RESUMEN

Five new coordination polymers (CPs) were obtained as a result of hydrothermal reactions of 2,2-dimethylglutaric acid (H2dmg) and 1,4-bis(1H-1,2,4-triazol-1-ylmethyl)benzene (pbtx)/1,2-bis(1H-1,2,4-triazol-1-ylmethyl)benzene (obtx) ligands with some metal ions [Co(µ-dmg)(µ-obtx)]n (1), [Zn(µ-dmg)(µ-obtx)]n (2), [Cd(µ-dmg)(µ-obtx)]n (3), [Co2(µ-dmg)2(µ-pbtx)2]n (4), and [Cd(µ-dmg)(H2O)(µ-pbtx)]n (5). All of the compounds were characterized by elemental analysis, FT-IR spectroscopy, single-crystal X-ray diffraction, powder X-ray diffraction, and thermal analysis techniques. The single-crystal X-ray studies show that all compounds exhibit 2D layer structures. To examine the ammonia sensing properties of five new coordination complexes (1-5), the absorption and emission spectra of CPs embedded in ethyl cellulose thin films were measured by exposure to different concentrations of ammonia (NH3) vapor. The [Co2(µ-dmg)2(µ-pbtx)2]n (4)-based sensor agent was found to show promising sensor properties in detecting NH3 vapor.

RESUMEN

8-Hydroxypyrene-1,3,6-trisulfonic acid (HPTS) dye, a fluorescent dye often used as a pH indicator, is embedded within the bioactive glass matrix and undergoes changes in its fluorescent properties when exposed to carbon dioxide (CO2). The aim of the current study is to investigate the use of bioactive glass (BG) particles containing γ-Fe2O3@ZnO to enhance the CO2 sensitivity of HPTS. X-ray diffraction, Fourier transform infrared, scanning electron microscopy, and photoluminescence spectroscopies were used to characterize the sol-gel synthesized powders. The sensing slides were prepared in the form of a thin film by immobilizing the fluorescent dye and γ-Fe2O3@ZnO-based additives into the poly(methyl methacrylate) matrix. The addition of γ-Fe2O3@ZnO nanoparticles with bioactive glass additives to the HPTS improves the performance characteristics of the sensor, including the linear response range, relative signal variation, and sensitivity. Meanwhile, the CO2 sensitivities were measured as 10.22, 7.73, 16.56, 17.82, 19.58, and 42.40 for the undoped form and M, M@ZnO, 5M@ZnO-BG, 10M@ZnO-BG, and 20M@ZnO-BG NP-doped forms of the HPTS-based thin films, respectively. The response and recovery times of the HPTS-based sensing slide along with 20M@ZnO-BG NPs have been measured as 44 and 276 s, respectively. The γ-Fe2O3/ZnO-containing BG particle-doped HPTS composites can be used as a promising sensor agent in the detection of CO2 gas in various fields such as environmental monitoring, medical diagnostics, and industrial processes.

RESUMEN

Fluorescent pH-sensitive indicator dye, 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS), has become known as a preferred alternative for continuous and accurate monitoring of dissolved and/or gaseous CO2 in chemistry, medical, and biochemical research. The objective of this work is to enhance the HPTS dye's CO2 sensitivity in the presence of Zn@SnO2 and Sn@ZnO additive particles. Sol-gel synthesized metal oxide semiconductors (MOSs) were characterized using XRD, XPS, and SEM. The fluorophore dye and the MOS additives were embedded in the ethyl cellulose (EC) polymeric matrix to prepare the sensing thin films. The steady-state and decay kinetic measurements of the HPTS-based composites were obtained by PL spectroscopy for the concentration ranges of 0-100% p[CO2]. As expected, the addition of MOSs improves the sensor characteristics, specifically its CO2 sensing ability, linear response range, and relative signal change compared to the free form of HPTS. The CO2 sensitivities of the HPTS-based thin films were found at 17.6, 23.2, and 40.9 for the undoped, Zn@SnO2,-doped, and Sn@ZnO-doped forms of the HPTS, respectively. Additionally, the response and recovery times of the HPTS-based sensor agent with Sn@ZnO were measured as 10 and 460 s, respectively. The obtained results demonstrate that materials composed of HPTS with MOSs are potential candidates for CO2 sensors.

RESUMEN

Improving the performance of optical oxygen sensors can be accomplished by adding metal oxide semiconductors (MOSs) additives to the composition comprising an oxygen-sensing agent immobilized in a polymeric thin film. For several decades, MOSs have attracted great interest in gas sensors due to their high sensitivity to many target gasses. Herein, meso-tetraphenylporphyrin (H2TPP) dye was immobilized into the poly(1-trimethylsilyl-1-propyne) (poly(TMSP)) silicone rubber in the presence of NiO, SnO2, Ni:SnO2 metal oxide particles as additives, and their thin films were prepared to investigate oxygen-sensitive optical chemical sensor properties. The characterizations of the synthesized metal oxide powders were carried out through XPS, XRD, FT-IR, PL spectroscopy and SEM methods. Intensity-based spectra and decay kinetics of H2TPP-based thin films were investigated for the concentration range of 0%-100% [O2]. The oxygen sensitivity (I0/I100) of the porphyrin was calculated as 70%. Whereas the relative signal intensity values of H2TPP-based sensor slides were measured as 75%, 80%, and 88% in the presence of NiO, SnO2, Ni:SnO2 additives, respectively. The H2TPP in combination with Ni:SnO2 semiconductor provided a higher I0/I100 value, larger response range, higher Stern-Volmer constant (KSV) value, and faster response time compared to the undoped form, and also NiO and SnO2 additive-doped forms of H2TPP. The response and the recovery times of the porphyrin-based sensing slide along with Ni:SnO2 additives have been measured as 12 and 50 s. These results make the H2TPP along with the MOSs promising candidates as oxygen probes.

Asunto(s)

Porfirinas , Compuestos de Estaño , Gases , Óxidos , Oxígeno , Polvos , Semiconductores , Elastómeros de Silicona , Espectroscopía Infrarroja por Transformada de Fourier , Compuestos de Estaño/química

RESUMEN

Coordination polymers (CPs), new functional hybrid materials, have received important attention due to their structural features and many different applications such as gas storage, catalysis, energy storage, small molecule adsorption, luminescence, and chemical sensors. In this study, two newly synthesized metal-organic frameworks (MOFs); [Mn2(µ4-dmg)-(µ4-dmg)(µ-bipy)]n (CP1) and [Mn2(µ4-dmg)(µ4-dmg)(µ-dpeten)]n (CP2); were used for sensing of gaseous carbon dioxide with a spectrofluorometric method with a dye, 8-hydroxypyrene-1, 3, 6-trisulfonic acid (HPTS) as matrix additive material for the first time. The ion-pair form of the HPTS was used in the polymethyl methacrylate matrix as a thin film form. When the HPTS based sensing slides along with the CPs, resulted in many advances such as high relative signal change and larger linear response range, improved sensor dynamics, and higher sensitivity with respect to the additive-free form. More specifically, in the presence of silver nanoparticles (AgNPs), the variation in relative signal intensities of CP1 and CP2 doped HPTS sensing agents were measured as 60 and 40% for the concentration range of 0-10% pCO2, respectively. The aim of this study is to enhance the CO2 response of HPTS with doped CPs due to their useful attributes and potential applications containing selective gas absorption.

Asunto(s)

Nanopartículas del Metal , Polímeros , Dióxido de Carbono , Plata , Espectrometría de Fluorescencia

RESUMEN

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.

RESUMEN

In this work, the ionic liquid 1-butyl-3-methylimidazolium thiocyanate ([BMIM][SCN]) was evaluated for the first time for its probable usage as new optical sensor reagent for the determination of several metal ions. The ionic liquid exhibited a selective and sensitive response to iron ions in acidic aqueous solutions among all of the tested metal ions. The ([BMIM][SCN]) was encapsulated in ethyl cellulose (EC) matrix in the form of continuous thin films. The effect of [BMIM][SCN] concentration and pH to iron response, the fluorescence quantum yield, the absorption, emission and excitation based characteristics of the ionic liquid in presence of Fe3+ and Fe2+ ions were investigated in both EC and [BMIM][SCN]/aqueous buffer solution mixtures. As a result, the highly sensitive, selective and rapid responding optical sensor reagent which does not need any time-consuming extraction, oxidation and reduction procedures was presented for the distinguishing determination of Fe3+ and Fe2+ in both aqueous solutions and solid thin film matrix. The ionic liquid exhibited a better emission and absorption based response for Fe3+ ions when compared with the Fe2+ ions. The molar absorptivity constant in presence of ionic liquid-based SCN- was enhanced 10 times to 1.21 × 104 L mol-1 cm-1 for Fe3+ ions in the solution phase. Linear absorption and emission-based calibration graphs were obtained for a wide concentration range of 8.0 × 10-8-6.2 × 10-4 M and 8.0 × 10-8-6.2 × 10-5 M for Fe3+, respectively. Limit of detection (LOD) values for absorption and emission-based methods were 2.48 × 10-5 and 2.4 × 10-8, respectively. The reaction is instantaneous and absorbance remains stable for over 4 months.