Non-protected fluid room temperature phosphorescence of several naphthalene derivatives

In our previous work, we reported that with TlNO(3) as a heavy atom perturber and Na(2)SO(3) as a deoxygenator, room temperature phosphorescence (RTP) emission of dansyl chloride and its amino acid derivatives can be induced directly from their aqueous solution without a protective medium. Is this kind of fluid luminescence phenomenon unique for the dansyl chloride compounds? The present work has shown that many naphthalene derivatives can also exhibit RTP emission in their aqueous solutions under similar conditions in the absence of a protective medium. Such an RTP emission phenomenon could be denoted as nonprotected fluid room temperature phosphorescence (NP-RTP). In order to further understand this new luminescence phenomenon, the substituent group effects and the favorable chemical structure of compounds for NP-RTP emissions are discussed in detail.     

Direct determination of naftopidil by non-protected fluid room temperature phosphorescence

A selective and sensitive room temperature phosphorimetric method for the direct determination of naftopidil in biological fluids is described. The method is based on obtaining a phosphorescence signal from this antihypertensive drug using TlNO3 as a heavy atom perturber and Na2SO3 as a deoxygenator agent without a protective medium. This technique is named non-protected room temperature phosphorescence (NP-RTP), and enables us to determine analytes in complex matrices without the need for a tedious prior separation process. The optimization of Na2SO3 (8.5 x 10(-3) M) and the accurate value of pH (9.0) were determined using a simplex as a method of optimization. Sodium carbonate-hydrogencarbonate buffer solution (5.0 x 10(-2) M) was used to adjust the suitable pH. The optimum concentration of Tl+ (8.5 x 10(-2) M) was also determined. The delay time, gate time and time between flashes selected were 200 microseconds, 200 microseconds and 5 ms, respectively. Under the above conditions we propose a method to determine naftopidil by direct measurement of phosphorescence intensity with an emission wavelength of 526 nm and an excitation wavelength of 296 nm in the concentration range 0.05-1.00 mg L-1. Under these conditions the phosphorescence signal appears in 3 min once the sample has been prepared. Optimization of the various conditions permitted the establishment of an NP-RTP method for the determination with a detection limit, according to the error propagation theory, of 21.0 ng mL-1. The repeatability was studied using 10 solutions of 0.20 mg L-1 of naftopidil; if error propagation is assumed, the relative error is 1.39%. The standard deviation for replicate samples was 1.1 x 10(-2) mg L-1. This method was successfully applied to the determination of naftopidil, in human urine with recoveries between 106 and 112%.     

Studies on properties and application of non-protected room temperature phosphorescence of propranolol

A direct and simple non-protected room temperature phosphorimetry (NP-RTP) for determine propranolol, which using I- as a heavy atom perturber and sodium sulfite as a deoxygenator, has been developed. The phosphorescence peak wavelength maxima lambda(ex)/lambda(em) = 288/494, 522 nm. The analytical curve of propranolol gives a linear dynamic range of 8.0 x 10(-8)-2.0 x 10(-5) mol l(-1) and a detection limit of 3 x 10(-8) mol l(-1). The influence of I- concentration on RTP lifetime of propranolol was studied and the luminescence kinetic parameters were calculated. It is found that the relation between I- concentration (x) and RTP lifetime (tau) can be expressed as tau = 1.25e(-0.477x) and the rate constants of phosphorescence emission k(p) was 0.800 per ms. The method was applied directly to determination of propranolol in urine and drug tablets with a satisfactory result. The recoveries were 96.6-97.4% and the relative standard deviation was 2% for the 1.00 x 10(-6)-4.00 x 10(-6) mol l(-1) propranolol in spiked urine sample.     

Study of properties on non-protected room temperature phosphorescence and delayed excimer fluorescence of pyrene solution

A strong and stable room temperature phosphorescence (RTP) and delayed excimer fluorescence signal located at 596 and 475 nm, respectively, can be induced for pyrene solution in the absence of any protective medium only use KI or TlNO3 as a heavy atom perturber (HAP) and Na2SO3 as a deoxygenator. Both lifetimes of RTP and the delayed fluorescence are in the order of X-ms and the intensities are changed with kind and amount of HAP, but the peak positions are same and there is a iso-luminescent point in the emission spectra corresponding to emission at 475 nm and at 596 nm. The optimum conditions and the effects of kind and amount of HAP and organic solvents on luminescence properties of pyrene solution were studies in detail, and the photophysical process in the presence of KI or TlNO3 for phosphorescence and delayed excimer fluorescence emission of pyrene solution was discussed.     

Cucurbit[n]urils-induced room temperature phosphorescence of quinoline derivatives

The cucurbit[7,8]urils (Q[7] and Q[8])-induced room temperature phosphorescence (RTP) of quinoline and its derivatives were firstly found in the cucurbit[n]urils chemistry. The luminophores (quinolines) and their RTP are affected by the concentration of different Q[n]s, heavy metal ions and amounts, and pH. The RTP lifetime of the luminophore has been investigated. In presence of Na₂SO₃, the cation Tl⁺ led to stronger Q[n]-induced RTP, while the RTP lifetimes of luminophore/Q[7 or 8]/KI were generally longer than that of luminophore/Q[7 or 8]/TlNO₃, the RTP lifetimes of these systems were between 0.18 and 47.4 ms. Contrary to the stable 1:2 Q[8]:guest ternary inclusion complexes at lower pHs, as suggested by ¹H NMR, electronic absorption and fluorescence spectroscopy, low Q[8]-induced room temperature phosphorescence was observed. However, at higher pHs, high intensity of cucurbit[n]urils-induced room temperature phosphorescence of these quinoline derivatives were observed, and a 1:1 Q[8]:guest inclusion complex was formed. Investigations of dependence of RTP intensity on concentration of Q[n] revealed that the highest intensity of the Q[n]-induced RTP was observed at a low mole ratio of host:guest, which is closed to 1:1. It was presumably resulted from the strong interaction of Q[n] and these guests due to the combined hydrophobic cavity interaction and the hydrophilic portal interaction of the cucurbit[n]urils with the nitrogen heterocycles guest.     

Direct determination of 1-naphthoxylactic acid in biological fluids by non-protected fluid room temperature phosphorimetry

A selective and sensitive room-temperature phosphorimetric method for the direct determination of 1-naphthoxylactic acid (NA) in biological fluids is described. It is based on obtaining a phosphorescence signal from NA using TlNO₃ as a heavy atom perturber and Na₂SO₃ as a deoxygenator without a protective medium. This technique is named non-protected room-temperature phosphorescence (NP-RTP), which allows to determine analytes in complex matrices without the need for tedious prior separation. Optimization of the operational conditions resulted in a detection limit for NA of 9.6 ng/mL according to the error propagation theory. The repeatability and standard deviation were also determined. This method was successfully applied to the determination of NA in urine and human serum.     

Determination of the pesticide carbaryl by chemical deoxygenation micellar-stabilized room temperature phosphorescence

This paper presents a convenient determination method for carbaryl in polluted water by micellar-stabilized room temperature phosphorescence with Na(2)SO(3) as oxygen scavenger. The effect of various experimental conditions on the determination of carbaryl is discussed in detail. The analytical curve of carbaryl gives a linear dynamic range of 2 x 10(-7)-6 x 10(-5) mol/l., and a detection limit of 2 x 10(-7) mol/l. A recovery of 90-100% was obtained for 0.05-0.1 ppm carbaryl.     

Direct determination of 1-naphthoxylactic acid in biological fluids by non-protected fluid room temperature phosphorimetry

A selective and sensitive room-temperature phosphorimetric method for the direct determination of 1-naphthoxylactic acid (NA) in biological fluids is described. It is based on obtaining a phosphorescence signal from NA using TlNO3 as a heavy atom perturber and Na2SO3 as a deoxygenator without a protective medium. This technique is named non-protected room-temperature phosphorescence (NP-RTP), which allows to determine analytes in complex matrices without the need for tedious prior separation. Optimization of the operational conditions resulted in a detection limit for NA of 9.6 ng/mL according to the error propagation theory. The repeatability and standard deviation were also determined. This method was successfully applied to the determination of NA in urine and human serum.     

Determination of the plant growth regulator beta-naphthoxyacetic acid by micellar-stabilized room temperature phosphorescence

This paper presents a method for the determination of the plant growth regulator beta-naphthoxyacetic acid (NOA) by micellar-stabilized room temperature phosphorescence with the surfactant Triton X-100 (TX-100) as the micellar medium, thallium nitrate as the heavy atom and sodium sulphite as the oxygen scavenger. A multivariate optimization approach using the blocked cube star design of central composite was carried out. The analytical curve of NOA gives a linear dynamic range of 0.4-3.0 mug ml(-1) and a detection limit of 0.13 mug ml(-1). A recovery of 93.6% was obtained for 1 mug ml(-1) NOA in spiked apple samples.     

Determination of nafronyl in pharmaceutical preparations by means of stopped-flow micellar-stabilized room temperature phosphorescence.

The stopped-flow mixing technique was applied to micellar-stabilized room temperature phosphorimetry by measuring the fast appearance of the phosphorescent signal yielded by nafronyl in the presence of sodium dodecyl sulfate and thallium nitrate. This mixing system diminishes the time required for the deoxygenation of micellar medium by sodium sulfite, allowing a kinetic curve that levels off within only 5 s to be obtained. Phosphorescence enhancers thallium(I) nitrate, sodium dodecyl sulfate and sodium sulfite were optimized to obtain maximum sensitivity and selectivity. A pH value of 10.5 was selected as adequate for phosphorescence development. Two rapid, straightforward and automatic methods were proposed using the slope and amplitude of the kinetic curve, which are directly proportional to the nafronyl concentration, as analytical parameters. Calibration graphs were linear for the concentration range from 30 to 600 ng ml-1. Praxilene, the only commercial formulation containing nafronyl, was analysed by both proposed methodologies. Suitable recovery values were obtained.     

Crystallization-induced phosphorescence of benzils at room temperature

Efficient room temperature phosphorescence (RTP) is rarely observed in pure organic luminogens. However, we have newly observed that benzil and its derivatives are nonluminescent in solvents and thin layer chromatography (TLC) plates, but become highly phosphorescent in crystal state at room temperature, exhibiting typical crystallization-induced phosphorescence (CIP) characteristics. The CIP phenomenon is ascribed to the restriction of intramolecular rotations in crystals owing to effective intermolecular interactions. Such intermolecular interactions greatly rigidify the molecular conformation and significantly decrease the nonradiative deactivation channels of the triplet excitons, thus giving boosted phosphorescent emission at room temperature.     

Iodinated molecularly imprinted polymer for room temperature phosphorescence optosensing of fluoranthene

A novel molecularly imprinted polymer (MIP) of high interest for room temperature phosphorescence (RTP) sensing systems is described; the synthesized MIP contains iodine as internal heavy atom in the polymeric structure and its applicability for RTP sensing of fluoranthene at microg L(-1) levels is demonstrated.     

Solid-supported room temperature phosphorescence from aflatoxins for analytical detection of Aspergillus spp. strains

A simple, direct and rapid analytical methodology for the detection of aflatoxin producing Aspergillus spp. strains based on the measurement of room temperature phosphorescence from aflatoxins is presented here.     

Study on aggregation of palladium-porphyrins using room temperature phosphorescence

This paper reported room temperature phosphorescence (RTP) behaviors of meso-tetra-(4-sulfonatophenyl) porphyrin palladium (Pd-TSPP) and meso-tetra-(4-trimethylaminophenyl) porphyrin palladium (Pd-TAPP) in bovine serum albumin (BSA) medium. It was found that Pd-TSPP self-aggregated with its increasing concentration and hetero-aggregated with Pd-TAPP when they were mixed together. The self-aggregation of Pd-TSPP resulted in the remarkably splitting of excitation spectra because of the strongly excitonic coupling and phosphorescence quenching excited by Soret band, while Q band always kept the increase in intensity. The hetero-aggregation was out of the ground-state interaction stronger than the former one owing to its electrostatic-interaction nature. It was also indicated that inorganic salts like KCl would be an aid to hetero-aggregation. The equilibrium constants of both kinds of aggregation were estimated, namely, K(hom)=1.9 x 10(5) l/mol (homo-aggregation), and K(het)=1.06 x 10(7) l/mol (hetero-aggregation).     

White-light emission and tunable room temperature phosphorescence of dibenzothiophene

Molecular materials exhibiting room temperature phosphorescence(RTP) have received much attention during last few years. It has been known that different stacking fashions(e.g., formation of polymorph) and aggregation/crystal states could largely influence the RTP efficiency. However, whether the crystal morphology or shape could play a key role in modulation of the RTP has not been detected yet. In this work, we report that the dibenzothiophene(DBT) with the same molecular stacking fashion but different crystal morphologies can present alternated RTP performances. By modulation of the fluorescence and phosphorescence dual emission, a direct warm-white color light-emitting has also been successfully achieved. Moreover, the RTP emission can be further tuned through hybridization with β-cyclodextrin in different ratios, with the longest lifetime of 0.43 s.     

Determination of carbaryl and biphenyl through optical fiber ccd-assisted flash lamp induced room temperature phosphorescence

A fiber-optic sensor for solid surface room temperature phosphorescence of carbaryl and biphenyl pesticides was designed. A xenon flash lamp was used as excitation source, and a cooled two-dimensional charge coupled device was employed as the detector. Room temperature phosphorescence spectra of carbaryl and biphenyl were recorded by an imaging spectrograph. Limits of detection at the picogram/spot level were obtained for the investigated compounds. The linear dynamic range extended over three orders of magnitude. The standard addition method and the internal standard method were employed to analyze the studied compounds in mixtures. The feasibility of the SS-RTP apparatus developed was evaluated by the identification of carbaryl in a real sample.     

Determination of carbaryl and biphenyl through optical fiber ccd-assisted flash lamp induced room temperature phosphorescence

A fiber-optic sensor for solid surface room temperature phosphorescence of carbaryl and biphenyl pesticides was designed. A xenon flash lamp was used as excitation source, and a cooled two-dimensional charge coupled device was employed as the detector. Room temperature phosphorescence spectra of carbaryl and biphenyl were recorded by an imaging spectrograph. Limits of detection at the picogram/spot level were obtained for the investigated compounds. The linear dynamic range extended over three orders of magnitude. The standard addition method and the internal standard method were employed to analyze the studied compounds in mixtures. The feasibility of the SS-RTP apparatus developed was evaluated by the identification of carbaryl in a real sample. Received: 26 November 1999 / Revised: 26 January 2000 / Accepted: 29 January 2000     

The development of room temperature phosphorescence into a new technique for chemical determinations: Part 2. Analytical considerations of room temperature phosphorimetry

The rapidly developing technique of room temperature phosphorimetry is discussed from a practical analytical standpoint in this second part of the review. Basic factors concerning the technique such as methods of sample preparation, special instrumentation employed, and quantitative capability are presented, together with a listing of the variety of organic compounds reported to display room temperature phosphorescence. Potential applications of room temperature phosphorimetry and the advantages of sensitivity and selectivity afforded by this technique are discussed.     

Determination of trace levels of mercury in water samples based on room temperature phosphorescence energy transfer

A novel method has been developed for the sensitive determination of mercury in aqueous media by room temperature phosphorescence (RTP). The measurement principle is based on the energy transfer (ET) from a phosphor molecule (acting as a donor) to a Hg-sensitive dye (acceptor). To our acknowledgment this is the first RTP method for mercury measurement developed so far. α-Bromonaphthalene (BrN) was selected as the phosphorescent donor molecule (BrN can produce significant RTP emission in aqueous media in a β-cyclodextrin rigid microenvironment without deoxygenation).The absorption spectrum of the complex formed between mercury and the dithizone dye possesses a desirable spectral overlap with the RTP emission spectrum of the donor (BrN), giving rise to a nonradiative ET from the phosphor molecules to the mercury complex. An increase in the concentration of Hg(II) causes an increase on the concentration of the dithizone complex (acceptor) with the subsequent increase of the absorbance and, therefore, resulting in a decrease of the RTP emission. Both, RTP intensities and triplet lifetimes of the BrN decreased with increases on the Hg(II) concentration.Possible interferences present in natural waters, including different cations and anions, which could affect the analytical response, were evaluated and the analytical performance characteristics investigated. The use of phosphorescence measurements (low background noise signals) resulted in an improvement on the sensitivity of the Hg(II) detection higher than five times as compared to the molecular absorption spectrophotometric method for Hg(II) detection based on dithizone as Hg-indicator. A detection limit (D.L.) of 14 ng ml⁻¹ of Hg(II) was obtained by RTP with a precision of ±4.8% for five replicates of 300 ng ml⁻¹ of Hg(II). The usefulness of the method was successfully evaluated by the determination of Hg(II) in spiked natural water samples.