J. Strzelecki

Nanomechanics of new materials — AFM and computer modelling studies of trichoptera silk

Caddisfly (Trichopera) can glue diverse material underwater with a silk fiber. This makes it a particularly interesting subject for biomimetcs. Better understanding of silk composition and structure could lead to an adhesive capable to close bleeding wounds or to new biomaterials. However, while spiderweb or silkworm secretion is well researched, caddisfly silk is still poorly understood. Here we report a first nanomechanical analysis of H. Angustipennis caddisfly silk fiber. An Atomic Force Microscope (AFM) imaging shows dense 150 nm bumps on silk surface, which can be identified as one of features responsible for its outstanding adhesive properties. AFM force spectroscopy at the fiber surface showed, among others, characteristic saw like pattern. This pattern is attributed to sacrificial bond stretching and enhances energy dissipation in mechanical deformation. Similarities of some force curves observed on Tegenaria domestica spiderweb and caddisfly silk are also discussed. Steered Molecular Dynamics simulations revealed that the strength of short components of Fib-H HA species molecules, abundant in Trichoptera silk is critically dependent on calcium presence.

Optical properties of metallophthalocyanine compounds thin films

This work contains investigation results of the linear and nonlinear optical properties of metallophthalocyanines (Cu, Co, Zn, and Mg) and metallophthalocyanine chlorides (Al, Ga) thin films which were grown by physical vapor deposition (PVD) technique in high vacuum on transparent (quartz) and semiconductor (silica) substrates. Spectral properties of these films were examined using transmission, SGH and THG technique. Structural properties were investigated by AFM measurements. Transmission spectra were shown a large influence of intermolecular interaction on spectral properties of metallophthalocyanines and metallophthalocyanine chlorides. The influence of films thickness and annealing process of samples on their optical properties were also determined. The thickness dependence was connected with morphology of the film while annealing was caused change in polymorph phase. The measurements of transmission, SHG and THG spectra were allowed to determine optical constant of these films.

Nanopuller-open data acquisition platform for AFM force spectroscopy experiments

Atomic Force Microscope (AFM) is a widely used tool in force spectroscopy studies. Presently, this instrument is accessible from numerous vendors, albeit commercial solutions are expensive and almost always hardware and software closed. Approaches for open setups were published, as with modern low cost and readily available piezoelectric actuators, data acquisition interfaces and optoelectronic components building such force spectroscopy AFM is relatively easy. However, suitable software to control such laboratory made instrument was not released. Developing it in the lab requires significant time and effort. Our Nanopuller software described in this paper is intended to eliminate this obstacle. With only minimum adjustments this program can be used to control and acquire data with any suitable National Instruments universal digital/analog interface and piezoelectric actuator analog controller, giving significant freedom and flexibility in designing force spectroscopy experiment. Since the full code, written in a graphical LabVIEW environment is available, our Nanopuller can be easily customized. In this paper we describe the program and test its performance in controlling different setups. Successful and accurate force curve acquisition for standard samples (single molecules of I27O reference titin polyprotein and DNA as well as red blood cells) is shown.

Pulsed laser deposition (PLD) of hafnium oxide thin films

This work contains the experimental investigation of optical properties of HfO2 (hafnium oxide) thin films grown on quartz and n-type silica substrates by pulsed laser deposition method. Cold pressed powders of hafnium oxide (HfO2 98% - Aldrich Chem. Co.) were used as the target for deposition process. The substrates was heated up to temperature in the range between 200 and 500 °C. Optical properties of the films were investigated by transmittance in the ultra-violet, visible and near infrared range and photoluminescence spectroscopy. We measure the photo-luminescence spectra and dynamics of luminescence process. Optical properties are closely related to the structure of the hafnium oxide thin films.

Effect of ampicillin on adhesive properties of bacteria examined by atomic force microscopy

Discovery of new antibacterial agents requires the development of novel techniques for bacteria surface characterization after treatment with antibiotics. In this study, we investigate the effect of ampicillin at MICs levels on adhesive properties of Gram-positive and Gram-negative bacteria, using atomic force microscopy (AFM). Our results revealed that the treatment leads to changes of bacterial surface properties, especially cell surface roughness. A nanomechanical alteration of the cells led to an increase of adhesive forces and rupture lengths. Changes in adhesive properties are determined not only by the modification of physicochemical cell properties but also by an increase in roughness, leading to an increase of the contact area with a cantilever tip. We discovered that the contribution of non-specific physicochemical interactions in the bacteria attachment to a substrate is not negligible and was significantly influenced by the presence of antibiotic. Ampicillin caused much greater change in the adhesion properties of Bacillus subtilis than Escherichia coli due to the mode of action of β-lactam antibiotic. Adhesion measurements may by a new way to investigate subtle changes of the bacterial surface properties caused by antibiotic, especially those targeting the bacterial cell wall. In contrast to nanoindentation assays, they provide information on adhesive properties of the bacteria surface.

Physical Vapor Deposition technique and its application to thin organometallic films

This work contains description of the Physical Vapor Deposition technique and its application to selected organometallic thin films deposition process. We investigation results of the structural and optical properties of the thin films containing metal (M = Zn, Cu and Al) and bis- or tris(8-hydroxyquinoline). The films were successfully grown by physical vapor deposition (PVD) technique in high vacuum on transparent (quartz) and semiconductor (n-type silicon) substrates kept at room temperature during the deposition process. Selected films were annealed after fabrication in ambient atmosphere for 24 hours at the temperature equal to 50 °C, 100 °C and 150 °C. Spectral properties of these films were examined using classical and time-dependent photoluminescence investigations. Nonlinear optical effects were studied using Third Harmonic Generation and Z-Scan techniques. Structural properties were investigated by optical images and AFM measurements. The Mqn (n = 2 or 3) films exhibit high structural quality regardless of the annealing process, but the stability of the film can be improved by using an appropriate temperature during the annealing process. We find that the optical properties were strictly connected with the morphology and the temperature of annealing process can change the structural as well as optical properties of the films.

Photophysical properties of thin films containing metal and 8-hydroxyquinoline complexes

This work contains investigation results of the structural and optical properties of the thin films containing metal (M = Zn, Cu and Al) and bis- or tris(8-hydroxyquinoline). The films were successfully grown by physical vapor deposition (PVD) technique in high vacuum on transparent (quartz) and semiconductor (n-type silicon) substrates kept at room temperature during the deposition process. Selected films were annealed after fabrication in ambient atmosphere for 24 hours at the temperature equal to 50 °C, 100 °C and 150 °C. Spectral properties of these films were examined using transmission, photoluminescence, SGH and THG technique. The experimental spectra were allowed to determine optical constant of the films. Structural properties were investigated by optical images and AFM measurements. The Mqn (n = 2 or 3) films exhibit high structural quality regardless of the annealing process, but the stability of the film can be improved by using an appropriate temperature during the annealing process. We find that the optical properties were strictly connected with the morphology and the annealing process can significantly change the structural properties of the films.

Structural and optical properties of as-grown and annealed Alq 3 thin films

This work contains investigation results of the structural and optical properties of aluminum (III) tris(8-hydroxyquinoline) - Alq3 thin films. The films were successfully grown by physical vapor deposition (PVD) technique in high vacuum on transparent (quartz) and semiconductor (n-type silica) substrates kept at room temperature during the deposition process. Selected films were annealed after fabrication in ambient atmosphere for 24 hours at the temperature equal to 50°C, 100°C and 150°C. Spectral properties of these films were examined using transmission, photoluminescence, SGH and THG technique. The experimental spectra were allowed to determine optical constant of the films. Structural properties were investigated by AFM measurements. The Alq3 films exhibit high structural quality regardless of the annealing process, but the stability of the film can be improved by using an appropriate temperature during the annealing process. We find that the optical properties were strictly connected with the morphology and the annealing process can significantly change the structural properties of the films.