Reduction In Melting Temperature Research Articles

Effects of the alkali metal oxides and bed material compositions on agglomeration phenomena in CFB boiler

Circulating fluidized bed boiler is environmentally friendly technology in power generation. However, agglomeration related operational standard has not been established yet. As a basis of establishing standard, the fixed bed agglomeration mechanism of bed inventory was investigated. The melting temperature reduction occurred with induced change of alkali metal compositions. The melting temperature reduction result in viscous surface on particles and ease of being agglomerated. The temperature reduction appeared more clearly in silica sand than bottom ash. This was caused by the high SiO2 composition of the sand and alkali silica reaction occurred because activated alkali compositions were reacted with SiO2 forming alkali silicates. Further analyses of agglomerates produced in bubbling fluidized bed reactor were conducted. The expected agglomeration effect has similar trend with melting temperature reduction. And the agglomeration effect appeared more in silica sand because of high SiO2 composition and sodium was more effective in forming agglomerates than potassium. Therefore, bottom ash can replace silica sand as bed material in CFB boiler. And sodium composition must be managed more strictly than potassium composition.

Effect of TiO2 and FeO on viscosity and structure of HIsmelt titanium-containing slag

HIsmelt is considered one of the most promising processes for future vanadium-titanium magnetite smelting. In this study, we investigated the effects of TiO2 and FeO on the viscosity and structure properties of HIsmelt titanium-containing slag using the rotating cylinder method, the Fourier Transform Infrared, and Raman. Experimental findings indicate a significant reduction in melting temperature with increasing TiO2 content, accompanied by a rapid decrease in slag viscosity followed by a gradual increase, reaching a minimum at 30 wt% TiO2. The FeO content exerts minimal influence on slag viscosity and melting temperature. FTIR spectroscopy results reveal a gradual depolymerization of the [SiO4] structure with the introduction of TiO2 and FeO while having little influence on [AlO4] and Si–O–Al structural changes. Raman spectroscopy results indicate an increase in Q0 and a decrease in Q1 and Q2 with elevated TiO2 and FeO content, leading to a reduction in the degree of polymerization (DOP) within the silicate structure and, consequently, lower slag viscosity. Maintaining FeO content within the range of 2–4% and TiO2 content at approximately 30 % will be advantageous for industrial production.

Recovery of lead and chlorine via thermal co-treatment of municipal solid waste incineration fly ash and lead-rich waste cathode-ray tubes: Analysis of chlorination volatilization mechanism

In this study, a new lead (Pb) and chlorine (Cl) recovery process via the thermal co-treatment of Municipal solid waste (MSW) incineration fly ash (FA) and waste cathode-ray tubes (CRT) was developed and the synergistic effects under different CRT ratios, temperatures, and residence times were comprehensively investigated. Thermogravimetric experiments revealed that the co-processing of FA and CRT exhibited a remarkable synergistic effect as evidenced by the considerable increase in mass loss and mass-loss rate when compared with the theoretical values. When the mixtures with 50% CRT addition was treated at 1200 °C for 60 min, Pb removal rate reached the maximum value of 98.67%, and the Cl removal rate considerably increased by 37.32% compared to that with FA treatment alone. Additionally, the Cl content in the residue was < 2%. It was mainly attributed to the volatilization of chlorides, such as PbCl2, NaCl, and KCl. CaCl2 generated from the decomposition of CaClOH in FA was conducive to improve Pb removal in CRT through indirect chlorination and destroying the glass structure in CRT. Co-processing of FA and CRT demonstrates promising potential for several benefits, including the reduction in melting temperature, recovery of Pb and Cl from secondary fly ash, and the reutilization of calcium-rich slag.

Melting and phase relations of Fe-Ni-Si determined by a multi-technique approach

Many studies have suggested silicon as a candidate light element for the cores of Earth and Mercury. However, the effect of silicon on the melting temperatures of core materials and thermal profiles of cores is poorly understood, due to disagreements among melt detection techniques, uncertainties in sample pressure evolution during heating, and sparsity of studies investigating the combined effects of nickel and silicon on the phase diagram of iron. In this study we develop a multi-technique approach for measuring the high-pressure melting and solid phase relations of iron alloys and apply it to Fe0.8Ni0.1Si0.1 (Fe-11wt%Ni-5.3wt%Si), a composition compatible with recent estimates for the cores of Earth and Mercury. This approach combines results (20-83 GPa) from two atomic-level techniques: synchrotron Mössbauer spectroscopy (SMS) and synchrotron x-ray diffraction (XRD). Melting is independently detected by the loss of the Mössbauer signal, produced exclusively by solid-bound iron nuclei, and the onset of a liquid diffuse x-ray scattering signal. The use of a burst heating and background updating method for quantifying changes in the reference background during heating facilitates the determination of liquid diffuse signal onsets and leads to strong reproducibility and excellent agreement in melting temperatures determined separately by the two techniques. XRD measurements additionally constrain the hcp-fcc phase boundary and in-situ pressure evolution of the samples during heating. We apply our updated thermal pressure model to published SMS melting data on fcc-Fe and fcc-Fe0.9Ni0.1 to precisely evaluate the effect of silicon on melting temperatures. We find that the addition of 10 mol% Si to Fe0.9Ni0.1 reduces melting temperatures by ∼250 K at low pressures (<60 GPa) and flattens the hcp-fcc phase boundary. Extrapolating our results, we constrain the location of the hcp-fcc-liquid quasi-triple point at 147±14 GPa and 3140±90 K, which implies a melting temperature reduction of 500 K compared with Fe0.9Ni0.1. The results demonstrate the advantages of combining complementary experimental techniques in investigations of melting under extreme conditions.

Use of colemanite and borax penta-hydrate in soda lime silicate glass melting - A strategy to reduce energy consumption and improve glass properties

In view of recent energy crisis and environmental considerations, reductions of melting temperature and CO2 emissions during the production of commercial soda lime silicate (SLS) glass at industrial scale are major intentions. Here we show that this goal can be achieved by using carbonate-free borate minerals such as colemanite (Ca2B6O11·5H2O) and borax penta-hydrate (BPH, Na2B4O7·5H2O) as alternative sources for CaO and Na2O, respectively. The SLS glass melting temperature has decreased successively by the incorporation of B2O3 with substitution of equivalent wt% SiO2 resulting from gradual utilization of colemanite and BPH. Hot Stage Microscopy (HSM) revealed that the melting temperature was decreased from 1650 °C, for the parent commercial SLS glass, to 1528 °C on use of colemanite and further down to 1072 °C on utilization of both colemanite and appropriate quantity of BPH up to which the properties of the pristine glass can be retained. Thus, energy consumption equivalent to reduction in melting temperature could be minimized during the glass production. Another important environmental benefit achieved by using carbonate free minerals is significant reduction (12%) of CO2 emissions during thermal decomposition in glass melting which could minimize greenhouse gas to the atmosphere at a great extent. Further, the addition of colemanite improved micro-hardness, elastic modulus and thermal properties of the pristine glass through polymerization of glass network structure. In contrast to the use of BPH as a source of more than 8 wt% Na2O deteriorated glass properties with the formation of non-bridging oxygens into the glass network.

The Effect of Dialkyl Peroxide Crosslinking on the Properties of LLDPE and UHMWPE.

Peroxide has been considered a chemical agent that can be used to tune the properties of polymeric materials. This research evaluated the influence of different concentrations of dialkyl peroxides on the mechanical, thermal, and morphological properties of linear low-density polyethylene (LLDPE) and ultra-high molecular weight polyethylene (UHMWPE). The neat polymer, as well as those with the addition of 1% and 2% by mass of dialkyl peroxides, were subjected to compression molding and immersion in water for 1 h, under controlled temperatures of 90 °C. The values of the gel content found in the samples indicated that the addition of peroxide to the LLDPE and to the UHMWPE promoted the formation of a reticulated network. The structure obtained by the crosslinking led to less reorganization of the chains during the crystallization process, resulting in the formation of imperfect crystals and, consequently, in the reduction in melting temperatures, crystallization and enthalpy. The mechanical properties were altered with the presence of the crosslinker. The polymers presented had predominant characteristics of a ductile material, with the occurrence of crazing with an increased peroxide content.

Combustion Characteristics of Nanoaluminium-Based Composite Solid Propellants: An Overview

The nanosized powders have gained attention to produce materials exhibiting novel properties and for developing advanced technologies as well. Nanosized materials exhibit substantially favourable qualities such as improved catalytic activity, augmentation in reactivity, and reduction in melting temperature. Several researchers have pointed out the influence of ultrafine aluminium (∼100 nm) and nanoaluminium (&lt;100 nm) on burning rates of the composite solid propellants comprising AP as the oxidizer. The inclusion of ultrafine aluminium augments the burning rate of the composite propellants by means of aluminium particle’s ignition through the leading edge flames (LEFs) anchoring above the interfaces of coarse AP/binder and the binder/fine AP matrix flames as well. The sandwiches containing 15% of nanoaluminium solid loading in the binder lamina exhibit the burning rate increment of about 20–30%. It was noticed that the burning rate increment with nanoaluminium is around 1.6–2 times with respect to the propellant compositions without aluminium for various pressure ranges and also for different micron-sized aluminium particles in the composition. The addition of nano-Al in the composite propellants washes out the plateaus in burning rate trends that are perceived from non-Al and microaluminized propellants; however, the burning rates of nanoaluminized propellants demonstrate low-pressure exponents at the higher pressure level. The contribution of catalysts towards the burning rate in the nanoaluminized propellants is reduced and is apparent only with nanosized catalysts. The near-surface nanoaluminium ignition and diffusion-limited nano-Al particle combustion contribute heat to the propellant-regressing surface that dominates the burning rate. Quench-collected nanoaluminized propellant residues display notable agglomeration, although a minor percentage of the agglomerates are in the 1–3 µm range; however, these are within 5 µm in size. Percentage of elongation and initial modulus of the propellant are decreased when the coarse AP particles are replaced by aluminium in the propellant composition.

Synthesis and Characterization of Lignin-grafted-poly(ε-caprolactone) from Different Biomass Sources

Modification of lignin with poly(ε-caprolactone) is a promising approach to valorize industrial low-value lignins and to advance the bioeconomy. We have synthesized lignin grafted poly(ε-caprolactone) (lignin-g-PCL) copolymers via ring-opening polymerization of ε-caprolactone with different types of lignins of varying botanical sources (G-type pine lignin, S/G-type poplar lignin, and C-type Vanilla seeds lignin) and lignin extraction methods (Kraft and ethanol organosolv pulping). The lignin-g-PCL copolymer showed remarkably improved compatibility and dispersion in acetone, chloroform, and toluene in comparison to non-modified lignins. The structure and thermal properties of the lignin-g-PCL were investigated using Fourier-transform infrared spectroscopy (FTIR), 31P nuclear magnetic resonance (NMR), 2D heteronuclear single quantum correlation (HSQC) NMR, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). We have found that all the technical lignins were reactive to the copolymerization reaction regardless of their plant source and isolation methods. The molecular weights of the synthesized lignin-g-PCL copolymers were positively correlated with the content of aliphatic lignin hydroxyls, suggesting that the copolymerization reaction tends to occur preferentially at the aliphatic hydroxyls rather than the phenolic hydroxyls of lignin. Thermal analyses of the lignin-g-PCL copolymers were studied, and in general, a reduction of melting temperature and crystallinity percentage in comparison to the neat PCL was observed. However, the thermal behavior of lignin-g-PCL copolymers varied depending on the lignin feedstocks employed in the copolymerization reaction.

Synthesis of multiphase binary eutectic Al–Mg alloy-nanoparticles by electrical wire explosion technique for high-energy applications, its characterisation and size-dependent thermodynamic and kinetic study

Abstract In the present study, Al–Mg binary eutectic alloy nanoparticles were synthesized through the electrical wire explosion technique (EWET) in an inert ambience. High-speed imaging was carried out to visualize sublimation process of alloy wire and subsequent formation of nanoparticle through the condensation process. The fundamental gas-phase kinetics is investigated by the embedded atom method (EAM) and reactive hard-sphere model to elucidate the mechanisms governing the formation of finer particles of eutectic Al-Mg alloy. The condensed phase transformations are analysed through size-dependent thermodynamics and growth kinetics modelling, which has shown that the adsorption controlled growth is responsible for the generation of polydispersed particles. The formation of Al20Mg23 nanoparticles and its morphological features were characterised through XRD and SEM/EDS analysis. High-resolution transmission electron microscopy (HRTEM) along with the selected area electron diffraction (SAED) confirmed the spherical morphology, crystallinity, lognormal particle size distribution and the multiphase microstructure of the eutectic AlMg nanoparticles. The formation of multiphase alloy nanoparticles is attributed to the insignificant difference in melting temperatures of Al and Mg and phase boundary modifications due to size-effect. Scanning transmission electron microscopy (STEM) revealed the spatial distribution of Al and Mg within the alloy nanoparticle. Differential scanning calorimetry (DSC) confirmed the reduction in melting temperature and fusion enthalpy of eutectic Al–Mg alloy nanoparticles. It is proposed as a potential substitute for Al nanoparticles to reduce the ignition temperature, agglomeration and two-phase flow losses for realising improved combustion performance in solid rocket propellants.

Profound softening and shear-induced melting of diamond under extreme conditions: An ab-initio molecular dynamics study

Diamond retains original crystal form and large elastic stiffness up to very high temperatures, and strengthens considerably under high pressures. These remarkable characters dictate its behaviors under extreme loadings such as those in laser-heated diamond anvil cells (LHDACs) or giant planetary interiors. Here we report surprising findings from ab initio molecular dynamics simulations revealing that diamond's mechanical strengths reduce precipitously at elevated temperatures, by 50% at 3000 K, despite that its elastic parameters remain little changed. Our results also unravel an extraordinary shear-induced reduction of melting temperature of diamond under (111)[112¯] shear strains by as much as 1150 K, greatly altering its pressure-temperature (p−T) phase diagram when shear deformations exist. These new benchmarks offer crucial insights for elucidating extreme mechanics of diamond at high p-T conditions, advancing fundamental knowledge with major implications for LHDAC operation and planetary modeling.

Evolution of the crystalline and amorphous phases of high-density polyethylene subjected to equal-channel angular pressing

In the current research, physical and morphological properties of high-density polyethylene (HDPE) were investigated after equal-channel angular pressing (ECAP) for up to three passes via route A, in which the sample is pressed without any rotation between individual passes, at the temperature of 80 °C. The results of density, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) represent a decrease in the polymer’s crystallinity after deformation, which is more evident after three passes of ECAP. Moreover, a phenomenological mechanism is proposed to explain the variations of crystallinity after ECAP processing. The occurrence of an additional crystalline peak in the XRD pattern, as well as melting doublet in the DSC curve of three-pass ECAP-deformed sample, demonstrate that some part of the initial orthorhombic crystalline phase of HDPE has been transformed to monoclinic crystal structure after ECAP deformation. Furthermore, a reduction in melting temperature and broadening of crystalline peaks show that the thickness of crystalline lamella may decline in one-pass ECAP-deformed sample, which could significantly affect dynamic mechanical behavior of HDPE. In addition, dilatometry results and observation of the impact-fractured surfaces of deformed samples reveal that oriented structures formed in amorphous and crystalline regions of the workpiece.

Cyclic Extrusion of Recycled High Density Polyethylene/Banana Fiber/Fly Ash Cenosphere Biocomposites: Thermal and Mechanical Retention Properties

AbstractDisposal of composite materials used vastly in structural applications raises the need to study the reprocessability of these systems for environmental benefits. In this paper, composites of recycled high density polyethylene (R) containing 30 wt.% banana fiber (BF)/7.5 wt.% fly ash cenospheres (FACS) were prepared with 3 wt.% maleic anhydride grafted high density polyethylene (MA-g-HDPE) as a coupling agent using twin screw extrusion followed by injection molding. The effects of thermal cycles (two times extrusion followed by injection molding) were studied on R and its composites. The samples were characterized by using tensile, flexural, izod impact tests, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetry (TGA) and dynamic mechanical analysis (DMA). The tensile and flexural properties were improved by addition of both BF/FACS into the R matrix. The percentage retention in tensile properties of R/BF/FACS(E2) biocomposites (i.e. two times extrusion followed by injection molding) is more than 80 %, while that for flexural properties is more than 90 %. This indicates that R/BF/FACS composites exhibit good retention ability in mechanical properties after subjecting to two times twin-screw extrusion followed by injection molding. DSC results revealed that repeated extrusion improved the crystallization temperature and crystallinity of the composites with a slight reduction in melting temperature. From the TGA results, it was observed that the thermal stability (e.g. Tonset) of R was reduced by the addition of BF/FACS. However, repeated extrusion showed an improvement in thermal stability of the composites.

Synthesis and characterization of magnesium ion conductivity in PVDF based nanocomposite polymer electrolytes disperse with MgO

Magnesium ion conducting nanocomposite polymer electrolytes with different wt% of MgO nano-filler in optimum conducting composition of solid polymer electrolyte have been prepared by solution cast technique and characterized by various electrical and thermal techniques. The thermal stability in polymer electrolyte films was confirmed by Thermogravimetric analysis (TGA), reduction in melting temperature was confirmed by Differential scanning calorimetry (DSC) and decrease in degree of crystallnity was confirmed by X-Ray Diffraction (XRD). It was found that dispersion of nano-filer enhances ionic conductivity and dielectric constant, confirmed by complex impedance spectroscopy (CIS). The impedance spectroscopy technique performed in the frequency range between 42 Hz and 5 MHz at different temperatures and obtain highest conductivity 1.04 × 10−4 S/cm for optimum conducting composition (OCC) i.e. 70 PVDF:30 Mg(NO3)2:3MgO of NCPE thin film. The magnesium ion conduction in NCPE was confirmed by transference number measurement.

Effect of melting temperature on microstructural evolutions, behavior and corrosion morphology of Hadfield austenitic manganese steel in the casting process

In this study, the effect of melting temperature on the microstructural evolutions, behavior, and corrosion morphology of Hadfield steel in the casting process is investigated. The mold was prepared by the sodium silicate/CO2 method, using a blind riser, and then the desired molten steel was obtained using a coreless induction furnace. The casting was performed at melting temperatures of 1350, 1400, 1450, and 1500°C, and the cast blocks were immediately quenched in water. Optical microscopy was used to analyze the microstructure, and scanning electron microscopy (SEM) and X-ray diffractrometry (XRD) were used to analyze the corrosion morphology and phase formation in the microstructure, respectively. The corrosion behavior of the samples was analyzed using a potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) in 3.5wt% NaCl. The optical microscopy observations and XRD patterns show that the increase in melting temperature led to a decrease of carbides and an increase in the austenite grain size in the Hadfield steel microstructure. The corrosion tests results show that with increasing melting temperature in the casting process, Hadfield steel shows a higher corrosion resistance. The SEM images of the corrosion morphologies show that the reduction of melting temperature in the Hadfield steel casting process induced micro-galvanic corrosion conditions.

Exploring the Shape Influence on Melting Temperature, Enthalpy, and Solubility of Organic Drug Nanocrystals by a Thermodynamic Model

This paper focuses on a thermodynamic model built to predict the reduction of organic drug melting temperature and enthalpy with nanocrystal size decrease. Indeed, this valuable information enables us to evaluate the increase of drug solubility, an aspect of paramount importance for poorly water-soluble organic drugs since a solubility increase is reflected in a bioavailability enhancement. In particular, the model considers the effect of nanocrystals shape (spherical, cylindrical, and parallelepiped-shaped) and morphology (from platelet to needle nanocrystals) on the melting temperature and enthalpy reduction with crystal size decrease. Nimesulide, a typical nonsteroidal and poorly water-soluble drug with anti-inflammatory action, has been chosen as a model drug to test model reliability. Model outcomes suggest that the reduction of melting temperature and enthalpy mainly depends on the ratio between crystals surface area and volume, i.e., on the ratio between the number of surface and bulk molecules con...

Effect of dynamic high pressure on functional and structural properties of bovine serum albumin

Dynamic high pressure (DHP) has been investigated as an innovative suitable method to induce protein modifications. This work evaluated the effect of DHP (up to three passes at 100, 150 and 200MPa, with an inlet temperature of 20°C) on functional and structural properties of bovine serum albumin (BSA). Results indicated that DHP process applied up to an energy limit of 100MPa increased the protein foaming capacity (FC) (p<0.05 - increase up to 63% after 1 pass at 100MPa) and the utilization of multiple passes at high pressure promoted a reduction in this property (p<0.05 - reduction up to 31.6% after 3 passes at 200MPa). Similar results were observed for sulfhydryl group, indicating an influence of free thiol groups on FC. Complementarily, DHP process promoted an increase of proteins particles size, suggesting a new rearrangement of their conformational structure. DHP did not affect tryptophan microenvironment in BSA; however, this process induced the rearrangement of secondary structure elements. In the first cycle, the pressure increase resulted in a loss of secondary structure, while in the second and third cycles the DHP process resulted in the gain of secondary structure elements. These results indicated that the second and third passes triggered a molecular rearrangement of the protein structure, giving rise to a novel and more stable conformational state. This conclusion was also supported by thermal unfolding studies (melting temperature reduction from 67.5 to 54.6°C after 1 pass at 200MPa), in which the additional cycles of DHP caused the occurrence of an initial denaturation at high temperatures, compared to the first cycle.

Investigating the Interaction of Fe Nanoparticles with Lysozyme by Biophysical and Molecular Docking Studies.

Herein, the interaction of hen egg white lysozyme (HEWL) with iron nanoparticle (Fe NP) was investigated by spectroscopic and docking studies. The zeta potential analysis revealed that addition of Fe NP (6.45±1.03 mV) to HEWL (8.57±0.54 mV) can cause to greater charge distribution of nanoparticle-protein system (17.33±1.84 mV). In addition, dynamic light scattering (DLS) study revealed that addition of Fe NP (92.95±6.11 nm) to HEWL (2.68±0.37 nm) increases suspension potential of protein/nanoparticle system (51.17±3.19 nm). Fluorescence quenching studies reveled that both static and dynamic quenching mechanism occur and hydrogen bond and van der Waals interaction give rise to protein-NP system. Synchronous fluorescence spectroscopy of HEWL in the presence of Fe NP showed that the emission maximum wavelength of tryptophan (Trp) residues undergoes a red-shift. ANS fluorescence data indicated a dramatic exposure of hydrophobic residues to the solvent. The considerable reduction in melting temperature (T(m)) of HEWL after addition of Fe NP determines an unfavorable interaction system. Furthermore circular dichoroism (CD) experiments demonstrated that, the secondary structure of HEWL has not changed with increasing Fe NP concentrations; however, some conformational changes occur in tertiary structure of HEWL. Moreover, protein–ligand docking study confirmed that the Fe NP forms hydrogen bond contacts with HEWL.

Pore formation of poly(ε-caprolactone) scaffolds with melting point reduction in supercritical CO2 foaming

Poly(ε-caprolactone) (PCL) is recently developed for bone tissue engineering applications due to its lasting degradation rate which matches the natural growth rate of a bone. In this work, batch foaming of PCL using supercritical CO2 was employed, and the effects of processing variables, namely soaking time, foaming temperature and pressure, depressurization rate on the pore morphology and structure were studied in detail. Results demonstrated that morphologies and structures of pores were significantly distinct astride foaming temperature of 40°C, which were characterized by melt-state foaming and solid-state foaming respectively. The dramatic reduction of melting temperature (Tm) caused by the presence of supercritical CO2 was found to be the key for this specific phenomenon. Above 40°C, the enhanced melting of PCL caused by the reduction of Tm led to wider pore size distribution, i.e. melt-state foaming, and the domino effect of variables on pore size was amplified; whilst below 40°C the foams showed dense and small pore morphology, i.e. solid-state foaming. By tuning processing variables, scaffolds with diameter of 12.5±0.1 to 344±54μm and porosity of 60.8±3.2% to 83.4±1.3% were fabricated. Furthermore, the interconnectivity of neat PCL scaffolds were mostly around 70%, which showed potential application in bone tissue engineering.

Studies on the morphology and conductivity of PEO/LiClO4

Polymer based ion conducting materials have potential applications as an electrolyte and separator in the field of lithium batteries. The present work is aimed at the optimization of LiClO4 loading in PEO/LiClO4 films for solid polymer electrolyte (SPE) applications. PEO was complexed at different wt% ratios (95:5), (92.5:7.5), (90:10), (87.5:12.5) and (85:15) and then made into films by solution casting. The PEO/LiClO4 films thus fabricated are characterized by X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM). The above studies have indicated enhancement in amorphous phase of polymer with increase of salt concentration. Further, a reduction in melting temperature (Tm) of PEO was observed from DSC results indicating increase in the flexibility of the polymer chains. Ionic conductivity studies were carried out as a function of frequency and temperature using Hioki LCR Hitester. The PEO/LiClO4 films with maximum salt concentration (85:15) have exhibited an enhancement in conductivity of about four orders of magnitude compared to host polymer electrolyte.

Immobilization-mediated reduction in melting temperatures of DNA–DNA and DNA–RNA hybrids: Immobilized DNA probe hybridization studied by SPR

Abstract The melting temperature of probe-target nucleic acid hybrids plays an important role in sensor performance. This study employed surface plasmon resonance (SPR) techniques to investigate the hybridization of both DNA and RNA targets to their complementary surface-bound DNA oligonucleotide and the corresponding melting temperatures. The target molecule was a 26 nucleotide strand of RNA selected because of its utility in detecting the tobacco mosaic virus, a common plant pathogen with an RNA genome. The melting temperatures of duplexes with immobilized probes were determined by hybridization of the DNA and RNA targets with the bound DNA probe at different temperatures using a custom-built thermostated dual-channel SPR cell. Hybridization conditions and binding efficiencies were compared for both DNA and RNA binding to the gold-coated surface-bound DNA probe. The melting temperature for the DNA–DNA duplex was approximately 15 °C higher than the DNA–RNA in the solid state. The melting temperature in solution was also measured for comparison to the surface values. For both RNA and DNA, the melting transitions were substantially lower (∼20 °C) for solid state binding relative to solution. Particularly for surface immobilized DNA–RNA hybrids, the melting temperature was reduced to room temperature or below. Since most biosensor platforms operate at room temperature, they may consequently exhibit poor sensor performance due to weakened probe-target interactions. This result emphasizes that for optimal sensor performance, the hybrid melting temperature should be considered. The ability to study and optimize the binding of complementary strands of genomic materials to bound DNA probes could facilitate the rapid detection and identification of plant viruses having genomic RNA using various biosensor rapid analytical techniques.