The present work describes the fabrication, characterization, and optimization of plasma polymerized pyrrole films, PPpy, prepared by continuous wave for application as the adhesion layers of bovine serum albumin (BSA). Plasma conditions used throughout the work produced significant differences in the chemical, physical, and electrochemical properties of the resultant PPpy films. Structural analysis and property characterizations of PPpy were carried out using Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and electrochemical workstation. Surface plasmon resonance spectroscopy was used to investigate the adsorption kinetics of BSA onto PPpy films. Moreover, when immersed in solutions or after BSA adsorption, the differences of electron transfer at the interfaces between the PPpy and the electrolyte solutions were determined by electro impedance spectroscopy. While there is a clear dependence of the protein adsorption affinity on the plasma polymerization condition employed during the film preparation. The relationship between film structure, electrochemical properties, polymer stability in aqueous buffer, and protein binding affinities are discussed.
Immobilization of biomolecules on solid surfaces is often combined with a partial loss of functionality. Therefore, smooth immobilization procedures are urgently required. Most recently, a Concanavalin A–Streptavidin (Con A–SAv) fusion protein was obtained, which allows the design of functionalized interfaces via self‐assembling. The protein was successfully produced in Escherichia coli and the functionality was tested by surface plasmon resonance (SPR) measurements as well as by the mean of reflectometric interference spectroscopy. A re‐generation of the mannan‐coated surfaces, by washing with buffer containing 10% methyl α‐D ‐mannopyranoside, could be demonstrated. This procedure should allow multiple measurements without replacing the chip. Investigation of the functionalized surfaces by atomic force microscopy showed a rather uniform coating with mannan and the fusion protein. In conclusion, the designed Con A–SAv fusion protein can be used as a universal linker between mannan‐coated surfaces and biotinylated biomolecules, e.g. biotinylated antibodies. 相似文献
The adsorption behavior and self-assembly of human plasma fibrinogen (HPF) on binary methyl- and amino-terminated self-assembled monolayers (SAMs) were investigated by atomic force microscopy (AFM). The binary SAMs were fabricated through self-assembly mechanism of organosilane molecules. The height of domains is the domain height is 0.8 ± 0.2 nm from the AFM topographic image. It corresponds to the domain height is 0.8 ± 0.2 nm from the AFM topographic image. It corresponds to the difference between the length of the alkyl chain of octadecyltrichlorosilane (OTS) and that of n-(6-aminohexyl)aminopropyltrimethoxysilane (AHAPS). The fibrinogen solution used ultrapure water as the solvent and its pH was adjusted at 3 and 10. From the AFM results at pH 3, HPF only formed network structures on the OTS domains of the binary SAM at early immersion times, and then the network structures expanded and connected between OTS domains through the AHAPS surface at long immersion times. In this case, a few HPFs are discretely adsorbed on the AHAPS surface. However, HPF is uniformly adsorbed on the binary SAM under the other conditions of pH. 相似文献
We have used a combination of physical diagnostics methods (laser probe, absorption spectroscopy, transmission electron microscopy)
to study an aqueous suspension of silver nanoparticles, formed by laser ablation of a metal target in the atmosphere. We have
established that application of the methods described allows us to obtain the most complete information about the state of
nanosized metal particles in optically transparent media.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 896–901, November–December, 2008. 相似文献
The preparation of very thin (at the scale of a few tens of nanometers) gold films by thermal evaporation and deposition on a solid substrate (glass) remains a key step for the elaboration of transparent and sensitive optical biosensors. We study the influence of the glass surface treatment and its thermal conductivity on the structure and composition of evaporated gold films. Using a combination of atomic force microscopy (AFM), high resolution surface plasmon resonance (SPR) imaging, and X-ray photoelectron spectroscopy (XPS), we demonstrate that the grafting of a layer of long chain mercaptant, using 11-mercaptoundecyltrimethoxysilane (SξSi), prior to gold deposition produces a drastic modification of gold inner and surface textures. A thorough investigation of AFM image topography by 2D wavelet-based segmentation method reveals the flat conical shape of the gold surface grains and their shape invariance with the glass surface chemical treatment. However, this treatment leads to a drastic decrease of the mean size and polydispersity of these grains by a factor of 2, thereby lowering the gold surface roughness. The rationale is that the combination of surface forces and thermal transfer drives the formation of homogeneous and flatter gold films. 相似文献
The interplay between size, shape, mechanical properties, and surface chemistry of nanoparticles orchestrates cellular internalization, toxicity, circulation time, and biodistribution. Therefore, the safety of nanoparticles hinges on our ability to quantify nanoscale physicochemical characteristics. Current characterization tools, due to their limited resolution, are unable to map these properties correlatively at nanoscale. An innovative use of atomic force microscopy‐based techniques, namely nano‐correscopy, overcomes this limitation and offers multiprobe capability to map mechanical (viscous and elastic) and chemical domains of nanoparticles correlatively. The strengths of this approach are demonstrated using polymer composite nanorods: m‐PEG‐PLGA ((m‐PEG–methoxy‐poly (ethylene glycol)‐b‐poly (lactic‐co‐glycolic) acid). Precise distribution of PLGA (monomers of lactide and glycolide) and poly(ethylene glycol) (PEG) polymer across nanorods is identified. The hydrophobic lactide component is found predominantly at the apex, while hydrophilic glycolide and PEG assembled at the body of the nanorods and correlate with a gradient of nanomechanical properties. New knowledge of how both nanochemical domains and nanomechanical properties are distributed across the nanorod will allow elucidating the interactions of nanorods with the proteins and biomolecules in the future, which will directly influence the fate of nanorods in vivo and will guide new synthesis methods. 相似文献
Metal films containing silver and gold layers having different thicknesses were evaporated on glass substrates. Two-beam interference technique was applied to irradiate the surfaces by the fourth harmonic of a pulsed mode Nd:YAG laser. The atomic force microscopical study showed that surface relief grating having a period of 900 nm corresponding to the interference pattern was developed on the metallic films. The modulation amplitude of the laser-induced gratings was increasable by enhancing the number of laser pulses at constant fluence, and a groove depth commensurable with the film thicknesses was generated at the average fluence of 39.5 mJ/cm2 on bimetallic layers. The surface structure was more regular, and the modulation amplitude was larger in case of bimetallic films containing thicker gold layers. The threshold fluences of the phase transitions were determined by numerical temperature model calculations for different metal layer compositions, and a good agreement was found between the calculated and experimentally observed threshold values. The division of the metal stripes into droplets and the development of holes were explained by the melting of the entire metal layers and by the vaporization of silver at higher fluences. The angle-dependent surface plasmon resonance spectroscopy realized in Kretschmann arrangement proved that the laser-induced grating formation was accompanied by the change in the optical thickness and by the modification of the structure of the bimetallic films. Broad side wings appeared on the resonance curves caused by grating-coupling in case of appropriate rotation angle and sufficiently large modulation depth of the grating's grooves, according to our calculations. The coupling on deep gratings developed on bimetallic films containing the thinnest gold layer and on monometallic silver films resulted in separated secondary resonance minimum development. The periodic adherence of native streptavidin on the metallic gratings was detected by tapping mode AFM, and based on the shift of the secondary resonance peak. 相似文献
Tuning the charge transport through a metal-molecule-metal junction by changing the interface properties is widely studied and is of paramount importance for applications in molecular electronic devices. We used current sensing atomic force microscopy (CSAFM) as a tool to study the contact resistance of metal-molecule-metal (MmM) junctions formed by sandwiching self-assembled monolayers (SAMs) of alkanethiols with various end groups (-CH3, -OH and -NH2) between Au(1 1 1) substrates and Au coated AFM tips. The effect of interface chemistry on charge transport through such SAMs with varying end groups was studied in an inert, non-polar liquid (hexadecane) environment. We find that the contact resistances of these MmM junctions vary significantly based on the end group chemistry of the molecules. 相似文献
A conductive tip in an atomic force microscope (AFM) has extended the capability from conventional topographic imaging to electrical surface characterization. The conductive tip acts as a voltage electrode to provide stimuli and monitor electrical surface properties. In this review article, we have organized the AFM electrical techniques based on whether the electrical properties are monitored at the cantilever tip or across the sample. Furthermore, the techniques are organized based on probe detection signal. A number of acronyms are used in the literature, and the more commonly used ones are identified. The principle of each technique is described, and representative applications are presented. A better understanding of the spectrum of techniques should serve as the driver to expand the application of electrical techniques to study interdisciplinary phenomena at the nanoscale. 相似文献
The heterogeneous character of thin gold films prepared by thermal evaporation and the dependence of this heterogeneity on the rate of their deposition must be considered when exploiting their optical properties for biosensor purposes. For instance, the performance of thin gold films for surface plasmon resonance (SPR) biosensors may drastically be degraded if care is not taken to prepare a film with a high fraction of gold (>95%). We use three different models to interpret the SPR response of gold films prepared by thermal evaporation. We show that the interpretation of the SPR curves requires considering both a global heterogeneity of the gold films and a surface roughness. Our conclusions are further corroborated by scanning surface plasmon microscope (SSPM) images of these thin gold films. 相似文献
Understanding electron and ion dynamics is an important task for improving modern energy materials, such as photovoltaic perovskites. These materials usually have delicate nano- and microstructures that influence the device parameters. To resolve detailed structure–function relationships on the relevant micro- and nanometer length scales, the current macroscopic and microscopic measurement techniques are often not sufficient. Here, nanoscale surface photovoltage spectroscopy (nano-SPV) and nanoscale ideality factor mapping (nano-IFM) via time-resolved Kelvin probe force microscopy are introduced. These methods can map nanoscale variations in charge carrier recombination, ion migration, and defects. To show the potential of nano-SPV and nano-IFM, these methods are applied to perovskite samples with different morphologies. The results clearly show an improved uniformity of the SPV and SPV decay distribution within the perovskite films upon passivation and increasing the grain size. Nevertheless, nano-SPV and nano-IFM can still detect local variations in the defect density on these optimized samples, guiding the way for further optimization. 相似文献
Knowledge of the interaction forces between colloidal particles and surfaces is a precondition for understanding the stability of dispersed systems and adhesion phenomena. One of the methods available for direct measurement of surface forces is the atomic force microscope (AFM). Based on this method the so called “colloidal probe technique” was developed more than 10 years ago. Using a micron‐sized particle glued to the end of an AFM cantilever as the force sensor, this technique is predestined for the study of colloidal interactions. In this review we describe the colloidal probe technique and give an overview of its application in the field of adhesion forces. 相似文献
The review describes electrochemical applications of tip-enhanced Raman spectroscopy (TERS). These applications combine the merits of both scanning probe microscopy (SPM) and Raman spectroscopy, which enables us to simultaneously obtain high-resolution images of surface morphology and chemical information under the electrochemical environment. This review, first summarizes the pioneering work done on the TERS systems that operate in liquid and electrochemical environments, and then gives an overview of the typical instrumentation of electrochemical TERS (EC-TERS) based on electrochemical scanning tunneling microscopy (EC-STM). Furthermore, this review summarizes the advancements in EC-TERS studies of events that occur at the interfaces. These include potential dependent structural changes and electrochemical reactions. Finally, we discuss the current issues and future prospects of EC-TERS for microscopic studies of electrochemical interfaces. 相似文献
