Synthesis, characterization and oxygen sensitivity of cyclophosphazene equipped-iridium (III) complexes.

In this work, synthesis, characterization and oxygen sensing abilities of the cyclophosphazene-free and phenyl and naphtoxy-substituted cyclophosphazene bearing iridium (III) complexes (Ir-I, Ir-II and Ir-III) were presented. The complexes were characterized by NMR, absorption and emission spectroscopies, luminescence lifetime and quantum yield measurements. The molecules were successfully embedded in the ethyl cellulose matrix to fabricate the oxygen sensing electrospun mats via electrospinning technique. Oxygen induced luminescence of the iridium complexes around 600 nm has been followed as the analytical signal during oxygen sensitivity studies. They exhibited blue shifted, quenched emission towards triplet oxygen. The napthoxy substituted derivative exhibited 2.70 fold enhanced I0/I100 ratio compared to the free form in terms of the relative signal change. Room-temperature luminescence abilities, high photostabilities, large Stoke's shift values extending to 200 nm and high spectral response, especially between 0 and 10% pO2 make them promising candidates as oxygen probes. The test materials can be stored at the ambient air of the laboratory for at least 24 months.

Investigation of Spectral Interactions between a SrAl2O4:Eu2+, Dy3+ Phosphor and Nano-Scale TiO2.

Herein, we studied light induced interactions between two well-known luminescent materials, SrAl2O4:Eu2+, Dy3+ and nano-scale TiO2 in poly(methyl methacrylate) (PMMA). These two materials were chosen due to their stable nature, efficient spectral properties and more specifically, overlapping excitation/emission bands. When these materials were used together in 1:1 ratio by weight (w/w), the composite exhibited 76% enhancement in the emission intensity with respect to the individual phosphor. Although the luminescence mechanism of both materials is clarified in the literature, spectral interactions of them have not been studied up to now. In our opinion, the TiO2 nano-particles (TiO2 NPs) act as light-harvesting agents for the phosphor particles creating a substantial enhancement on the light absorption efficiency of the phosphor. Additionally, the TiO2 nanoparticles suggest a promising way to boost the phosphorescent activity of the SrAl2O4:Eu2+, Dy3+ by a cost-effective way and further investigation of the mechanism may be subject of future studies.

Enhanced Luminescence Based Response towards pH in Highly Acidic Environments by the Silver Nanoparticles and Ionic Liquids.

Correct measurement of the pH in highly acidic environments is still a challenge. In such conditions most of the pH indicators suffer from instability in air or leaching from host matrices due to the solubility considerations. In this work, two different fluorescent probes were used along with silver nanoparticles (AgNPs) and ionic liquid (IL) in the polymeric matrices for sensing of the pH in harsh conditions. The pH sensitivities of the probes were tested after exposure to strong acid vapors by steady-state, lifetime based and kinetic mode measurements. The sensing materials were fabricated in form of thin films and electrospun nanofibers. The ionic liquid; 1-butyl-3-methylimidazolium tetrafluoroborate was exploited as additive to enhance the stability as well as response towards pH. Spectral changes were tested in a large scale; between pH 3.00-12.00. Utilization of the dyes in ethyl cellulose and polymethyl methacrylate along with AgNPs in form of electrospun fibers resulted in many advantages such as enhanced long term stability, sensitivity and improvement in all sensor dynamics. Sensing characteristics of the offered designs were tested after exposed to vapors of HCl, H2SO4 and HNO3, respectively.

Lifetime-Based Oxygen Sensing Properties of palladium(II) and platinum(II) meso-tetrakis(4-phenylethynyl)phenylporphyrin.

High oxygen permeable [poly(TMSP)] nanofibers incorporating porphyrin macrocycle as luminescence indicators were prepared by electrospinning technique. The porphyrins involves were modified by i) introducing phenylacetylide substituents on the para position of the phenyl moieties and ii) varying the metal centers [Pt(II) or Pd(II)] of the meso-tetrakisphenylporphyrins. A set of nanofibers; (Pt-TPP)NF, (Pd-TPP)NF, (Pt-TPA)NF and (Pd-TPA)NF were obtained to study their structure-activity relationship toward oxygen. The lifetime-based technique was privileged to take advantage of their long-lived phosphorescent properties. A two-fold enhancement was observed for (Pt-TPA)NF and (Pd-TPA)NF compared to (Pt-TPP)NF and (Pd-TPP)NF demonstrating the positive effect of the phenylacetylide moieties on the lifetime. Also, Silver nanoparticles were included in nanofibers to investigate their influence on lifetime-based oxygen sensitivity, showing that the presence of AgNPs only affects (Pd-TPA)NF.

Polyoxy-Derivatized Perylenediimide as Selective Fluorescent Ag (I) Chemosensor.

Recent investigations indicated that same concentrations of the ionic silver have harmful effects on aquatic life, bacteria and human cells. Herein we report chemosensory properties of N,N ' -Bis(4-{2-[2-(2-methoxyethoxy)ethoxy] eth- oxy}phenyl) -3,4:9,10-perylene tetracarboxydiimide (PERKAT) towards ionic silver. The dye doped sensing agents were prepared utilizing ethyl cellulose (EC) and poly (methylmethacrylate) (PMMA) and then forwarded to electrospinning to prepare sensing fibers or mats. The PERKAT exhibited bright emission in embedded forms in EC or in the solvents of N,N-Dimethylformamide (DMF), Dichloromethane (DCM), Tetrahydrofurane (THF) and in the mixture of DCM/ethanol. The PERKAT exhibited selective and linear response for ionic silver in the concentration range of 10-10 - 10-5 M Ag (I) at pH 5.5. Detection limits were found to be 2.6 × 10-10 and 4.3 × 10-11 M, in solution phase studies and PERKAT doped sensing films, respectively. Cross sensitivity of the PERKAT towards pH and some metal ions was also studied. There were no response for the Li+, Na+, K+, Ca2+, Ba2+, Mg2+, NH4+, Ni2+, Co2+, Cu2+,Pb2+, Al3+, Cr3+,Mn2+, Sn2+, Hg+, Hg2+, Fe2+ and Fe3+ in buffered solutions. To the best of our knowledge, this is the first study investigating silver sensing abilities of the PERKAT.

An ultra sensitive fluorescent nanosensor for detection of ionic copper.

A stable and ultra sensitive nano-scale fluorescent chemo-sensor for trace amounts of Cu(2+) was proposed. The Cu(2+) selective fluoroionophore 2-{[(2-aminophenyl)imino]methyl}-4,6-di-tert-butylphenol (DMK-7) was encapsulated in polymeric ethyl cellulose. The sensing membranes were fabricated in form of nanofibers and thin films. When embedded in polymers, the exploited DMK-7 dye exhibited enhanced photophysical characteristics in absorbance, Stoke's shift, fluorescence quantum yield, and short and long-term photostability with respect to the solution phase. Sensing abilities of the nanofibers and thin films were tested by steady state and time resolved fluorescence spectroscopy. To our knowledge, this is the first attempt using the DMK-7-doped electrospun nanofibrous materials for copper sensing. The offered sensor displayed a sensitive response with a detection limit of 3.3×10(-13) M for Cu(2+) ions over a wide concentration range of 5.0×10(-12)-5.0×10(-5). Additionally, exhibited high selectivity over convenient cations; Na(+), K(+), Ca(2+), Mg(2+), NH4(+) and Ag(+), Al(3+), Ba(2+), Co(2+), Cr(3+), Fe(3+), Fe(2+), Hg(2+), Li(+), Mn(2+), Ni(2+), Pb(2+), Sn(2+) and Zn(2+).

Copper ion sensing with fluorescent electrospun nanofibers.

In this work, the use of electrospun nanofibrous materials as highly responsive fluorescence quenching-based copper sensitive chemosensor is reported. Poly(methyl methacrylate) and ethyl cellulose were used as polymeric support materials. Sensing slides were fabricated by electrospinning technique. Copper sensors based on the change in the fluorescence signal intensity of fluoroionophore; N'-3-(4-(dimethylamino phenly)allylidene)isonicotinohydrazide. The sensor slides exhibited high sensitivities due to the high surface area of the nanofibrous membrane structures. The preliminary results of Stern-Volmer analysis show that the sensitivities of electrospun nanofibrous membranes to detect Cu(II) ions are 6-20-fold higher than those of the continuous thin films. By this way we obtained linear calibration plots for Cu(II) ions in the concentration range of 10(-12)-10(-5)M. The response times of the sensing slides were less than 1 min. Stability of the employed ionophore in the matrix materials was excellent and when stored in the ambient air of the laboratory there was no significant drift in signal intensity after 6 months. Our stability tests are still in progress.

Optical CO2 sensing with ionic liquid doped electrospun nanofibers.

The first use of electrospun nanofibrous materials as highly responsive fluorescence quenching-based optical CO(2) sensors is reported. Poly(methyl methacrylate) and ethyl cellulose were used as polymeric materials. Sensing slides were fabricated by electrospinning technique. A fiber-optic bundle was used for the gas detection. CO(2) sensors based on the change in the fluorescence signal intensity of ion pair form of 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS). The sensor slides showed high sensitivities due to the high surface area-to-volume ratio of the nanofibrous membrane structures. The preliminary results of Stern-Volmer analysis show that the sensitivities of electrospun nanofibrous membranes to detect CO(2) are 24 to 120 fold higher than those of the thin film based sensors. The response times of the sensing reagents were short and the signal changes were fully reversible. The stability of ion pair form of HPTS in the employed matrix materials was excellent and when stored in the ambient air of the laboratory there was no significant drift in signal intensity after 7 months. Our stability tests are still in progress.

A long wavelength excitable fluorophore; chloro phenyl imino propenyl aniline (CPIPA) for selective sensing of Hg (II).

In this study, a very sensitive and highly selective irreversible optical chemical sensor (optode) for mercury ions was described. The sensing scheme was based on the interaction of Hg (II) with a newly synthesized fluoroionophore; chloro phenyl imino propenyl aniline (CPIPA) in plasticized PVC membrane. The sensor membranes were tested for the determination of mercury ion in aqueous solutions by batch and flow-through methods. The optodes allow determination of Hg (II) in the working range of 1.0 x 10(-9)-1.0 x 10(-5) M with a detection limit of 4.3 ppb. The sensor exhibited excellent selectivity for Hg (II) with respect to several common alkali, alkaline earth and transition metal ions. The association constant of the 1:1 complex formation for Hg (II) was found to be K(a) = 1.86 x 10(5) M(-1). The CPIPA exhibited high fluorescence quantum yield, long excitation and emission wavelength and high Stokes' shift values in the solid matrix which makes it compatible with solid state optics.

Ratiometric sensing of CO2 in ionic liquid modified ethyl cellulose matrix.

In this study emission-based ratiometric response of ion pair form of 1-hydroxy-3,6,8-pyrenetrisulfonate (HPTS) to gaseous CO(2) has been evaluated in ionic liquid (IL) containing ethyl cellulose (EC) matrix. The ionic liquid: 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF(4)); provided longer storage time and highly stable microenvironment for the HPTS molecule due to the buffering effect. The utilization of ionic liquid in ethyl cellulose matrix resulted with superior spectral characteristics. The excitation spectra of HPTS exhibited an atypical isoemmissive point in modified EC matrix at 418 nm which allows ratiometric processing of the signal intensities. EMIMBF(4)-doped sensor films exhibited enhanced linear working range between 0 and 100% pCO(2). The signal changes were fully reversible and the shelf life of the EMIMBF(4)-doped films was extended from 15 to 95 days.

Photocharacterization of novel ruthenium dyes and their utilities as oxygen sensing materials in presence of perfluorochemicals.

Photophysical constants of three novel ruthenium dyes derived from tridentate pyridinediimine (pydim) ligands has been declared and their photoluminescent properties were investigated in solvents of dichloromethane (DCM), tetrahydrofuran (THF) and ethanol (EtOH) by UV-Visible absorption, emission and excitation spectra. The quantum yield, fluorescence decay time, molar extinction coefficient and Stoke's shift values of the novel ruthenium complexes were determined. The perfluoro compound (PFC) nonadecafluorodecanoic acid which is also known as medical gas carrier has been used for the first time together with newly synthesized Ruthenium complexes in ethyl alcohol. The utilities of oxygen sensing materials were investigated in EtOH in presence of chemically and biochemically inert PFC.

Spectral characterization of a newly synthesized fluorescent semicarbazone derivative and its usage as a selective fiber optic sensor for copper(II).

In this work photoluminescent properties of highly Cu(2+) selective organic fluoroionophore, semicarbazone derivative; bis(naphtho[2,1-b]furan-2-yl)methanone semicarbazone (BNF) was investigated in different solvents (dichloromethane, tetrahydrofuran, toluene and ethanol) and in polymer matrices of polyvinylchloride (PVC) and ethyl cellulose (EC) by absorption and emission spectrometry. The BNF derivative displayed enhanced fluorescence emission quantum yield, Q(f)=6.1 x 10(-2) and molar extinction coefficient, epsilon=29,000+/-65 cm(-1)M(-1) in immobilized PVC matrix, compared to 2.6 x 10(-3) and 24,573+/-115 in ethanol solution. The offered sensor exhibited remarkable fluorescence intensity quenching upon exposure to Cu(2+) ions at pH 4.0 in the concentration range of 1.0 x 10(-9) to 3.0 x 10(-4)M [Cu(2+)] while the effects of the responding ions (Ca(2+), Hg(+), Pb(2+), Al(3+), Cr(3+), Mn(2+), Mg(2+), Sn(2+), Cd(2+), Co(2+) and Ni(2+)) were less pronounced.

Fiber optic pH sensing with long wavelength excitable Schiff bases in the pH range of 7.0-12.0.

Most of the fluorescent pH probes work near neutral or acidic regions of the pH scale. In this work, two different fluorescent Schiff bases, chloro phenyl imino propenyl aniline (CPIPA) and nitro phenyl imino propenyl aniline (NPIPA), have been investigated for pH sensing in the alkaline region. Absorption and emission based spectral data, quantum yield, fluorescence lifetime, photostability and acidity constant (pK(a)) of the Schiff bases were determined in conventional solvents and in PVC. The long wavelength excitable immobilized Schiff bases CPIPA (lambda(ex)=556 nm) and NPIPA (lambda(ex)=570 nm) exhibited absorption and emission based optical response to proton in the pH range of 8.0-12.0 and 7.0-12.0, respectively. Response of the CPIPA was fully reversible within the dynamic working range. The response times were between 3-13 min. A relative signal change of 95% and 96% have been achieved for sensor dyes of CPIPA and NPIPA, respectively. The CPIPA displayed better fluorescence quantum yield (varphi(F)=3.7 x 10(-1)) and higher matrix compatibility compared to NPIPA (varphi(F)=1.6 x 10(-1)) in immobilized PVC. The CPIPA and NPIPA exhibited a slight cross sensitivity to the ions of Hg(+) and Fe(3+), respectively.

Emission-based optical carbon dioxide sensing with HPTS in green chemistry reagents: room-temperature ionic liquids.

We describe the characterization of a new optical CO(2) sensor based on the change in the fluorescence signal intensity of 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) in green chemistry reagents--room-temperature ionic liquids (RTILs). As far as we are aware, this is the first time RTILs, 1-methyl-3-butylimidazolium tetrafluoroborate (RTIL-I) and 1-methyl-3-butylimidazolium bromide (RTIL-II), have been used as matrix materials with HPTS in an optical CO(2) sensor. It should be noted that the solubility of CO(2) in water-miscible ionic liquids is approximately 10 to 20 times that in conventional solvents, polymer matrices, or water. The response of the sensor to gaseous and dissolved CO(2) has been evaluated. The luminescence intensity of HPTS at 519 and 521 nm decreased with the increasing concentrations of CO(2) by 90 and 75% in RTIL-I and RTIL-II, respectively. The response times of the sensing reagents were in the range 1-2 min for switching from nitrogen to CO(2), and 7-10 min for switching from CO(2) to nitrogen. The signal changes were fully reversible and no significant hysteresis was observed during the measurements. The stability of HPTS in RTILs was excellent and when stored in the ambient air of the laboratory there was no significant drift in signal intensity after 7 months. Our stability tests are still in progress.

Characterization of a reservoir-type capillary optical microsensor for pCO(2) measurements.

A reservoir type of capillary microsensor for pCO(2) measurements is presented. The sensor is based on the measurement of the fluorescence intensity of the anionic form of the pH indicator 1-hydroxy-3,6,8-pyrenetrisulfonate in the form of its ion pair with a quaternary ammonium base in an ethyl cellulose matrix. The glass capillary containing the reservoir sensor was prepared by immersing the tip of the optical fiber into the sensing agent very close to the sensor tip thus providing a very small volume for the sensing reaction. The purpose of the sensing approach is to regenerate the dye/buffer system by diffusion, which may be poisoned by interfering acids, or bleach by photolysis. The fresh cocktail from the reservoir takes the place of protonated form of the dye. The internal buffer system also makes the protonation-deprotonation equilibria reversible. The distal tip of the internal buffer containing reservoir is coated with a gas-permeable but ion-impermeable teflon membrane. The dynamic range for the detection of pCO(2) is between 1 and 20 hPa, which corresponds to the range of dissolved CO(2) in water. The response time is 15 s and the detection limit is 1 hPa of pCO(2.) The recovery performance of this sensor can be improved by means of mechanical adjustment of the sensor tip in a micrometric scale.

Enhanced optical oxygen sensing using a newly synthesized ruthenium complex together with oxygen carriers.

In this article, an emission based, simple and fast method is proposed for the determination of gaseous oxygen. A newly synthesized fluorophore, dichloro-{2,6-bis[1-(4-dimethylamino-phenylimino) ethyl]pyridine}ruthenium(II) has been used for oxygen sensing together with oxygen carrier perfluorochemicals (PFCs) in silicon matrix. It should be noted that the solubility of oxygen in fluorocarbons is about three to ten times large as that observed in the parent hydrocarbons or in water, respectively. Employed PFCs are chemically and biochemically inert, have high dissolution capacities for oxygen, and, once doped into sensing film, considerably enhance the response of sensing agent.

Fiber optic sodium and potassium sensing by using a newly synthesized squaraine dye in PVC matrix.

In recent years squarines received attention as fluorescent labels. Their very promising spectral properties such as long wavelength absorption and emission, high extinction coefficients and quantum yields could lead novel sensing technologies. In this work newly synthesized fluoroinophores named bis[4-N-(1-aza-4,7,10,13-tetraoxacyclopentadecyl)-3,5-dihydroxyphenyl]squaraine, azacrown-1 and 2 bis[4-N-(1-aza-4,7,10,13,16-pentaoxacyclooctadecyl)-3,5-dihydroxyphenyl]squaraine, azacrown-2 have been used for sodium and potassium sensing in plasticized PVC matrix. The squaraine derivatives exhibited fluorescence emission based optical responses to sodium and potassium with a detection limit of 1.10(-9) M. The sensor compositions exhibited wide response ranges between 10(-9) and 10(-5) M Na(+)or K(+), and, therefore, may be an alternative method to flame emission spectroscopy. The sensor is fully reversible within the dynamic range and the response time is 3 min under batch conditions. Cross sensitivity to pH is negligible in the pH range of 6.2-7.3. Throughout fiber optic based studies a relative signal change of 54-56% has been achieved. The azacrown dyes have the advantage that they can be excited with long wavelength light and, are, therefore, LED compatible. The cross sensitivity of azacrown-1 and -2 to Ba(2+), Ca(2+) and NH(4)(+)were also tested in separate solutions.