scholarly journals Comparative Analysis of Attachment to Chalcopyrite of Three Mesophilic Iron and/or Sulfur-Oxidizing Acidophiles

Minerals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 406 ◽  
Author(s):  
Qian Li ◽  
Baojun Yang ◽  
Jianyu Zhu ◽  
Hao Jiang ◽  
Jiaokun Li ◽  
...  

Adhesion plays an important role in bacterial dissolution of metal sulfides, since the attached cells initiate the dissolution. In addition, biofilms, forming after bacterial attachment, enhance the dissolution. In this study, interactions between initial adhesion force, attachment behavior and copper recovery were comparatively analyzed for Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, and Leptospirillum ferrooxidans during bioleaching of chalcopyrite. The adhesion forces between bacteria and minerals were measured by atomic force microscopy (AFM). L. ferrooxidans had the largest adhesion force and attached best to chalcopyrite, while A. ferrooxidans exhibited the highest bioleaching of chalcopyrite. The results suggest that the biofilm formation, rather than the initial adhesion, is positively correlated with bioleaching efficiency.

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Pei Yu ◽  
Chuanyong Wang ◽  
Jinglin Zhou ◽  
Li Jiang ◽  
Jing Xue ◽  
...  

Zirconia is becoming a prevalent material in dentistry. However, any foreign bodies inserted may provide new niches for the bacteria in oral cavity. The object of this study was to explore the effect of surface properties including surface roughness and hydrophobicity on the adhesion and biofilm formation ofStreptococcus mutans(S. mutans) to zirconia. Atomic force microscopy was employed to determine the zirconia surface morphology and the adhesion forces between theS. mutansand zirconia. The results showed that the surface roughness was nanoscale and significantly different among tested groups (P<0.05): Coarse (23.94±2.52 nm) > Medium (17.00±3.81 nm) > Fine (11.89±1.68 nm). The contact angles of the Coarse group were the highest, followed by the Medium and the Fine groups. Increasing the surface roughness and hydrophobicity resulted in an increase of adhesion forces and early attachment (2 h and 4 h) ofS. mutanson the zirconia but no influence on the further development of biofilm (6 h~24 h). Our findings suggest that the surface roughness in nanoscale and hydrophobicity of zirconia had influence on theS. mutansinitial adhesion force and early attachment instead of whole stages of biofilm formation.


2016 ◽  
Vol 3 (10) ◽  
pp. 160248 ◽  
Author(s):  
X. Jin ◽  
B. Kasal

This study attempts to address the interpretation of atomic force microscopy (AFM) adhesion force measurements conducted on the heterogeneous rough surface of wood and natural fibre materials. The influences of wood surface roughness, tip geometry and wear on the adhesion force distribution are examined by cyclic measurements conducted on wood surface under dry inert conditions. It was found that both the variation of tip and surface roughness of wood can widen the distribution of adhesion forces, which are essential for data interpretation. When a common Si AFM tip with nanometre size is used, the influence of tip wear can be significant. Therefore, control experiments should take the sequence of measurements into consideration, e.g. repeated experiments with used tip. In comparison, colloidal tips provide highly reproducible results. Similar average values but different distributions are shown for the adhesion measured on two major components of wood surface (cell wall and lumen). Evidence supports the hypothesis that the difference of the adhesion force distribution on these two locations was mainly induced by their surface roughness.


2018 ◽  
Vol 9 ◽  
pp. 900-906 ◽  
Author(s):  
Ying Wang ◽  
Yue Shen ◽  
Xingya Wang ◽  
Zhiwei Shen ◽  
Bin Li ◽  
...  

The detection of local dielectric properties is of great importance in a wide variety of scientific studies and applications. Here, we report a novel method for the characterization of local dielectric distributions based on surface adhesion mapping by atomic force microscopy (AFM). The two-dimensional (2D) materials graphene oxide (GO), and partially reduced graphene oxide (RGO), which have similar thicknesses but large differences in their dielectric properties, were studied as model systems. Through direct imaging of the samples with a biased AFM tip in PeakForce Quantitative Nano-Mechanics (PF-QNM) mode, the local dielectric properties of GO and RGO were revealed by mapping their surface adhesion forces. Thus, GO and RGO could be conveniently differentiated. This method provides a simple and general approach for the fast characterization of the local dielectric properties of graphene-based materials and will further facilitate their applications in energy generation and storage devices.


Atmosphere ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 489
Author(s):  
Kohei Ono ◽  
Yuki Mizushima ◽  
Masaki Furuya ◽  
Ryota Kunihisa ◽  
Nozomu Tsuchiya ◽  
...  

A new method, namely, force–distance curve mapping, was developed to directly measure the adhesion force of individual aerosol particles by atomic force microscopy. The proposed method collects adhesion force from multiple points on a single particle. It also takes into account the spatial distribution of the adhesion force affected by topography (e.g., the variation in the tip angle relative to the surface, as well as the force imposed upon contact), thereby enabling the direct and quantitative measurement of the adhesion force representing each particle. The topographic effect was first evaluated by measuring Polystyrene latex (PSL) standard particles, and the optimized method was then applied on atmospherically relevant model dust particles (quartz, ATD, and CJ-1) and inorganic particles (ammonium sulfate and artificial sea salt) to inter-compare the adhesion forces among different aerosol types. The method was further applied on the actual ambient aerosol particles collected on the western coast of Japan, when the region was under the influence of Asian dust plume. The ambient particles were classified into sea salt (SS), silicate dust, and Ca-rich dust particles based on individual particle analysis (micro-Raman or Scanning Electron Microscope/Energy Dispersive X-ray Spectroscopy (SEM-EDX)). Comparable adhesion forces were obtained from the model and ambient particles for both SS and silicate dust. Although dust particles tended to show smaller adhesion forces, the adhesion force of Ca-rich dust particles was larger than the majority of silicate dust particles and was comparable with the inorganic salt particles. These results highlight that the original chemical composition, as well as the aging process in the atmosphere, can create significant variation in the adhesion force among individual particles. This study demonstrates that force–distance curve mapping can be used as a new tool to quantitatively characterize the physical properties of aerosol particles on an individual basis.


2020 ◽  
Vol 4 (3) ◽  
pp. 41
Author(s):  
Illia Dobryden ◽  
Elizaveta Mensi ◽  
Allan Holmgren ◽  
Nils Almqvist

Dispersion and aggregation of nanomagnetite (Fe3O4) and silica (SiO2) particles are of high importance in various applications, such as biomedicine, nanoelectronics, drug delivery, flotation, and pelletization of iron ore. In directly probing nanomagnetite–silica interaction, atomic force microscopy (AFM) using the colloidal probe technique has proven to be a suitable tool. In this work, the interaction between nanomagnetite and silica particles was measured with AFM in aqueous Ca2+ solution at different pH levels. This study showed that the qualitative changes of the interaction forces with pH and Ca2+ concentrations were consistent with the results from zeta-potential measurements. The repulsion between nanomagnetite and silica was observed at alkaline pH and 1 mM Ca2+ concentration, but no repulsive forces were observed at 3 mM Ca2+ concentration. The interaction forces on approach were due to van der Waals and electrical double-layer forces. The good fitting of experimental data to the DLVO model and simulations supported this conclusion. However, contributions from non-DLVO forces should also be considered. It was shown that an increase of Ca2+ concentration from 1 to 3.3 mM led to a less pronounced decrease of adhesion force with increasing pH. A comparison of measured and calculated adhesion forces with a few contact mechanics models demonstrated an important impact of nanomagnetite layer nanoroughness.


2007 ◽  
Vol 1025 ◽  
Author(s):  
Sahar Maghsoudy-Louyeh ◽  
Bernhard R. Tittmann

AbstractThe deposition of films and coatings is sometimes influenced by the presence of small amounts of moisture, which can affect the nucleation and growth processes. It is important to understand the behavior of coating materials–especially in semiconductors–in terms of hydrophilicity/hydrophobicity along with adhesion forces. Our technical approach centers on the use of the atomic force microscope (AFM) which was found to be a reliable tool for studying the surface characteristics of materials. In addition to obtaining topographic information, the AFM can also probe attractive or repulsive forces between the tip and the sample surfaces. In this research, a systematic study of the influence of humidity on the adhesion forces between different AFM tips (silicon and silicon nitride) and both hydrophilic and hydrophobic materials (quartz, calcite, mica, graphite) has been conducted using atomic force microscopy. Several force-distance curves measured by the M5 AFM have been gathered at a series of different humidity levels and different locations on the samples. In this paper, measurements of the adhesion force for hydrophobic and hydrophilic materials versus humidity are presented. The results show that the adhesion force on graphite which has hydrophobic character is independent of humidity variation. Results also show that the adhesion force for fused quartz, mica, and calcite which are hydrophilic materials, change dramatically with increasing humidity due to capillary forces. This is in good agreement with theoretical calculations.


Holzforschung ◽  
2016 ◽  
Vol 70 (12) ◽  
pp. 1115-1123 ◽  
Author(s):  
Christian Ganser ◽  
Katrin Niegelhell ◽  
Caterina Czibula ◽  
Angela Chemelli ◽  
Christian Teichert ◽  
...  

Abstract Xylan-coated cellulose thin films has been investigated by means of atomic force microscopy (AFM) and force mapping experiments. The birch xylan deposition on the film was performed under control by means of a multiple parameter surface plasmon resonance spectroscopy (MP-SPR) under dynamic conditions. The coated films were submitted to AFM in phase imaging mode to force mapping with modified AFM tips (sensitive to hydrophilic OH and hydrophobic CH3 groups) in order to characterize and localize the xylan on the surfaces. At the first glance, a clear difference in the adhesion force between xylan-coated areas and cellulose has been observed. However, these different adhesion forces originate from topography effects, which prevent an unambiguous identification and subsequent localization of the xylan on the cellulosic surfaces.


Author(s):  
Nikolai Mitiurev ◽  
Michael Verrall ◽  
Svetlana Shilobreeva ◽  
Alireza Keshavarz ◽  
Stefan Iglauer

Wettability of sedimentary rock surface is an essential parameter that defines oil recovery and production rates of a reservoir. The discovery of wettability alteration in reservoirs, as well as complications that occur in analysis of heterogeneous sample, such as shale, for instance, have prompted scientists to look for the methods of wettability assessment at nanoscale. At the same time, bulk techniques, which are commonly applied, such as USBM (United States Bureau of Mines) or Amott tests, are not sensitive enough in cases with mixed wettability of rocks as they provide average wettability values of a core plug. Atomic Force Microscopy (AFM) has been identified as one of the methods that allow for measurement of adhesion forces between cantilever and sample surface in an exact location at nanoscale. These adhesion forces can be used to estimate wettability locally. Current research, however, shows that the correlation is not trivial. Moreover, adhesion force measurement via AFM has not been used extensively in studies with geological samples yet. In this study, the adhesion force values of the cantilever tip interaction with quartz inclusion on the shale sample surface, have been measured using the AFM technique. The adhesion force measured in this particular case was equal to the capillary force of water meniscus, formed between the sample surface and the cantilever tip. Experiments were conducted with a SiconG cantilever with (tip radius of 5 nm). The adhesion forces between quartz grain and cantilever tip were equal to 56.5 ± 5 nN. Assuming the surface of interaction to be half spherical, the adhesion force per area was 0.36 ± 0.03 nN/nm2. These measurements and results acquired at nano-scale will thus create a path towards much higher accuracy-wettability measurements and consequently better reservoir-scale predictions and improved underground operations.


Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 900
Author(s):  
Maria Vardaki ◽  
Aida Pantazi ◽  
Ioana Demetrescu ◽  
Marius Enachescu

In this work we present the results of a functional properties assessment via Atomic Force Microscopy (AFM)-based surface morphology, surface roughness, nano-scratch tests and adhesion force maps of TiZr-based nanotubular structures. The nanostructures have been electrochemically prepared in a glycerin + 15 vol.% H2O + 0.2 M NH4F electrolyte. The AFM topography images confirmed the successful preparation of the nanotubular coatings. The Root Mean Square (RMS) and average (Ra) roughness parameters increased after anodizing, while the mean adhesion force value decreased. The prepared nanocoatings exhibited a smaller mean scratch hardness value compared to the un-coated TiZr. However, the mean hardness (H) values of the coatings highlight their potential in having reliable mechanical resistances, which along with the significant increase of the surface roughness parameters, which could help in improving the osseointegration, and also with the important decrease of the mean adhesion force, which could lead to a reduction in bacterial adhesion, are providing the nanostructures with a great potential to be used as a better alternative for Ti implants in dentistry.


Sign in / Sign up

Export Citation Format

Share Document