Room-temperature ionic liquids, particularly those based on substituted imidazolium cations, are currently being extensively studied for a variety of applications. Herein, we explore the suitability several salts in optical applications by carefully examining electronic absorption and fluorescence behavior these substances, generally believed to be transparent most UV region fully visible region. It is shown that all liquids characterized significant entire long tail extends into These...

The fluorescence behavior of several dipolar molecules has been studied in three room-temperature ionic liquids, namely, [BMIM][BF4], [EMIM][BF4], and [BMIM][PF6], as a function the excitation wavelength. Although large majority these systems show normal with no wavelength dependence, few surprisingly exhibit fairly strong excitation-wavelength-dependent media. shift maximum is measured to be between 10 35 nm. various parameters have carefully examined determine factors that contribute this...

The molecular origin of the photoluminescence carbon dots (CDs) is shown.

Photophysical behavior of 3-hydroxyflavone (HF), a molecule that exhibits excited-state intramolecular proton-transfer reaction and has been studied extensively in the past, reinvestigated hydrogen bond donating solvents. In neat alcohols or an acetonitrile−methanol mixture, long wavelength absorption band (λmax ≈ 410 nm) observed for first time. It is found selective excitation this does not produce characteristic fluorescence "normal" form tautomer; instead, emission characterized by...

While the imidazolium ionic liquids have been studied for some time, little is known about pyrrolidinium liquids. In this work, steady-state and picosecond time-resolved fluorescence behavior of three electron donor−acceptor molecules, coumarin-153 (C153), 4-aminophthalimide (AP), 6-propionyl-2-dimethylaminonaphthalene (PRODAN), has in a liquid, N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, abbreviated here as [bmpy][Tf2N]. The data systems suggest that microenvironment...

The molecular origin of the photoluminescence (PL) carbon dots (CDs) is not fully understood. In this article it shown that CDs are composed aggregated 2-pyridone derivatives employing π–π stacking and H-bonding, etc. PL quantum yield CD quite high in aqueous medium (∼75%). Unlike literature reports emission maximum excitation wavelength independent, decay follows a single-exponential equation. These have long lifetime (from ∼10 to 15 ns), so solvation complete before emission. extent trap...

Perovskite quantum dots (PQDs) are known to be defect-tolerant, possessing a clean band gap with optically inactive benign defect states. However, we show that there exist significant deep trap states beyond the conduction minimum, although extent of shallow is observed minimal. The minimum seems in PQDs; however, less than even robust CdSe- and InP-based core/alloy-shell QDs. In-depth analyses based on ultrafast transient absorption ultrasensitive single-particle spectroscopic...

Abstract Single crystals of optoelectronic materials that respond to external stimuli, such as mechanical, light, or heat, are immensely attractive for next generation smart materials. Here we report single a green fluorescent protein (GFP) chromophore analogue with irreversible mechanical bending and associated unusual enhancement the fluorescence, which is attributed strained molecular packing in perturbed region. Soft crystalline fluorescence intensity modulations occurring response...

There is no literature report of simultaneously achieving near-unity PLQY (ensemble level) and highly suppressed blinking (ultrasensitive single-particle spectroscopy (SPS) in a toxic-metal-free QD. In this Letter we accomplishing (96%) (>80% ON fraction) CuInS2/ZnSeS Core/Alloy-Shell (CAS) addition, (i) gigantic enhancement (from 15% (Core) to 96% (CAS QD)), (ii) ultrahigh stability over 1 year without significant reduction at the ensemble level, (iii) high magnitude (nearly 3 times)...

Time-resolved fluorescence behavior of Nile Red (NR) has been studied using a streak camera in room temperature ionic liquid, [bmim]PF6. Wavelength dependent decay and time Stokes shift have observed. The time-correlated spectral function, C(t), indicator for solvation dynamics NR [bmim]PF6, is found to be biexponential with two well-separated constants: 0.13 1.25 ns. short the long component explained terms translational motion anion collective cation anion, respectively. effect different...

InP based quantum dots (QDs) are coming in a big way as an alternative to toxic Cd, or Pb QDs. Unlike many literature reports this work, green-yellow-orange-red emitting highly photoluminescent (PLQY high 65%) and photostable InP/ZnSeS core/alloy shell (CAS QDs) have been synthesized using less toxic, air-stable aminophosphine precursor (P(DMA)3). predictions paper, we show that alloyed QDs can be prepared with InCl3 only. We report here the hitherto unobserved quite interesting excitation...

Hybrid systems consisting of core/shell semiconductor quantum dots (QDs) and organic rylene dyes have been prepared characterized. Complex formation is mediated by bidentate carboxylate moieties covalently linked to the dye molecules. The complexes were very stable with respect time (at least months), dilution (sub nM), precipitation. After preparation in solvent, could be easily transferred into water. strong quenching QD emission molecules (transfer efficiencies up 95%) was satisfactorily...

We have demonstrated that the nonbonding molecular orbital (NBMO) of phenalenyl (PLY) cation can be used as a Lewis acid catalyst for different organic transformations. Detailed computational and spectroscopic studies aminolysis reaction epoxide reveal this catalysis works through mechanism, activates amine moiety using its empty NBMO, which triggers ring-opening reaction. It has been shown energy NBMO PLY plays key role in modulating catalytic activity. This study establishes cationic state...

Highly luminescent (photoluminescence quantum yield (PLQY) as high 96%) CdSe-based core/gradient alloy shell/shell (CGASS) dots (QDs) have been synthesized in "one pot" using the reactivity difference between Cd and Zn precursors Se S precursors. This procedure is highly reproducible quite useful for large-scale synthesis. Upon photoexcitation these QDs show a multiexponential excited state decay behavior. Interestingly, with growth of shell overall PL gets faster. All traces fitted well...

We report the synthesis and dynamical behavior of a carbon dot (CD) with near 100% photoluminescence quantum yield in water for very large pH range (1-12). This CD exhibits rotational correlational time only ∼130 ps, signifying whole is not exhibiting photoluminescence. Unlike most carbon-based nanoparticles (which act as quencher fluorescence), this could donor, Förster model account experimental observables resonance energy transfer (RET) experiment quite well. Based on two measurements,...

Core/alloy-shell/shell quantum dots (CASS QDs) have been shown to exhibit excitation energy dependent PL efficiency. The magnitude of the normalized transient population has increase more than 5-fold with decreasing energy. For high cooling exciton (predominantly electron) band edge is much slower (rise time ∼526 fs) in comparison low <∼100 fs). Time constant associated dynamics hot electron trapping ∼1 ps. related independent hole ∼35 Truncation obtained from single particle investigation...

It has been shown recently that aggregated dyes are responsible for very high fluorescence in a carbon dot (CD). However, what is the location of fluorescing moiety CD? Is it inside CD or attached to CD's surface? In order answer these intriguing questions regarding CD, we performed rotational anisotropy decay dynamics and resonance energy transfer (RET) dynamics. Rotational correlation time ∼120 picoseconds nullifies fact whole fluorescing. Instead, can say either embedded surface linked...

CdSe-based core/gradient alloy shell/shell semiconductor quantum dots (CGASS QDs) have been shown to be optically quite superior compared core-shell QDs. However, very little is known about CGASS QDs at the single particle level. Photoluminescence blinking dynamics of four differently emitting (blue (λem = 510), green 532), orange 591), and red 619)) having average sizes <∼7 nm probed in our home-built total internal reflection fluorescence (TIRF) microscope. All samples possess an...

Dual fluorescence of GFP chromophore analogues has been observed for the first time. OHIM (o-hydroxy imidazolidinone) shows only a charge transfer (CT) band, CHBDI (p-cyclicamino o-hydroxy benzimidazolidinone) comparable intensity CT and PT (proton transfer) MHBDI (p-methoxy higher band. It could be shown that differential optical behavior is not due to conformational variation in solid or solution phase. Rather, control excited state electronic energy level acidity constant by functional...

Abstract Single crystals of optoelectronic materials that respond to external stimuli, such as mechanical, light, or heat, are immensely attractive for next generation smart materials. Here we report single a green fluorescent protein (GFP) chromophore analogue with irreversible mechanical bending and associated unusual enhancement the fluorescence, which is attributed strained molecular packing in perturbed region. Soft crystalline fluorescence intensity modulations occurring response...

Suppressed blinking has been reported in large (diameter ∼14.1 nm) core/shell InP quantum dots (QDs) under reduced air environment. We report here suppressed with approximately four times smaller ∼3.6 core/alloy-shell/shell QDs ambient atmosphere. The ⟨ON fraction⟩ obtained to be 0.65. Approximately 26% of the single exhibit ON fraction >80%. exponent (1.19) magnitude comparison OFF (1.45) indicates longer events are interrupted by events. event truncation time is ∼1.5 that event, signifying...

The importance of alloy-shelling in optically robust Core/Alloy-Shell (CAS) QDs has been described from structural and energetic aspects. Unlike fluorescent dyes, both Core/Shell (CS) CAS exhibit excitation-energy-dependent photoluminescence quantum yield (PLQY). For CdSe InP (with metal- nonmetal-based alloy-shelling, respectively), with increasing excitation energy, (a) the ultrafast rise-time or relaxation-time to band-edge increases (b) magnitude normalized bleach signal decreases....