Search

Purpose: The purpose of the paper is to design a nonlinear dynamic inversion (NDI) based robust fault-tolerant control (FTC) for aircraft longitudinal dynamics subject to system nonlinearities, aerodynamic parametric variations, external wind disturbances and fault/failure in actuator. Design/methodology/approach: An uncertainty and disturbance estimator (UDE) technique is used to provide estimate of total disturbance enabling its rejection and thereby achieving robustness to the proposed NDI controller. As needed in the NDI design, the successive derivatives of the output are obtained through an UDE robustified observer making the design implementable. Further, a control allocation scheme consigns control command from primary actuator to the secondary one in the event of fault/failure in the primary actuator. Findings: The robustness is achieved against the perturbations mentioned above in the presence of actuator fault/failure. Practical implications: Lyapunov analysis proves practical stability of the controller–observer structure. The efficacy and superiority of the proposed design has been demonstrated through Monte-Carlo simulation. Originality/value: Unlike in many FTC designs, robustness is provided against system nonlinearities, aerodynamic parametric variations, external wind disturbances and sinusoidal input disturbance using a single control law which caters for fault-free, as well as faulty actuator scenario. [ABSTRACT FROM AUTHOR]

Free vibration analysis of a twisted, double-tapered blade mounted on a rotating disk undergoing overall motion is presented here. The Lagrangian approach is adapted to study the modal characteristics of the blade modeled as a rotating Rayleigh beam. The expressions for the kinetic energy and potential energy of the cantilever blade are derived using hybrid deformation variables. The continuous deformation variables in these equations are discretized using a series of basis functions that satisfy all boundary conditions of the cantilever beam. The equations governing the coupled stretch–bending–torsion motion of the rotating blade are derived using Lagrange's approach. The equations are then transformed into a non-dimensional form which are then solved for the eigenvalue problem for the modal characteristics of the blade. The results of the present model are verified with the results available in the literature. The variation of the natural frequencies with the rotating speed, taper ratio and pre-twist angle is presented. The tuned angular speed of the blade at which the angular frequency matches with any of the natural frequency of the blade resulting in the resonance is investigated. The Campbell diagram is plotted for the specific problem to identify the resonance where the natural frequency matches with the harmonics of the rotating speed. [ABSTRACT FROM AUTHOR]

Bifurcation analysis of the nonlinear vibration of an inextensible cantilever beam is analyzed by using the nonlinear normal mode concept. Two flexural modes of the cantilever beam, one in each transverse plane is considered. Two degrees-of-freedom nonlinear model for the vibration in the transverse direction is obtained by the discretization of the governing equation using Galerkins method based on the eigenmodes in each direction. The method of multiple scales is used to derive two first-order nonlinear ordinary differential equations governing the modulation of the amplitude and the phase of the dominant mode for the case of 1:1 internal resonance. The bifurcation diagrams are computed considering the frequency of excitation and the magnitude of the excitation as the control parameters. The stability of the fixed point is determined by examining the eigenvalues of the Jacobian matrix. The results show that a saddle-node-type bifurcation of the solution can occur under certain parameter conditions. [ABSTRACT FROM AUTHOR]

Grid fins are unconventional control and lifting surfaces consisting of an outer frame supporting an inner grid of small chord intersecting planar surfaces. Credited for their enhanced lifting characteristics at high angles of attack and wider Mach number regimes, minuscule hinge moments, and increased drag, these have been used in numerous aerospace applications. Removal of their cross-members leads to its simplified variant called cascade fins. The present study carries out numerous viscous computational fluid dynamics simulations at subsonic speed and high angles of attack to investigate and compare the impact of the horizontal planar member cross-sectional shape on cascade fin aerodynamics by elucidating the effects of using a NACA 0012 airfoil cross-section instead of a rectangular cross-section and varying the gap between their members. Appreciably higher aerodynamic efficiency attributed to drag reduction and comparable lifting characteristics along with steeper and hastened stall characteristics was deciphered for airfoil cascades. It was also found that optimally reducing the gap alleviates the stall tendency. These trends were further explained using pressure distribution plots and flow visualization analysis for the respective variant. Thus, planar member cross-section and gap selection should be done based on the aerodynamic efficiency requirement, desired maneuverability, and manufacturing cost. [ABSTRACT FROM AUTHOR]

A robust controller for an octocopter is essential for flight stability. The presence of matched and unmatched disturbances can deteriorate a stable performance. This work proposes a robust controller for an octocopter to reject the matched and unmatched disturbances. The effects of fast varying external disturbances and parametric uncertainty on octocopter are considered matched disturbances and sensor measurement noise is modeled as unmatched disturbances. To alleviate the effects of disturbances an alpha uncertainty and disturbance estimator based integral sliding mode (ISMC-Alpha UDE) control law is proposed. The Lyapunov theory is used for stability analysis of the proposed ISMC-Alpha UDE control law. Comparative numerical simulations along with root mean square error (RMSE) analysis are presented to show the better performance of the proposed controller. The proposed controller offers reduced and smooth control efforts to achieve robust state tracking performance by mitigating the effects of matched and unmatched disturbances. The Monte Carlo simulations are performed to validate the efficacy of the proposed design. [ABSTRACT FROM AUTHOR]

Context: Quantum mechanical calculations involving electron correlation, frequency dispersion, and solvent effects were carried out to examine the second-order nonlinear optical response of various acceptor, X (-CF3, -CN, -NO2) substituted in N,N-dimethylaniline (DMA) and julolidine(JLD). Here, both DMA and JLD acts as donor and the three substituted groups, X (-CF3, -CN and -NO2) at the para position of both the ring systems as acceptor. The NLO response (βHRS) of -CF3 and -CN substituted DMA and JLD is relatively lower compared to DMA-NO2 and JLD-NO2. The charge distribution is found higher in case of -NO2 substituted DMA and JLD (±443 and ±449) compared to their -CF3 or –CN substitution. Electronic characteristics such as UV-Vis absorption spectra, crucial excited state parameters and charge transfer contribution to βHRS have been used to explain the NLO parameter of DMA-X and JLD-X. Variation of the incident optical frequency of light shows fluctuation of βHRS value and highest values of βHRS are obtain at the λmax frequency of each compound. Solvent polarity variation study on βHRS shows that βHRS varies linearly with the Kirkwood-Onsagar dielectric factor (D). Methods: All computational studies have been carried out using density functional theory (DFT) based method. Since CAM-B3LYP based hybrid functional improves the asymptotic behavior of the exchange interaction by dividing into short-range and long-range components, first hyperpolarizability values in the present study were computed using DFT/ CAM-B3LYP/ 6-31G+(d,p) level of theory. [ABSTRACT FROM AUTHOR]

The vortex-induced vibration (VIV) of a rotating blade is studied in this paper. Uniform Euler–Bernoulli cantilever beam equation is used to model the rotating blade, while the nonlinear oscillator satisfying Van der Pol equation is used to represent the vortex shedding. The fluctuating lift force on the blade due to the wake dynamics is expressed such that it is proportional to the square of the magnitude of the relative velocity at which the blade interacts with the fluid. An unsteady lift due to vortex shedding acts on the blade, where as the blade is coupled with the fluid through a linear inertial coupling, resulting in a fluid–structure interaction problem. The coupled equations are discretized by using modal functions which satisfy the Eigenvalue problem. The work attempts to understand the interaction between the blade modes and the wake modes. The influence of the mass ratio and the reduced flow velocity on the coupling of the modes is explored. It is concluded form the study that the first mode is dominant and the effect of higher modes is less significant. Therefore, the single mode approximation is considered to study the instabilities associated with the frequency lock-in phenomenon of a rotating blade. The influence of fluid and blade damping, mass ratio and the coupling parameter on the lock-in phenomenon is investigated in this study. [ABSTRACT FROM AUTHOR]

Purpose: The requirement of robust cooperative control is essential to achieve consensus between unmanned aerial vehicles (UAVs) operating in swarm formation. Often the performance of these swarm formations is affected by wind gust disturbances. This study proposes an effective robust consensus protocol, which will ensure the UAVs in swam formation to collectively meet the desired objective in real-time scenario. Design/methodology/approach: In this work, the swarm of UAVs are modeled as multiagent systems by using the concepts of algebraic graph theory. To address the challenges of a complex and dynamic environment, an adaptive sliding mode control (SMC)-based consensus protocol is proposed. The closed loop stability analysis is established through Lyapunov theory. Findings: The efficacy of the discussed robust consensus controller is analyzed through numerical simulations. Further, the quantitative analysis using Monte-Carlo simulations validates performance of the proposed robust consensus protocol. The presented consensus protocol can be easily implementable as robust flight controller for swarm of UAVs. Also, as the consensus theory is based on the algebraic graph theory, the proposed design is scalable for a large number of UAVs in swarm formation. Originality/value: The proposed adaptive SMC achieves robust consensus of longitudinal dynamics states between all the UAVs by mitigating the effects of wind gust disturbances. Also, the adaptive SMC offers chattering-free control efforts. [ABSTRACT FROM AUTHOR]

A numerical study of two microramp geometries has been conducted to study their effectiveness in controlling swept shock wave-boundary-layer interactions. The planar shock wave is generated by placing a 20 deg sharp fin in a supersonic flow at Mach 4. The heights of microramps were varied as 30,40,50,60,70, and 90% of the boundary-layer thickness. The effect of microramp width and spacing is also studied. It is observed that boundary-layer separation is delayed significantly, downstream of the devices. Further, larger ramp heights were found to be more beneficial in delaying the separation. [ABSTRACT FROM AUTHOR]

The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) is well recognized for its contributions toward development of advanced materials and structures for aerospace propulsion and power systems. The Structures and Materials Division conducts research across a broad range of technical areas relevant to the agency's future aeronautics and space mission requirements. This paper will introduce the technical areas of strategic importance in the Structures and Materials Division today and briefly address some of the specific research activities within these areas. A broad look at how the research areas of emphasis have evolved over time, beginning in the early 1940s when the GRC was first formed, will be discussed. Examples of some of the more notable research accomplishments and their impact on the aerospace industry over this time period will be included. A discussion of the division's planned technical directions believed to be required to meet the longer-term national aeronautics and space exploration goals will also be addressed. [ABSTRACT FROM AUTHOR]

Abstract: A facile one step method for the synthesis of wormlike silver nanoparticles has been carried out in methyl cellulose matrix. Synthesis is based on the reduction of AgNO3 by sodium borohydride (NaBH4) in aqueous methyl cellulose (MC). Synthesized nanoparticles are mostly mono disperse in size and their aggregation is controlled by varying the concentration of AgNO3. Silver nanoparticles are analyzed using transmission electron microscope (TEM), UV–vis spectroscopy and X-ray diffraction (XRD) technique. It has been found that the concentration of AgNO3 has a significant effect on the morphology of Ag nanostructures. Worm like nanostructures showed excellent catalytic activity in the borohydride reduction of p-nitrophenol compared to spherical shaped nanoparticles. [Copyright &y& Elsevier]

The article focuses on a study which described the use of Kirchhoff's steady-state stall model for the modeling of nonlinear longitudinal aerodynamics linked to single/cascade fin models at high angles of attack. Geometric models for the flat plate (FP) and airfoil (AF) along with the parameters of the models as length, chord and thickness of the planar fin are shown. The equation used to calculate the steady-state flow separation point based on Kirchhoff's theory of flow separation is given.

Examines the use of phosphorescence and optical detection of magnetic resonance in determining the triplet state of diamidino-phenyl indole (DAPI). Alteration of biomolecular processes of DNA; Structure of the dication of DAPI; Characterization of DNA complex.

Examines the characterization of tryptophan residues of Escherichia coli alkaline phosphatase. Phosphorescence and optically detected magnetic resonance of tryptophan; Decay kinetics of tryptophan; Interactions with polar residues.

Examines the effects of nucleic acid binding on the triplet state properties of tetrapeptides containing tryptophan and 6-methyltryptophan. Use of phosphorescence and optically detected magnetic resonance spectroscopy; Account on the binding of poly(A) or poly(U) nucleic acids to tetrapeptides; Details on limiting types of tryptophan-base interaction.

Presents a study which investigated the magnetic field effect on the radical pair generated by the electron transfer from photoexcited [Ru(bpy)[sub 2](H[sub 3]pzbzim)](CIO[sub 4)[sub 2] to methyl viologen in aqueous sodium laurate micellar solution by using laser flash photolytic technique. Methodology; Results and discussion; Conclusions.

The corrosion of Ni, Co, Ni-10Cr, Co-21Cr, and IN738 was studied at 750°C in the presence of molten sulfate mixtures (NaSO-LiSO and NaSO-CoSO) and in an atmosphere consisting of O+0.12% SO-SO. The corrosion was observed to be similar for both NaSO-LiSO and NaSO-CoSO melts. The corrosion of Ni and Co tookplace by the formation of a mixed oxide plus sulfide scale, very similar to the corrosion in SO or SO alone. The initial stage for the corrosion of Ni-10Cr involved the formation of a thick NiO+NiS duplex scale, and Cr sulfide was formed during the later stages. A pitting type of morphology was observed for both Co-21 Cr and IN738. The pit was Cr sulfide at the beginning, and subsequently the sulfides oxidized to CrO. A base-metal oxide layer was present above the pit, and this was observed to be formed very early in the corrosion process. A mechanism is proposed to explain this. In general, the formation of sulfides appears to be the primary mode of degradation in mixed sulfate melts. [ABSTRACT FROM AUTHOR]

The hot corrosion of a nickel-base superalloy, Udimet 700, has been studied in the temperature range 900-950°C. The effect of the amount of NaSO on the corrosion kinetics was determined. Large weight gains and severe corrosion were associated with two different modes of degradation: (1) formation of large, interconnected sulfides beneath the external scale, and (2) formation of a NaMoO-MoO melt. The corrosion due to formation of the NaMoO-MoO melt occurred for all the salt-coating thicknesses, whereas, large sulfides were formed only for the heavier coatings of NaSO. The formation of NaMoO-MoO melt required an induction period, and the length of the induction period was observed to be a function of the amount of NaSO and of temperature. [ABSTRACT FROM AUTHOR]

Alkali atom-doped hexalithioborazine (B3N3Li6-M) as a novel class of super-alkali complex has been investigated for their exceptionally high first-order and second-order electrical responsive properties. The stability of resulting complexes, B3N3Li6-M (M = Li, Na, and K), is confirmed by the ADMP simulation and the negative values of thermodynamic parameters such as binding energy (∆Eb) and Gibbs free energy (∆G). The relationship between aromaticity (NICS) and first hyperpolarizability of B3N3Li6-M follows linear relationship. Diffuse electron cloud around the central ring and doped alkali metal in the HOMO of B3N3Li6-M complexes has been attributed to the charge transfer from peripheral Li to the dopant metal (M) atom. The dipole moment of B3N3Li6-M varies between 0.507 D (M = Na) and 1.608 D (M = Li) due to charge transfer in these complexes. The mean polarizabilities (αav) of B3N3Li6-M ranging from 573.08 to 1598.86 a.u are observed. Exceptionally high value of second-order NLO parameter (βav = 5.133 × 105 a.u and βHRS = 2.166 × 106 a.u) are observed in case of Li-doped B3N3Li6 in this series. Thus, the first hyperpolarizability (βav and βHRS) values of the complexes produced by the interactions between alkali metal atoms (M) and B3N3Li6 are strong enough to demonstrate as potential second-order NLO materials. [ABSTRACT FROM AUTHOR]

A designed aggregation-induced emission enhancement (AIEE) active fluorescence probe 2,3-Bis-[(2-hydroxy-napthalen-1-ylmethylene)-amino]-but-2-enedinitrile (L) was synthesized via one step condensation method. The probe shows swift sensitivity and selectivity toward Al3+over other relevant metal ions and also exhibits significant AIEE phenomena in methanol/water mixture. Significant enhancement of fluorescence intensity is triggered via chelation-enhanced fluorescence through complex (Al3+-L) formation. A 2:1 metal to ligand ratio is observed from Job's plot based on UV − Vis absorption titration and detection limit (LOD) is found as low as 31.14 nM. Moreover, 1H NMR titrations and fluorescence reversibility by adding Al3+ and EDTA sequentially had been performed to establish the binding site of sensor complex (Al3+-L). Time-resolved photoluminescence, dynamic light scattering, optical microscopy, and on-site visualization studies have been performed to understand the AIEE mechanism of L in different volume percentage of water and methanol mixture. An INHIBIT molecular logic gate has been constructed utilizing the fluorescence behavior of the probe, L in presence of Al3+ and strong chelating ligand EDTA. [ABSTRACT FROM AUTHOR]

Effect of donor–acceptor substitution position on the electrical responsive properties like polarisability, first hyper polarisability of donor–acceptor substituted azulene derivatives have been investigated using HF and Density functional theory with various hybrid functional and basis. It is observed that among the DFT methods, CAM-B3LYP hybrid functional with correlation consistent polarised triple-zeta, cc-pVTZ basis show less overestimated value of polarisability and first hyperpolarisability compare to other hybrid functional and it is again advantageous than HF with similar basis in term of its price and performance ratio. An apparent violation of minimum polarisability principle among the studied azulene derivatives are observed and it has been explain due to non-constancy of the potential functions upon substitution of donor (NMe2) and acceptor (NO2) groups at different position of azulene ring. Computed βav values are in accordance with the extent of charge transfer character of the azulene with a few exceptions. Position of donor and acceptor group at the five- and seven-member ring also play a big role in determining the electrical responsive parameter has been discussed. It is also observed that 2 and 6 carbon atom of azulene are highly sensitive towards donor acceptor substitution. [ABSTRACT FROM AUTHOR]

Fluorescent chemosensor, 3-(Anthracen-2-yliminomethyl)-benzene-1,2-diol (ANB) has been synthesized by one-step condensation of 2-aminoanthracene and 2,3-dihydroxybenzaldehyde and characterized using 1H-NMR, FT-IR and Mass spectroscopic techniques. The probe ANB was found to be an efficient 'turn-on' fluorescence chemosensor for the selective detection of Al3+ ion over other metal ions in an aqueous solution. The chemosensor exhibits ~ 27-fold enhancement of emission intensity in presence of Al3+ ion. Fluorescence quantum values for ANB and (Al3+-ANB)-complex are 0.004 and 0.097, respectively. In addition, the binding constant and the limit of detection were found to be 1.22 × 104 M−1 and 0.391 µM, respectively. The chemosensor ANB binds to Al3+ ions in 2:1 stoichiometric ratio which was supported by Job's plot, 1H-NMR titration and florescence titration. Fluorescence reversibility of the sensor complex was well established by adding EDTA in the same condition and a molecular INHIBIT logic gate was fabricated using this reversible nature of the sensor complex. Additionally, the chemosensor ANB shows a novel aggregation-induced enhanced emission phenomenon, where the aggregate hydrosol of ANB shows enhance emission intensity. [ABSTRACT FROM AUTHOR]

The endeavor to improve the aerodynamic efficiency of supersonic flying bodies has been constant and significant ever since. Notably it has a significant contribution towards the growth of Aerospace industry. The rigorous experiments carried out on aerodynamic efficiency have led to the optimization of flying body design involving structural, aerodynamic or chemical performance parameters. Aerodynamic efficiency is the basis of energy-efficient flying model, and low drag is the basis of aerodynamic efficiency. The relative impact of drag depends upon the flight regime and specific design requirements. Hence, in the search of improving the aerodynamic efficiency and reducing the undesirable flight properties, specifically in supersonic regime, a channelised study has been carried out, as also being carried out many researchers across the world through different processes. Since shock waves create a considerable amount of drag, which can result in extreme drag on the supersonic body, it forms a significant area of study while aiming at improving the aerodynamic efficiency of a supersonic flying object. Hence, this paper deals with the reduction of wave drag by adopting cascade fin, which is a kind of fin that is still evolving in the aerospace environment. A cascade is a control surface which is composed of an external frame supporting an internal cascade of planar surfaces having small chord length. Various properties of cascade fin impact the aerodynamic efficiency individually and also in consonance with other properties. However specific properties of angle of attack and leading edge shape of cascade fin have been considered in this paper to evaluate their effect in reducing the wave drag of a supersonic flying object. This paper deals with these properties of cascade fin individually in isolation, in order to study and understand their impact in detail. The study on wave drag reduction by varying the angle of attack of cascade fins, in supersonic flow regime, has been carried out by adopting computational fluid dynamics simulation, performed for a Mach number of 2 and angle of attack of 0° and 5°. The study on wave drag reduction by varying the leading edges of cascade fins, in supersonic flow regime, has been carried out by adopting computational fluid dynamics simulation, performed for a Mach number of 2 and angle of attack of 0°. The study of varied leading edges considered have displayed significant variation of wave drag, but in practical application, a particular leading edge needs to be chosen as part of the larger scheme of aerodynamic designing process. [ABSTRACT FROM AUTHOR]

A multi responsive fluorescent probe, N',2-bis(E-4-(diethylamino)-2-hydroxybenzylidene)hydrazine-1-carbothiohydrazideV(H2L) has been synthesized through one step condensation method. Probe, H2L shows 'turn-on' dual sensing properties towards Cd2+ and H2AsO4− at two distinct wavelength. The probe (H2L) is spectroscopically characterized and the chemo-sensing mechanism has been demonstrated through 1H NMR, absorption, steady state and time resolved emission study. The most promising advantage of the probe is its application in the one-pot detection of Cd2+ (λem = 462 nm) and H2AsO4−(λem = 492 nm) where intense emission appears at two different wavelengths and the observed limit of detection (LOD) of H2L towards Cd2+ and H2AsO4− are 2.67 × 10–8 M and 5.14 × 10–6 M respectively. Further the 'turn-on' emission property of H2L towards Cd2+ is applied to construct INHIBIT logic gate. [ABSTRACT FROM AUTHOR]

The contrast of the second-order nonlinear optical response between the enol (anti and syn) and keto tautomeric equilibrium of 7-Phenyl-7H-benzo[1,2-b;4,5-b']difuran-2,3,6-trione (PBDT) with donor/acceptor substitution at the para position of phenyl group have been computed involving electron correlation, frequency dispersion, and solvent polarity effects. The Hyper Rayleigh Scattering (HRS) first-hyperpolarisability contrast between the enol and keto forms for PBDT and Nitro-substituted PBDT is 3.5 and 2.8, respectively. However, in NMe2-substituted PBDT, a large contrast (~12 times) of HRS first hyper-polarisability between enol (anti and syn) and keto form is observed. Present study reveals that electron donor group (-NMe2) in PBDT plays a pivotal role for obtaining very high contrast in the first hyper-polarisability (ßHRS and ßvec) values between the enol and keto forms compare to the electron acceptor (-NO2) group substitution at the same position. The solvent effect also plays a significant role in further improving the first hyper-polarisability value and its switching behaviour between the enol and keto forms of NMe2-PBDT. NLO switching contrast between the enol and keto forms of donor/acceptor substituted PBDT is also explained using the electronic features including UV-Vis absorption spectra, HOMO-LUMOelectron densities, optical energy gaps, charge transfer contribution etc. [ABSTRACT FROM AUTHOR]

A Fluorescent chemosensor based on pyrene scaffold, 5-diethylamino-2-(pyren-1-yliminomethyl)-phenol (PDS) is synthesized using condensation method. It displays novel aggregation-induced emission (AIE) phenomena in its aggregated/solid state. The AIE characteristic of PDS is studied in CH3CN/H2O mixtures at different volume percentage of water and morphology of the aggregated particles are investigated by DLS and optical fluorescence microscopic study. The probe is aggregated into ordered one-dimensional (1-D) rod like microcrystals and exhibit high efficiency of solid-state emission with green colour. By taking advantage of its interesting AIE feature, the aggregated hydrosol has been utilized as 'off–on' type fluorescence switching chemosensor with superb selectivity and sensitivity towards Cu2+ions and the limit of detection (LOD) was calculated as low as 6.3 µM. A high Stern–Volmer quenching constant was estimated to be 2.88 × 105 M−1. The proposed chemosensor with AIE feature reveals a prospective view for the on-site visual recognition of Cu2+ ions in fluorescent paper strips and the synthesized probe is also exploited to find out the concentration of Cu2+ions in real water samples. [ABSTRACT FROM AUTHOR]

Potential energy (PE) curves along the proton transfer co-ordinate of ground and excited states of 9-Hydroxy-phenalen-1-one (9HPO) and 6-Hydroxy-benzo[de]anthracen-7-one (6HBAO) have been studied using DFT-CAM-B3LYP/6-311G(d,p) and TD-DFT-CAM-B3LYP/6-31G(d) level of theory, respectively. The choice of these two molecules is based on their symmetric and asymmetric nature for their intramolecular H-bonded six-membered ring systems. Ground and excited states of PE calculations show that due to lower potential energy barrier, 9-Hydroxy-phenalen-1-one (9HPO) and 6-Hydroxy-benzo[de]anthracen-7-one (6HBAO) can be in equilibrium with their enol and keto tautomeric forms. Computed values of global reactivity descriptors, that is, average polarisability (αav) and chemical hardness (η) along the proton transfer co-ordinate of both the molecules are very small although their variations conform with their respective optimum principles. Inspired by the significant variation of the first hyperpolarisabilty along the proton transfer co-ordinate of both the compounds, it is concluded that the first hyperpolarisability can serve as a better parameter to identify enol or keto tautomeric forms in enol keto equilibrium. The variation of average first hyper polarisability (βav) along the proton transfer co-ordinate follows the optical gap rule in both the molecules. [ABSTRACT FROM AUTHOR]

Abstract: Monodispersed sodium alginate (SA) stabilized silver nano bar and hydroxyl propyl methyl cellulose (HPMC) stabilized silver nano bar have been synthesized by photochemical method. The nanoparticles are characterized by UV–VIS–NIR spectroscopy, transmission electron microscopy (TEM) and selected area electron diffraction (SAED) study. Catalytic reduction of 4-nitrophenol (4-NP) by sodium borohydride in presence of nanoparticles is also evaluated. The kinetic data obtained by monitoring the change in UV–Vis absorption spectra of 4-NP are explained by Langmuir–Hinshelwood model. It is observed that the rate of reduction is higher in SA stabilized Ag nano bar than the HPMC stabilized Ag nano bar. [Copyright &y& Elsevier]

Nonlinear longitudinal aerodynamics of planar fins and aircraft at high angles of attack near stall have been modeled using Kirchhoff's formulation. Both the steady-stall and quasi-steady stall models have been applied on the longitudinal aerodynamic data at high angles of attack pertaining to planar fins and Hansa-3 aircraft, respectively. The National Wind Tunnel Facility (NWTF) in the department of Aerospace Engineering at the Indian Institute of Technology, Kanpur was used to generate the wind tunnel data for planar fins with rectangular and NACA-0012 airfoil cross-sections whereas flight test data near stall for Hansa-3 aircraft were generated by executing a quasi-steady stall maneuver (QSSM). The Kirchhoff's steady-state stall model was applied to wind tunnel data for modeling the flow-separation point and to estimate the parameters characterizing stall. The Kirchhoff's quasi-steady stall model was applied to the compatible real flight test data to model the nonlinear longitudinal aerodynamics and estimate the aerodynamic parameters. An approach of fixing the parameters to their reasonably accurate values was followed during the estimation of quasi-steady stall characteristics and the longitudinal aerodynamic parameters using the maximum likelihood (ML) method from the nonlinear flight data pertaining to QSSM. The results obtained using both models were found to be encouraging and are presented in graphical as well as in tabular form. The estimated parameters using both models have been compared with the reference results. A well-matched comparison of the model's estimated and real flight data hysteresis loop is also presented. [ABSTRACT FROM AUTHOR]

Abstract: We present here the hybrid DFT level study of a series of dipeptide at 6-31g∗ basis. A rigorous computation has been performed on a series of dipeptide (keeping valine as a fixed component in the N-terminus and the component in the C-terminus are varied with eight different combinations) to investigate various geometrical parameters to understand the effect of amino acid sequence in the dipeptides. Bond lengths, bond angles have been reported. Geometry around α-carbon atom is discussed. The analysis of dihedral angles shows deviations from planarity. This has been explained in terms of the cumulative effect of steric hindrance of –R group and H-bonding. To get an idea about its conformational stability, a rigid potential energy scan has also been performed on valine by rotating –COOH and –CH(CH3)2 groups separately. [Copyright &y& Elsevier]

1-(Pyridin-2-yl-hydrazonomethyl)-naphthalen-2-ol (PNOH) is a naphthalene-based fluorescence dual chemo-sensor for Al3+ and Zn2+. The probe (PNOH) is spectroscopically characterised and the chemo-sensing mechanism has been demonstrated through 1H NMR, absorption and both steady state and time resolved fluorescence study. The 'turn-on' luminescence property of PNOH is used for the selective detection of trace amount of Al3+and Zn2+via chelation enhanced fluorescence (CHEF) through complex formation. The 1:1 stoichiometry of each sensor-metal complex is observed from Job's plot based on UV-Vis titration. Most promising advantage of the probe (PNOH) is its application in the one-pot detection of Al3+ (λem- 460 nm) and Zn2+ (λem- 510 nm) exciting at same wavelength (λex- 420 nm) while high intense emission appears at two different wavelengths. Limit of detection (LOD) of PNOH towards Al3+ & Zn2+ are found to be 60 nM & 365 nM respectively. Real water sample analysis has also been demonstrated by using the probe PNOH. [ABSTRACT FROM AUTHOR]

Ground and excited-state proton transfer and electrical responsive properties along the proton transfer co-ordinate of four donor–acceptor substituted pyrazole derivatives have been investigated using the density function-based range separated hybrid GGA functional ωB97XD with 6-311G(d) basis. Both intrinsic reaction coordinate (IRC) and distinguished co-ordinate (variation of O–H distance of the enol tautomer) have been chosen as a proton transfer co-ordinate of the titled compounds for comparison. Our study reveals that the various electrical responsive parameters like average polarizability (αav), first hyperpolarizability (βav) and global reactivity descriptors e.g., chemical hardness (η), electrophilicity index (ω) along the proton transfer co-ordinate are in conformity with the respective optimum principles. Maximum value of βav is found in the case of nitro substituted pyrazole derivative. Variation of βav along the proton transfer co-ordinate for all compounds have been correlated with the variation of Δµf0/(S1-S0)3 using two-level approximation and electronic special extent () along the proton transfer coordinate. [ABSTRACT FROM AUTHOR]

The frequency lock-in during the nonlinear vibration of a turbomachinery blade is modeled using a spring-mounted airfoil coupled with a van der Pol Oscillator (VDP) oscillator. The proposed reduced-order model uses the nonlinear VDP oscillator to represent the oscillatory nature of wake dynamics caused by the vortex shedding. The damping term in the VDP oscillator is assumed to be nonlinear. The coupled equations governing the pitch and plunge motion of an airfoil are used to approximate the vibration of a turbomachinery blade. Springs having cubic-order nonlinearity for their stiffnesses are used to mount the airfoil. The unsteady lift acting on the blade is modeled using a self-excited nonlinear wake oscillator. The model for wake dynamics takes into account the influence of blade inertia. The nonlinear coupled three degrees of freedom (dof) aeroelastic system is studied for instability resulting in the frequency lock-in phenomenon. The equations are transformed into non-dimensional form, and then the frequencies of the coupled system are plotted to demonstrate the frequency lock-in. Further, the method of multiple scales is used to derive modulation equations which represent the amplitude and phase of the oscillation. The results obtained using the method of multiple scales are compared with direct numerical solutions to verify the present modeling method. The steady-state amplitudes of the response are plotted against the detuning parameter, which represents the frequency response curve. Further, the sensitivity of non-dimensional parameters such as coupling coefficients, mass ratio, reduced velocity, static unbalance, structural damping coefficient and the ratio of uncoupled pitch and plunge natural frequencies on the frequency response is investigated. The study revealed that parameters such as mass ratio, reduced velocity, structural damping coefficient, and coupling coefficients have a stronger influence in suppressing the amplitude of vibration. Meanwhile, parameters such as the frequency ratio, static unbalance, reduced velocity, and mass ratio significantly affect the range of frequency in which the lock-in phenomenon happens. Further, linear perturbation analysis is done to understand the qualitative effect of the system parameters such as coupling coefficients, mass ratio, frequency ratio, and static unbalance on the range of lock-in. [ABSTRACT FROM AUTHOR]

A simple antipyrine based fluorescent probe, 4-[(2-hydroxy-3-methoxy-benzylidene)-amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one (OVAP), has been successfully synthesized using a one-step condensation method. It exhibits dual sensing properties toward Al3+ and Zn2+ in the presence of other relevant metal ions and also displays novel aggregation induced emission enhancement (AIEE) characteristics in its aggregated/solid state. Aggregated OVAP microstructures with interesting morphologies have been synthesized using SDS as a morphology directing agent. Morphologies of the particles are characterized using optical microscopy. Photophysical properties of the as-synthesized OVAP hydrosol are studied using UV–Vis absorption, steady state and time resolved fluorescence spectroscopy. The 'turn on' luminescence property of OVAP is used for the selective detection of trace amounts of Al3+ and Zn2+ and a significant turn on fluorescence enhancement over ∼100-fold is triggered via chelation-enhanced fluorescence (CHEF) through complex formation. The 1 : 1 stoichiometry of each sensor metal ion complex is observed from Job's plot based on UV-Vis absorption titration. The LODs for Al3+ and Zn2+ are found to be 1.05 nM and 2.35 nM, respectively. Notably, the sensor, OVAP, is further demonstrated using a molecular INHIBIT logic gate. [ABSTRACT FROM AUTHOR]

A 2,6-diformyl-p-cresol (DFC)-4-amino antipyrine (AP) based dual signaling fluorescent Schiff base ligand (DFCAP) is found to exhibit colorimetric and fluorescence turn on selective sensing towards metal ions, Zn2+ and Al3+. It also exhibits a significant aggregation induced emission (AIE) phenomenon by controlling the water–THF solvent ratio which provides robust green emissive fluorogenic aggregates with well-defined morphologies. Turn-on fluorescence enhancements as high as 195 fold and 168 fold in methanol for Al3+ and Zn2+ at 480 nm and 508 nm, respectively, were noticed. The binding constants and stoichiometry determined from the fluorescence titration data are K = 7.63 × 104 M−1 and 3.42 × 104 M−1 and 1 : 1 complexation for both Al3+ and Zn2+ respectively, supported by Job's method. DFCAP shows high sensitivity towards the detection of Zn2+ and Al3+ ions with very low detection limit values of ca. ∼21 nM and 30 nM respectively. Besides by applying its attractive AIE feature, the green emissive hydrosol functions as a good chemosensor with high sensitivity for a selected explosive TNP through ground state complexation with a LOD value of ca. ∼1.74 μM and especially a high Stern–Volmer quenching constant of ca. ∼4.14 × 105 M−1. For instant 'naked eye' response for the trace detection of TNP in the solution state, we fabricated a simple paper strip that could detect TNP on-site in a fast, inexpensive and simple way. [ABSTRACT FROM AUTHOR]

N, N'-dimethyl-4, 4'-bipyridinium dichloride (paraquat) is a widely used synthetic, nonselective contact herbicide. Ingestion of toxic doses of paraquat can be fatal with life-threatening effects on the lungs, gastrointestinal (GI) tract, kidney, liver, heart, and other organs. Till date, there are no specific antidotes and none of the current treatments have proven efficacious. The prognosis is uniformly poor worldwide, including those who treat aggressively with multimodal therapies. Long-term survivors are few, and have GI and pulmonary complications. Hence, prevention needs to be the utmost priority, and on exposure, aggressive decontamination should be initiated. Although it is a very common herbicide, there are very few cases reported from India and awareness among people needs to be widened. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel Rhodamine-Quinoline based probe has been synthesized. • It has been used to detect trace amount of Al3+, Cr3+ and HSO 4 − ions in water. • DFT & TD-DFT calculation were done to justify the experimental results. • Turn-on emission property of the probe is utilized to fabricate molecular INHIBIT logic gate. • Cytotoxicity and cell imaging on TPC-1 & HtH-7 cell lines. A designed Rhodamine-B-quinoline based Schiff base chemosensor (RhBQ) has been synthesized and characterized using various spectroscopic techniques. It shows 'turn on' fluorescence emission and also colorimetric sensitivity and selectivity towards trivalent metal ions (Al3+ and Cr3+) and anion (HSO 4 −) present in aqueous medium. Stoichiometry of both metal (Al3+ & Cr3+) - RhBQ complexes are found to be 1:1 using Job's plot. A notable enhancement in emission intensity for RhBQ-Al3+ (∼341 fold), RhBQ-Cr3+ (∼292 fold), and RhBQ-HSO 4 − (∼136 fold) complexes compare to RhBQ are observed. Sensing mechanism i.e. opening of spirolactam ring of RhBQ has been confirmed through various spectroscopic techniques such as; 1H NMR, 13C NMR, ESI-MS, TRPL, FT-IR, and DFT based computational study. The limit of detection (LOD) for Al3+, Cr3+, and HSO 4 − are found to be 2.2 × 10−8 M, 2.12 × 10−8 M and 8.63 × 10−7 M respectively. An advanced level 3 input OR–INHIBIT logic gate are constructed using chelating ligand EDTA. For onsite detection, TLC paper strip spot of the probe, RhBQ is prepared and the detection of Al3+ in few antacid drug are presented. In addition, cell-imaging analysis of Al3+, Cr3+, and HSO 4 − ions in the Human papillary thyroid carcinoma cell line (TPC-1) & Human anaplastic thyroid cancer cell lines (HtH-7) are presented and shows promising concentration and time-dependent detection results. [ABSTRACT FROM AUTHOR]

Rhodamine and its derivatives have been widely used in designing fluorescent ‘turn on’ cation sensors, while very few rhodamine based fluorescent probes have been reported to date for the detection of anions in water. In this article, a new rhodamine based facile and convenient ‘turn on’ fluorescent chemosensor 2-(2-(1-hydroxynaphthyllideneamino)ethyl)-3′,6′-bis(diethylamino)spiro [isoindoline-1,9′-xanthen]-3-one (RAHN) has been developed by Schiff base condensation and characterized by standard techniques for selective detection of bisulfite anions in water. A faintly yellow colour solution of RAHN turns pink upon addition of bisulfite. Again RAHN is weakly emissive in solution but becomes strongly emissive on addition of bisulfite and the emission intensity increases gradually in the presence of increasing concentration of bisulfite. No other analytes can cause emission enhancement of RAHN, suggesting the selectivity of the probe towards bisulfite. The detection limit for bisulfite was found to be ∼0.4 μM. [ABSTRACT FROM AUTHOR]

The effect of donor-acceptor (D-A) substituent and chain length on the electrical polarisabilities and first hyper polarisability of cis and trans biphenyl oligomeric compounds have been investigated using density functional theory-based hybrid functional CAM-B3LYP with 6-311G (2d,2p) basis set. Our extensive computational study reveals that both average polarisability and first hyper polarisability of the studied compounds increase with the increasing ethylene spacer chain length. Again the substitution of donor (NMe2) and acceptor (C≡N) at the para position of the phenyl rings to each oligomer shows order of magnitude increase of both αav and βav value compared to the unsubstituted one. This increased αav and βav values have been explained due to increasing charge transfer contribution resulting from decreasing optical energy gap (ΔE = S1 − S0) upon D-A substitution. It is also observed that the charge transfer contribution to first hyperpolarisability (βCT) is more than the polarisability (αCT) for the studied molecules. The electronic spatial extent () which is a measure of electron density volume around the molecule is found to play a major role along with the intramolecular charge transfer character to explain the non-linear variation of first hyperpolarisability (βav) as a function of ethylene spacer chain length (n) and D-A substitution. [ABSTRACT FROM AUTHOR]

The original article can be found online at https://doi.org/10.1007/s43630-023-00392-7. The correct name is given below: Rodrigo Ramirez-Tagle Universidad de las Américas, Facultad de Salud y Ciencias Sociales, Santiago, Chile The original article has been corrected. [Extracted from the article]

A novel material showing aggregation induced emission (AIE) is developed by reprecipitation method using 9‑Anthraldehyde (9-AC), where Sodium dodecyl sulfate (SDS) was used as morphology directing agent. 1-dimension rod and 2-dimension elongated hexagon shaped morphology of 9-AC aggregates have been synthesized. Morphology of the materials was characterized using optical microscopy. Photophysical properties of the hydrosol were studied using UV–Vis, steady state and time resolved fluorescence emission techniques. Computation of second order Fukui parameter as local reactivity descriptor on each atomic center of the titled compound also substantiate that the neighboring 9-AC molecules are arranged in trans conformation in its aggregated structures and this is in conformity with the crystal structure of 9-AC. The ‘turn off’ fluorescence property of aggregated 9-AC has been utilized for selective detection of picric acid and the fluorescence quenching has been explained due to ground state complexation between 9-AC and picric acid. The observed detection limit of picric acid was found as low as 8.07 μM. [ABSTRACT FROM AUTHOR]

An Anthracene based fluorescent probe, 1-(Anthracen-2-yliminomethyl)-napthalen-2-ol (AIN), was synthesized via simple one-pot reaction from inexpensive reagents. Intriguingly, it exhibited novel AIE characteristics in H 2 O-THF mixtures at high water content. Size and growth process of particles in different volume percentage of water and THF mixtures were investigated using TRPL, DLS, SEM and optical microscope. The fluorescent aggregates exhibited distinct Hg 2+ -selective “on-off” type fluorescence switching upon binding. Additionally, the fluorescence quenching showed a linear correlation in the Hg 2+ concentration range from 0.3 to 3.6 μM and the limit of detection was estimated as low as ∼3 ppb. The drastic decrease in emission intensity of AIN aggregates was observed in the presence of mercury ions via a complex interplay through the ground state complexation between AIN and Hg 2+ ions and external heavy atom induced perturbation by Hg 2+ ions to the excited states of the AIN. A large Stern–Volmer quenching constant was estimated to be 2.54 × 10 5  M −1 . The proposed analytical system with clear AIE characteristics demonstrates a potential outlook for the on-site visual detection of Hg 2+ in paper strips. Finally, the sensory probe was also applied to determine the concentration of Hg 2+ in real water samples to demonstrate its practical applications. [ABSTRACT FROM AUTHOR]

Global reactivity descriptors, e.g. average polarisabilty (αav), chemical hardness (η), electrophilicity index (ω) of two donor–acceptor substituted biphenyl, i.e. Dimethyl-(4ʹ-Nitro-biphenyl-4-yl)-amine (NBA) and 4ʹ-Dimethylamino-biphenyl-4carbonitrile (DBC), were computed along the torsional potential of two biphenyl ring systems. Density functional-based hybrid functional B3LYP with 6-31G(d) basis were used to all the computational study. It is observed that variation of the global reactivity descriptors η, ω as a function of torsional angle of biphenyl ring of NBA are in accordance with the maximum hardness and minimum electrophilicity principle. But the variations of αav, η, ω for DBC and αavfor NBA are not in accordance with the respective extremum principles. These apparent violations of extremum principles have been explained as the non-constancy of external potential within the tolerance limit for the respective parameters during the variation of torsional angle. The variation of first hyperpolarisability (βav) as a function of dihedral angle has been explained with the extent of charge transfer character of conformers for both NBA and DBC. It is also observed that the variation of first hyper polarisability is a function ofS0−S1optical energy gap rather than HOMO–LUMO gap of the titled compounds. [ABSTRACT FROM AUTHOR]

2-Phenylquinoline (PhQ) displayed novel aggregation induced emission enhancement (AIEE) characteristics in its aggregate/solid state. It also allows reversible fluorescence switching in acidic and basic media and changes the emission color from sky blue to intense blue in its aggregate state through protonation. Such behavior enables it to be utilized as a fluorescent pH sensor in acidic and basic media. PhQ microparticles with distinct morphologies are synthesized through a reprecipitation method and SDS is used as the morphology directing agent. The photophysical properties, size and growth process of the particles are characterized by UV-Vis absorption, steady state and time resolved spectroscopy, optical and scanning electron microscopy studies. The “turn off” luminescence property of the aggregated PhQ hydrosol in the presence of 2,4,6-trinitrophenol (TNP) is used for the selective detection of trace amounts of TNP in water and the super-amplified fluorescence quenching has been explained as due to ground state complexation between PhQ and TNP. [ABSTRACT FROM AUTHOR]

A heteroatom containing Schiff base, 4-[(2-Hydroxy-naphthalen-1-ylmethylene)-amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one (NDAP) has been synthesized using one step condensation method. Compound, NDAP is weakly emissive in solution state but a strong emission is observed in its aggregated state due to the restriction of intramolecular rotation (RIR) and large amplitude vibrational modes of NDAP. This phenomenon is known as aggregation induced emission enhancement (AIEE). Various morphologies of NDAP microstructures have been synthesized using reprecipitation method. SDS is also used as a morphology directing agent. Morphologies of the particles are characterized using optical and scanning electron microscopy (SEM). Photophysical properties of aggregated NDAP hydrosol are studied using UV–vis absorption, steady state and time resolved fluorescence spectroscopy. The ‘turn off’ luminescent property of aggregated NDAP hydrosol is used for the selective detection of trace amounts of picric acid in aqueous medium and the fluorescence quenching is explained due to ground state complexation between NDAP and picric acid with quenching constant (K q ), 1.91 × 10 5 M −1 . [ABSTRACT FROM AUTHOR]

• A novel Phenolphthalein based probe has been synthesized. • It has been used to detect trace amount of Zn2+ and Al3+ ions in water. • Turn-on emission property of the probe is utilized to fabricate molecular INHIBIT logic gate. • It also displays the novel AIE phenomenon. A phenolphthalein based fluorescent probe, 3, 3-Bis-[4-hydroxy-3-(pyridine-2-yliminomethyl)-phenyl]-3H-isobenzofu ran-1-one (PHPA), has been synthesized. It exhibits high sensitivity and selectivity towards Zn2+ and Al3+over other relevant water soluble metal ions and also display novel aggregation-induced emission enhancement (AIEE) characteristics. Both complexes followed 2:1 metal to ligand stoichiometry calculated from Job's plot. A significant fluorescence enhancement with a turn-on ratio of ∼94-fold was triggered via chelation-enhanced fluorescence through sensor complex (Zn2+-PHPA) and∼245-fold increase for sensor complex Al3+-PHPA. In addition, the binding sites of both sensor complexes (PHPA-Zn2+ & PHPA-Al3+) have been confirmed through 1H NMR, 13C NMR, FT-IR and ESI-MS spectroscopy. The detection limits is found to be 8.5 × 10−8 M for complex PHPA-Zn2+ and 1.88 × 10−7 M for complex PHPA-Al3+, respectively. The reversible detection of Zn2+ and Al3+ complexes in methanol are also ascertained in the presence of Na 2 EDTA, enabling the construction of a molecular Logic gate. An advanced-level NOT-AND-OR logic gate has been constructed from a different chemical combinational input and emission output. Human serum albumin (HSA) binding studies were performed by various spectroscopic methods to expound possible bioactivity of PHPA. Interestingly; the AIEE properties of PHPA may advance its impact as studied in methanol-water mixtures with high water contents. To gain the knowledge into the AIEE mechanism of the PHPA, the size and growth process of particles in different volume percentage of water and methanol mixture were studied using time-resolved photoluminescence, dynamic light scattering, and optical microscopic image. The probe PHPA has also been used to detect intracellular Zn2+ ion in A549 cells. [Display omitted] [ABSTRACT FROM AUTHOR]

Aggregate/solid-state fluorescence switching organic material, 4-((pyren-1-yl)methyleneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (PAP) was synthesized via simple one-step synthetic process. It exhibited novel aggregation induced emission (AIE) phenomenon by controlling water ratio in solutions which provide sturdy cyan emissive fluorogenic aggregates with diverse well-defined morphologies, especially tuning the morphologies from 0-D to 1-D microcrystals that show obvious optical waveguide effect. Dynamic light scattering, time-resolved photoluminescence, optical fluorescence microscope and scanning electron microscope were exploited to gain insight into the AIE mechanism and discrimination of the different aggregated morphologies such as 0-D hollow spheres, 1-D hexagonal, hexagonal 1-D growth, rods and wires with distinct emissions tuning in solid state. Intriguingly, triple excitation induced triple emissions of green, yellow and red lights were emanated from microstructures in solid state for the first time which completely covered visible spectral region. By taking the advantage of its attractive AIE feature, the fluorescent hydrosol employed itself as a fluorescent chemosensor with superb selectivity and sensitivity toward explosive TNP through ground state complexation with a detection limit as low as 16 nM and very high Stern–Volmer quenching constant of 4.7 × 10 5 M −1 . An instant ‘naked eye’ response for trace detection of TNP in solid state, we prepared the fluorescent paper strips which make the protocol simple, fast, inexpensive and practical for on-site visualization. [ABSTRACT FROM AUTHOR]

A novel material showing aggregation induced enhanced emission (AIEE) is developed by reprecipitation method using 2,2′ biquinoline (BQN) in aqueous medium. Morphologies of the particles are characterized using optical and scanning electron microscopic (SEM) study. The selective fluorescence and absorbance response of aggregated BQN towards Zn 2+ and H + have been explained due to ground state complexation and protonation of BQN with Zn 2+ and H + respectively. Protonated BQN exhibits charge transfer character in transoid form with yellowish green emission but in BQN-Zn 2+ complex, BQN changes to cis planer conformation and displays considerable intra ligand charge transfer (ILCT) character with sky blue color under UV excitation. A 2:1 BQN-Zn 2+ complex have been confirmed using Job’s plot. Our study revealed that BQN hydrosol act as selective turn-on fluorescence sensor for Zn 2+ ion both in acidic and alkaline medium. Further, the proton induced charge transfer character and the proposed binding modes of the receptor with Zn 2+ have been supported by DFT based computational study. [ABSTRACT FROM AUTHOR]

Here, we report solvatochromic effect of N , N ′-bis(3-pentyl)perylene-3, 4, 9, 10-bis(dicarboximide) [EP-PDI] in THF-DMF mixture. Fibroid like microstructure of EP-PDI has been synthesized by re-precipitation method using SDS as morphology directing soft template. Morphology of the particles is characterized using optical and scanning electronic microcopy (SEM). Photophysical properties of the aggregated hydrosol and also the solvatochromic effect of EP-PDI are carried out using UV–vis, steady state and time-resolved fluorescence study. The fluorescence spectra of EP-PDI in THF show structured emission band and aggregated hydrosol exhibits E-type and Y-type excimer emission. The intense fluorescence emission property of EP-PDI is used for sensing the presence of nitroaromatics in the medium. Among the different nitroaromatics, picric acid (PA) strongly quenches the fluorescence emission intensity of EP-PDI and this quenching property of PA is being used to detect PA in THF having concentration as low as 3.0 μM. The mechanism of this quenching has been explained due to ground state complexation between EP-PDI and PA. [ABSTRACT FROM AUTHOR]