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A facile solution based chemical route has been developed for the synthesis of cuprous oxide (Cu2O) octahedrons employing polyvinylpyrrolidone (PVP ∼ 10k) at a relatively low temperature (50 °C) in aqueous medium and their response towards electrochemical non-enzymatic glucose sensing has been precisely investigated. The amperometric analysis reveals two calibration ranges (0.1 μM–1 mM and 1–7 mM) for the modified electrodes, with an excellent glucose specific selectivity over other interfering materials like sucrose, fructose, ascorbic acid (AA) and dopamine (DA). Careful analysis of the amperometric outcomes unveils a low limit of detection (LOD) of 0.96 μM (S/N = 3) along with exceptionally good stability and repeatability. Furthermore, the octahedral Cu2O modified electrodes exhibit a fast response time (∼1.5 s) with acceptable sensitivity and are found to be exceedingly reliable for the real time analysis of human serum samples (relative error

The present contribution depicts a unique approach to generate tunable Förster resonance energy transfer (FRET) emission with variation of pH of the medium. The pH sensitive absorption of Doxorubicin leads to modification of spectral overlap between emission spectra of donor (Pyrazoline) and absorption spectra of acceptor (Doxorubicin) thereby sensing maximum FRET efficiency in an optimum pH (near pK

Photocatalysts are important milestone for harvesting chemical energy from light energy in the era of massive energy consumption. Cerium oxide nanoparticle, having wide applications from catalysis to biomedical field, has drawback as photocatalyst due to its large band gap. Herein, a conducting polymer, polyaniline has been chosen as an active catalyst support to upgrade photocatalytic activity of cerium oxide nanoparticle. In this work, at first spherical shaped cerium oxide nanoparticle was synthesized by hydrothermal method. Later, polyaniline was decorated on cerium oxide nanoparticle surface via in-situ oxidative polymerization of aniline monomer. The as synthesized polyaniline/cerium oxide nanocomposite exhibits remarkable enhanced photocatalytic efficiency in comparison to cerium oxide nanoparticle or polyaniline in the degradation of a model organic pollutant Rhodamine B in waste water under UV light irradiation. Effects of different pH, Rhodamine B concentration and polyaniline content on photocatalytic activity were also analyzed. The experimental findings demonstrate that nanocomposite with polyaniline and cerium oxide nanoparticle molar ratio 1:1 degrades 91% Rhodamine B in 2 h whereas cerium oxide nanoparticle shows only 10% degradation in same time. The first order rate constant in presence of nanocomposite increases eight fold relative to that in presence of cerium oxide nanoparticle only. The enhanced photocatalytic mechanism is attributed to the synergistic effect between polyaniline and cerium oxide nanoparticle, which reduces recombination rate of photoinduced electron hole pair. Furthermore the nanocomposite is stable upto several cycles of catalysis as evident from their activity study and Field Emission Scanning Electron Microscope images. Thus combination of a conducing polymer with a semiconductor provides an advanced pathway for achieving enhanced photocatalytic activity.

The synthesis and solvatochromic behavior of pyrimidine based Schiff-base (PYPH) were studied to develop a fluorescent chemo sensor for the detection of Hg2+ in aqueous solution. The characterization of PYPH was investigated on the basis of UV–vis, FTIR, 1H-NMR and mass spectral data. PYPH displays selective fluorescent turn-off response to Hg2+ in aqueous solution. The sensitivity and selectivity of PYPH toward Hg2+ among different metal ions was examined by absorption, fluorescence, 1H-NMR and mass spectral studies. Binding stoichiometry (2:1) has been confirmed by a Job’s plot, HRMS spectral studies and 1H-NMR analysis. A low detection limit was 4.2 × 10−6 M for Hg2+. Ground state geometry of PYPH has been optimized using density functional theory (DFT). These results demonstrate that PYPH has promise to detect Hg2+ ion in environmental analysis systems.

The past few decades have witnessed significant advances in the development of functionalized gold nanoparticles (GNPs) for diverse applications in various fields such as chemistry, biology, pharma...

Development of stable self-assembled nanostructures (especially vesicles and liposomes), and understanding their physicochemical behaviors in aqueous solution is a long-standing topic of interest in chemical and biochemical research. In this progressive area, we report for the first-time formation of mixed micelles (at pH 12), and vesicles of anionic bolaamphiphiles (dicarboxylic acids viz. HOOC - ( CH 2 ) n - COOH , with moderate values of n 10, 11, 12, and 14) in combination with a cationic surfactant decyltrimethylammonium bromide (C10TAB) in buffered aqueous medium at different pH (6.0, 6.5, 6.8, and 8.0 for bola 10, 11, 12, and 14, respectively). Three pH dependent states of the solutions are observed: clear (high pH > 8), turbid and translucent (mid pH ≈ 6–8), and viscous inhomogeneous oil-like state (low pH

Interest in synthesizing and characterizing (IR, NMR and HRMS spectroscopic methods) a pyrimidine based Schiff-base ligand, 2-(2-(Anthracen-9-ylmethylene) hydrazinyl)-4,6-dimethyl pyrimidine (ANHP) has been developed for its application to ascertain the conformational change of protein and sensitivity towards fluorescence resonance energy transfer (FRET) process. Location of ANHP in bovine serum albumin (BSA) and human serum albumin (HSA) proteins environment has been determined using different spectroscopic techniques. Weakly fluorescent ANHP have shown greater protein induced fluorescence enhancement (PIFE) in case of HSA than BSA, though in both cases energy transfer efficiency are almost same but difference in binding constant values encourages us to find the location of ANHP within the complex protein environment. From the FRET parameter and α-helicity change, it has been found that ANHP bound with Trp-214 of HSA and surface Trp-134 of BSA. Conformational changes of proteins have been observed more for HSA than BSA in presence of ANHP, which has confirmed the location of ANHP in both the protein environments. Coupled with experimental studies, molecular docking analysis has also been done to explain the locations and distance dependent FRET process of ANHP in both proteins.

A study of the comparative drug carrier properties of cucurbituril[7] (CB7) and β-cyclodextrin (β-CD) with a naphthalimide derivative, [2-(2-aminoethyl)-1H-benzo[deisoquinoline-1,3(2H)-dione] (NAP) and its release in aqueous solution using micellar environment, is the key research interest of this work. The profound changes in the different spectroscopic behavior have been attributed to the formation of a 1:1 inclusion complex for NAP:CB7 system. Several experimental outcomes clearly interpreted that CB7 has better drug carrier properties for NAP compared to β-CD. It has been also focused on the systematic release of NAP molecule from CB7 by using different ionic and non ionic surfactants. Before releasing the drug molecules from CB7 the interaction between NAP and the three different types of surfactants has also been investigated separately. The selectivity of drug carrier and releaser has been monitored, using different spectroscopic techniques like absorbance, fluorescence, fluorescence decay life time and 1 H NMR spectroscopy. Besides, a theoretical approach has been followed for a proper geometrical optimized structure of NAP molecule and molecular arrangement of NAP:CB7 inclusion complex. From Density Functional Theory (DFT) it has been seen that NAP molecule is oriented as a t-bone like structure in its optimized form.

Research is going on to synthesize materials for acting as sensors of metal ions and are also published in different journals but the cause for sensing has not been clearly explained. In this paper, the reason for selective sensing of Cu2+ ions has been explained. A novel Schiff base fluorescent probe 3-[(2-hydroxy-naphthalen-1-ylmethylene)-hydrazono]-butan-2-one oxime (NPTH) was designed and synthesized to use as Cu2+ sensor. From our recent experiments, it has been found that only Cu2+ among different metal ions has been sensed by the synthesized ligand. The reason for selection and sensing of Cu2+ by the ligand was established by different spectroscopic techniques. The detection limit of NPTH was calculated as low as 4.11 ​× ​10-4M for Cu2+. Therefore, these results indicate that sensor NPTH has great prospective to detect Cu2+ ion in environmental analysis systems. Density functional theory (DFT) calculations have been done to ascertain the ground state geometry of NPTH.

Two tri-block copolymers P123 (PEO19PPO69PEO19) and F127 (PEO100PPO65PEO100) have been employed to form polymeric nanomicelles and function as potential nanocarriers for an anticancer pyrazoline derivative (PYZ) in aqueous buffer solution for biological studies. Encapsulation within these nanomicelles considerably enhanced the fluorescence of the PYZ compared to its low fluorescence in aqueous buffer medium. The effect of the micellar structures on the photophysical properties of PYZ have been demonstrated by means of steady state and time resolved fluorescence spectroscopy. Variation in hydrophilicity of the corona region was found to be a prime factor in modulating the location of the PYZ within the micelles which in turn influenced its corresponding enhanced emission and cytotoxicity. These drug encapsulated nanomicelles were found to be successfully internalized into the MCF-7 cells to demonstrate high-quality fluorescent images. The location of PYZ within the polymeric micelles influenced the CAC (Critical Aggregation Concentration)/CMC (Critical Micellar Concentration) ratio which modulated their drug release capacity resulting in a variation in their cytotoxicity.

The present work reveals the study of interaction of a promising chemotherapeutic drug ciprofloxacin (CFX) with a model transport protein bovine serum albumin (BSA). The occurrence of the drug-protein interaction is found to result in significant modulations of the fluorescence excitation and emission spectroscopic properties of CFX following interaction with BSA. However, the major focus of the study underlies a critical insight into the quantitation of the drug-protein interaction phenomenon. To this end, we have exploited the isothermal titration calorimetric (ITC) technique to quantify the affinity constant (K a ) and stoichiometry (n) of the CFX-BSA interaction with simultaneous revelation of the accompanying thermodynamics of the interaction process. In this context, our discussion also sheds light on the lacuna surrounding various experimental methodologies for evaluation of drug-protein binding parameters. Our endeavor also extends to elucidation of the kinetic parameters and energy of activation (E a ) of the CFX-BSA interaction. The present study also delineates the modulation of the dynamical aspects of CFX following interaction with BSA. The rotational relaxation dynamics of the protein-bound drug reveals the not-so-common “ dip-rise-dip ” anisotropy decay. Furthermore, the effect of drug binding on the native protein conformation has been evaluated from circular dichroism (CD) spectroscopy which reveals partial rupture of the protein secondary structure.

Significant Fluorescence Resonance Energy Transfer (FRET) process was observed between Naproxen (NPX) and a pharmaceutically important 3-pyrazolyl-2-pyrazoline derivative (PYZ) in bulk aqueous and heterogeneous cyclodextrin medium. The FRET efficacy of NPX-PYZ pair varied considerably in different cyclodextrin environments. Variation in the FRET efficacy mainly occurs due to a change in microenvironment of the fluorophores from bulk to a confined one. The structures of the FRET-pair and their interactions with cyclodextrins invoke a change in their spatial arrangement and proximity, which noticeably affects the FRET efficacy. The plausible explanations for this modulation in FRET efficacy has been established by employing steady state and time resolved fluorescence techniques in which simultaneous time–correlated analysis of the donor decay was observed to be reduced through FRET rather than some other relaxation pathway. Molecular Docking Analysis provided evidence of the possible modes of spatial orientation of the FRET pair in different cyclodextrin nano-cavities. Further TD-DFT calculations using B3LYP/6-31G/(d,p) method provided an intriguing insight about the medium dependent changes in the energies of the frontier molecular orbitals (HOMO-LUMO) associated with the corresponding FRET pair.

Gold Nanomaterials (GNMs) interact with fluorophores via electromagnetic coupling under excitation. In this particular work we carried out (to the best of our knowledge for the first time) a comprehensive study of systematic quenching of a blue emitter 2-Anthracene Sulfonate (2-AS) in the presence of gold nanoparticles of different size and shape. We synthesized gold nanomaterials of four different dimensions [nanoparticle (0D), nanorod (1D), nanotriangle (2D) and nanobipyramids (3D)] and realized the underlying effect on the emitting dipole in terms of steady and time resolved fluorescence. Nanometal Surface Energy Transfer (NSET) has already been proved to be the best long range spectroscopic ruler so far. Many attempts have been made to understand the interaction between a fluorescent molecule and gold nanomaterials. But not a single model can interpret alone the interaction phenomena. We have opted three different models to compare the experimental and theoretical data. Due to the presence of size dependent absorptivity and dielectric function, modified CPS-Kuhn model was proved to be the worthiest to comprehend variance of behavior of an emitting dipole in close proximity to nanometal surface by coupling with the image dipole of gold nanomaterials.

This study focuses on the understanding of the interaction of phenothiazinium dyes methylene blue (MB), new methylene blue (NMB), azure A (AZA) and azure B (AZB) with tRNAPhe with particular emphasis on deciphering the mode and energetics of the binding. Strong intercalative binding to tRNAPhe was observed for MB, NMB and AZB, bound by a partial intercalative mode. AZA has shown groove binding characteristics. From spectroscopic studies binding affinity values of the order of 105 M-1 were deduced for these dyes; the trend varied as MB > NMB > AZB > AZA. The binding was characterized by an increase of thermal melting temperatures and perturbation in the circular dichroism spectrum of tRNA. All the dyes acquired optical activity upon binding to tRNA. The binding was predominantly entropy driven with a favorable enthalpy term that increased with temperature in all the cases. Dissection of the Gibbs energy to polyelectrolytic and non-polyelectrolytic terms revealed a major role of the non-electrostatic forces in the binding. The small but significant heat capacity changes and the observed enthalpy-entropy compensation phenomenon confirmed the involvement of multiple weak non-covalent forces driving the interaction. The mode of binding was confirmed from quenching, viscosity and cyclic voltammetric results. Using density functional theory, ground state optimized structures of the dyes were calculated to provide insight into theoretical docking studies to correlate the experimental approaches. The modeling results verified the binding location as well as the binding energy of complexation. The results may provide new insights into the structure-activity relationship useful in the design of effective RNA targeted therapeutic agents.

Molecules capable of inducing self-structure in poly(A) may arrest protein synthesis by preventing poly(A) chain elongation thereby inhibiting the function of mRNA. We examined whether new methylene blue can induce such structural organization in single stranded poly(A) and compared the results with those of the phenothiazinium dyes thionine and toluidine blue O. Strong association between the dyes and poly(A) was revealed from the spectroscopy and cyclic voltammetry. Thionine has a higher affinity compared to toluidine blue O and new methylene blue at 50 mM and 100 mM, but at 200 mM [Na + ] new methylene blue exhibited the highest binding affinity. Negative enthalpy and positive entropy changes, and enthalpy-entropy compensation behaviour were characteristic features for the complexation. Involvement of hydrophobic forces in the binding process is correlated to the negative heat capacity changes. Differential scanning calorimetry and circular dichroism results revealed that the dyes bind poly(A) and induce a stable secondary structure with a melting temperature of 333.15 K. The binding constants increased in the range of 50–200 mM [Na + ]. Molecular docking results revealed that not only van der Waals forces of attraction but hydrogen bonding also plays a crucial role in dye-poly(A) binding. Recognition and binding of small molecules to single stranded poly(A) may present a new avenue for therapeutic intervention.

The fluorescent property of the aqueous solution of a metal organic framework (MOF) of Mn(II), having a sedimentary rocks like microstructure in solid-state, has been investigated. The luminescent feature of the the aqueous solution of MOF has been employed for studying the interactions of MOF with different surfactants including neutral, cationic, and anionic types in water medium. Interestingly, the MOF can very selective sense Triton X-100 based micelle in water medium. During the sensing process the fluorescent monomer of the MOF gets accommodated at the palisade layer of Triton X-100 in water medium and this has also been justified by simple fluorescence spectral and FE-SEM microstructural analysis. Thus, a MOF of Mn(II) can act as a selective fluorescent sensor for Triton X-100 based organized medium in water.

A new fluorescent sensor, 5-methyl-1H-pyrazole-3-carboxylic acid (6-methoxy-naphthalen-2-ylmethylene)-hydrazide (PYN), composed of a naphthalene group as the fluorogenic unit and a pyrazole carbohydrazide as the binding unit for metal ions has been designed and synthesized. The sensor shows excellent selectivity and sensitivity with a fluorescence enhancement towards Zn2+ and Mg2+ over other cations in aqueous acetonitrile solution. Turn-on fluorescent enhancements (FE) as high as ∼49 fold and ∼41 fold in mixed media for Zn2+ and, Mg2+ respectively were noticed. The signal enhancement of the sensor is based on chelation-enhanced fluorescence (CHEF) effect of PYN-Zn2+/Mg2+ with the inhibition of the photoinduced electron transfer (PET) effect. Moreover, the Job's plot established 1 : 1 stoichiometry of the complex formation between PYN and Zn2+ or Mg2+ ions. The limit of detection for Zn2+ and Mg2+ is as low as 2.2 × 10−7 M and 3.9 × 10−7 M respectively. PYN exhibited a second mode of selectivity for Zn2+ as it displaces Mg2+ from the PYN-Mg2+ complex. Density Functional Theory (DFT) calculations have been performed in order to show the structure and electronic properties of PYN and its complexes [PYN-Zn2+/Mg2+]. Cell imaging experiments confirmed that PYN can be used for monitoring intracellular Zn2+ and Mg2+ levels in living cells in vitro.

The present study primarily emphasizes the polymer-directed synthesis of cerium oxide nanoparticles (CeONP). Prior to the synthesis of CeONP, nanoflakes of the precursor cerium oxalate (CeOX) were first prepared by employing an AOT/lecithin/iso-octane/H2O mixed reverse microemulsion system and a polymer was added to the reaction medium to accomplish a dual purpose as both an additive and a structure-directing agent. Three polymers, namely, P123 (triblock copolymer), 17R4 (reverse triblock copolymer) and polyvinylpyrrolidone (PVP), were used as additives. Interestingly, the use of various polymers caused the synthesis of spherical cerium oxide nanoparticles within different size ranges (≈28.56 nm, 24.33 nm and 14.28 nm). Characterization of the synthesized CeONP was conducted by field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction spectroscopy (XRD) and Raman spectroscopy. The latter part of the study investigated their size-dependent catalytic activity in three-component reactions between nitrostyrene, 1,3-dicarbonyl compound, and aromatic primary amines to produce N-arylpyrrole as the desired product. The surface area of nanoceria (CeO2) was determined by BET measurements. Variations in size were found to directly affect the yield of the reactions. TEM analysis both before and after catalysis indicated the participation of the edges of the particles in the reaction.

We have studied the effect of interaction of surfactants on the FRET process in aqueous solution from transport proteins, BSA and HSA to the probe molecule, sodium salt of anthracene 1,5-disulphonate (1,5-AS). Cationic surfactant CTAB and gemini, anionic surfactant SDS and nonionic surfactant igepal-630 have been used for our investigation as surfactants and micellar solution. In organized media denaturation of protein occurs. Denaturation of protein has also been observed in presence of 1,5-AS. This has been established from steady state, time resolved fluorescence and circular dichroism (CD) studies in homogeneous and heterogeneous environments. Helecity calculations from CD spectra have also supported the results. Nonionic and ionic micellar solutions have been found to directly affect the protein helicity and the FRET parameters. The FRET parameters and denaturation of proteins in homogeneous and heterogeneous media have been compared.

Many biologically active water-insoluble drug molecules have limited clinical application because of strong hydrophobicity. Recently triblock copolymers have attracted enormous interest as potential drug carriers. For the purpose of delivering the 5-(1-(bromohexa-1,3,5-triyn-1-yl)-3a,4,5,6,7,7a-hexahydro-1H-4,7-methanoindazol-3-yl)-3-methyl-1-phenyl-1H-pyrazole-4-carbonitrile (PYZ) molecule, triblock copolymers are used. In order to understand the delivery of this water-insoluble probe through triblock copolymers (TBP), the solvent-dependent fluorescence properties of this compound have been examined in different homogeneous solvents. Besides the experimental work, theoretical studies have also been conducted to explain actual orientation of atoms in PYZ through optimized structures to support the experimental findings. Moreover, the three TBP polymers P-123 (PEO19 PPO69 PEO19 ), F-127 (PEO100 PPO65PEO100 ) and L-64 (PEO13 PPO30 PEO13 ) have been treated here as potential carriers that encapsulate a pyrazoline derivative. The consequence of spatial captivity on the emission properties was systematically visualized by means of steady-state and time-resolved fluorescence spectroscopy. From DLS measurements the size variation with the polydispersity index of TBP in the presence and absence of PYZ in different triblock copolymers was also monitored. Furthermore these measurements have been supported by TEM imaging also.

Department of Chemistry, Jadavpur University, Kolkata-700 032, India E-mail: diptisingharoy@gmail.com, sbjuchem@yahoo.com Manuscript received 16 July 2018, accepted 24 August 2018 Fluorescence resonance energy transfer (FRET) from trypsin to a probe molecule, sodium salt of anthracene-1,5-disulfonate (1,5-AS) has specifically been used to monitor the extent of protein denaturation in buffer media. The data obtained from steady state fluorescence spectral studies and time resolved measurement indicated that the FRET from tryptophan (Trp) residue of trypsin to 1,5-AS occurred effectively in buffer medium. The stability of the complex formed between albumins and the probe has been recognized from the conformational changes of proteins. Steady state and time resolved studies in association with circular dichroism study have experimentally established the FRET efficiency and protein denaturation.

Department of Chemistry, Jadavpur University, Kolkata-700 032, India E-mail: sbjuchem@yahoo.com, scbhattacharyya@chemistry.jdvu.ac.in Fax: 91-33-24146584 Government General Degree College, Keshiary-721 135, Paschim Medinipur, West Bengal, India Manuscript received 16 July 2018, accepted 23 August 2018 Effect of folic acid functionalized nanoceria on fibrillation of lysozyme has been studied using spectroscopic and microscopic tools. Both bare and functionalized CeONP are capable to retard fibrillation of lysozyme. Also interaction of lysozyme with nanoceria has been studied employing multiple biophysical techniques. The intrinsic fluorescence of lysozyme is quenched in presence of nanoceria. Adsorption of lysozyme causes significant reduction on fibrillization of lysozyme. Mechanism of quenching has been interpreted.

Accumulation of amyloid fibrils of proteins in different organs is a pathological indication for various neurogenerative disorders. Recently nanotechnology is at the centre of interest to tackle with those disorders. In this study we have chosen hen egg white lysozyme as our model protein which is responsible for hereditary systemic Amyloidosis disease. Here we have reported effect of cerium oxide nanoparticle (CeONP), folic acid functionalized CeONP (FA-CeONP) and polyacrylic acid functionalized CeONP (PAA-CeONP) (all of them having size ∼18 nm) on fibrillation of hen egg white lysozyme (Lyz). The amyloid growth is monitored by Thioflavin T (ThT), Congo Red (CR), 8-anilinonapthalene-1-sulfonic acid (ANS) assay, time resolved fluorescence anisotropy, intrinsic fluorescence, circular dichroism, atomic force microscopy and fluorescence microscopy study. Results demonstrate that all nanoparticle (NP) shows antiamyloid activity by broadening lag phase and suppressing growth phase of Lyz amyloid growth, but PAA-CeONP shows maximum inhibitory effect. These bare and functionalized CeONP shows dose dependent antiamyloid activity. We have also demonstrated that such inhibition of amyloid formation is associated with reduction of β-sheet content of protein. The inhibition efficiency is quantified by half maximal inhibition concentration IC50 values. A mechanistic pathway is explained on the basis of electrostatic interaction between NP and Lyz by ζ- potential measurement. This interaction is also analyzed theoretically by docking analysis. Thus our study provides a basis for use of CeONP as a promising candidate in therapeutic application in amyloid related disorders.

Interaction between the anionic double tail AOT (sodium bis (ethylhexyl) sulfosuccinate) and the zwitterionic single tail TPS ( N -tetradecyl- N , N -dimethyl-3-ammoino-1-propane sulfonate) in water and at the air/water interface has been studied. The surfactants synergistically interact with the solution as well as at the air/water interface forming mixed assemblies. The physicochemical properties of the free amphiphile monomers up to the point of their critical micelle concentration (CMC) have been evaluated and discussed. The interactions between the two amphiphiles in the mixed micelles in the bulk, and the adsorbed mixed assemblies at the air/solution interface have been analyzed using Rubingh and Rosen formalisms. The mixed systems have been found to undergo composition dependent salt induced micelle → vesicle → micelle forming transitions (MVMT). This has been supported by the fluorescence anisotropy measurements of the DPH probe, and the hydrodynamic diameter determined by the DLS method. Stable vesicle formation has been confirmed from the calcein dye encapsulation experiments, and the high resolution transmission electron microscopy (HRTEM) measurements. Nano-structured gold particles (GNPs) have been synthesized in the pure and mixed micelles of the AOT and TPS by the reduction of the HAuCl 4 by NaBH 4 . The morphology of the nano-structured materials was characterized from the UV and HRTEM measurements.

Nanometal surface energy transfer (NSET) from 2-anthracene sulfonate (2-AS) to gold nanoparticles in water-soluble triblock copolymers (TBP) P123 (PEO19PPO69PEO19) and F127 (PEO100PPO65PEO100) is systematically investigated. Fluorescence lifetime and anisotropy experiments provide thorough information on the locations of the 2-AS within these micelles. Variation in the size of the micellar corona region of the TBP is found to be the prime factor for different positions of 2-AS in them. Of late, nanometal surface energy transfer (NSET) from the donor probe to the surface of the metal nanoparticles has emerged as a potential tool for sensing and biolabeling. In the present work, the quenching of emission of the water-soluble 2-AS confined in the two different triblock copolymers in the proximity of a monolayer of the gold nanoparticles has been explored. Closer agreement between the experimental and theoretical characteristic distances has been found across the full wavelength range by the NSET approach. Understanding the location of the water-soluble dye in the vicinity of a polymeric drug delivery system is of significant importance, and how altered locations can trigger different controlled energy transfer efficiency from the 2-AS to the surfaces of gold nanoparticles (GNPs) has been discussed. This strategy could offer a new prospect in designing novel optical materials for chemical sensing and light harvesting endeavors.

Self-aggregation behavior in aqueous medium of four naphthalimide derivatives has exhibited substitution-dependent, unusual, aggregation induced emission enhancement (AIEE) phenomena. Absorption, emission, and time-resolved study initially indicated the formation of J-type fluorescent organic nanoaggregates (FONs). Simultaneous applications of infrared spectroscopy, theoretical studies, and dynamic light scattering (DLS) measurements explored the underlying mechanism of such substitution-selective aggregation of a chloro-naphthalimide organic molecule. Furthermore, transmission electron microscopy (TEM) visually confirmed the formation of ring like FONs with average size of 7.5-9.5 nm. Additionally, naphthalimide FONs also exhibited selective and specific cysteine amino acid sensing property. The specific behavior of NPCl aggregation toward amino acids was also employed as a molecular logic gate in information technology (IT).

Photophysical and spectroscopic properties of a fluorescent analogue, 2-(5-selenocyanato-pentyl)-6-chlorobenzo- [de]isoquinoline-1,3-dione (NP) in different solvents has been described in this paper using steady-state, time resolved spectroscopy and density functional theory (DFT) calculation. Stoke's shifted emission band in different solvents clearly demonstrate the highly polar character of the excited state, which is also supported by the enhancement of dipole moment of the molecule upon photoexcitation. Spectroscopic studies and multiple linear regression analysis method reveal that the solvatochromic behavior of the probe depends not only on the polarity of the medium but also on the hydrogen bonding interaction with the solvents. When the solvent effect was taken into account, the computed results show encouraging agreement with known experimental data. This article reveals the excellent correlation between the predicted and experimental spectral data of 1,8-naphthalimide derivative, providing a useful tool in the design of new fluorogenic probes having potential therapeutic activity.

The emerging development of rare earth nanotechnology in daily science has aroused serious concerns regarding its impact on health care systems. Despite the potential uses of rare earth (RE) nanoparticles for targeted drug delivery, detection/diagnosis and imaging, potential nanoparticle toxicity must be investigated before any in vivo medicinal applications can move forward. In this account, we illustrate the toxicological assessment of polyethylene glycol (PEG) functionalised Ln3+ (Ce3+, Tb3+) doped rare earth phosphate (LaPO4) nanorods. The first part of the work describes the synthesis of the nanorods employing a biologically compatible reaction environment using a H2O–EtOH solvent mixture, reflux temperature and a ligand exchange methodology. Thereafter, the synthesized materials have been purified and characterized. The later part of the work discusses the in vivo toxicity of the nanomaterial. Synthesized nanorods were suspended in a buffer and administered to mice through intraperitoneal (IP) injection over a period of 7 days (high dose 125 mg kg−1) and 28 days (high dose 125 mg kg−1 and low dose 12.5 mg kg−1). Analysis of the serum biochemistry and haematology followed by histopathology indicates inflammation in the liver. The biodistributions of rare earth ions (La3+, Ce3+ and Tb3+) were analyzed using inductively coupled plasma mass spectrometry (ICPMS). Additionally, cellular viability of the synthesized nanorods was also studied using spleen mononuclear cells of Swiss albino mice.

A new colorimetric, “turn-on” fluorescent chemosensor (DEAS-BPH) was synthesized for selective and sensitive recognition of Hg2+ ions with no interference from environmentally relevant metal ions in a mixed organo-aqueous medium. It was found that the presence of mercury induced nearly 27-fold fluorescence enhancement. This was attributed to the 1 : 2 metal–ligand complexation, ascertained by a Job's plot, NMR titration and HRMS studies. A theoretical study was conducted to rationalize the colorimetric sensing behaviour of the probe on the basis of an intramolecular charge transfer (ICT) mechanism. In addition, morphological alteration upon complexation with mercury was explored with the aid of Field Emission Scanning Electron Microscope (FESEM) measurement. Results of MTT assay and fluorescence microscopic studies unveiled that the probe is cell permeable with low cytotoxicity. Furthermore, the reversibility of the sensor and its efficacy to function in a wide range of pH values designated the suitability to image intracellular Hg2+ ions in living HepG2 and Escherichia coli bacterial cells.

Supramolecular interaction between an intramolecular charge transfer (ICT) probe, N,N-dimethylaminonaphthyl-(acrylo)-nitrile (DMANAN), and two well-recognized macrocyclic hosts, cucurbit[7]uril (CB7) and β-cyclodextrin (β-CD), has been studied in aqueous medium by absorption, emission, time-resolved measurements, and (1)H NMR spectroscopic methods. The changes in the profiles of the fluorescence spectra illustrate significant modifications in fluorescence intensity, decay time, and quantum yield upon confinement of probe within the hydrophobic cavity of the hosts. Using the Benesi-Hildebrand relationship, the stoichiometric ratio as well as the binding constant of the host-guest complexation has been estimated. The stable inclusion complexes of the probe with different hosts have been supported by DFT and ONIOM based quantum chemical calculations. These methods of measurement establish that the acceptor group of the probe resides inside the hydrophobic cavity of the macrocycle. The competitive binding of metal ions and cationic surfactants to CB7 has been excellently mapped with this guest fluorosensor.

Many proteins can abnormally fold to form pathological amyloid deposits/aggregates that are responsible for various degenerative disorders called amyloidosis. Here we have examined the anti-amyloidogenic potency of an ionic liquid, 1-butyl-3-methylimidazolium bromide, using lysozyme as a model system. Thioflavin T fluorescence assay demonstrated that the ionic liquid suppressed the formation of lysozyme fibrils significantly. This observation was further confirmed by the Congo red assay. Fluorescence microscopy, intrinsic fluorescence studies, nile red fluorescence assay, ANS binding assay and circular dichroism studies also testified diminishing of the fibrillogenesis in the presence of ionic liquid. Formation of amyloid fibrils was also characterized by α to β conformational transition. From far-UV circular dichroism studies it was observed that the β-sheet content of the lysozyme samples decreased in the presence of the ionic liquid which in turn implied that fibrillogenesis was supressed by the ionic liquid. Atomic force microscopy imaging unequivocally established that the ionic liquid attenuated fibrillogenesis in lysozyme. These results may be useful for the development of more effective therapeutics for amyloidosis.

The sole existence of a t-bone-shaped naphthalimide derivative [2-(2-aminoethyl)-1H-benzo[de]isoquinoline-1,3(2H)dione] (NAP), which gives rise to a photoinduced electron transfer (PET) mechanism, has been established using a combination of experimental and theoretical studies. In parallel an in vitro-in cell PET mechanism has also been shown. To understand the photophysics of NAP, solvent studies have been carried out in different solvents. In addition, theoretical calculations have been conducted to explain the spectroscopic properties through optimized structures. A "turn off" PET mechanism has also been observed in the presence of specific metal ions, namely, Cr3+ , Fe3+ and Hg2+ among a series of metal ions. Theoretical studies reveal that NAP-Cr3+ , NAP-Fe3+ and NAP-Hg2+ have their HOMO energy states lying in between a HOMO-LUMO energy state of the t-bone-type NAP molecule. On the contrary, the HOMO state of the other metal ion-NAP conjugate (NAP-Mn+ ) does not lie in between the HOMO-LUMO energy gap of the t-bone-type NAP molecule. Coupled with in vitro studies, in cell investigations reveal an enhancement of fluorescence intensity of NAP upon cytosolic metal sensing. Furthermore, a very high cell viability of NAP treated cells as tested by MTT assay and a fast permeation of the said compound as revealed by flow cytometry suggest NAP to be a potential candidate in metal sensing and bioimaging applications.

This study focuses on the understanding of the interaction of phenothiazinium dyes methylene blue (MB), new methylene blue (NMB), azure A (AZA) and azure B (AZB) with tRNA

For high-fidelity selective and sensitive fluorescent detection of zinc ions (Zn2+), a new pyrimidine based Schiff-base ligand PyMD (2,2′-((1Z, 1′Z)-(2,2′-(pyrimidine-2,4-diyl)bis(hydrazin-2-yl-1-ylidene))bis(ethan-1-yl-1-ylidene))diphenol) was designed and synthesized. In 4:1 methanol (MeOH)–water mixture, zinc (Zn2+) binding was found to promote ∼23 fold fluorescence enhancement of PyMD at wavelength 469 nm. The limit of detection (LOD) of Zn2+ was calculated to be 6.9 × 10−7 M according to fluorometric titration. The 1:1 binding mode of the metal complex was established by combined UV–vis, fluorescence, NMR and HRMS spectroscopic methods. Photophysical investigations including steady-state and time resolved analysis suggested a mechanism for the fluorescent zinc response that involved a ligand-to-metal charge transfer (LMCT) pathway. The experimental observations were further confirmed by DFT (Density Functional Theory) calculations of the free sensor molecule (i.e., PyMD) and the complex structure (PyMD-Zn2+). Finally, newly synthesized PyMD was applied for detection of free zinc in real samples, e.g., cabbage, banana, banana stem juice and commercial fruit juice. Besides, fluorescence behavior of PyMD-Zn2+ complex was also employed for Escherichia coli bacterial cell imaging study.

High selectivity and fluorescence sensitivity of a well-recognized antiexcitotoxic and anticonvulsant drug, kynurenic acid (KA), toward Cd II ion has been demonstrated by UV–vis, fluorescence, 1 H NMR spectroscopy in combination with computational calculations. Upon complexation with Cd II , KA exhibits a distinct excimer emission at 528 nm along with monomer emission at 402 nm. The sensing ability of drug KA toward Cd II ion is distinctly different from sensing for Hg II or Cu II ion. KA can form dimer by intermolecular O–H⋯O hydrogen bonding between the –COOH groups. Presence of Cd II metal ions promotes dimer formation in the excited state which exhibits excimer fluorescence.

In the present contribution, we have explored ground and excited state spectroscopic properties of an antiexcitotoxic and anticonvulsant drug, Kynurenic acid (KA), through steady-state absorption, emission and time-resolved emission spectroscopy and quantum chemical calculations. The main focus of this article is to illustrate the effects of various parameters such as the nature of the solvents and pH of the medium on the spectral properties of KA which confirms the presence of different neutral and ionic species in the ground and excited states. The molecule KA exists mainly as keto- or anionic form in the ground state, whereas the main contribution of its emission is arising from the keto tautomer in the excited state. Quantum chemical calculations by Density Functional Theory (DFT) method has been effectively employed to correlate the experimental findings. The ground and excited state properties of KA ascertained by means of experimental and theoretical method reveal that it resembles well with other two compounds, 4-hydroxyquinoline and xanthurenic acid formed by the decomposition of UV filters.

Sodium dicarboxylates (or Bola salts) with methylene spacers 0, 2, 4, 6, 8, and 10 were studied in aqueous solution to investigate their influence on the micellization of cetyltrimethylammonium bromide (CTAB). Since bolas with spacer length ≤12 are known not to micellize in general, the herein used sodium dicarboxylates were treated as 2:1 amphiphilic electrolytes which reduced surface tension of water (except sodium oxalate with zero spacer) without self-association. Their concentration dependent conductance was also linear without breaks. The bolas affected the micellization of CTAB but acted like salts to decrease its CMC. Their combinations did not form bilayer aggregates as found in vesicles. Nevertheless, they synergistically interacted with CTAB at the air/water interface as revealed from Rosen's thermodynamic model. Hydrodynamic radius (Rh), Zeta-potential (ζ), and electrical double layer behavior of bola interacted CTAB micelles were assessed. From SANS measurements, micelle shape, shape parameters, aggregation number (Nagg), surface charge of the bola influenced CTAB micelles were also determined. NMR study as well supported the non-mixing of bolas with the CTAB micelles. They interacted in solution like "amphiphilic electrolytes" to influence the surface and micelle forming properties of CTAB.

The detailed aggregation behavior of sodiumdodecyl sulfate (SDS) in tetrahydrofuran (Tf)-water (W) and formamide (Fa)-water (W) media at varied volume percent compositions has been investigated. Surface tension (ST), conductance (Cond), viscosity (Visc), isothermal titration calorimetry (ITC), nuclear magnetic resonance (NMR) and small angle neutron scattering (SANS) were used in this study. The presence of nonaqueous solvents affected the critical micelle concentration (CMC) of SDS, the counter-ion binding of the micelle, the energetics of the air/water interfacial adsorption and micellization of the amphiphiles in the bulk, the ion-association (ion-pair, triple-ion, quadruple, etc. between Na(+) and DS(-) ions) as well as the weakly soluble (aggregation less) amphiphile solution. Tf has been observed to produce a "dead zone" or "non-micelle formation zone" in the mixed Tf-W domain of 10-40 vol%. Fa influenced the SDS aggregation up to 70 vol%, at higher proportions (below the Krafft temperature (K(T))), instead of the micelle, "randomly arranged globular assembly" (RAGA) was formed. The correlation of the standard free energy of micellization (ΔG(m)(0)) with different solvent parameters (1) dielectric constant (ε), (2) viscosity (η0), (3) Reichardt parameter (E(T)(30)), (4) Gordon parameter (G), and (5) Hansen-Hildebrand hydrogen bonding parameter (δ(h)) has been attempted. It has been found that δ(h) produced a master correlation between ΔG(m)(0) and δ(h) for different binary mixtures such as Tf-W, Fa-W, Ml-W and Dn-W.

The medium charge specific excited state behaviour of a bio-active and fluorescent 3-pyrazolyl-2-pyrazoline derivative (PYZ) was systematically monitored in aqueous solutions of ionic (CTAB, SDS) and non-ionic (Triton X-100) micelles, applying steady state and time resolved fluorescence spectroscopy in addition to theoretical molecular simulations. PYZ displays complementary emission characteristics according to the nature of the effective charge of the micelles which was rationalized on the very fundamental basis of the frontier molecular orbital approach as obtained from quantum chemical calculations involving Time Dependent Density Functional Theory (TD-DFT) in combination with B3LYP exchange correlation function using 6-31G(d,p) as the basis set. Dynamic Light Scattering (DLS) measurements provided crucial information regarding the fluorescence quenching pattern of micelle bound PYZ by quencher CpCl. This study essentially accentuates PYZ's photophysical response in different micellar media in conjunction with their individual mode of electrostatic interaction therein. The theoretically calculated HOMO–LUMO energy gap values provide adequate information about the emissive behaviour of PYZ in ionic micellar media. The variation in the lifetime values of PYZ in aqueous and micellar media act as added evidence of the fact that PYZ basically resides in different micro-environments as introduced by the respective micelles. Conclusively it was observed that, in the excited state, PYZ responded promptly and uniquely according to the nature of the micellar charge.

In this work, a pyridine containing Schiff-base, 1-((anthracen-10-yl)methylene)-2-(pyridin-2-yl)hydrazine (AP) and a pyrimidine containing Schiff-base 2-(2-(Anthracen-9-ylmethylene) hydrazinyl)-4, 6-dimethyl pyrimidine (ANHP) have been synthesized and characterized by IR, NMR, HRMS and different spectroscopic methods. Two different tri block co polymers (P-123 and F-127) have been used as delivering system of this poor water soluble drug molecule AP and ANHP which are the main investigation of this work. To find out which one is the better delivering systems of AP and ANHP, spectroscopic studies have been carried out in P-123 and F-127 polymeric media. From the interactions of AP and ANHP with P-123 and F-127 polymers individually, binding constant values have been determined. The drug delivering efficiency of block co polymers has been investigated by using different spectroscopic techniques like absorbance, fluorescence, DLS and time resolved fluorescence measurements. All these experimental results indicate that P-123 is the better AP and ANHP delivering system than F-127 polymer. In addition, the structural properties like bond length, bond angles etc. of AP have been calculated by using density functional theory (DFT).

We herein report a simple and effective soft template mediated synthesis protocol for the room temperature preparation of highly crystalline cerium (Ce3+) and terbium (Tb3+) doped lanthanum phosphate (LaPO4) nanorods (NRs) and nanoflowers. Anionic surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/n-alkane soft template was chosen since it forms stable reverse micelles (RMs). Transmission electron microscopy (TEM) analysis corroborated successful formation of LaPO4:Ce3+,Tb3+ NRs having different aspect ratios (ranging from 2.8:1 to 7.6:1) under varying reaction conditions. The crystalline nature of the nanomaterials (NMs) was ascertained by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and small-area electron diffraction (SAED) studies. Energy-dispersive X-ray (EDX) and Fourier transform infrared (FTIR) spectroscopy further verified the elemental existence of the desirably synthesized nanostructures. Experimental results from thermogravimetric-differential therma...

Entrapping of a drug molecule having prospective therapeutic activity in microhetrogeneous environments and modulating important photophysical properties is of immense importance in various potential applications. The photophysical properties of a newly synthesized bioactive 7-oxy(5-selenocyanato-pentyl)-2H-1-benzopyran-2-one (PCM) has been studied in micellar solutions of anionic sodium dodecyl sulfate (SDS), cationic cetyl trimethyl ammonium bromide (CTAB) and nonionic p-tert-octylphenoxy polyoxyethanol (TX-100) micelle using steady state, time resolved fluorescence and fluorescence anisotropy techniques. The present effort illustrates the degree of accessibility of the fluorophore toward the heavy ion quencher in the presence of micelles of different surface charge characteristics. Iodide induced quenching leads to a decrease in the fluorescence intensity in case of SDS and TX-100 micelles, where as in CTAB micelles enhancement of fluorescence intensity is observed. Quantitative estimation of the micropolarity at the binding site of the probe has been determined. The imposed motional restriction of the microenvironment around the probe has been established from environment dependent fluorescence parameter, fluorescence anisotropy (r) value.

Interaction of bovine serum albumin (BSA) with the solvent spread monolayer of a catanionic surfactant, octadecyltrimethylammonium dodecylsulfate, (C18TA+DS−) at the air–buffer interface was investigated by measuring the surface pressure with time and change in surface area. Dipalmitoylphosphatidylcholine (DPPC) was used as reference. Kinetics of BSA desorption from the interface to the buffer subphase, that of C18TA+DS− and DPPC through their interaction with BSA, were also studied at different BSA concentrations (in the subphase) and surface pressures. Surface pressure (π)–area (A) isotherms (at pH = 5.4, μ = 0.01, T = 298 K) revealed that the coacervate/DPPC monolayer becomes expanded in the presence of BSA at low π while their protein bound species are released into the subphase at high π. Film morphology, studied by epifluorescence microscopy (EFM) and atomic force microscopy (AFM), reveals that the sizes of the domains of both DPPC and coacervate decrease in the presence of BSA. Presence of BSA in the coacervate and DPPC monolayer was supported from AFM data analysis.

Fluorescence recognition and sensing of aqueous anionic species is a challenging task and is being increasingly appreciated as far as potential biological and environmental issues of such systems are concerned. In the present contribution, we introduce for the first time fluorescence amplified recognition of a naphthalimide derivative (NAP) being embedded in a cationic alkyl trimethyl ammonium bromide micellar (CnTAB) units by various anions applying steady state and time resolved fluorescence techniques. Strongly quenched NAP emission in micellar framework has been effectively recovered upon intervention of various anions (such as H2PO4−, HPO42−, PO43−, SO42−, Cl−, etc.) with different sensitivities. The sensing process based on ion displacement mechanism, which principally governs a proficient fluorescence enhancement to various anions in a simple and efficient way, has been demonstrated. Optimization of sensor is achieved by altering surfactant chain length. The intermolecular approach used here seems to be rather flexible and appealing to design interface oriented fluorescent sensors to convene different analytic purposes for a wide variety of anion targets.

A novel fluorescent probe and pharmaceutically significant: 3-pyrazolyl-2-pyrazoline derivative (PYZ) has been selected as an acceptor molecule for fluorescence resonance energy transfer (FRET) interaction with serum albumins. Steady state and time resolved fluorescence techniques were applied to elucidate the nature of interaction of PYZ with serum albumins (BSA and HSA). Negligible FRET mediated emission occurred in the case of HSA but an efficient FRET mediated emission resulted in case of BSA. To gain further insight into the FRET selectivity of PYZ with the proteins, FRET from L-tryptophan (donor; native tryptophan) to PYZ (acceptor) was performed with the aim of getting an idea about the steric restrictions imposed on PYZ by the other groups present in BSA and HSA. The studies revealed that the surface bound Trp-134 in BSA allows an efficient FRET process with PYZ while the buried Trp-214 in HSA does not. The unusual selectivity for FRET in case of PYZ and the serum albumins has also been attributed to the complex structure of PYZ due to the presence of bulkier phenyl moieties in it. The complex nature of the excited state photophysics of tryptophan (Trp) in proteins also accounts for this FRET selectivity of PYZ with BSA and HSA.