Cure characterization of unsaturated polyester resin by fluorescence spectroscopy

A strong fluorescence emission was observed during cure of an unsaturated polyester resin containing about 30% styrene by weight. As the cure proceeded, the emission intensity at 306 nm increased. Model compound studies confirmed that the unsaturated polyester component exhibited negligible fluorescence when excited at 250 nm where styrene has strong absorption. Based on the studies of styrene/polystyrene mixtures, the fluorescence emission at 306 nm was attributed to a reduced inner‐filter effect of styrene monomer. Fluorescence intensity changes following cure at 75°C were correlated to the extent of styrene conversion determined by FT‐IR spectroscopy, demonstrating that the fluorescence measurement is more sensitive to styrene conversion in the later stages of cure than conventional IR measurements. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2446–2450, 2004     

Characterization and Elemental Quantification of Natural Hydroxyapatite Produced from Cow Bone

The demand for hydroxyapatite (HA) is increasing annually due to the growing number of orthopedic patients, but it is a challenge to meet this growing demand without interfering with the integrity of the environment. Here, natural HA was produced from cow bone through ultrasound treatment followed by a calcination process at various temperatures. Characterization of the produced HA was performed by techniques such as thermogravimetric analysis, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and X‐ray diffraction analysis. The elemental composition of the HA was quantified through X‐ray photoelectron spectroscopy, energy dispersive X‐ray spectroscopy, X‐ray fluorescence, as well as carbon, hydrogen, nitrogen, sulfur (CHNS) analysis. The results demonstrate that pure HA was produced after calcination at 950 °C, corresponding to pure HA phase.     

Metallopolymers based on a polyazomethine ligand containing rigid oxadiazole and flexible tetramethyldisiloxane units

Soluble, easily processable polymer–metal complexes with improved optical and dielectric properties for optoelectronic functional materials were obtained. For this, a new polyazomethine (PAZ2) was prepared by the reaction of a siloxane dialdehyde and bis(formyl‐p‐phenoxymethyl) tetramethyldisiloxane with 2,5‐bis(p‐aminophenyl)‐1,3,4‐oxadiazole, and it was used as a ligand for Cu(II), Co(II), and Zn(II) ions on the basis of the presence of the electron‐donor nitrogen atoms from the azomethine group and oxadiazole ring. The structure of the PAZ2 was determined by spectral [Fourier transform infrared (FTIR) and ¹H‐NMR spectroscopy] techniques. The metal complexation was proven by FTIR spectroscopy, and the silicon‐to‐metal ratios in the complexes were established by energy‐dispersive X‐ray fluorescence. The new materials were characterized by gel permeation chromatography, thermogravimetric analysis, and differential scanning calorimetry. The optical properties of PAZ2 and the derived metal complexes were studied by ultraviolet–visible and fluorescence spectroscopies. PAZ2 shows fluorescence emission, and it was significantly enhanced by metal complexation. The emission was enhanced by protonation; this behavior is useful, especially for sensors. The electrical properties were investigated by dielectric spectroscopy at various frequencies and temperatures, and this emphasized the existence of dipolar relaxations. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41631.     

Intramolecular charge-transfer fluorescence as a mobility probe in poly(methylmethacrylate)

The (time-resolved) fluorescence spectra of 1-phenyl-4-(4-cyano-1-naphthylmethylene)piperidine (1) have been measured during the polymerization of methylmethacrylate (MMA). It was found that the fluorescence maximum of 1 shows a large hypsochromic shift as polymerization of the MMA medium progresses. While the emission maximum is located at 565 nm in the monomer, it is found at 450 ± 5 nm in the polymer (PMMA). The polarization of the fluorescence increases strongly during the polymerization, indicating that the rotational motion of 1 ceases on the timescale of the fluorescence lifetime (about 10 ns). Fluorescence measurements performed with a detection time delay with respect to the exciting laser pulse showed that within the time range 0–100 ns the molecule 1 undergoes reorientation and/or internal relaxation even in a PMMA matrix; a red shift of the emission with time occurs, together with a decrease of the degree of fluorescence polarization.     

Synthesis and study of a new polyorganophosphazene

In this study, a new polyorganophosphazene with pendant carbazolyl groups was synthesized, and its structure was characterized by IR, ¹H‐NMR, and ³¹P‐NMR spectroscopy. To understand its carrier photogeneration and transport property, we also studied fluorescence spectra and photovoltage spectra. Fluorescence spectra show that the polymer possesses properties dissimilar to those of PVK. There are only two emission peaks at ≈ 360 nm in its spectra, which coincides with that of the monomer model compound, 9‐ethylcarbazole. This may be because of the influence of the spacer. The results of SPS shows that band–band transition mainly comes from electron π–π* transition, and the polymer is a p‐type semiconductor. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1446–1451, 2001     

Local microstructure characterization of rare earth‐doped PMMA with low‐ion content by fluorescence EXAFS

Fluorescence‐extended X‐ray absorption fine structure (EXAFS), and emission spectrum and excitation spectrum (ESES) were used to characterize the local structure of rare earth‐doped poly(methyl methacrylate)s (Re‐PMMAs) with ion concentration of 600–1000 ppm. Fluorescence EXAFS shows that the chemical state of Sm in Sm‐PMMA is the same as that in Sm₂O₃ and samarium octanoate (SOA), while that of Eu in Eu‐PMMA is different from that in Eu₂O₃ and europium octanoate. ESES also proves the concomitance of Eu²⁺ with Eu³⁺ ions in Eu‐PMMA. And, the almost identical peak positions of Eu L₃ edge at ～6976.7 eV in fluorescence EXAFS of Eu‐PMMA with various Eu content suggests the proportions of Eu²⁺ to Eu³⁺ are the same in these samples. The simulation of fluorescence EXAFS shows that the first‐shell coordination number of Sm³⁺ in Sm‐PMMA is 9.12, and the average first‐shell distance around Sm³⁺ in Sm‐PMMA is 2.43 Å. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1294–1298, 2006     

Controlling the Fluorescence of Benzofuran‐Modified Uracil Residues in Oligonucleotides by Triple‐Helix Formation

We developed fluorescent turn‐on probes containing a fluorescent nucleoside, 5‐(benzofuran‐2‐yl)deoxyuridine (dU^BF) or 5‐(3‐methylbenzofuran‐2‐yl)deoxyuridine (dU^MBF), for the detection of single‐stranded DNA or RNA by utilizing DNA triplex formation. Fluorescence measurements revealed that the probe containing dU^MBF achieved superior fluorescence enhancement than that containing dU^BF. NMR and fluorescence analyses indicated that the fluorescence intensity increased upon triplex formation partly as a consequence of a conformational change at the bond between the 3‐methylbenzofuran and uracil rings. In addition, it is suggested that the microenvironment around the 3‐methylbenzofuran ring contributed to the fluorescence enhancement. Further, we developed a method for detecting RNA by rolling circular amplification in combination with triplex‐induced fluorescence enhancement of the oligonucleotide probe containing dU^MBF.     

Synthesis and characterization of water‐soluble polypyrrole/multi‐walled carbon nanotube composites

Water‐soluble polypyrrole (PPy)/multi‐walled carbon nanotube (MWCNT) composites were prepared by mixing chemically modified MWCNTs carrying carboxylic groups (c‐MWCNTs) and sulfonated PPy (SPPy) aqueous colloids in solution. Fourier transform infrared spectroscopy, Raman spectroscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction, field‐emission scanning electron microscopy and high‐resolution transmission electron microscopy were used to characterize the structure and morphology of the resulting composites. Raman and X‐ray photoelectron spectra demonstrate the presence of electrostatic interactions between the radical species of the SPPy and the carboxylic acid species of the c‐MWCNTs. The addition of c‐MWCNTs into SPPy efficiently enhances its thermal stability and electrical conductivity. Owing to the doping effect and one‐dimensional linear structure of the c‐MWCNTs, the conductivity of SPPy/c‐MWCNT composites at room temperature is increased by two orders of magnitude by the introduction of 5 wt% c‐MWCNTs into the SPPy matrix. Copyright © 2010 Society of Chemical Industry     

Fluorescence quenching of fluoranthene by maleic anhydride in solution and during nonreactive and reactive twin‐screw extrusion

Fluorescence quenching of fluoranthene by maleic anhydride (MAH) in polypropylene (PP) during twin‐screw extrusion (TSE) was investigated using an online fluorescence measurement system. The fluorescence quenching effect was clearly seen from the decrease of the peak intensity and integrated area of the residence time distribution (RTD) curves when MAH was introduced into PP. Fluorescence quenching effect in TSE was compared with that in chloroform solution and in both cases, it followed the linear Stern‐Volmer equation although it showed lower quenching effect in TSE than in solution. Using this quenching phenomenon, it was possible to measure online the grafting degree of PP with MAH in the TSE. The obtained results showed that MAH grafting degree and total conversion measured by both fluorescence technique and by Fourier transform infrared spectroscopy were in good agreement for MAH weight concentrations up to 0.8 wt%. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Formation of conjugated carbon bonds on poly(vinyl chloride) films by microwave‐discharge oxygen‐plasma treatments

Conjugated polyene bonds on poly(vinyl chloride) (PVC) films were rapidly formed by the treatment of oxygen plasma produced by microwave discharge. Changes affecting the formation of conjugated carbon bonds on PVC were studied with respect to plasma emission diagnostic and surface properties of the film with fluorescence, refractant absorption spectroscopy, X‐ray photoelectron spectroscopy analysis, and Raman spectroscopy. The formation of polyene bonds on the film surface was responsible for both the dechlorination and dehydrogenation of PVC in the plasma atmosphere. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 589–594, 2005     

Interactions between cationic conjugated polyelectrolyte and DNA and a label‐free method for DNA detection based on conjugated polyelectrolyte complexes

The electrostatic complexes of single‐stranded deoxyribonucleic acid (ssDNA) and a cationic conjugated polyelectrolyte (CPE), poly{9,9‐di[3‐(1‐ethyl‐1,1‐dimethyl ammonio)propyl]‐2,7‐fluorenyl‐alt‐1,4‐phenylene dibromide} (PFN), were investigated. Fluorescence emission of PFN solution (10 μmol/L) can be drastically quenched to about one fourth of its original intensity in the presence of a trace amount (2.6 μmol/L) of ssDNA. The effect of oligonucleotide length on the fluorescence quenching behavior was also investigated. In contrast to single‐stranded DNA with 20 bases (ssDNA‐20), ssDNA with 40 bases (ssDNA‐40) induces a relatively higher quenching efficiency and larger red‐shift of PFN emission maximum. The binding constant of ssDNA‐20 and PFN is estimated to be 1.12 × 10²¹. At extremely low concentration (10 nmol/L), PFN can respond to 0.2 nmol/L (or 2 × 10^?10 mol/L) of ssDNA‐20 by significant enhancement of its emission intensity. The result is contrary to the observation in the relative higher concentration, and its mechanism is postulated. Based on the high binding ability of ssDNA with cationic CPE, a label‐free method for ssDNA detection is designed. It uses an electrostatic complex of cationic PFN and an anionic CPE, which exhibits fluorescence resonance energy transfer (FRET) between the two components. Addition of ssDNA improves the FRET extent, indicated by obvious change of fluorescence spectra of the conjugated polyelectrolyte complex. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The differentiation of biodegradable and non‐biodegradable dissolved organic matter in wastewaters using fluorescence spectroscopy

The chemical and biochemical oxygen demand values of a number of synthetic and wastewater samples were determined using fluorescence spectroscopy. Treated and untreated sewage samples were obtained from a local sewage treatment works while synthetic samples were analysed before, during, and after treatment via a rotating biodisc contactor. Fluorescence intensities were normalised using the water Raman signal as an internal standard and corrections applied to take into account the attenuation effects caused by the sample matrix. The fluorescence emission spectra (λ_exc = 280 nm) of synthetic and sewage samples were very similar in that two main fluorescence bands centred around 350 nm and 440 nm were observed in all samples. Normalised fluorescence data, centred at 350 nm, correlate well with corresponding BOD, COD and TOC values (R² values ranging between 0.93 and 0.98). Using BOD, COD and TOC data the fluorescence at 350 nm and 440 nm can be apportioned to biodegradable and non‐biodegradable dissolved organic matter respectively. The findings of this research show that fluorescence data can be used to quantify oxygen demand values (chemical and biochemical) and total organic carbon values. Furthermore, the fluorescence spectral response can be apportioned to biodegradable (BOD) and non‐biodegradable (COD ? BOD) dissolved organic matter. The potential of using fluorescence spectroscopy as a possible tool for real‐time monitoring of sewage wastes is discussed. © 2002 Society of Chemical Industry     

Reducing ammonia emission from poultry manure composting via struvite formation

Composting can provide a viable alternative for poultry manure management in the Fraser Valley of British Columbia, Canada. However, it has a high potential for ammonia emission because of the high nitrogen content of poultry litter. The objective of this study was to reduce ammonia emission by precipitating ammonia into struvite before it can volatilize from the composting matrix. Nitrogen transformation occurs during composting, but struvite formation can help to conserve nitrogen, and does not allow a large amount of nitrogen to be released into the environment as ammonia or nitrate, because ammonium‐nitrogen becomes bound in struvite. It would also be possible to remove phosphorus from the manure. A laboratory‐scale experiment was conducted to examine the feasibility of struvite formation during poultry manure composting. Magnesium and phosphate salts were supplemented to create favorable conditions to form struvite. Results indicated that ammonia emission was reduced by 40% to 84%, while the nitrogen retention in compost was enhanced. The struvite formed in compost was confirmed by means of X‐ray diffraction; and scanning electron microscopy with energy dispersive X‐ray spectroscopy. Copyright © 2007 Society of Chemical Industry     

Decay Lifetimes of Para-Substituted Polystyrene in Solid Films and in Dichloromethane

The fluorescence decay times of polystyrene, poly(4-bromostyrene), poly(4-chlorostyrene), poly(4-methylstyrene), poly(α-methylstyrene), poly(4-methoxystyrene), and poly(4-tert butylstyrene) were measured in solid films and in dichloromethane solution. A detailed analysis of the emission profile performed by nanosecond time resolved fluorescence spectroscopy confirmed the presence of monomer fluorescence as well as excimer fluorescence in both media. Monomer fluorescence decay times gave shorter times compared with that of excimer decay times in dichloromethane solution. Fluorescence from substituted polystyrene was mainly excimer fluorescence with shift of maximum emission to longer wavelength. The ratio of monomer to excimer contributions was found to be dependent on the emission wavelength, but was not affected by polymer concentration. Both monomer and excimer fluorescence lifetimes as well as excimer intensity increase with increasing emission wavelength. An accompanying decrease in monomer contribution is also observed is solution in comparison with that in solid films.     

Nano‐hydroxyapatite (HAp) and hydroxyapatite/platinum (HAp/Pt) core shell nanorods: Development,structural study,and their catalytic activity

The development of a new kind of material that is a nanostructured catalytic material with an environmentally benign nature that can be used for alternative energy has acquired significance in recent years. In this context, the use of heterogeneous catalysts for the transesterification of vegetable oils has gained prominence due to their eco‐friendly and reusable nature. Hence in the present study, pure hydroxyapatite (HAp) and hydroxyapatite/platinum (HAp/Pt) nanostructured particles have been prepared successfully through a facile chemical method without templates and surfactants and their catalytic activity investigated for transesterification of natural vegetable oil to bioenergy (biodiesel). The textural and structural features of pure HAp and HAp/Pt were investigated using various characterization techniques such as x‐ray diffraction, Fourier transform infrared (FTIR) and Raman spectroscopy, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The elements present in the prepared nanostructures were confirmed through energy dispersive spectroscopy (EDS) and x‐ray photoelectron spectroscopy (XPS) techniques. The XPS analysis also confirms the metallic nature of the platinum in HAp/Pt. The specific surface area and porous nature of the prepared nanostructured catalysts were studied using the N₂ physisorption Brunauer‐Emmett‐Teller‐Barrett‐Joyner‐Halenda (BET‐BJH) method. The catalytic activity of the pure HAp nanoparticles and HAp/Pt core shell nanorods with the Simarouba glauca plant seed oil was investigated. The obtained results indicate that the pristine HAp nanoparticles and HAp/Pt core shell nanorods (NRs) show 91.4% and 87.1% fatty acid methyl ester (FAME) conversion, respectively, potentially offering environmental benign biocatalysts for biofuel production from natural feed stock.     

Activated Carbon from Renewable Material as an Efficient Support for Palladium Oxidation Catalysts

Activated carbon prepared from cocoa pod husk, which is an abundant agricultural waste, was employed as a green support for palladium oxidation catalysts. Systematic characterization of the support and palladium catalysts by atomic emission spectroscopy, N₂ and CO₂ physisorption measurements, X‐ray powder diffraction, infrared spectroscopy, electron microscopy, temperature‐programmed reduction by hydrogen, and temperature‐programmed desorption of NH₃ and CO₂ allowed detailed monitoring of their characteristics. Subsequently, the catalytic performance and selectivity in the oxidation of ethanol as a model volatile organic compound (VOC) was studied and linked to physicochemical properties of the catalysts.     

Combined Adsorption/Ultrafiltration of Secondary Effluents Using Powdered Zeolites

The performance of powdered zeolite (PZ) adsorption/ultrafiltration (UF) with real secondary effluents is investigated. With the assistance of PZs, the membrane fouling rate was reduced and the permeate flux recovery as well as the advanced treatment of the secondary effluents were enhanced. 3D excitation emission matrix (3D‐EEM) fluorescence spectra indicate that the removal of fluorescence intensity for aromatic proteins, fulvic acid‐like materials, soluble microbial by‐product‐like materials, and humic acid‐like organics could be improved by PZs. UF membranes with PZs can increase the removal efficiency of organics, especially of those with low molecular weight. The characteristics of the cake layer on the surface of an UF membrane were determined by scanning electron microscopy and electron energy‐dispersive X‐ray spectroscopy for the combined adsorption/UF membrane.     

Effect of TeO2 on Near‐Infrared Emission from Bismuth Centers in Borogermanate Glasses

Bi‐doped xTeO₂–(60?x)GeO₂–15B₂O₃–20MgO–5Al₂O₃ glasses were prepared by the conventional melt‐quenching method and their absorption and fluorescence spectra were characterized. Broadband near‐infrared (NIR) emission from Bi centers centered around 1240 nm with a full width at half maximum (FWHM) of 250 nm was observed, and the position of the emission peak strongly depends on the excitation wavelength. Increasing TeO₂ concentration results in the strong coloration of the glass, leading to the reduction and finally, complete quenching of the NIR emission. Based on Raman, X‐ray photoelectron spectroscopy and transmission microscopy observation, the coloration of the glass at high TeO₂ concentration can be ascribed to the precipitation of elemental Te nanoparticles of around 3–8 nm, which effectively suppresses the NIR emission by reabsorption. The precipitation of Te nanoparticles in an oxide glass may find novel applications in photonics and relevant fields.     

The charge state of titanium ions in Pd‐doped Ti:CMAS glass and glass‐ceramics

We have investigated the role of charge state of Ti in the electronic properties and structure of electrically conductive CMAS‐TiO₂‐Pd glass and glass‐ceramics by X‐ray photoelectron spectroscopy, electron paramagnetic resonance, positron annihilation lifetime spectroscopy, and fluorescence spectroscopy. These studies suggest the concentration of Ti³⁺ ions was, at most, ~0.1 wt% in glass‐ceramics devitrified in the reducing atmosphere of forming gas; no other glass or glass‐ceramic samples exhibited measurable levels of Ti³⁺. The observed fluorescence at liquid nitrogen temperature in parent glasses and glass‐ceramics obtained in air is explained by UV‐induced charge‐transfer processes involving Ti⁴⁺ ions and oxygen surroundings. The X‐ray photoelectron spectroscopy data are correlated with rutile, anorthite, diopside, and titanite crystalline phases identified in Pd‐free and Pd‐doped Ti:CMAS glass‐ceramics earlier.     

Effect of octa(aminopropyl) polyhedral oligomeric silsesquioxane (OapPOSS) functionalized graphene oxide on the mechanical,thermal, and hydrophobic properties of waterborne polyurethane composites

A novel graphene nanomaterial functionalized by octa(aminopropyl) polyhedral oligomeric silsesquioxane (OapPOSS) was synthesized and then confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), Raman spectroscopy, X‐ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy with energy‐dispersive X‐ray spectroscopy (SEM EDX), atomic force microscopy, and X‐ray diffraction. The obtained functionalized graphene (OapPOSS‐GO) was used to reinforce waterborne polyurethane (WPU) to obtain OapPOSS‐GO/WPU nanocomposites by in situ polymerization. The thermal, mechanical, and hydrophobic properties of nanocomposites as well as the dispersion behavior of OapPOSS‐GO in the polymer were investigated by TGA, a tensile testing machine, water contact angle tests, and field emission SEM, respectively. Compared with GO/WPU and OapPOSS/WPU composites, the strong interfacial interaction between OapPOSS‐GO and the WPU matrix facilitates a much better dispersion and load transfer from the WPU matrix to the OapPOSS‐GO. It was found that the tensile strength of the OapPOSS‐GO/WPU composite film with 0.20 wt % OapPOSS‐GO exhibited a 2.5‐fold increase in tensile strength, compared with neat WPU. Better thermal stability and hydrophobicity of nanocomposites were also achieved by the addition of OapPOSS‐GO. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44440.