Performance and characterization of the FinEstBeAMS beamline at the MAX IV Laboratory.

FinEstBeAMS (Finnish-Estonian Beamline for Atmospheric and Materials Sciences) is a multidisciplinary beamline constructed at the 1.5 GeV storage ring of the MAX IV synchrotron facility in Lund, Sweden. The beamline covers an extremely wide photon energy range, 4.5-1300 eV, by utilizing a single elliptically polarizing undulator as a radiation source and a single grazing-incidence plane grating monochromator to disperse the radiation. At photon energies below 70 eV the beamline operation relies on the use of optical and thin-film filters to remove higher-order components from the monochromated radiation. This paper discusses the performance of the beamline, examining such characteristics as the quality of the gratings, photon energy calibration, photon energy resolution, available photon flux, polarization quality and focal spot size.

Strong, Rapid, and Reversible Photochromic Response of Nb Doped TiO2 Nanocrystal Colloids in Hole Scavenging Media.

Understanding photochromicity is essential for developing new means of modulating the optical properties and optical response of materials. Here, we report on the synthesis and exciting new photochromic behavior of Nb5+ doped TiO2 nanoparticle colloids (NCs). We find that, in hole scavenging media, Nb5+ doping significantly improves the photochromic response time of TiO2 nanoparticles. In the infrared regime, Nb-doped TiO2 NCs exhibit 1 order of magnitude faster photoresponse kinetics than the pristine TiO2. Enhanced photochromic response is observed in the visible light regime as well. The transmittance of Nb-doped TiO2 NCs drops to 10% in less than 2 min when irradiated by UV-light in the 500 nm range. The photochromic reaction is fully reversible. The physical origin of the high reaction rate is the high Nb5+ concentration. As a donor dopant, Nb5+ builds up a significant positive charge in the material, which leads to highly efficient electron accumulation during the UV irradiation and results in a rapid photoresponse. EPR experiments identify a new defect type from Nb5+ doping, which alters the physical mechanisms available for transmittance modulation. Our new NCs are economic to synthesize and highly suitable for switchable photochromic applications, e.g., smart windows for modulating visible light and infrared transmittance in built-environments.

Improved antifouling properties and selective biofunctionalization of stainless steel by employing heterobifunctional silane-polyethylene glycol overlayers and avidin-biotin technology.

A straightforward solution-based method to modify the biofunctionality of stainless steel (SS) using heterobifunctional silane-polyethylene glycol (silane-PEG) overlayers is reported. Reduced nonspecific biofouling of both proteins and bacteria onto SS and further selective biofunctionalization of the modified surface were achieved. According to photoelectron spectroscopy analyses, the silane-PEGs formed less than 10 Å thick overlayers with close to 90% surface coverage and reproducible chemical compositions. Consequently, the surfaces also became more hydrophilic, and the observed non-specific biofouling of proteins was reduced by approximately 70%. In addition, the attachment of E. coli was reduced by more than 65%. Moreover, the potential of the overlayer to be further modified was demonstrated by successfully coupling biotinylated alkaline phosphatase (bAP) to a silane-PEG-biotin overlayer via avidin-biotin bridges. The activity of the immobilized enzyme was shown to be well preserved without compromising the achieved antifouling properties. Overall, the simple solution-based approach enables the tailoring of SS to enhance its activity for biomedical and biotechnological applications.

Biofunctional hybrid materials: bimolecular organosilane monolayers on FeCr alloys.

Hybrid organic-inorganic interfaces are the key to functionalization of stainless steel (SS). We present a solution-based deposition method for fabricating uniform bimolecular organosilane monolayers on SS and show that their properties and functionalities can be further developed through site-specific biotinylation. We correlate molecular properties of the interface with its reactivity via surface sensitive synchrotron radiation mediated high-resolution photoelectron spectroscopy (HR-PES) and chemical derivatization (CD), and we demonstrate specific bonding of streptavidin proteins to the hybrid interface. The method facilitates efficient growth of uniform bimolecular organosilane monolayers on SS under ambient conditions without the need to prime the SS surface with vacuum-deposited inorganic buffer layers. The obtained insights into molecular bonding, orientation, and behaviour of surface-confined organofunctional silanes on SS enable a new generic approach to functionalization of SS surfaces with versatile nanomolecular organosilane layers.