Quartz Crystal Micro Research Articles

The pre-addition of “blocking” proteins decreases subsequent cellulase adsorption to lignin and enhances cellulose hydrolysis

The pre-adsorption of non-catalytic/blocking proteins onto the lignin component of pretreated biomass has been shown to significantly increase the effectiveness of subsequent enzyme-mediated hydrolysis of the cellulose by limiting non-productive enzyme adsorption. Layer-by-layer adsorption of non-catalytic proteins and enzymes onto lignin was monitored using Quartz Crystal Micro balancing combined with Dissipation monitoring (QCM-D) and conventional protein adsorption. These methods were used to assess the interaction between soft/hardwood lignins, cellulases and the three non-catalytic proteins BSA, lysozyme and ovalbumin. The QCM-D analysis showed higher adsorption rates for all of the non-catalytic proteins onto the lignin films as compared to cellulases. This suggested that the “blocking” proteins would preferentially adsorb to the lignin rather than the enzymes. Pre-incubation of the lignin films with blocking proteins resulted in reduced adsorption of cellulases onto the lignin, significantly enhancing cellulose hydrolysis.

Molecularly Imprinted Chitosan-Based Thin Films with Selectivity for Nicotine Derivatives for Application as a Bio-Sensor and Filter.

This study reports the feasible use of chitosan as a thin film biosensor on the very sensitive quartz crystal micro balance system for detection of blends of multiple templates within a single matrix. The development of chitosan-based thin film materials with selectivity for nicotine derivatives is described. The molecular imprinting of a combination of nicotine derivatives in N-diacryloyl pipiradine-chitosan-methacrylic acid copolymer films on quartz crystal resonators was used to generate thin films with selectivity for nicotine and a range of nicotine analogues, particularly 3-phenylpyridine. The polymers were characterized by spectroscopic and microscopic evaluations; surface area, pore size, pore volume using Breuner-Emmet-Teller method. Temperature characteristics were also studied. The swelling and structure consistency of the Chitosan was achieved by grafting with methylmethacrylic acid and cross-linking with N-diacrylol pipiradine. A blend of 0.002 g (0.04 mmol) of Chitosan, 8.5 μL Methylmethacrylic Acid and 1.0 mg N-diacrylol pipradine (BAP) presented the best blend formulation. Detections were made within a time interval of 99 s, and blend templates were detected at a concentration of 0.5 mM from the Quartz crystal microbalance resonator analysis. The successful crosslinking of the biopolymers ensured successful control of the swelling and agglomeration of the chitosan, giving it the utility potential for use as thin film sensor. This successful crosslinking also created successful dual multiple templating on the chitosan matrix, even for aerosolized templates. The products can be used in environments with temperature ranges between 60 °C and 250 °C.

Membrane-bound mucins of the airway mucosal surfaces are densely decorated with keratan sulfate: revisiting their role in the Lung's innate defense.

Understanding the basic elements of the airway mucosal surfaces and how they form a functional barrier is essential in understanding disease initiation, progression, pathogenesis and ultimately treating chronic lung diseases. Using primary airway epithelial cell cultures, atomic force microscopy (AFM), multiangle light scattering and quartz crystal micro balance with dissipation monitoring techniques, here we report that the membrane bound mucins (MBMs) found in the periciliary layer (PCL) of the airway surface are densely decorated with keratan sulfate (KS). AFM and immunoblotting show that the KS sidechains can be removed enzymatically with keratanase II (KII) treatment, and the antibody accessibility for B2729 (MUC1), MUCH4 (MUC4) and OC125 (MUC16) was substantially enhanced. Light scattering analysis confirmed that KII treatment removed ~40% of the mass from the mucin fractions. Surface binding experiments indicated that MBMs were able to pack into a tighter conformation following KS removal, suggesting that negatively charged KS sidechains play a role in mucin-mucin repulsion and contribute to "space filling" in the PCL. We also observed that soluble filtrate from the common airway pathogen Pseudomonas aeruginosa is capable of stripping KS from MBMs. Altogether, our findings indicate that KS glycosylation of MBMs may play an important role in the integrity of the airway mucosal barrier and its compromise in disease.

Thermochromatic vanadium dioxide (VO2) thin films synthesized by atomic layer deposition and post-treatments

As a thermochromatic material showing metal–insulator transition behavior below 70 ℃, crystalline films of vanadium dioxide (VO2) have potential applications in many fields. In this work, amorphous vanadium oxide (VxOy) films were deposited on glass substrates by atomic layer deposition (ALD). The film growth mechanism and growth rate were studied by quartz crystal micro balance, and a constant growth rate of about 0.5 Å/cycle was obtained. X-ray diffraction and X-ray photoelectron spectroscopy characterizations demonstrated that the as-deposited ALD VxOy film was amorphous with mostly V4+ oxidation state. Crystalline V2O5 films were prepared by annealing the as-deposited ALD VxOy films at 300 ℃ under O2 flow. Subsequently, different annealing methods and conditions were tested for transforming V2O5 films to VO2 films. It turned out that high purity crystalline VO2 films could be obtained by heating the V2O5 films in an oxidizing environment at a reduced pressure. Results of transmittance measurements revealed that these crystalline VO2 films had excellent thermochromatic properties with a reversible change in transmittance at about 65 ℃.

Absolute cross section for electron emission from uracil upon ion collision using velocity map imaging technique

SynopsisIon-induced electron emission from RNA base uracil has been measured using a newly developed experimental set-up based on velocity map imaging (VMI) technique. Electrons emitted in a solid angle of 4π steradians are extracted and analyzed in energy and angle by the multi-electrodes VMI spectrometer. By monitoring the target density, the projectile ion beam intensity and the beams overlap with the use of a quartz crystal micro balance and an ion beam profiler, we were able to estimate absolute singly- and doubly-differential cross sections for electron emission.

Asia-Pacific solid oxide fuel cells market, 2018-2023 - market is projected to grow at a CAGR of more than 15%

As a thermochromatic material showing metal–insulator transition behavior below 70 ℃, crystalline films of vanadium dioxide (VO2) have potential applications in many fields. In this work, amorphous vanadium oxide (VxOy) films were deposited on glass substrates by atomic layer deposition (ALD). The film growth mechanism and growth rate were studied by quartz crystal micro balance, and a constant growth rate of about 0.5 Å/cycle was obtained. X-ray diffraction and X-ray photoelectron spectroscopy characterizations demonstrated that the as-deposited ALD VxOy film was amorphous with mostly V4+ oxidation state. Crystalline V2O5 films were prepared by annealing the as-deposited ALD VxOy films at 300 ℃ under O2 flow. Subsequently, different annealing methods and conditions were tested for transforming V2O5 films to VO2 films. It turned out that high purity crystalline VO2 films could be obtained by heating the V2O5 films in an oxidizing environment at a reduced pressure. Results of transmittance measurements revealed that these crystalline VO2 films had excellent thermochromatic properties with a reversible change in transmittance at about 65 ℃.

Ultra-sensitive and selective label free electrochemical DNA detection at layer-by-layer self-assembled graphene oxide and vesicle liposome nano-architecture

Liposomes are self-assembled successfully on graphene oxide/reduced graphene oxide (GO/rGO) composite supported on a gold electrode for the ultra-sensitive and selective label free detection of target DNA in presence of gold nanoparticle electrochemically for the first time. This work used the chemically synthesized GO for controlling the bilayer to vesicle structure of cationic DOTAP by the simultaneous control of GO hydrophobic character and oxy functional group spacing. This has been achieved by two different approaches: (i) the traditional physical mixing of ascorbic acid reduced GO with the unreduced GO to form a trilayered rGO/GO/rGO network and (ii) in another method, the rGO was prepared electrochemically by the controlled potential reduction of acid functional groups on the GO in sulphuric acid medium (ErGO). Both these methods produce graphene surfaces with evenly spaced functional groups and low hydrophobic character which are essential to prevent liposome vesicle fusion on the GO surface. Electrochemical and quartz crystal micro balance techniques (QCM) suggest more adsorption of the vesicles on the ErGO than on the GO/rGO assembly. These surfaces are further decorated with gold nanoparticles to anchor single stranded DNA to detect target DNA ultrasensitively in the presence of ferri/ferro cyanide redox probe. When the complementary hybridization decreases the redox peak current in cyclic voltammetry, the non-complementary hybridization does not show any obvious change in the peak currents. The intact spherical liposome on the GO/rGO and ErGO promotes the ultrasensitive detection of target DNA and showed the lowest detection limit of 1.29×10−17M with a broad linear range 10−17–10−8M. The bilayered liposome/AuNP structures on the AuE, GO and rGO do not show any selectivity for DNA detection. The constructed sensor is stable, selective and sensitive with fast response time ensuing its applicability in molecular diagnosis.

Deposition of methylammonium iodide via evaporation - combined kinetic and mass spectrometric study.

Methylammonium lead halide perovskites have recently emerged as a very attractive and versatile material for solar cell production. Several different perovskite fabrication methods can be used though most of them involve either spin coating, evaporation under high vacuum or a combination hereof. In this study we focus on thermal evaporation of methylammonium iodide (MAI), or more specifically, why this process, in terms of a physical vapour deposition, requires such a high deposition pressure to be successful. We use quartz crystal micro balance (QCM) measurements as well as mass spectrometry. The results indicate that MAI has a very low sticking especially if the substrate is held at elevated temperatures and is furthermore observed to evaporate with disproportionation into primarily CH3NH2 and HI. Even when PbCl2 is deposited on the QCM crystal, so that CH3NH3PbI(3−x)Clx perovskite can form, the MAI sticking remains low, possibly due to the requirement that both species be present on the film surface at the same time to form the perovskite. The results provide guidelines for designing a perovskite deposition chamber and additionally fundamental information about MAI evaporation.

Fundamental issues on the influence of starch in amine adsorption by quartz

Apart from being a resource for iron/steel production, the iron oxide mineral, hematite, is used in the paint, cosmetics, and other industries as a pigment. Reverse flotation of quartz from hematite is used extensively in the processing of iron ore containing quartz as the gangue mineral. It has been observed that depression of quartz takes place when excessive starch is used in the reverse flotation of iron ore, thus reducing the grade of the hematite concentrate. In the present work, the reason for the depression of quartz in the presence of excess starch has been investigated. Contact angle, bubble attachment time, quartz crystal micro balance with dissipation (QCM-D), and sum frequency vibrational spectroscopy (SFVS) measurements have been used to examine the interaction between mono ether amine and starch, and molecular dynamics simulation (MDS) was used to visualize the interaction between the amine and starch molecules. On the basis of these measurements it appears that a clathrate interaction takes place in such a way that the starch masks the hydrophobic tail of the mono ether amine, decreasing the contact angle at the quartz surface to 43° from 62° in the presence of excess starch.

Quartz Crystal Micro–Balance Gas Sensor with Ink–Jet Printed Nano–Diamond Sensitive Layer

Abstract the paper presents fabrication and characterization of a Quartz Crystal Microbalance based gas sensor with a diamond powder sensitive layer deposited using the ink-jet printing technique. The sensor was exposed to a low concentration of ammonia, acetone vapors and different levels of humidity. Impedance characteristics close to the natural resonant frequency of 10 MHz were examined. The sensor exhibits significant shifts in serial resonant frequency under different gas environments.

Super Sensitive Mass Detection in Nonlinear Regime

Nonlinear dynamics of a clamped–clamped micro-beam exposed to a two sided electrostatic actuation is investigated to determine super sensitive regions for mass detection. The objective is to investigate the sensitivity of the frequency spectrum of various regions in the phase space to the added mass and force the system to operate in its super sensitive regions by applying an appropriate pulse to its control electrodes. The electrostatic actuation in the top electrode is a combination of a DC, AC and a pulse voltage, the excitation on the lower electrode is only a DC and a pulse voltage. The governing equation of the motion, derived using the Hamiltonian principle, is discretized to an equivalent single-degree of freedom system using the Galerkin method. Depending on the applied electrostatic voltage to the micro-beam, it is demonstrated that the number and types of equilibrium points of the system can be modified. In this study, the level of the DC electrostatic voltage is chosen such a way that the system has three equilibrium points including two centers and a saddle node where the homoclinic orbit originates. According to the reported results, the mass sensing sensitivity depends on the operating orbit; some orbits exhibit considerably higher mass detection sensitivity to the added mass compared to that of a typical quartz crystal micro balance instrument.

Influences of the pH on the adsorption properties of an antimicrobial peptide on titanium surfaces

The adsorption behavior of the Tet-124 antimicrobial peptide and the Tet-124 peptide modified at the C- and N-terminus with the sequence glycine-3,4-dihydroxyphenylalanine-glycine (G-DOPA-G) on titanium surfaces was studied using quartz crystal micro balance with dissipation (QCM-D). At a low pH level (4.75) Tet-124 and Tet-124-G-DOPA-G form rigid layers. This is attributed to the electrostatic interactions of the positively charged lysine and arginine residues in the peptide sequence with the negatively charged titanium oxide layer. At an elevated pH level (6.9) Tet-124 shows a lower mass adsorption at the surface than Tet-124-G-DOPA-G. This is attributed to the interaction of the catechol due to the formation of complexes with the titanium oxide and titanium surface layer. The C terminal and N terminal modification with the sequence G-DOPA-G shows similar adsorption rate and mass adsorption coverage at saturation; however it is presented a more loosely layers on the G-DOPA-G-TeT-124. Fibroblast adhesion and the biocompatibility test of both the surfaces following modification with Tet-124-G-DOPA-G and the titanium alloy control showed similar results. In addition, no changes in the adhesion of E. coli bacteria due to the modification of the surface were detected.

Multilayer films by blending heparin with semisynthetic cellulose sulfates: Physico-chemical characterization and cell responses

Here, we report fabrication of polyelectrolyte multilayers by blending a natural glycosaminoglycan (heparin) with semisynthetic cellulose sulfates as polyanions paired with polycation chitosan. Two types of polyanionic blends were prepared by mixing heparin with either cellulose sulfates (CS) of high (CS2.6) or intermediate (CS1.6) sulfation degree in equal mass ratios. Multilayer growth was monitored by surface plasmon resonance (SPR) and quartz crystal micro balance with dissipation monitoring (QCM-D) where as surface wettability was measured by water contact angle measurements (WCA). Both SPR and QCM-D showed differences in biomolecular mass adsorption and dissipation values for different multilayers and also helped in estimating the hydration levels of layers. WCA indicated arrangement of polyanion and polycation layers within the multilayer systems, weather distinct layers, or more intermingled multilayers were established. Overall physico-chemical characterization data suggested a dominating incorporation of heparin over CS in blend multilayer systems. Biological interactions of these blend multilayers investigated with C2C12 cells also indicated a leading contribution of heparin in the blend systems. This current study suggested that heparin was preferentially incorporated over CS that are highly sulfated and points towards the dominance of carboxylic groups over sulfate groups in interacting with amino groups of chitosan.

S1140102 脂肪酸吸着膜のナノ機械特性と潤滑性との関係に関する研究([S114-01]トライボロジーの基礎と応用(1),機素潤滑設計部門)

Components of a lubricant are divided into base oil and additives. Base oil dominates basic fluid properties of a lubricant. Additives support to improve the lubrication performance of oils. Oiliness additives have the friction decreasing effect due to the formation of the adsorption layer preventing contact of the sliding surfaces. Previous studies about oiliness additives were performed using a single additive in base oil. However, commercial lubricant contains several additives, which interacts each other. The interaction between the additives is not elucidated. In this research, tribological characteristics of adsorption layers of stearic acid, oleic acid and the mixture of both of them were studied for elucidating the interaction of the additives by using a pendulum type friction tester, AFM (Atomic Force Microscopy) and QCM (Quartz Crystal Micro balance). The friction reduction effect of mixed additives was higher than that of single additives. In case of the mixed additives, the ratio of oleic acid and stearic acid was calculated to be 2:3 by each occupied area in the adsorption layer. The relationship between the adsorption property and friction behavior was discussed based on the experimental results.

A Multichannel Chemical Sensing Method Using Single Quartz Resonator and Micro Flow Channel

In this paper, the development of a multi chemical sensing method using a single quartz crystal resonator and micro flow channel has been reported. In the developed device, samples pass through two capacitors that are mounted as sensing parts in a microchannel with a time lag. Connecting the capacitors to the single quartz crystal resonator, one can obtain frequency change ΔF of the resonator as time lag signals depending on the relative permittivity of samples. The optimization of resonator diameter was also carried out in this paper. Using the proposed method, we can realize multi chemical sensing with a single resonator.

Study on multilayer structures prepared from heparin and semi-synthetic cellulose sulfates as polyanions and their influence on cellular response

Multilayer coatings of polycationic chitosan paired with polyanionic semi-synthetic cellulose sulfates or heparin were prepared by the layer-by-layer method. Two different cellulose sulfates (CS) with high (CS2.6) and intermediate (CS1.6) sulfation degree were prepared by sulfation of cellulose. Multilayers were fabricated at pH 4 and the resulting films were characterized by several methods. The multilayer ‘optical’ mass, measured by surface plasmon resonance, showed little differences in the total mass adsorbed irrespective of which polyanion was used. In contrast, ‘acoustic’ mass, calculated from quartz crystal micro balance with dissipation monitoring, showed the lowest mass and dissipation values for CS2.6 (highest sulfation degree) multilayers indicating formation of stiffer layers compared to heparin and CS1.6 layers which led to higher mass and dissipation values. Water contact angle and zeta potential measurements indicated formation of more distinct layers with using heparin as polyanion, while use of CS1.6 and CS2.6 resulted into more fuzzy intermingled multilayers. CS1.6 multilayers significantly supported adhesion and growth of C2C12 cells where as only few cells attached and started to spread initially on CS2.6 layers but favoured long term cell growth. Contrastingly cells adhered and grew poorly on to the layers of heparin. This present study shows that cellulose sulfates are attractive candidates for multilayer formation as potential substratum for controlled cell adhesion. Since a peculiar interaction of cellulose sulfates with growth factors was found during previous studies, immobilization of cellulose sulfate in multilayer systems might be of great interest for tissue engineering applications.

A portable quartz micro balance for physical vapor deposition techniques

A portable quartz crystal micro balance for physical vapor deposition techniques is presented. The device is used for the calibration of evaporators employed in the preparation of thin film systems that are studied in surface science. The design is based upon a portable sample setup, highly versatile and customizable. It can be transported within an ultrahigh vacuum system, stored in a sample garage and be used in front of different evaporators. Details of the setup are described. Finally, the performance of the device is demonstrated and compared to scanning tunneling microscopy measurements.

Study on the Equivalent Circuit of Quartz Crystal Microbalance (QCM) with Material Properties

The quartz crystal micro balances (QCM) principle is simply introduces. LEM model can accurately describe TSM sensors with surface the load, instead of complicated TLM model. The configuration of sensor has pure quality load, liquid load in fluid Newton system, the sticky elastic thin film, and viscoelastic membrane plus half infinite liquid. Two kinds of material properties model prediction deviate with no more than 3% error. The rule of Judging TLM to be the LEM is Zl/Zq<0.1

Homo- and hetero-epitaxial deposition of Au by surface limited redox replacement of Pb underpotentially deposited layer in one-cell configuration

This work reports on homo- and hetero-epitaxial Au deposition realized by surface limited redox replacement (SLRR) of Pb underpotentially deposited (UPD) layer by [AuCl4]− ions in one-cell configuration. An over-stoichiometric amount of deposited Au hinted at by the electrochemical quartz-crystal micro balance (EQCM) kinetic experiments and validated by separate pulse experiments has been attributed to reduction in each SLRR event of a pre-adsorbed layer of [AuCl4]− ions. This phenomenology, known as “spontaneous deposition”, along with strict control over the Pb UPD coverage enables a fine tunable epitaxial Au deposition in the sub-monolayer to monolayer range. After as little as one replacement event on Pt (111) the deposit displays a Pb UPD cyclic voltammetry (CV) curve as would be observed on an Au (111) substrate. High quality epitaxial Au has been grown for up to 40 SLRR events as evidenced by CV and ex situ scanning tunneling microscopy (STM). However, growth of thicker films yields a significant surface roughness evolution of 2.5 times. The thicker deposit features a dendritic structure when viewed via scanning electron microscopy. X-ray photoelectron spectroscopy shows less than 0.1at% Pb in the Au deposit and rules out defect induced roughening. STM results suggest that the surface roughness is likely due to formation of Au islands that grow rapidly in vertical direction and serve eventually as seeds of the dendritic growth transition. Despite its complexity, SLRR of Pb by Au proves to be a viable method for quick and cost effective growth of continuous homo- or hetero-epitaxial Au ultra-thin films.

Experimental Study of Amyloidogenic Protein Adsorption to Supported Lipid Bilayers

The amyloid beta peptide and alpha synuclein are the main proteins associated with Alzheimer's and Parkinson's disease respectively. In both diseases, interactions between the relevant protein and lipid membranes are hypothesized to be important in disease onset and propagation. We have in earlier studies developed methodology to study kinetics of amyloid fibril formation with high reproducibility [1] and showed that membrane composition affects the kinetics of amyloid beta peptide fibril formation [2]. We now focus on the protein-membrane interaction and study adsorption of alpha synuclein and the amyloid beta peptide to supported lipid bilayers using techniques such as quartz crystal micro balance (QCM), surface plasmon resonance (SPR) and neutron reflectometry. We see a large dependence on electrostatics and to be able to characterize the contributing effects we vary pH and salt concentration in the solution to alter the protein net charge and the electrostatic screening. The lipid bilayer is composed of zwitterionic POPC with or without incorporation of anionic DOPS or Cardiolipin, which in a biologically relevant way present molecular net negative charge of one and two respectively.1. E. Hellstrand, B. Boland, D. M. Walsh and S. Linse, Ab aggregation produces highly reproducible kinetic data and occurs by a two-phase process, ACS Chem. Neurosci., 2010, 1, 13-18.2. E. Hellstrand, E. Sparr and S. Linse, Retardation of Abeta Fibril formation by phospholipid vesicles depends on membrane phase behavior, Biophys. J., 2010, 98, 2206-2214.