Effect of aqueous solution on functional plasma polymerized films

The direct plasma-induced deposition of tri(ethylene glycol) monoallyl ether is reported. RF plasma polymerization of this monomer was carried out under both continuous wave (CW) and pulsed plasma operation. The major focus of this work was optimization of the degree of retention of the C-O-C bonds of the starting monomer during the deposition process. This successfully was accomplished using low RF power during the CW runs and low RF duty cycles during the pulsed plasma experiments. Spectroscopic analysis of the plasma films revealed a strong dependence of film composition on the RF power and duty cycles employed. In particular, an unusually high level of film chemistry compositional control was demonstrated for the pulsed plasma studies, with film composition varying in a steady, progressive fashion with sequential changes in the ratios of plasma on to plasma off times. This film chemistry controllability is demonstrated despite the relatively low volatility of the starting monomer. The utility of this plasma deposition approach in introducing polyethylene oxide (PEO) structures on solid substrates was evaluated via protein adsorption studies. Radiolabeled bovine albumin adsorption was studied on plasma-modified poly(ethylene teraphthalate) (PET) substrates. Dramatic reductions in both initial adsorption and retention of this protein were observed on PET samples having maximal PEO content relative to its adsorption on untreated PET surfaces. Good stability and adhesion of the plasma films to the underlying PET substrates were observed, as evidenced from prolonged immersion of plasma-treated surfaces in aqueous solution. Overall, the results obtained from the present work provide additional support for the utility of one-step plasma process to reduce biological fouling of surfaces via deposition of PEO surface units.

In this research, surface plasmon resonance (SPR) spectroscopy was used for sensing copper ion by combining the SPR with nanocrystalline cellulose modified by hexadecyltrimethylammonium bromide and graphene oxide composite (CTA-NCC/GO) thin film. The binding of Cu2+ on CTA-NCC/GO thin film was monitored by using SPR spectroscopy. By using the obtained SPR curve, detection range, binding affinity, sensitivity, full width at half maximum (FWHM), data accuracy (DA), and signal-to-noise ratio (SNR) have been calculated. The results showed that the sensor detection range was 0.01 until 0.5 ppm, and that it reached a saturation value. Moreover, the resonance angle shift followed the Langmuir isotherm model with a binding affinity constant of 4.075 × 103 M-1. A high sensitivity of 3.271° ppm-1 also was obtained for low Cu2+ concentration ranged from 0.01 to 0.1 ppm. For the FWHM, the lowest value calculated was at 0.08 and 0.1 ppm, which is 3.35°. The DA of the SPR signal consecutively highest at 0.08 and 0.1 ppm. Besides that, the SNR of the SPR signal increases with the Cu2+ concentrations. The CTA-NCC/GO thin film morphological properties were also studied by using atomic force microscopy. The rms roughness values, which were obtained before and after in contact with Cu2+, were 3.51 nm and 2.46 nm, respectively.

Surface plasmon resonance (SPR) spectroscopy is used to follow the swelling and shrinking processes of a polyaniline redox-active polymer; SPR provides a reading signal for the electrochemical stimuli that activate the polymer.

We report in this paper, the utilization of Surface Plasmon Resonance (SPR) spectroscopy to distinct the adsorption type of dye molecules into an Aluminium-doped Zinc Oxide (AZO) mesoporous layer. This was performed in a Kretschmann configuration by measuring the SPR spectra at various incident angles. The SPR spectral dips were then compared with the simulation results calculated on the basis of the transfer-matrix method. There is an agreement between the simulation results and experimental results, which confirm two different kinds of dye adsorption. The first type is pure dye adsorption into the mesoporous layer, while the second type is dye adsorption accompanied by dye deposition on the mesoporous surface.

Analysis of the molecular interaction of glycosylated proteins with rabbit liver asialoglycoprotein receptors using surface plasmon resonance spectroscopy

When using self-assembled monolayers (SAMs) with ionizable functional groups, such as COOH and NH2, the dissociation constant (pKd) of the surface is an important property to know, since it defines the charge density of the surface for a given bulk solution pH. In this study, we developed a method using surface plasmon resonance (SPR) spectroscopy for the direct measurement of the pKd of a SAM surface by combining the ability of SPR to detect the change in mass concentration close to a surface and the shift in ion concentration over the surface as a function of surface charge density. This method was then applied to measure the pKd values of both COOH- and NH2-functionalized SAM surfaces using solutions of CsCl and NaBr salts, respectively, which provided pKd values of 7.4 and 6.5, respectively, based on the bulk solution pH. An analytical study was also performed to theoretically predict the shape of the SPR plots by calculating the excess mass of salt ions over a surface as a function of the difference between the solution pH and surface pKd. The analytical relationships show that the state of surface charge also influences the local hydrogen ion concentration, thus resulting in a substantial local shift in pH at the surface compared to the bulk solution as a function of the difference between the bulk solution pH and the pKd of the surface.

Surface plasmon resonance (SPR) spectroscopy is employed for the study of biotinylated DNA assembly on streptavidin modified gold surfaces for target DNA hybridization. Two immobilization strategies are involved for constructing streptavidin films, namely, (1) physical adsorption on biotin-containing thiol treated surfaces through biotin-streptavidin links and (2) covalent attachment to 11-mercaptoundecanoic acid (MUA) treated surfaces through amine coupling. To understand the structural properties of the streptavidin films, a quartz crystal microbalance with energy dissipation monitoring (QCM-D) is used to monitor the streptavidin immobilization procedures. The simultaneously measured frequency (Deltaf) and dissipation factor (DeltaD) changes, together with the SPR angle shifts (Deltatheta), suggest that the streptavidin film assembled on the biotin-containing surface is highly rigid with a well-ordered structure while the streptavidin film formed through amine coupling is highly dissipative and less structured. The subsequent biotinylated DNA (biotin-DNA) assembly and target hybridization results show that the streptavidin film structure has distinct effects on the biotin-DNA binding amount. On the streptavidin matrix, not only the probe DNA density but also the strand orientation mediated by the streptavidin films has distinct effects on hybridization efficiency. Particularly, the molecularly ordered streptavidin films formed on the biotin-containing surfaces ensure a well-ordered DNA assembly, which in turn allows for a higher efficiency in target DNA capture and for a higher sensitivity in the hybridization analysis when compared to the biotin-DNA assembled on the less structured streptavidin films formed through amine coupling.

Excised damaged base determines the turnover of human N-methylpurine-DNA glycosylase

Cell membrane proteins from Geobacillus thermodenitrificans DSM465 were converted into the adenosine (As) recognition materials by adopting 9-ethyladenine (9-EA) as a print molecule. The converted molecular recognition sites gave the affinity constant of 4.62 × 104 mol–1 dm3 toward As, which was determined by SPR spectroscopy. It was demonstrated that cell membrane proteins from G. thermodenitrificans DSM465 would be one of candidate materials to be converted into molecular recognition materials via an alternative molecular imprinting.

Fabrication of self-assembled protein A monolayer and its application as an immunosensor

We study the potentialities of a two-color Surface Plasmon Resonance (SPR) spectroscopy nanosizer by monitoring the assembling of a colloidal dispersion of citrate stabilized gold nanoparticles (AuNPs) on SiO2 surface. When the AuNPs/water composite's optical density layer is negligible and the electron mean-free path limitation is taken into account in the AuNPs' dielectric constant;s formulation, the surface density σ of the nanoparticle array and the statistical mean size <r> of the nanoparticles can be straightly determined by using two-color SPR spectroscopy in the context of Maxwell's Garnett theory. The optical method, demonstrated experimentally for AuNPs with a nominal mean diameter of 15 nm, can, theoretically, be extended to bigger nanoparticles, based on a simple scaling relation between the extinction cross section of the single nanoparticle σext and the surface density σ. The experimental results, comparable to those obtained by AFM, transmission electron microscopy and dynamic light scattering technique, establish a novel insight on the SPR spectroscopy's potential to accurately characterize nanomaterials.

Nanostructured silicon thin films were deposited by a pulsed plasmaenhanced chemical vapour deposition process using an argon-silane mixture.For each deposition temperature (TS), the plasma modulation was chosen insuch a way that the discharge was switched off just before the onset of powderformation. The optical and electrical properties of the films wereinvestigated as a function of TS and compared to those of films depositedunder the same plasma conditions but with a continuous wave (CW) plasma. Whilethe CW films show a gradual improvement in their properties with increasingTS, a drastic change appears in the optical and electrical properties ofhydrogenated nanostructured silicon (ns-Si:H) films for TS>50 °C. Inparticular, for a deposition temperature of 150 °C a more compactmaterial with a small surface roughness and a high conductivity was obtained.This improvement is correlated to the discharge conditions and particularly tothe small size of the clusters embedded in the deposited film.

Desired wettability has been achieved on highly hydrophobic boron nitride nanotube (BNNT) films using nitrogen/hydrogen (N2/H2) gas plasma treatments under controlled input energies and modes. Both hydrophilicity (contact angle (CA) ∼60°) and superhydrophilicity (CA < 5°) are demonstrated on BNNT films with little change of the surface morphology or the structure of individual BNNTs. The combination of continuous wave and pulse mode (CW+P) plasma shows more effective wettability modification and introduces more amine functional groups than the continuous wave (CW) plasma alone at a given input energy. (Super)hydrophilic/hydrophobic patterns have been created on BNNT films using masked plasma methods. The cell response to BNNT films is investigated for the first time. The proliferation of human primary mammary fibroblasts and a transformed mammary cell line (TXP RFP3) shows that the untreated hydrophobic BNNT films can support the growth of both cell lines, but the plasma treatments greatly enhance (up to ...

This paper presents a novel harmonic-selective clocking scheme that facilitates concurrent downconversion of spectrally distant radio frequency (RF) signals using a single low-frequency local oscillator (LO) in an N-path receiver architecture. The proposed scheme selectively generates LO harmonics aligned with multiple RF bands, enabling simultaneous downconversion without modification of the passive mixer topology. The receiver employs a 4-path passive mixer configuration to enhance harmonic selectivity and provide flexible frequency planning.The architecture is implemented on a printed circuit board (PCB) and validated through comprehensive simulation and experimental measurements under continuous wave and modulated signal conditions. Measured results demonstrate a sensitivity of −55dBm and a conversion gain varying from −2.5dB to −9dB depending on the selected harmonic pair. The receiver’s performance is further corroborated by concurrent (dual band) reception of real-world signals, including a GPS signal centered at 1575 MHz and an LTE signal at 1179 MHz, both downconverted using a single 393 MHz LO. Signal fidelity is assessed via Normalized Mean Square Error (NMSE) and Error Vector Magnitude (EVM), confirming the proposed architecture’s effectiveness in maintaining high-quality signal reception under concurrent multiband operation. The results highlight the potential of harmonic-selective clocking to simplify multiband receiver design for wireless communication and global navigation satellite system (GNSS) applications.

The directional optical loss properties of photonic crystal double heterostructure cavities are analyzed using the three-dimensional finite-difference time-domain method. It is found that these high quality factor cavities are dominated by vertical radiation loss, and the addition of heat-sinking lower substrates exacerbates the vertical loss problem. An alternative heterostructure geometry based on introducing a glide-plane is proposed and is shown to significantly reduce out-of-plane radiation. This new geometry is a promising candidate for building chip-scale edge-emitting photonic crystal lasers operating under continuous wave conditions. Alternative vertical slab structures are investigated, and the plausibility of forming electrically injected photonic crystal lasers is discussed.