Publications by authors named "Gianaurelio Cuniberti"

178 Publications

A nanographene disk rotating a single molecule gear on a Cu(111) surface.

Nanotechnology 2022 Jan 13. Epub 2022 Jan 13.

Institute for Materials Science, Technische Universität Dresden, Hallwachsstr. 3, Dresden, Sachsen, 01062, GERMANY.

We perform molecular dynamics simulations to study the collective rotation of a graphene nanodisk functionalized on its circumference by tert-butylphenyl chemical groups in interaction with a molecule-gear hexa-tert-butylphenylbenzene supported by a Cu(111) surface. The rotational motion can be categorized underdriving, driving and overdriving regimes calculating the locking coefficient of this machinery as a function of external torque applied. Moreover, the rotational friction with the surface of both the phononic and electronic contributions is investigated. It shows that for small size graphene nanodisks the phononic friction is the main contribution, whereas the electronic one dominates for the larger disks putting constrains on the experimental way of achieving the transfer of rotation from a graphene nanodisk to single molecule-gear.
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http://dx.doi.org/10.1088/1361-6528/ac4b4bDOI Listing
January 2022

Graphene Biodevices for Early Disease Diagnosis Based on Biomarker Detection.

ACS Sens 2021 11 25;6(11):3841-3881. Epub 2021 Oct 25.

Leibniz Institute for Solid State and Materials Research Dresden, Dresden D-01171, Germany.

The early diagnosis of diseases plays a vital role in healthcare and the extension of human life. Graphene-based biosensors have boosted the early diagnosis of diseases by detecting and monitoring related biomarkers, providing a better understanding of various physiological and pathological processes. They have generated tremendous interest, made significant advances, and offered promising application prospects. In this paper, we discuss the background of graphene and biosensors, including the properties and functionalization of graphene and biosensors. Second, the significant technologies adopted by biosensors are discussed, such as field-effect transistors and electrochemical and optical methods. Subsequently, we highlight biosensors for detecting various biomarkers, including ions, small molecules, macromolecules, viruses, bacteria, and living human cells. Finally, the opportunities and challenges of graphene-based biosensors and related broad research interests are discussed.
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http://dx.doi.org/10.1021/acssensors.1c01172DOI Listing
November 2021

Multicolor Patterning of 2D Semiconductor Nanoplatelets.

ACS Nano 2021 Oct 19. Epub 2021 Oct 19.

Institute of Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, Dresden 01062, Germany.

Nanocrystal micro/nanoarrays with multiplexed functionalities are of broad interest in the field of nanophotonics, cellular dynamics, and biosensing due to their tunable electrical and optical properties. This work focuses on the multicolor patterning of two-dimensional nanoplatelets (NPLs) two sequential self-assembly and direct electron-beam lithography steps. By using scanning electron microscopy, atomic force microscopy, and fluorescence microscopy, we demonstrate the successful fabrication of fluorescent nanoarrays with a thickness of only two or three monolayers (7-11 nm) and a feature line width of ∼40 nm, which is three to four NPLs wide. To this end, first, large-area thin films of red-emitting CdSe/ZnCdS and green-emitting CdSeS/ZnCdS core/shell NPLs are fabricated based on Langmuir-type self-assembly at the liquid/air interface. By varying the concentration of ligands in the subphase, we investigate the effect of interaction potential on the film's final characteristics to prepare thin superlattices suitable for the patterning step. Equipped with the ability to fabricate a uniform superlattice with a controlled thickness, we next perform nanopatterning on a thin film of NPLs utilizing a direct electron-beam lithography (EBL) technique. The effect of acceleration voltage, aperture size, and e-beam dosage on the nanopattern's resolution and fidelity is investigated for both of the presented NPLs. After successfully optimizing EBL parameters to fabricate single-color nanopatterns, we finally focus on fabricating multicolor patterns. The obtained micro/nanoarrays provide us with an innovative experimental platform to investigate biological interactions as well as Förster resonance energy transfer.
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http://dx.doi.org/10.1021/acsnano.1c05400DOI Listing
October 2021

On-Surface Formation of Cyano-Vinylene Linked Chains by Knoevenagel Condensation.

Chemistry 2021 Dec 21;27(69):17336-17340. Epub 2021 Oct 21.

Center for Advancing Electronics Dresden (cfaed), TU Dresden, 01062, Dresden, Germany.

The rapid development of on-surface synthesis provides a unique approach toward the formation of carbon-based nanostructures with designed properties. Herein, we present the on-surface formation of CN-substituted phenylene vinylene chains on the Au(111) surface, thermally induced by annealing the substrate stepwise at temperatures between 220 °C and 240 °C. The reaction is investigated by scanning tunneling microscopy and density functional theory. Supported by the calculated reaction pathway, we assign the observed chain formation to a Knoevenagel condensation between an aldehyde and a methylene nitrile substituent.
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http://dx.doi.org/10.1002/chem.202103094DOI Listing
December 2021

One-way rotation of a chemically anchored single molecule-rotor.

Nanoscale 2021 Oct 8;13(38):16077-16083. Epub 2021 Oct 8.

Center for Advancing Electronics Dresden, TU Dresden, 01062 Dresden, Germany.

We present the chemical anchoring of a DMBI-P molecule-rotor to the Au(111) surface after a dissociation reaction. At the temperature of 5 K, the anchored rotor shows a sequential unidirectional rotational motion through six defined stations induced by tunneling electrons. A typical voltage pulse of 400 mV applied on a specific location of the molecule causes a unidirectional rotation of 60° with a probability higher than 95%. When the temperature of the substrate increases above 20 K, the anchoring is maintained and the rotation stops being unidirectional and randomly explores the same six stations. Density functional theory simulations confirm the anchoring reaction. Experimentally, the rotation shows a clear threshold at the onset of the C-H stretch manifold, showing that the molecule is first vibrationally excited and later it decays into the rotational degrees of freedom.
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http://dx.doi.org/10.1039/d1nr04583kDOI Listing
October 2021

Applications of Carbon Nanotubes in the Internet of Things Era.

Nanomicro Lett 2021 Sep 11;13(1):191. Epub 2021 Sep 11.

Institute for Materials Science and Max Bergmann Center of Biomaterials, Center for Advancing Electronics Dresden, Technische Universität Dresden, 01069, Dresden, Germany.

The post-Moore's era has boosted the progress in carbon nanotube-based transistors. Indeed, the 5G communication and cloud computing stimulate the research in applications of carbon nanotubes in electronic devices. In this perspective, we deliver the readers with the latest trends in carbon nanotube research, including high-frequency transistors, biomedical sensors and actuators, brain-machine interfaces, and flexible logic devices and energy storages. Future opportunities are given for calling on scientists and engineers into the emerging topics.
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http://dx.doi.org/10.1007/s40820-021-00721-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8435483PMC
September 2021

Selective and self-validating breath-level detection of hydrogen sulfide in humid air by gold nanoparticle-functionalized nanotube arrays.

Nano Res 2021 Sep 2:1-10. Epub 2021 Sep 2.

Institute for Materials Science, Max Bergmann Center of Biomaterials, Technische Universität Dresden, Dresden, 01062 Germany.

We demonstrate the selective detection of hydrogen sulfide at breath concentration levels under humid airflow, using a self-validating 64-channel sensor array based on semiconducting single-walled carbon nanotubes (sc-SWCNTs). The reproducible sensor fabrication process is based on a multiplexed and controlled dielectrophoretic deposition of sc-SWCNTs. The sensing area is functionalized with gold nanoparticles to address the detection at room temperature by exploiting the affinity between gold and sulfur atoms of the gas. Sensing devices functionalized with an optimized distribution of nanoparticles show a sensitivity of 0.122%/part per billion (ppb) and a calculated limit of detection (LOD) of 3 ppb. Beyond the self-validation, our sensors show increased stability and higher response levels compared to some commercially available electrochemical sensors. The cross-sensitivity to breath gases NH and NO is addressed demonstrating the high selectivity to HS. Finally, mathematical models of sensors' electrical characteristics and sensing responses are developed to enhance the differentiation capabilities of the platform to be used in breath analysis applications.

Electronic Supplementary Material: Supplementary material (details on the dielectrophoretic deposition, AuNP functionalization optimization, full range of experimental and model HS sensing response up to 820 ppb, and sensing response to NO gas) is available in the online version of this article at 10.1007/s12274-021-3771-7.
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http://dx.doi.org/10.1007/s12274-021-3771-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8412394PMC
September 2021

Describing chain-like assembly of ethoxygroup-functionalized organic molecules on Au(111) using high-throughput simulations.

Sci Rep 2021 Jul 19;11(1):14649. Epub 2021 Jul 19.

Center for Advancing Electronics Dresden, Technische Universität Dresden, 01062, Dresden, Germany.

Due to the low corrugation of the Au(111) surface, 1,4-bis(phenylethynyl)-2,5-bis(ethoxy)benzene (PEEB) molecules can form quasi interlocked lateral patterns, which are observed in scanning tunneling microscopy experiments at low temperatures. We demonstrate a multi-dimensional clustering approach to quantify the anisotropic pair-wise interaction of molecules and explain these patterns. We perform high-throughput calculations to evaluate an energy function, which incorporates the adsorption energy of single PEEB molecules on the metal surface and the intermolecular interaction energy of a pair of PEEB molecules. The analysis of the energy function reveals, that, depending on coverage density, specific types of pattern are preferred which can potentially be exploited to form one-dimensional molecular wires on Au(111).
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http://dx.doi.org/10.1038/s41598-021-93724-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8290052PMC
July 2021

Applications of 2D-Layered Palladium Diselenide and Its van der Waals Heterostructures in Electronics and Optoelectronics.

Nanomicro Lett 2021 Jun 14;13(1):143. Epub 2021 Jun 14.

Institute for Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, 01069, Dresden, Germany.

The rapid development of two-dimensional (2D) transition-metal dichalcogenides has been possible owing to their special structures and remarkable properties. In particular, palladium diselenide (PdSe) with a novel pentagonal structure and unique physical characteristics have recently attracted extensive research interest. Consequently, tremendous research progress has been achieved regarding the physics, chemistry, and electronics of PdSe. Accordingly, in this review, we recapitulate and summarize the most recent research on PdSe, including its structure, properties, synthesis, and applications. First, a mechanical exfoliation method to obtain PdSe nanosheets is introduced, and large-area synthesis strategies are explained with respect to chemical vapor deposition and metal selenization. Next, the electronic and optoelectronic properties of PdSe and related heterostructures, such as field-effect transistors, photodetectors, sensors, and thermoelectric devices, are discussed. Subsequently, the integration of systems into infrared image sensors on the basis of PdSe van der Waals heterostructures is explored. Finally, future opportunities are highlighted to serve as a general guide for physicists, chemists, materials scientists, and engineers. Therefore, this comprehensive review may shed light on the research conducted by the 2D material community.
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http://dx.doi.org/10.1007/s40820-021-00660-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8203759PMC
June 2021

Multiscale Modeling Strategy of 2D Covalent Organic Frameworks Confined at an Air-Water Interface.

ACS Appl Mater Interfaces 2021 Jun 26;13(22):26411-26420. Epub 2021 May 26.

Institute for Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, 01062 Dresden, Germany.

Two-dimensional covalent organic frameworks (2D COFs) have attracted attention as versatile active materials in many applications. Recent advances have demonstrated the synthesis of monolayer 2D COF via an air-water interface. However, the interfacial 2D polymerization mechanism has been elusive. In this work, we have used a multiscale modeling strategy to study dimethylmethylene-bridged triphenylamine building blocks confined at the air-water interface to form a 2D COF via Schiff-base reaction. A synergy between the computational investigations and experiments allowed the synthesis of a 2D-COF with one of the linkers considered. Our simulations complement the experimental characterization and show the preference of the building blocks to be at the interface with a favorable orientation for the polymerization. The air-water interface is shown to be a key factor to stabilize a flat conformation when a dimer molecule is considered. The structural and electronic properties of the monolayer COFs based on the two monomers are calculated and show a semiconducting nature with direct bandgaps. Our strategy provides a first step toward the polymerization of 2D COFs at air-water interfaces capturing the initial steps of the synthesis up to the prediction of electronic properties of the 2D material.
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http://dx.doi.org/10.1021/acsami.1c05967DOI Listing
June 2021

Olfactory Perception in Relation to the Physicochemical Odor Space.

Brain Sci 2021 Apr 28;11(5). Epub 2021 Apr 28.

Institute for Materials Science, Technische Universität Dresden, 01062 Dresden, Germany.

A growing body of research aims at solving what is often referred to as the in olfactory perception. Although computational efforts have made it possible to predict perceptual impressions from the physicochemical space of odors, studies with large psychophysical datasets from non-experts remain scarce. Following previous approaches, we developed a physicochemical odor space using 4094 molecular descriptors of 1389 odor molecules. For 20 of these odors, we examined associations with perceived pleasantness, intensity, odor quality and detection threshold, obtained from a dataset of 2000 naïve participants. Our results show significant differences in perceptual ratings, and we were able to replicate previous findings on the association between perceptual ratings and the first dimensions of the physicochemical odor space. However, the present analyses also revealed striking interindividual variations in perceived pleasantness and intensity. Additionally, interactions between pleasantness, intensity, and olfactory and trigeminal qualitative dimensions were found. To conclude, our results support previous findings on the relation between structure and perception on the group level in our sample of non-expert raters. In the challenging task to relate olfactory stimulus and percept, the physicochemical odor space can serve as a reliable and helpful tool to structure the high-dimensional space of olfactory stimuli. Nevertheless, human olfactory perception in the individual is not an analytic process of molecule detection alone, but is part of a holistic integration of multisensory inputs, context and experience.
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http://dx.doi.org/10.3390/brainsci11050563DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8146962PMC
April 2021

Thermoelectric Energy Harvesting from Single-Walled Carbon Nanotube Alkali-Activated Nanocomposites Produced from Industrial Waste Materials.

Nanomaterials (Basel) 2021 Apr 23;11(5). Epub 2021 Apr 23.

Institute of Construction Materials, Faculty of Civil Engineering, Dresden University of Technology, 01069 Dresden, Germany.

A waste-originated one-part alkali-activated nanocomposite is introduced herein as a novel thermoelectric material. For this purpose, single-walled carbon nanotubes (SWCNTs) were utilized as nanoinclusions to create an electrically conductive network within the investigated alkali-activated construction material. Thermoelectric and microstructure characteristics of SWCNT-alkali-activated nanocomposites were assessed after 28 days. Nanocomposites with 1.0 wt.% SWCNTs exhibited a multifunctional behavior, a combination of structural load-bearing, electrical conductivity, and thermoelectric response. These nanocomposites (1.0 wt.%) achieved the highest thermoelectric performance in terms of power factor (PF), compared to the lower SWCNTs' incorporations, namely 0.1 and 0.5 wt.%. The measured electrical conductivity () and Seebeck coefficient () were 1660 S·m and 15.8 µV·K, respectively, which led to a power factor of 0.414 μW·m·K. Consequently, they have been utilized as the building block of a thermoelectric generator (TEG) device, which demonstrated a maximum power output () of 0.695 µW, with a power density (PD) of 372 nW·m, upon exposure to a temperature gradient of 60 K. The presented SWCNT-alkali-activated nanocomposites could establish the pathway towards waste thermal energy harvesting and future sustainable civil engineering structures.
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http://dx.doi.org/10.3390/nano11051095DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8145496PMC
April 2021

Coexistence of fluorescent strains in millifluidic droplet reactors.

Lab Chip 2021 04;21(8):1492-1502

Institute for Materials Science, Max Bergmann Center of Biomaterials, Technische Universität Dresden, 01062 Dresden, Germany. and Helmholtz-Zentrum Dresden Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328 Dresden, Germany.

Understanding competition and cooperation within microbiota is of high fundamental and clinical importance, helping to comprehend species' evolution and biodiversity. We co-encapsulated and cultured two isogenic Escherichia coli strains expressing blue (BFP) and yellow (YFP) fluorescent proteins into numerous emulsion droplets and quantified their growth by employing fluorescence measurements. To characterize and compare the bacterial growth kinetics and behavior in mono and co-culture, we compared the experimental observations with predictions from a simple growth model. Varying the initial ratio (R0) of both cell types injected, we observed a broad landscape from competition to cooperation between both strains in their confined microenvironments depending on start frequency: from a nearly symmetric situation at R0 = 1, up to the domination of one subpopulation when R0 ≫ 1 (or R0 ≪ 1). Due to competition between the strains, their doubling times and final biomass ratios (R1) continuously deviate from the monoculture behavior. The correlation map of the two strains' doubling times reveals that the R0 is one of the critical parameters affecting the competitive interaction between isogenic bacterial strains. Thanks to this strategy, different species of bacteria can be monitored simultaneously in real-time. Further advantages include high statistical output, unaffected bacteria growth, and long-time measurements in a well-mixed environment. We expect that the millifluidic droplet-based reactor can be utilized for practical clinical applications, such as bacterial antibiotic resistance and enzyme reaction kinetics studies.
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http://dx.doi.org/10.1039/d0lc01204aDOI Listing
April 2021

Impact of surface charge on the motion of light-activated Janus micromotors.

Eur Phys J E Soft Matter 2021 Mar 23;44(3):39. Epub 2021 Mar 23.

Helmholtz-Zentrum Dresden-Rossendorf e.V., Institute of Radiopharmaceutical Cancer Research, Bautzner Landstrasse 400, 01328, Dresden, Germany.

Control over micromotors' motion is of high relevance for lab-on-a-chip and biomedical engineering, wherein such particles encounter complex microenvironments. Here, we introduce an efficient way to influence Janus micromotors' direction of motion and speed by modifying their surface properties and those of their immediate surroundings. We fabricated light-responsive Janus micromotors with positive and negative surface charge, both driven by ionic self-diffusiophoresis. These were used to observe direction-of-motion reversal in proximity to glass substrates for which we varied the surface charge. Quantitative analysis allowed us to extract the dependence of the particle velocity on the surface charge density of the substrate. This constitutes the first quantitative demonstration of the substrate's surface charge on the motility of the light-activated diffusiophoretic motors in water. We provide qualitative understanding of these observations in terms of osmotic flow along the substrate generated through the ions released by the propulsion mechanism. Our results constitute a crucial step in moving toward practical application of self-phoretic artificial micromotors.
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http://dx.doi.org/10.1140/epje/s10189-021-00008-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7987638PMC
March 2021

Determining the Diffusion Coefficient of Lithium Insertion Cathodes from GITT measurements: Theoretical Analysis for low Temperatures*.

Chemphyschem 2021 May 3;22(9):885-893. Epub 2021 May 3.

Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, 01062, Dresden, Germany.

Accurate knowledge of transport properties of Li-insertion materials in application-relevant temperature ranges is of crucial importance for the targeted optimization of Li-ion batteries (LIBs). Galvanostatic intermittent titration technique (GITT) is a widely applied method to determine Li-ion diffusion coefficients of electrode materials. The well-known calculation formulas based on Weppner's and Huggins' approach, imply a square-root time dependence of the potential during a GITT pulse. Charging the electrochemical double layer capacitance at the beginning of a GITT pulse usually takes less than one second. However, at lower temperatures down to -40 °C, the double layer charging time strongly increases due to an increase of the charge transfer resistance. The charging time can become comparable with the pulse duration, impeding the conventional GITT diffusion analysis. We propose a model to describe the potential change during a galvanostatic current pulse, which includes an initial, relatively long-lasting double layer charging, and analyze the accuracy of the lithium diffusion coefficient, derived by using the Weppner-Huggins method within a suitably chosen time interval of the pulse. Effects leading to an inaccurate determination of the diffusion coefficient are discussed and suggestions to improve GITT analyses at low temperature are derived.
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http://dx.doi.org/10.1002/cphc.202001025DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8252744PMC
May 2021

Investigating a Combined Stochastic Nucleation and Molecular Dynamics-Based Equilibration Approach for Constructing Large-Scale Polycrystalline Films.

J Chem Theory Comput 2021 Feb 12;17(2):1266-1275. Epub 2021 Jan 12.

Dresden Center for Computational Materials Science, Technische Universität Dresden, 01062 Dresden, Germany.

The morphology of small-molecule organic semiconducting materials can vary from single crystals via polycrystalline films with varying grain sizes to amorphous structures, depending on the process conditions. This structural variety affects the electronic properties and, thus, the performance of organic electronic devices. A nucleation-equilibration approach is investigated, whose focus is on the construction of morphologies with controlled variations in the average grain size. Its computational requirements are low because nucleation is purely based on geometrical considerations, thus allowing the construction of model systems of experimentally relevant sizes. Its application is demonstrated for C and pentacene by generating single-component films that vary from amorphous to crystalline structures. It is further generalized to two-component films and applied to C: pentacene blends as well as dilute n-doped C structures. When combined with electronic structure calculations in the future, the nucleation-equilibration approach can offer insights into the impact of polycrystallinity on electronic and charge-transport properties in the absence of any knowledge about the growth mechanism and for a broad set of systems.
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http://dx.doi.org/10.1021/acs.jctc.0c01196DOI Listing
February 2021

Predicting the bulk modulus of single-layer covalent organic frameworks with square-lattice topology from molecular building-block properties.

Nanoscale 2021 Jan;13(2):1077-1085

Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, 01062 Dresden, Germany. and Dresden Center for Computational Materials Science (DCMS), TU Dresden, 01062 Dresden, Germany.

Two-dimensional Covalent Organic Frameworks (2D COFs) have attracted a lot of interest because of their potential for a broad range of applications. Different combinations of their molecular building blocks can lead to new materials with different physical and chemical properties. In this study, the elasticity of different single-layer tetrabenzoporphyrin (H2-TBPor) and phthalocyanine (H2-Pc) based 2D COFs is numerically investigated using a density-functional based tight-binding approach. Specifically, we calculate the 2D bulk modulus and the equivalent spring constants of the respective molecular building-blocks. Using a spring network model we are able to predict the 2D bulk modulus based on the properties of the isolated molecules. This provides a path to optimize elastic properties of 2D COFs.
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http://dx.doi.org/10.1039/d0nr07666jDOI Listing
January 2021

Determination of the Entire Stent Surface Area by a New Analytical Method.

Materials (Basel) 2020 Dec 10;13(24). Epub 2020 Dec 10.

Fraunhofer Institute for Ceramic Technologies and Systems IKTS, Maria-Reiche-Strasse 2, 01109 Dresden, Germany.

Stenting is a widely used treatment procedure for coronary artery disease around the world. Stents have a complex geometry, which makes the characterization of their corrosion difficult due to the absence of a mathematical model to calculate the entire stent surface area (ESSA). Therefore, corrosion experiments with stents are mostly based on qualitative analysis. Additionally, the quantitative analysis of corrosion is conducted with simpler samples made of stent material instead of stents, in most cases. At present, several methods are available to calculate the stent outer surface area (SOSA), whereas no model exists for the calculation of the ESSA. This paper presents a novel mathematical model for the calculation of the ESSA using the SOSA as one of the main parameters. The ESSA of seven magnesium alloy stents (MeKo Laser Material Processing GmbH, Sarstedt, Germany) were calculated using the developed model. The calculated SOSA and ESSA for all stents are 33.34%(±0.26%) and 111.86 mm (±0.85 mm), respectively. The model is validated by micro-computed tomography (micro-CT), with a difference of 12.34% (±0.46%). The value of corrosion rates calculated using the ESSA computed with the developed model will be 12.34% (±0.46%) less than that of using ESSA obtained by micro-CT.
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http://dx.doi.org/10.3390/ma13245633DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7764317PMC
December 2020

STM induced manipulation of azulene-based molecules and nanostructures: the role of the dipole moment.

Nanoscale 2020 Dec;12(48):24471-24476

Center for Advancing Electronics Dresden, TU Dresden, 01062 Dresden, Germany.

Among the different mechanisms that can be used to drive a molecule on a surface by the tip of a scanning tunneling microscope at low temperature, we used voltage pulses to move azulene-based single molecules and nanostructures on Au(111). Upon evaporation, the molecules partially cleave and form metallo-organic dimers while single molecules are very scarce, as confirmed by simulations. By applying voltage pulses to the different structures under similar conditions, we observe that only one type of dimer can be controllably driven on the surface, which has the lowest dipole moment of all investigated structures. Experiments under different bias and tip height conditions reveal that the electric field is the main driving force of the directed motion. We discuss the different observed structures and their movement properties with respect to their dipole moment and charge distribution on the surface.
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http://dx.doi.org/10.1039/d0nr06809hDOI Listing
December 2020

Nanosensor-Based Real-Time Monitoring of Stress Biomarkers in Human Saliva Using a Portable Measurement System.

ACS Sens 2020 12 3;5(12):4081-4091. Epub 2020 Dec 3.

Institute for Materials Science, Max Bergmann Center for Biomaterials, Technische Universität Dresden, 01069 Dresden, Germany.

Small molecules with no or little charge are considered to have minimal impact on signals measured by field effect transistor (FET) sensors. This fact typically excludes steroids from the family of analytes, detected by FETs. We present a portable multiplexed platform based on an array of nanowire sensors for label-free monitoring of daytime levels of the stress hormone cortisol in saliva samples, obtained from multiple donors. To achieve an effective quantification of the cortisol with FETs, we rely on the specific DNA aptamer sequences as receptors, bringing the complex "target-receptor" closer to the nanowire surface. Upon binding, cortisol induces conformational changes of negatively charged aptamers, wrapping it into a close proximity to the silicon nanowires, to efficiently modulate their surface potential. Thus, the sensors allow for a real-time assessment of the steroid biomarkers at low nanomolar concentration. The measurement platform is designed in a building-block concept, consisting of a modular measuring unit and a customizable biochip board, and operates using a complementary metal-oxide-semiconductor-integrated multiplexer. The platform is capable of continuous and simultaneous measurement of samples from multiple patients. Cortisol levels detected with the presented platform agreed well with the results obtained with a commercial high-sensitivity immunoassay.
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http://dx.doi.org/10.1021/acssensors.0c02267DOI Listing
December 2020

Comparative Studies of Light-Responsive Swimmers: Janus Nanorods versus Spherical Particles.

Langmuir 2020 Oct 14;36(42):12504-12512. Epub 2020 Oct 14.

Institute of Materials Science and Ion Beam Research, Helmholtz Center Dresden Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany.

The shape of objects has a strong influence on their dynamics. Here, we present comparative studies of two different motile objects, spherical Ag/AgCl Janus particles and polystyrene Janus nanorods, that move due to an ionic self-diffusiophoretic propulsion mechanism when exposed to blue light. In this paper, we propose a method to fabricate Janus rodlike particles with high aspect ratios and hemispherical tip shapes. The inherent asymmetry due to the ratio between capped and uncapped parts of the particles as well as the shape anistropy of Janus nanorods enables imaging and quantification of rotational dynamics. The dynamics of microswimmers are compared in terms of velocities and diffusion coefficients. We observe that despite a small amount of the Ag/AgCl reagent on the surface of rodlike objects, these new Janus micromotors reveal high motility in pure water. While the velocities of spherical particles reach 4.2 μm/s, the single rodlike swimmers reach 1.1 μm/s, and clusters reach 1.6 μm/s. The effect of suppressed rotational diffusion is discussed as one of the reasons for the increased velocities. These Janus micro- and nanomotors hold the promise for application in light-controlled propulsion transport.
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http://dx.doi.org/10.1021/acs.langmuir.0c01913DOI Listing
October 2020

Synthesis of Vinylene-Linked Two-Dimensional Conjugated Polymers via the Horner-Wadsworth-Emmons Reaction.

Angew Chem Int Ed Engl 2020 Dec 22;59(52):23620-23625. Epub 2020 Oct 22.

Chair of Molecular Functional Materials, Center for Advancing Electronics Dresden (cfaed) and Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, 01062, Dresden, Germany.

In this work, we demonstrate the first synthesis of vinylene-linked 2D CPs, namely, 2D poly(phenylenequinoxalinevinylene)s 2D-PPQV1 and 2D-PPQV2, via the Horner-Wadsworth-Emmons (HWE) reaction of C -symmetric 1,4-bis(diethylphosphonomethyl)benzene or 4,4'-bis(diethylphosphonomethyl)biphenyl with C -symmetric 2,3,8,9,14,15-hexa(4-formylphenyl)diquinoxalino[2,3-a:2',3'-c]phenazine as monomers. Density functional theory (DFT) simulations unveil the crucial role of the initial reversible C-C single bond formation for the synthesis of crystalline 2D CPs. Powder X-ray diffraction (PXRD) studies and nitrogen adsorption-desorption measurements demonstrate the formation of proclaimed crystalline, dual-pore structures with surface areas of up to 440 m  g . More importantly, the optoelectronic properties of the obtained 2D-PPQV1 (E =2.2 eV) and 2D-PPQV2 (E =2.2 eV) are compared with those of cyano-vinylene-linked 2D-CN-PPQV1 (E =2.4 eV) produced by the Knoevenagel reaction and imine-linked 2D COF analog (2D-C=N-PPQV1, E =2.3 eV), unambiguously proving the superior conjugation of the vinylene-linked 2D CPs using the HWE reaction.
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http://dx.doi.org/10.1002/anie.202010398DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7814668PMC
December 2020

Interactions of Long-Chain Polyamines with Silica Studied by Molecular Dynamics Simulations and Solid-State NMR Spectroscopy.

Langmuir 2020 10 24;36(39):11600-11609. Epub 2020 Sep 24.

Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, 01062 Dresden, Germany.

The investigation of molecular interactions between silica phases and organic components is crucial for elucidating the main steps involved in the biosilica mineralization process. In this respect, the structural characterization of the organic/inorganic interface is particularly useful for a deeper understanding of the dominant mechanisms of biomineralization. In this work, we have investigated the interaction of selectively C- and N-labeled atoms of organic long-chain polyamines (LCPAs) with Si-labeled atoms of a silica layer at the molecular level. In particular, silica/LCPA nanocomposites were analyzed by solid-state NMR spectroscopy in combination with all-atom molecular dynamics simulations. Solid-state NMR experiments allow the determination of Si-N and Si-C internuclear distances, providing the parameters for direct verification of atomistic simulations. Our results elucidate the relevant molecular conformations as well as the nature of the interaction between the LCPA and a silica substrate. Specifically, distances and second moments suggest a picture compatible with (i) LCPA completely embedded in the silica phase and (ii) the charged amino groups located in close vicinity of silanol groups.
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http://dx.doi.org/10.1021/acs.langmuir.0c02157DOI Listing
October 2020

Electrochemical detection of ascorbic acid in artificial sweat using a flexible alginate/CuO-modified electrode.

Mikrochim Acta 2020 08 27;187(9):520. Epub 2020 Aug 27.

Institute for Materials Science and Max Bergmann Center for Biomaterials, Technische Universität Dresden, Dresden, Germany.

A flexible sensor is presented for electrochemical detection of ascorbic acid in sweat based on single-step modified gold microelectrodes. The modification consists of electrodeposition of alginate membrane with trapped CuO nanoparticles. The electrodes are fabricated at a thin polyimide support and the soft nature of the membrane can withstand mechanical stress beyond requirements for skin monitoring. After characterization of the membrane via optical and scanning electron microscopy and cyclic voltammetry, the oxidative properties of CuO are exploited toward ascorbic acid for amperometric measurement at micromolar levels in neutral buffer and acidic artificial sweat, at ultralow applied potential (- 5 mV vs. Au pseudo-reference electrode). Alternatively, measurement of the horizontal shift of redox peaks by cyclic voltammetry is also possible. Obtaining a limit of detection of 1.97 μM, sensitivity of 0.103 V log (μM) of peak shift, and linear range of 10-150 μM, the effect of possible interfering species present in sweat is minimized, with no observable cross-reaction, thus maintaining a high degree of selectivity despite the absence of enzymes in the fabrication scheme. With a lateral flow approach for sample delivery, repeated measurements show recovery in few seconds, with relative standard deviation of about 20%, which can serve to detect increased loss or absence of vitamin, and yet be improved in future by optimized device designs. This sensor is envisioned as a promising component of wearable devices for e.g. non-invasive monitoring of micronutrient loss through sweat, comprising features of light weight, low cost, and easy fabrication needed for such application. Graphical Abstract Schematic depiction of the cyclic voltammetry signal change as the sweat flows over the sensor surface.
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http://dx.doi.org/10.1007/s00604-020-04510-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7452922PMC
August 2020

Transmitting Stepwise Rotation among Three Molecule-Gear on the Au(111) Surface.

J Phys Chem Lett 2020 Aug 11;11(16):6892-6899. Epub 2020 Aug 11.

CEMES, Université de Toulouse, CNRS, 31055 Toulouse, France.

The realization of a train of molecule-gears working under the tip of a scanning tunneling microscope (STM) requires a stable anchor of each molecule to the metal surface. Such an anchor can be promoted by a radical state of the molecule induced by a dissociation reaction. Our results, rationalized by density functional theory calculations, reveal that such an open radical state at the core of star-shaped pentaphenylcyclopentadiene (PPCP) favors anchoring. Furthermore, to allow the transmission of motion by STM manipulation, the molecule-gears should be equipped with specific groups facilitating the tip-molecule interactions. In our case, a -butyl group positioned at one tooth end of the gear benefits both the tip-induced manipulation and the monitoring of rotation. With this optimized molecule, we achieve reproducible and stepwise rotations of the single gears and transmit rotations for up to three interlocked units.
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http://dx.doi.org/10.1021/acs.jpclett.0c01747DOI Listing
August 2020

Role of Exchange Interactions in the Magnetic Response and Intermolecular Recognition of Chiral Molecules.

Nano Lett 2020 10 2;20(10):7077-7086. Epub 2020 Sep 2.

Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, 01062 Dresden, Germany.

The physical origin of the so-called chirality-induced spin selectivity (CISS) effect has puzzled experimental and theoretical researchers over the past few years. Early experiments were interpreted in terms of unconventional spin-orbit interactions mediated by the helical geometry. However, more recent experimental studies have clearly revealed that electronic exchange interactions also play a key role in the magnetic response of chiral molecules in singlet states. In this investigation, we use spin-polarized closed-shell density functional theory calculations to address the influence of exchange contributions to the interaction between helical molecules as well as of helical molecules with magnetized substrates. We show that exchange effects result in differences in the interaction properties with magnetized surfaces, shedding light into the possible origin of two recent important experimental results: enantiomer separation and magnetic exchange force microscopy with AFM tips functionalized with helical peptides.
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http://dx.doi.org/10.1021/acs.nanolett.0c02216DOI Listing
October 2020

Nanocytometer for smart analysis of peripheral blood and acute myeloid leukemia: a pilot study.

Nano Lett 2020 09 27;20(9):6572-6581. Epub 2020 Aug 27.

Max Bergmann Center of Biomaterials and Institute for Materials Science, Dresden University of Technology, Budapesterstrasse 27, 01069 Dresden, Germany.

We realize an ultracompact nanocytometer for real-time impedimetric detection and classification of subpopulations of living cells. Nanoscopic nanowires in a microfluidic channel act as nanocapacitors and measure in real time the change of the amplitude and phase of the output voltage and, thus, the electrical properties of living cells. We perform the cell classification in the human peripheral blood (PBMC) and demonstrate for the first time the possibility to discriminate monocytes and of lymphocytes in a label-free format. Further, we demonstrate that the PBMC of acute myeloid leukemia and healthy samples grant the label free identification of the disease. Using the algorithm based on machine learning, we generated to discriminate healthy donors and leukemia patients. Such a solution has the potential to improve the traditional diagnostics approaches with respect to the overall cost and time effort, in a label-free format, and restrictions of the complex data analysis.
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http://dx.doi.org/10.1021/acs.nanolett.0c02300DOI Listing
September 2020

In vitro characterization of osteoblast cells on polyelectrolyte multilayers containing detonation nanodiamonds.

Biomed Mater 2020 08 21;15(5):055026. Epub 2020 Aug 21.

Institute for Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, Dresden, Germany. Bio- and Nanotechnology, Fraunhofer Institute for Ceramic Technologies and Systems IKTS Material Diagnostics, Dresden, Germany. Both authors contributed equally to this manuscript.

Nanoparticle-enhanced coatings of bone implants are a promising method to facilitate sustainable wound healing, leading to an increase in patient well-being. This article describes the in vitro characterization of osteoblast cells interacting with polyelectrolyte multilayers, which contain detonation nanodiamonds (NDs), as a novel class of carbon-based coating material, which presents a unique combination of photoluminescence and drug-binding properties. The cationic polyelectrolyte, namely polydiallyldimethylammonium chloride (PDDA), has been used to immobilize NDs on silica glass. The height of ND-PDDA multilayers varies from a minimum of 10 nm for one bilayer to a maximum of 90 nm for five bilayers of NDs and PDDA. Human fetal osteoblasts (hFOBs) cultured on ND-PDDA multilayers show a large number of focal adhesions, which were studied via quantitative fluorescence imaging analysis. The influence of the surface roughness on the filopodia formation was assessed via scanning electron microscopy and atomic force microscopy. The nano-rough surface of five bilayers constrained the filopodia formation. The hFOBs grown on NDs tend to show not only a similar cell morphology compared to cells cultured on extracellular matrix protein-coated silica glass substrates, but also increased cell viability by about 40%. The high biocompatibility of the ND-PDDA multilayers, indicated via high cell proliferation and sound cell adhesion, shows their potential for biomedical applications such as drug-eluting coatings and biomaterials in general.
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http://dx.doi.org/10.1088/1748-605X/ab9bafDOI Listing
August 2020

Effective Hamiltonian model for helically constrained quantum systems within adiabatic perturbation theory: Application to the chirality-induced spin selectivity (CISS) effect.

J Chem Phys 2020 Jun;152(21):214105

Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, 01062 Dresden, Germany.

The chirality-induced spin selectivity effect has been confirmed experimentally for a large class of organic molecules. Adequately modeling the effect remains a challenging task, with both phenomenological models and first-principles simulations yielding inconclusive results. Building upon a previously presented model by K. Michaeli and R. Naaman [J. Phys. Chem. C 123, 17043 (2019)], we systematically investigate an effective 1-dimensional model derived as the limit of a 3-dimensional quantum system with strong confinement and including spin-orbit coupling. Having a simple analytic structure, such models can be considered a minimal setup for the description of spin-dependent effects. We use adiabatic perturbation theory to provide a mathematically sound approximation procedure applicable to a large class of spin-dependent continuum models. We take advantage of the simplicity of the models by analyzing its structure to gain a better understanding how the occurrence and magnitude of spin polarization effects relate to the model's parameters and geometry. The obtained spin polarization is not strongly dependent on the strength of the spin-orbit interaction, but it rather results from breaking time-reversal invariance upon selection of a given angular momentum of the incoming electrons.
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http://dx.doi.org/10.1063/5.0005181DOI Listing
June 2020

Design and Performance of Novel Self-Cleaning g-CN/PMMA/PUR Membranes.

Polymers (Basel) 2020 Apr 7;12(4). Epub 2020 Apr 7.

Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, 01062 Dresden, Germany.

In the majority of photocatalytic applications, the photocatalyst is dispersed as a suspension of nanoparticles. The suspension provides a higher surface for the photocatalytic reaction in respect to immobilized photocatalysts. However, this implies that recovery of the particles by filtration or centrifugation is needed to collect and regenerate the photocatalyst. This complicates the regeneration process and, at the same time, leads to material loss and potential toxicity. In this work, a new nanofibrous membrane, g-CN/PMMA/PUR, was prepared by the fixation of exfoliated g-CN to polyurethane nanofibers using thin layers of poly(methyl methacrylate) (PMMA). The optimal amount of PMMA was determined by measuring the adsorption and photocatalytic properties of g-CN/PMMA/PUR membranes (with a different PMMA content) in an aqueous solution of methylene blue. It was found that the prepared membranes were able to effectively adsorb and decompose methylene blue. On top of that, the membranes evinced a self-cleaning behavior, showing no coloration on their surfaces after contact with methylene blue, unlike in the case of unmodified fabric. After further treatment with HO, no decrease in photocatalytic activity was observed, indicating that the prepared membrane can also be easily regenerated. This study promises possibilities for the production of photocatalytic membranes and fabrics for both chemical and biological contaminant control.
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http://dx.doi.org/10.3390/polym12040850DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7240415PMC
April 2020
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