Induced Room Temperature Phosphorescence Research Articles

Insights on aggregation induced room temperature phosphorescence properties: A QM/MM study

Organic room temperature phosphorescence (RTP) molecules have attracted significant attention recently due to their promising application in security, bioimaging, sensing and organic light emitting diodes (OLEDs). Nevertheless, limited RTP molecules were reported until now and most of RTP phenomena were observed in crystal. Moreover, the underlying mechanisms of RTP still remain ambiguous. In this paper, excited-state properties of CZs-CN with RTP features in three crystals are theoretically studied using the combined quantum mechanics and molecular mechanics (QM/MM) method. Moreover, the photophysical properties of CZs-CN in solvent are also investigated by polarizable continuum model (PCM). The mechanism of aggregation induced RTP is revealed which is mainly contributed by the enhanced phosphorescence rates in aggregation, rather than the traditional restricted intramolecular motion mechanisms which usually bring decreased non-radiative decay rates. In addition, different crystal structures could induce different phosphorescence properties, and the emission spectra of the molecule in three crystals and THF are explained reasonable. Furthermore, dimers are confirmed to be involved in the emission when the intermolecular interaction is strong enough in aggregation. Our theoretical results provide inner perspective for aggregation induced RTP mechanism and could help one to better understand the different light-emitting properties in aggregation and solvent.

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 Na 2SO 3, 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]/TlNO 3, 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.

Flow-through optosensing of 1-naphthaleneacetic acid in water and apples by heavy atom induced–room temperature phosphorescence measurements

A sensitive and selective phosphorimetric method for the determination of 1-naphthaleneacetic acid (1-NAA) based on a flow-injection system connected to a flow cell packed with a solid support and placed in the sample compartment of a conventional luminescence spectrometer is described. A non-ionic solid polymeric resin Amberlite XAD-7 is used for the packing. After injection of the sample, 1-NAA is on-line retained in the packed resin and measurements of the heavy atom induced (HAI)–room temperature phosphorescence (RTP) emission ( λ ex/ λ em = 292/490 nm) from this native luminescent compound are taken. The optimum experimental conditions were investigated by injecting 2 ml samples of an aqueous solution of 1-NAA in the flow system. A concentration 0.15 mol l −1 of thallium(I) ions, as heavy atom, both in the samples and the carrier flow, was finally selected. Also, a concentration of 6 mmol l −1 of sulphite was optimal for ensuring the necessary deoxygenation of the system at the selected flow rate of 0.8 ml min −1. After measurement, the solid support was efficiently regenerated by injecting 1 ml of a mixture water:acetone in a ratio 1:1 (v/v) into the flow. The detection limit (3 σ criterion) was 1.2 ng ml −1 of 1-NAA. The repeatability (R.S.D.) for five replicates of a sample containing 50 ng ml −1 of analyte turned out to be ±3% and the calibration graphs proved to be linear up to 500 ng ml −1 of 1-NAA (maximum concentration assayed). The effect of potential interferences from other organic species which can be also used as plant growth regulators, as well as from various inorganic cations and anions, has been investigated as well. The method was successfully applied to the determination of low levels of this plant growth regulator in natural waters (river and fountain waters) and apples.

Heavy atom induced room temperature phosphorescence: a tool for the analytical characterization of polycyclic aromatic hydrocarbons

We have developed a heavy atom induced room temperature phosphorescence (HAI-RTP) procedure for the analytical characterization of 15 polycyclic aromatic hydrocarbons (PAHs). This methodology is based on the measurement of the native RTP emission from the analytes. RTP measurements are made directly in fluid aqueous solution, without the need of a protective medium but in the presence of high concentrations of heavy atom perturbers. Efficient deoxygenation conditions should be ensured using sodium sulfite as the oxygen scavenger. In such conditions, 15 PAHs, identified as major pollutants by the Environmental Protection Agency (EPA), naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, chrysene, benzo(a)anthracence, benzo(k)fluoranthene, benzo(b)fluoranthene, benzo(a)pyrene, indeno(1,2,3-cd)pyrene, benzo(g,h,i)perylene and dibenzo(a,h)anthracence, have been studied and analytically characterized using the proposed HAI-RTP procedure. To our knowledge, this is the first time that an analytically useful RTP emission of some of the PAHs under study in aqueous media has been observed. Once optimized the chemical variables affecting the phosphorescence phenomenon in solution, the phosphorescence spectral characteristic of all of the selected toxic compounds (excitation and emission wavelengths and triplet lifetimes) were obtained. Under the optimal experimental conditions, calibration graphs and detection limits (in the ng ml −1 level) were established for the 15 PAHs under study. Potential applicability of the developed methodology will be discussed.

Heavy atom induced room temperature phosphorescence: a tool for the analytical characterization of polycyclic aromatic hydrocarbons

Heavy atom induced room temperature phosphorescence: a tool for the analytical characterization of polycyclic aromatic hydrocarbons

FACILE ANALYSIS OF CARBAZOLE IN COMMERCIAL ANTHRACENE BY HEAVY ATOM–INDUCED ROOM TEMPERATURE PHOSPHORESCENCE

The applicability of heavy atom–induced room temperature phosphorescence (HAI-RTP) in real samples is demonstrated in this work. In this methodology only two reagents, potassium iodide as heavy atom salt and sodium sulfite as oxygen scavenger, were used to obtain the phosphorescent signal of carbazole in solution while anthracene did not show phosphorescence under these experimental conditions. In this study a new simple, rapid, and selective phosphorimetric method is proposed, using HAI-RTP methodology for the determination of carbazole in high-purity anthracene. The phosphorescence intensity was measured at 438 nm with excitation at 290 nm. Phosphorescence was fully developed instantly. A linear concentration range between 0 and 250 ng/mL−1 with a detection limit of 1.05 ng/mL−1 (10.5 ng of CBZ in 600 ng of anthracene), an analytical sensitivity of 1.7 ng/mL−1, and standard deviation of 0.71% at 150 ng/mL−1 concentration level was obtained. The method has been successfully applied to the analysis of carbazole in spiked anthracene samples.

Simple determination of propranolol in pharmaceutical preparations by heavy atom induced room temperature phosphorescence

The applicability of heavy atom induced room temperature phosphorescence in real samples is demonstrated in this work. In this methodology only two reagents, potassium iodide as heavy atom salt and sodium sulphite as oxygen scavenger, were used to obtain phosphorescent signal of propranolol in solution. Thus a new simple, rapid and selective phosphorimetric method is proposed for propranolol determination in pharmaceutical preparations. The phosphorescence intensity was measured at 492 nm exciting at 294 nm. Phosphorescence was fully developed instantly, obtaining a linear concentration range between 0 and 500 ng ml −1 with a detection limit of 14.4 ng ml −1, an analytical sensitivity of 6.7 ng ml −1 and a standard deviation of 1.4% at a 300 ng ml −1 concentration level. The method has been successfully applied to the analysis of propranolol in an antidepressive pharmaceutical preparation and it was validated using standard addition methodology.

The use of modified simplex method to optimize the room temperature phosphorescence variables in the determination of an antihypertensive drug

In the present paper, the modified simplex method (MSM) has been applied, for the first time, to determine compounds by a luminescence technique. The method was based on the optimization of chemical and instrumental variables affecting phosphorescence using a geometric simplex in two and three dimensions of space, respectively. As application, we have determined a novel antihypertensive drug, naftopidil, in urine and serum, by heavy atom induced room temperature phosphorescence (HAI-RTP); this technique enables us to determine analytes in complex matrices, biological fluids, without the need for a tedious prior separation process. With the proposed method, the maximum signal of phosphorescence appears instantly once the sample has been prepared and the intensity was measured at λ ex=287 nm and λ em=525 nm. Overall least-squares regression was used to find the straight line that fitted the experimental data. The detection limit, as well as the repeatability and the standard deviation (S.D.) for replicate sample, were also determined.

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.

A Simple and Rapid Phosphorimetric Method for the Determination of α-Naphthaleneacetamide in Fruit Samples

A simple and rapid phosphorimetric method for the determination of α-naphthaleneacetamide residues in fruit samples is presented. The method is based on a new, simple and sensitive methodology: Heavy Atom Induced Room Temperature Phosphorescence (HAI-RTP). The effect of different heavy atom salts and sodium sulfite concentration over the phosphorescence signals was investigated. The resultant HAI-RTP spectra were successfully applied for determining α-naphthaleneacetamide concentrations in the range of 7.8 to 100 μg·L−1, with relative standard deviations between 2.6 and 5.7%.

Heavy Atom Induced Room Temperature Phosphorescence Method for the Determination of the Plant Growth Regulator β-Naphthoxyacetic Acid

A simple, selective, and sensitive heavy atom induced room temperature phosphorimetric method (HAI-RTP) is described for the determination of the plant growth regulator β-naphthoxyacetic acid (NOA) in spiked apple samples. A careful selection of the different variables (heavy atom and sodium sulfite) to obtain the phosphorescence signal constitutes the basis of a HAI-RTP method for the determination of NOA. The analytical curve of NOA gives a linear dynamic range of 0−625 ng mL-1 and a detection limit of 30.5 ng mL-1. A recovery of 108.8% was obtained for 500 ng mL-1 NOA in spiked apple samples. Keywords: β-Naphthoxyacetic acid; heavy atom induced room temperature phosphorescence (HAI-RTP)

Study of new facile deoxygenation methods in cyclodextrin induced room temperature phosphorescence

The traditional deoxygenation techniques in cyclodextrin induced room temperature phosphorescence (CD-RTP) include N 2(g) purging and Na 2SO 3 chemical deoxygenation. In this paper, we propose two new deoxygenation methods in which oxygen is eliminated by hydrogen gas and carbon dioxide produced by the reactions Zn(s)/HCl and Na 2CO 3/HCl in the measuring media. With 1-bromocyclohexane (BCH) as an external heavy atom perturber and phenanthrene as a model compound compared with traditional deoxygenation techniques, the two new methods: (1) are facile and do not need any complicated supplementary equipment; (2) are rapid, deoxygenation time needed is only 1–2 min; (3) have a wider acidic condition, which is a supplement of chemical deoxygenation by Na 2SO 3; (4) can maintain RTP signal without decay for 10 min; (5) have good analytical characteristics.

Beta-cyclodextrin induced room temperature phosphorescence from 1-bromonaphthalene in the presence of naphthalene and 1-butanol

Intense room temperature phosphorescence (RTP) from host-guest inclusion complex of beta-cyclodextrin (β-CD) with 1-bromonaphthalene (1-BrN), stabilized by naphthalene (N) and 1-butanol (B), has been investigated. The spectral characteristics of luminescence emission and optimal conditions involved are reported. It has been confirmed that N and B are incorporated into the nonpolar cavity of β-CD as the second and third guests. The extra space inside the cavity is more filled by N and B, and δ-CD more effectively shields 1-BrN from quencher in aqueous solution. B completely hinders the formation of N excimer. Greater rigidity of the complex was achieved. Consequently, much more intense fluorescence and phosphorescence appear in comparison with the ternary β-CD:1-BrN:B complex. The limit of detection is 7.38 × 10 −8mol 1 −1 for 1-BrN and 1.36 × 10 −6mol 1 −1 for N.

Investigation of heavy atom effect of halide alkanes in β-cyclodextrin induced room temperature phosphorimetry

Twenty-one alkyl halides were examined in detail for their heavy atom effect in β-cyclodextrin induced room temperature phosphorescence (β-CD-RTP) with five polycyclic aromatic as mode compounds. The following conclusions were drawn from the experimental results. (1) The heavy atom enhancement effect (HAEE) of halogens in halide alkane are increased in the trend of Br > Cl ⪢ I. (2) Among the bromoalkanes examined, dibromoalkanes have the strongest HAEE, next the monobromoalkanes. For tri- and tetrabromoalkanes, very weak HAEE was observed. (3) A new heavy atom pertuber, t-butyl chloride, was found to have excellent ability of inducing RTP of polycyclic aromatic compounds. (4) The phosphorescence decay characteristics of the phosphorescent molecules, τ p , had been measured in the presence of halide alkanes and used to explain the luminescence mechanism of CD-RTP.

Cyclodextrin induced room temperature phosphorescence of some polyaromatic hydrocarbons and nitrogen heterocycles in the presence of cyclohexane

Room temperature phosphorescence (RTP) of some polyaromatic hydrocarbons (PAHs) and nitrogen heterocycles (NHC) can be induced in the β-cyclodextrin cyclohexane (CD/CH) system. RTP spectra characteristics of these compounds in the system are investigated. Different actions for cyclohexane and bromoalkane in β-cyclodextrin induced RTP are suggested. In the CD/CH system the limits of phenanthrene and 7,8-benzoquinoline may reach 2.3 × 10 −7 M and 4.5 × 10 −7 M, respectively. The relative standard deviation (RSD) is less than 7.6%.

PHOTOPHYSICAL STUDIES OF PYRENE INCORPORATED IN NAFION MEMBRANES*

Abstract— High concentrations of organic chromophores, in particular pyrene, were found to incorporate into the cluster network of water swollen Nation. The vibrational structure of the fluorescent molecule and its fluorescence lifetime were used to probe the location of pyrene in this structure. Strong heavy‐atom induced room temperature phosphorescence was observed from the chromophore in the water swollen membrane. Excimer formation in tm‐butanol swollen Nation was observed and was utilized to estimate the micro viscosity in this system.