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The physico-chemical characteristics of wet fibre surfaces and their role in fibre bonding and paper properties have been under debate and research for decades. The gel-likeness of the fibre surfaces has been addressed in many studies but has not been explicitly demonstrated. In this study, the structure of wet beaten kraft pulp fibre surface and its similarity with microfibrillated cellulose (CMF) was shown using helium ion microscopy (HIM) imaging. Beaten kraft fibres and CMF were dried using two mild drying methods to preserve the delicate fibrillated structures. The fibre surface had a strong resemblance with gel-like CMF material. The amount of external fibrillation varied along the fibre length and was often shown to extend tens of micrometers from the fibre surface. The gel-like behaviour of wet fibrillated material was demonstrated using rheological tests. The examined CMF and CNF samples with solids contents of 1.97% and 1.06%, respectively, showed gel-like behaviour. A low gelling point suggests that fibrillated fibre surfaces have the ability to transfer forces at very low consistencies, and that the ability increases as a power function of the solids content. This is assumed to play a remarkable role in increasing inter-fibre adhesion and in transmitting inter-fibre forces within consolidating webs, whether arising from external tensions or internal drying stresses.

The elongation of spherical Au nanoparticles embedded in SiO2 under swift heavy ion (SHI) irradiation is an extensively studied phenomenon. The use of a TEM grid as a substrate facilitates the identification of the same nanoparticle before and after the irradiation. Since the underdensification of SiO2 inside the ion track plays a key role, the elongation is sensitive to the matrix material properties. Therefore, we studied the elongation process of SHI irradiated Au spherical nanoparticles of various diameters (5–80 nm) embedded either in atomic layer deposition (ALD) or plasma-enhanced chemical vapor deposition (PECVD) SiO2. The results show that a different elongation ratio is achieved depending on the particle initial size, ion fluence, and a different SiO2 deposition method. The embedded nanoparticles in ALD SiO2 elongate roughly 100% more than the nanoparticles embedded in PECVD SiO2 at the biggest applied fluence (5×1014ions/cm2). On the other hand, at fluences lower than 1014ions/cm2, nanoparticles elongate slightly more when they are embedded in PECVD SiO2 peerReviewed

In this work hydrogen and oxygen migration and exchange reactions in the atomic layer deposited (ALD) Al2O3 thin films were studied together with hydrogen incorporation by varying deposition parameters. Al2O3 films deposited at low temperatures can contain more than 20 at. % of hydrogen. Both higher temperature and longer purge length decrease the hydrogen and carbon concentrations significantly. In order to track the hydrogen and oxygen movement in the films, heavy water (2H216O) and oxygen-18 enriched water (1H218O) were used as precursors in combination with trimethylaluminium (TMA). Different isotopes of the same element were quantified by means of time-of-flight elastic recoil detection analysis (ToF-ERDA). It was found out that 1H/2H exchange reactions take place even at room temperature if the hydrogen concentration is high enough. On the other hand, oxygen atoms in the films do not migrate notably. peerReviewed

TEMPO-oxidized cellulose nanofibrils (TCNFs) have unique properties, which can be utilised in many application fields from printed electronics to packaging. Visual characterisation of TCNFs has been commonly performed using Scanning Electron Microscopy (SEM). However, a novel imaging technique, Helium Ion Microscopy (HIM), offers benefits over SEM, including higher resolution and the possibility of imaging non-conductive samples uncoated. HIM has not been widely utilized so far, and in this study the capability of HIM for imaging of TCNFs was evaluated. Freeze drying and critical point drying (CPD) techniques were applied to preserve the open fibril structure of the gel-like TCNFs. Both drying methods worked well, but CPD performed better resulting in the specific surface area of 386 m 2 g -1 when compared to 172 m 2 g -1 and 42 m 2 g -1 of freeze dried samples frozen in propane and nitrogen, respectively. HIM imaging of TCNFs was successful but high magnification imaging was challenging because the ion beam tended to degrade the TCNFs. The effect of the imaging parameters on the degradation was studied and an ion dose as low as 0.9 ion per nm 2 was required to prevent the damage. This study points out the differences between the gentle drying methods of TCNFs and demonstrates beam damage during imaging like none previously reported with HIM. The results can be utilized in future studies of cellulose or other biological materials as there is a growing interest for both the HIM technique and bio-based materials.

In this research we introduce a plasmonic nanoparticle based optical biosensor for monitoring of molecular binding events. The sensor utilizes spotted gold nanoparticle arrays as sensing platform. The nanoparticle spots are functionalized with capture DNA sequences complementary to the analyte (target) DNA. Upon incubation with the target sequence, it will bind on the respectively complementary functionalized particle spot. This binding changes the local refractive index, which is detected spectroscopically as the resulting changes of the localized surface plasmon resonance (LSPR) peak wavelength. In order to increase the signal, a small gold nanoparticle label is introduced. The binding can be reversed using chemical means (10 mM HCl). It is demonstrated that multiplexed detection and identification of several fungal pathogen DNA sequences subsequently on one sensor array are possible by this approach. peerReviewed

Atomic layer deposition (ALD) was used to grow TixAlyN and TixAlyC thin films using trimethylaluminum (TMA), titanium tetrachloride and ammonia as precursors. Deposition temperature was varied between 325 °C and 500 °C. Films were also annealed in vacuum and N2-atmosphere at 600–1000 °C. Wide range of characterization methods was used including time-of-flight elastic recoil detection analysis (ToF-ERDA), X-ray diffractometry (XRD), X-ray reflectometry (XRR), Raman spectroscopy, ellipsometry, helium ion microscopy (HIM), atomic force microscopy (AFM) and 4-point probe measurement for resistivity. Deposited films were roughly 100 nm thick and contained mainly desired elements. Carbon, chlorine and hydrogen were found to be the main impurities. peerReviewed

Nanopore technology has been extensively investigated for analysis of biomolecules, and a success story in this field concerns DNA sequencing using a nanopore chip featuring an array of hundreds of biological nanopores (BioNs). Solid-state nanopores (SSNs) have been explored to attain longer lifetime and higher integration density than what BioNs can offer, but SSNs are generally considered to generate higher noise whose origin remains to be confirmed. Here, we systematically study low-frequency (including thermal and flicker) noise characteristics of SSNs measuring 7 to 200 nm in diameter drilled through a 20-nm-thick SiNx membrane by focused ion milling. Both bulk and surface ionic currents in the nanopore are found to contribute to the flicker noise, with their respective contributions determined by salt concentration and pH in electrolytes as well as bias conditions. Increasing salt concentration at constant pH and voltage bias leads to increase in the bulk ionic current and noise therefrom. Changing pH at constant salt concentration and current bias results in variation of surface charge density, and hence alteration of surface ionic current and noise. In addition, the noise from Ag/AgCl electrodes can become predominant when the pore size is large and/or the salt concentration is high. Analysis of our comprehensive experimental results leads to the establishment of a generalized nanopore noise model. The model not only gives an excellent account of the experimental observations, but can also be used for evaluation of various noise components in much smaller nanopores currently not experimentally available. peerReviewed