Lateral force removal of fungal spores to demonstrate how surface properties affect fungal spore retention.

Microbial biofouling on polymer surfaces can lead to their biodeterioration. This may result in deterioration of the surface, leading to cracking and fracturing. Fungal spores from Aspergillus niger 1957, Aspergillus niger 1988 and Aureobasidium pullulans were tested to determine their strength of attachment on three surfaces, p(γ-MPS-co-MMA), p(γ-MPS-co-LMA) and spin-coated poly(methyl methacrylate) (PMMAsc), using lateral force measurements. The results demonstrate that A. niger 1957 and A. niger 1988 spores were most easily removed from the p(γ-MPS-co-MMA) surface, which was the surface with the highest Ra value. The A. niger 1957 and A. pullulans spores were most difficult to remove from the PMMAsc surface, which was the hardest surface. A. niger 1988 spores were the most difficult to remove from p(γ-MPS-co-LMA), the most hydrophobic surface. The results with A. pullulans were difficult to elucidate since the spores bound to all three surfaces and were removed with similar rates of force. The lateral force results demonstrate that spore attachment to a surface is a multi-factorial process, and independent surface and microbial factors influence spore binding. Thus, each environmental scenario needs to be considered on an individual basis, since a solution to one biofouling issue will probably not translate across to other systems. This article is part of the theme issue 'Nanocracks in nature and industry'.

Ferrocenyl-Pyrenes, Ferrocenyl-9,10-Phenanthrenediones, and Ferrocenyl-9,10-Dimethoxyphenanthrenes: Charge-Transfer Studies and SWCNT Functionalization.

The synthesis of 1-Fc- (3), 1-Br-6-Fc- (5 a), 2-Br-7-Fc- (7 a), 1,6-Fc2 - (5 b), 2,7-Fc2 -pyrene (7 b), 3,6-Fc2 -9,10-phenanthrenedione (10), and 3,6-Fc2 -9,10-dimethoxyphenanthrene (12; Fc=Fe(η5 -C5 H4 )(η5 -C5 H5 )) is discussed. Of these compounds, 10 and 12 form 1D or 2D coordination polymers in the solid state. (Spectro)Electrochemical studies confirmed reversible Fc/Fc+ redox events between -130 and 160 mV. 1,6- and 2,7-Substitution in 5 a (E°'=-130 mV) and 7 a (E°'=50 mV) influences the redox potentials, whereas the ones of 5 b and 7 b (E°'=20 mV) are independent. Compounds 5 b, 7 b, 10, and 12 show single Fc oxidation processes with redox splittings between 70 and 100 mV. UV/Vis/NIR spectroelectrochemistry confirmed a weak electron transfer between FeII /FeIII in mixed-valent [5 b]+ and [12]+ . DFT calculations showed that 5 b non-covalently interacts with the single-walled carbon nanotube (SWCNT) sidewalls as proven by, for example, disentangling experiments. In addition, CV studies of the as-obtained dispersions confirmed exohedral attachment of 5 b at the SWCNTs.

Use of spherical particles to understand conidial attachment to surfaces using atomic force microscopy.

Binding of particles and spores to surfaces is a natural phenomenon which is a prerequisite for biofilm formation. Perpendicular force measurements were carried out using atomic force microscopy cantilevers modified with a polystyrene or glass sphere. The attachment of the spheres was tested against glass, PVAc, p(γ-MPSco-MMA), p(γ-MPS-co-LMA), PMMAsc, and silicon surfaces. The polystyrene spheres demonstrated less varied force and strength of attachment measurement to the surfaces than the glass spheres. The force of attachment of the polystyrene spheres was also influenced by mobility of the co-polymer surfaces. Surface wettability did not affect the force of polystyrene or glass sphere attachment. The force measurements of the non-biological spheres were similar to those seen in biological systems with fungal conidia, and this was due to their size, shape, and binding energies. The use of non-biological systems may present an insight into understanding the fundamentals of more complex biological processes.

Diverse surface properties reveal that substratum roughness affects fungal spore binding.

Binding to surfaces by fungal spores is a prerequisite to biofilm formation. The interactions of polytetrafluoroethylene (PTFE), glass, and silicon with three fungal spores, of differing shapes and sizes (Aspergillus niger 1957, Aspergillus niger 1988, and Aureobasidium pullulans), were investigated. A multifractal analysis was conducted to provide quantitative measures of density, dispersion, and clustering of spores on the surfaces. The PTFE, glass, and silicon surfaces presented a range of surface topographies and wettabilities. PTFE was the roughest and most non-wettable surface, whereas silicon was the opposite in terms of both these aspects. The A. niger species were more non-wettable than A. pullulans. Overall, A. niger 1957 attached in higher numbers to PTFE, whereas A. niger 1988 and A. pullulans bound in highest numbers to glass. The results of this work demonstrated that the overall substratum surface roughness influenced spore binding rather than the physicochemical or chemical properties of surfaces or spores.

Crystal structure of (2-acetyl-ferrocen-1-yl)boronic acid.

(2-Acetyl-ferrocen-1-yl)boronic acid, [Fe(C5H5)(C7H8BO3)] or 2-C(O)CH3-1-B(OH)2-Fc [Fc = Fe(η5-C5H3)(η5-C5H5)], crystallizes in the centrosymmetric space group P21/n. The boronic acid functionality inter-acts via intra-molecular hydrogen bonds with the acetyl group and with the -B(OH)2 functionality of an adjacent mol-ecule. The resulting centrosymmetric dimer exhibits an anti-positioning of the ferrocenyl moieties towards the central B2O4 plane. Consequently, an (Rp ,Sp )-, i.e. a meso configuration is present for this dimer. In the crystal, weak C-H⋯O hydrogen bonds consolidate the mol-ecular packing.

Ferrocenyl naphthalenes: substituent- and substitution pattern-depending charge transfer studies.

The synthesis of a series of ferrocenyl-functionalized naphthalenes of type 2-Fc-C10H7 (3a), 1-Fc-2-R-C10H6 (3b, R = OMe; 3c, R = Me; 3d, R = H; 3e, R = CH(O)), 1,1'-(C10H7)2Fc' (4), 1-Br-4-Fc-C10H6 (6a), 1-Br-5-Fc-C10H6 (6b), 1-Br-8-Fc-C10H6 (6c), 2-Br-6-Fc-C10H6 (6d), 1,4-Fc2-C10H6 (7a), 1,5-Fc2-C10H6 (7b), 1,8-Fc2-C10H6 (7c) and 2,6-Fc2-C10H6 (7d) (Fc = Fe(η5-C5H4)(η5-C5H5), Fc' = Fe(η5-C5H4)2) is reported. They are accessible either by the Suzuki-Miyaura or Negishi C,C cross-coupling reaction of FcB(OH)2 (1a) or FcZnCl (1b) with the appropriate bromo-naphthalenes 2a-e and 5a-d, respectively. The molecular structures of 3a-c, 3e, 4, 6b-d and 7a-d in the solid state were determined by single-crystal X-ray diffraction analysis. They show inter- (3b,c,e, 6b,d, 7a) and intramolecular (7c) π-interactions in the form of T-shaped or parallel displaced π arrangements (3c,e, 6b), whereby 3e displays a columnar stacking of the condensed aromatic unit with plane distances of 3.485(5) to 3.525(5) Å. The (spectro)electrochemical behaviour of 3-4 and 6-7 in dichloromethane in the presence of the weakly coordinating anion [B(C6F5)4]- is discussed, showing reversible redox events in the range of -140-150 mV vs. FcH/FcH+. The electrochemical response of 3a-e and 4 depends on the electron-withdrawing and -donating groups present. The redox processes of mono Fc-substituted 6a-d are affected by the naphthalene substitution pattern, which also influences the redox separations ΔE of Fc2-naphthalenes 7a-d, confirming a significant effect of the different electron transfer pathways through the aromatic core. The UV/vis/NIR spectra of mixed-valent [7a,b,d]+ show broad and weak absorptions in the NIR region, allowing a classification as weakly coupled class II systems according to Robin and Day.

Synthesis of Mg and Zn diolates and their use in metal oxide deposition.

The synthesis of complexes [M(OCHMeCH2NMeCH2)2] (5, M = Mg; 7, M = Zn) is described. Treatment of MeHNCH2CH2NMeH (1) with 2-methyloxirane (2) gave diol (HOCHMeCH2NMeCH2)2 (3), which upon reaction with equimolar amounts of MR2 (4, M = Mg, R = Bu; 6, M = Zn, R = Et) gave 5 and 7. The thermal behavior and vapor pressure of 5 and 7 were investigated to show whether they are suited as CVD (= chemical vapor deposition) and/or spin-coating precursors for MgO or ZnO layer formation. Thermogravimetric (TG) studies revealed that 5 and 7 decompose between 80-530 °C forming MgO and ZnO as evidenced by PXRD studies. In addition, TG-MS-coupled experiments were carried out with 7 proving that decomposition occurs by M-O, C-O, C-N and C-C bond cleavages, as evidenced from the detection of fragments such as CH4N+, C2H4N+, C2H5N+, CH2O+, C2H2O+ and C2H3O+. The vapor pressure of 7 was measured at 10.4 mbar at 160 °C, while 5 is non-volatile. The layers obtained by CVD are dense and conformal with a somewhat granulated surface morphology as evidenced by SEM studies. In addition, spin-coating experiments using 5 and 7 as precursors were applied. The corresponding MO layer thicknesses are between 7-140 nm (CVD) or 80 nm and 65 nm (5, 7; spin-coating). EDX and XPS measurements confirm the formation of MgO and ZnO films, however, containing 12-24 mol% (CVD) or 5-9 mol% (spin-coating) carbon. GIXRD studies verify the crystalline character of the deposited layers obtained by CVD and the spin-coating processes.

The effect of surface properties on the strength of attachment of fungal spores using AFM perpendicular force measurements.

Polymeric substrata may be biodegraded by fungal species resulting in damaged, weakened and unsightly materials. This process typically begins with fungal spore attachment to the surface. In order to better understand the processes that precedes a biofouling event, fungal spore attachment to a range of surfaces, was determined using perpendicular force measurements. This was carried out using atomic force microscope cantilevers modified with fungal spores from Aspergillus niger 1957 (5µm diameter, non-wettable, spherical), Aspergillus niger 1988 (5µm diameter non-wettable, spikey) or Aureobasidium pullulans (5µm-10µm sized, wettable, ellipsoidal). The strength of attachment of the spores was determined in combination with seven surfaces (nitric acid cleaned glass, cast poly(methylmethacrylate) sheet [c-PMMA], polytetrafluoroethylene [PTFE], silicon wafers spin coated with poly(3-methacryloxypropyltrimethoxy silane (γ-MPS)-co-methylmethacrylate (MMA)) [p(γ-MPS-co-MMA)], poly (γ-MPS-co-lauryl methacrylate) [p(γ-MPS-co-LMA)] [both in a ratio of 10-90], PMMA dissolved in a solvent [PMMAsc] and silicon wafers). Perpendicular force measurements could not be related to the R(a) values of the surfaces, but surface wettability was shown to have an effect. All three spore types interacted comparably with the surfaces. All spores attached strongly to c-PMMA and glass (wettable surfaces), and weakly to PTFE, (p(γ- MPS-co-LMA)) (non-wettable) and (p(γ-MPS-co-MMA)). Spore shape also affected the strength of attachment. Aureobasidium pullulans spores attached with the widest range of forces whilst A. niger 1957 attached with the smallest. Findings will inform the selection of surfaces for use in environments where biofouling is an important consideration.