment modulation of a self-assembled probe.

This report demonstrates a unique route for translating a non-responsive fluorophore into a responsive one to optically recognize uric acid (UA) in physiological-mimicking conditions. The explicit 'turn ON-turn OFF' fluorescence switching upon sequential disaggregation-reaggregation of the self-aggregated 3,3'-bisindolyl(phenyl)methane molecules materializes a straightforward, trouble-free supramolecular UA sensing platform.

Critical Assessment of Micellar Surface Charge-Dependent Disaggregation and Reaggregation of a Bis-Indole Self-Aggregate: What Should Be Our Case-Dependent Choice?

"Aggregation-caused quenching" is a deep-seated mechanism and has been widely used by the researchers as the possible basis for new sensor development. Contrast to aggregation, its turn around process, disaggregation, has gained much less consideration so far. Unfortunately, study of the further scope for reaggregation of the disaggregated probe assembly in the same solution, as and when required, is still under the rare category.

Hydrogen bond directed high-fidelity optical detection of picric acid: A single driver on diverse roads towards the same destiny.

High-fidelity optical detection of picric acid (PA) is necessary due to its toxic and explosive nature. Moreover, PA is a molecule with versatile features, such as hydrogen bond or proton donor-acceptor centers, extremely low p, highly electron-deficient center, high water solubility, . These unique features and concerns stimulated us to write this review article on the small-molecule-based optical detection of PA.

Disaggregation-induced resurgence of quenched emission of a self-assembled bis-indole system: photophysics, energetics, and dynamics.

Disaggregation-induced emission enhancement was studied using a self-aggregated bis-indole derivative, 3,3'-bisindolyl(phenyl)methane (BIPM), and β-CD molecules were employed for the emission recovery. In our recent study, BIPM molecules were found to exhibit weak emission efficiency in pure water due to aggregation-caused quenching (ACQ) effects. In the present study, we employed a simple, effective, biologically benign, and sustainable strategy in an attempt to disaggregate the BIPM self-aggregates into monomers to restore their emission efficiency.

Controlled tuning of radiative-nonradiative transition solvent perturbation: Franck-Condon emission aggregation caused quenching.

Organic molecules with tunable fluorescence quantum yield are attractive for opto-electronic applications. A fluorophore with tunable fluorescence quantum yield should be a better choice for a variety of applications that demand fluorophores with different quantum yields. Here organic emitters with a continuous bell-shaped fluorescence yield profile would be promising in view of sustainability and reusability; however, fluorophores with these properties are rarely reported.

A New Compound for Sequential Sensing of Picric Acid and Aliphatic Amines: Physicochemical Details and Construction of Molecular Logic Gates.

Picric acid (PA) at low concentration is a serious water pollutant. Alongside, aliphatic amines (AAs) add to the queue to pollute surface water. Plenty of reports are available to sense PA with an ultralow limit of detection (LOD).

Hydrogen bond regulated hydrogen sulfate ion recognition: an overview.

Hydrogen sulfate possesses substantial biological importance, having a colossal impact on physiological and environmental events. Therefore, several scientific groups have devoted serious effort to the development of versatile colorimetric and fluorimetric HSO4- sensors. Along with the scope, challenges, and significance, this review emphasizes the advancement of the optical recognition of HSO4- based on hydrogen bonding during the past two decades.

Circumstantial Overdose Management of an Efficient Cancer Cell Photosensitizer with Preclinical Evidence: A Biophysical Study.

In this article, pharmacological management of circumstantial overdose of an anticancer drug, Harmine (HM), under in vitro and in vivo conditions is described and further validated by employing in silico methods. HM, an efficient cancer cell photosensitizer, interacts extensively with nontoxic β-cyclodextrin (β-CD). Steady-state fluorescence studies and molecular docking analysis established differential nature of molecular inclusion depending on the relative concentrations of β-CD.

Excitation wavelength as logic operator.

Multiple molecular logic gates were harvested on a single synthesized material, (E)-2-(2-hydroxy-3-methoxybenzylideneamino)phenol (MBAP), by combining excitation wavelength dependent multi-channel fluorescence outputs and the same chemical inputs. Interestingly, the effortless switching of logic behavior was achieved by simply tweaking the excitation wavelength and sometimes the emission wavelengths with no alteration of chemical inputs and the main device molecule, MBAP. Additionally, new generation purely optically driven memory units were designed on the same system supporting an almost infinite number of write-erase cycles since inter-conversion of memory states was completely free from chemical interferences and impurity issues.

Doping Dopamine in Carbon Nanoparticles: A New Multifunctional Logic-Based Decision-Making Molecule.

A dopamine-functionalized carbon nanoparticle (CNP)-based platform is designed to reversibly control the optical signal, leading to a multifunctional logic system regulated by pH and light. pH-regulated unique reversible transformation of oxidized and reduced forms of a neurotransmitter, dopamine, conjugated with CNPs plays a decisive role in capturing the final output of the logic function. Inspired by this phenomenon, herein, we report the use of dopamine-docked CNPs to construct different molecular logic gates with an intention to develop the next-generation molecular logic gates.

A newly developed highly selective Zn-AcO ion-pair sensor through partner preference: equal efficiency under solitary and colonial situation.

Unusual self-sorting of an ion-pair under highly crowded conditions driven by a synthesized intelligent molecule 2-((E)-(3-((E)-2-hydroxy-3-methoxybenzylideneamino)-2-hydroxypropyl imino)methyl)-6-methoxyphenol, hereafter HBP, is described. When a mixture of various metal salts was allowed to react with HBP, only a specific ion-pair Zn/AcO in the solution simultaneously reacted, resulting in high-fidelity ion-pair recognition of HBP. This phenomenon was evidenced by significant changes in the absorption spectra and huge enhancement in emission intensity of HBP.

Shipment of a photodynamic therapy agent into model membrane and its controlled release: A photophysical approach.

Harmine, an efficient cancer cell photosensitizer (PS), emits intense violet color when it is incorporated in well established self assembly based drug carrier formed by cationic surfactants of identical positive charge of head group but varying chain length, namely, dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB) and cetyltrimethylammonium bromide (CTAB). Micelle entrapped drug emits in the UV region when it interacts with non-toxic β-cyclodextrin (β-CD). Inspired by these unique fluorescence/structural switching properties of the anticancer drug, in the present work we have monitored the interplay of the drug between micelles and non-toxic β-CDs.

A Strategic Design of an Opto-Chemical Security Device with Resettable and Reconfigurable Password Based Upon Dual Channel Two-in-One Chemosensor Molecule.

A simple strategy is proposed to design and develop an intelligent device based on dual channel ion responsive spectral properties of a commercially available molecule, harmine (HM). The system can process different sets of opto-chemical inputs generating different patterns as fluorescence outputs at specific wavelengths which can provide an additional level of protection exploiting both password and pattern recognitions. The proposed system could have the potential to come up with highly secured combinatorial locks at the molecular level that could pose valuable real time and on-site applications for user authentication.

pH triggered reversible photoinduced electron transfer to and from carbon nanoparticles.

Dopamine functionalized carbon nanoparticles (CNPs) that can act as efficient photoinduced electron donor-acceptor systems depending on the pH of the medium have been synthesized. In acidic media, dopamine on CNPs exists as hydroquinone and serves as an electron donor while under alkaline conditions the corresponding quinone form of dopamine serves as a strong electron acceptor. Application of external NADH to the system can invert the donor-acceptor roles under alkaline conditions.

FRET-based characterisation of surfactant bilayer protected core-shell carbon nanoparticles: advancement toward carbon nanotechnology.

Surfactant bilayer protected core-shell carbon nanoparticles (CNPs) have been synthesised. Förster resonance energy transfer (FRET) between the core-shell CNPs and two strategically chosen organic dyes has been exploited to characterise the protective surfactant bilayer.

Photophysical and photodynamical study of fluoroquinolone drug molecule in bile salt aggregates.

Photophysical properties of two widely used antibiotic fluoroquinolone drugs, namely Norfloxacin (NOR) and Ofloxacin (OFL) have been investigated in biomimicking environments formed by bile salts. Experimental results demonstrate that photophysical enhancement and fall of a particular prototropic species are sensitive to the excitation wavelength in bile salt aggregates. Excitation at shorter wavelengths reveals quenching of fluorescence of these fluoroquinolone with addition of sodium deoxycholate (NaDC), sodium taurocholate (NaTC) and sodium glycodeoxycholate (NaGDC).

A newly developed highly selective ratiometric fluoride ion sensor: spectroscopic, NMR and density functional studies.

A new easy-to-synthesize chemosensor, 3,3'-bis(indolyl)-4-chlorophenylmethane (hereafter S), was designed, synthesized and employed as a selective optical chemosensor for fluoride ions.(1)H NMR and density functional studies on the system have been carried out to determine the nature of the interaction between S and X(-) (X = inorganic anions) responsible for the significant fluoride-induced changes in the absorption properties of S. The experimental results reveal that abstraction of an acidic proton of S by the fluoride ion, leading to the formation of anionic species, is responsible for the spectral changes.

Norharmane: old yet highly selective dual channel ratiometric fluoride and hydrogen sulfate ion sensor.

Norharmane provides a simple unexplored class of anion receptor, that allows for the ratiometric selective detection of F(-) and HSO(4)(-) ions. The presence of a strong base can easily form hydrogen bonds with the acidic hydrogen bond donor moiety and the relatively strong acid can easily protonate the basic hydrogen bond acceptor moiety, which can modulate the optical response and can detect the anions efficiently with high selectivity. In view of that, it is promising to conceive the use of these systems in various sensing applications as well as in other situations, such as anion transport and purification, where the availability of cheap and easy-to-make anion receptors, would be advantageous.

Fluorescence photoswitching of a diarylethene-perylenebisimide dyad based on intramolecular electron transfer.

A fluorescent photochromic molecule, which is composed of a photochromic diarylethene (DE) and a fluorescent perylenebisimide (PBI), was synthesized and its fluorescence photoswitching was studied. The fluorescence quantum yield of the open-ring isomer is constant irrespective of solvent polarity, while that of the closed-ring isomer decreases with an increase in the dielectric constant of solvents. Femtosecond time-resolved transient and fluorescence lifetime measurements revealed that the fluorescence quenching of the closed-ring isomer is attributed to the intramolecular electron transfer from the PBI chromophore to the DE unit.

Effect of surfactant chain length on the binding interaction of a biological photosensitizer with cationic micelles.

Steady-state and time-resolved fluorometric techniques have been exploited to study the photophysical and distribution behavior of an efficient cancer cell photosensitizer, norharmane (NHM), in well-characterized, biomimicking nanocavities formed by cationic micelles with varying surfactant chain length. Amphiphiles like dodecyl trimethyl ammonium bromide (DTAB), tetradecyl trimethyl ammonium bromide (TTAB), and cetyl trimethyl ammonium bromide (CTAB) have been used for the purpose. Emission behavior of NHM is very much dependent on the surfactant concentration as well as their hydrophobic chain length.

Application of anionic micelle for dramatic enhancement in the quenching-based metal ion fluorosensing.

We introduce a simple and efficient strategy to enhance the efficiency of a quenching-based fluorosensor for metal ions by several orders of magnitude by using commercially available anionic surfactants varying hydrophobic chain length. Anionic surfactants with a proper choice of hydrophobic chain length at their optimum concentrations are efficient to boost up the efficiency of copper ion sensor dramatically. This simple and convenient strategy is, in general, applicable to quenching-based fluorosensors, new or established, in aqueous solution.

Photophysics of a cationic biological photosensitizer in anionic micellar environments: combined effect of polarity and rigidity.

A steady-state and time-resolved photophysical study of a cationic phenazinium dye, phenosafranin (PSF), has been investigated in well-characterized biomimetic micellar nanocavities formed by anionic surfactants of varying chain lengths, namely, sodium decyl sulfate (S(10)S), sodium dodecyl sulfate (S(12)S), and sodium tetradecyl sulfate (S(14)S). In all these micellar environments, the charge transfer fluorescence of PSF shows a large hypsochromic shift along with an enhancement in the fluorescence quantum yield as compared to that in aqueous medium. A reduction in the nonradiative deactivation rate within the hydrophobic interior of micelles led to an increase in the fluorescence yield and lifetime.

Effect of cyclodextrin nanocavity confinement on the photophysics of a beta-carboline analogue: a spectroscopic study.

Interaction of a beta-carboline based biologically active molecule, 3-acetyl-4-oxo-6,7-dihydro-12H indolo-[2,3-a] quinolizine (AODIQ), with alpha-, beta-, and gamma-cyclodextrins (CDs) in aqueous solution has been studied using steady state and time-resolved fluorescence and steady-state fluorescence anisotropy techniques. Polarity dependent intramolecular charge transfer (ICT) process is responsible for the remarkable sensitivity of this biological fluorophore to the CD environments. Upon encapsulation, the CT fluorescence exhibits hypsochromic shift along with enhancements in the fluorescence yield, fluorescence anisotropy (r), and fluorescence lifetime.

Surfactant chain-length-dependent modulation of the prototropic transformation of a biological photosensitizer: norharmane in anionic micelles.

A photophysical study of norharmane (NHM), an efficient cancer cell photosensitizer, has been undertaken in well-characterized biomimetic micellar nanocavities formed by anionic surfactants of varying chain length, namely, sodium decyl sulfate (S10S), sodium dodecyl sulfate (S12S), and sodium tetradecyl sulfate (S14S), using steady-state and time-resolved fluorescence spectroscopy. The effect of the hydrophobic chain length on the structural dynamism of the fluorophore has been reported. Experimental results demonstrate that the equilibrium of this dynamism is sensitive to the environment.

Binding interaction of a biological photosensitizer with serum albumins: a biophysical study.

A photophysical study on the binding interaction of an efficient cancer cell photosensitizer, norharmane (NHM), with model transport proteins, bovine serum albumin (BSA) and human serum albumin (HSA), has been performed using a combination of steady-state and time-resolved fluorescence techniques. The emission profile undergoes a remarkable change upon addition of the proteins to the buffered aqueous solution of the photosensitizer. The polarity-dependent prototropic transformation is responsible for the remarkable sensitivity of this biological fluorophore to the protein environments.