Beilstein Journal of Nanotechnology
ISSN / EISSN : 2190-4286 / 2190-4286
Published by: Beilstein-Institut (10.3762)
Total articles ≅ 2,113
Latest articles in this journal
Beilstein Journal of Nanotechnology, Volume 12, pp 1151-1172; https://doi.org/10.3762/bjnano.12.86
This paper presents a detailed computational protocol for the atomistic simulation of formation and growth of metal-containing nanostructures during focused electron beam-induced deposition (FEBID). The protocol is based upon irradiation-driven molecular dynamics (IDMD), a novel and general methodology for computer simulations of irradiation-driven transformations of complex molecular systems by means of the advanced software packages MBN Explorer and MBN Studio. Atomistic simulations performed following the formulated protocol provide valuable insights into the fundamental mechanisms of electron-induced precursor fragmentation and the related mechanism of nanostructure formation and growth using FEBID, which are essential for the further advancement of FEBID-based nanofabrication. The developed computational methodology is general and applicable to different precursor molecules, substrate types, and irradiation regimes. The methodology can also be adjusted to simulate the nanostructure formation by other nanofabrication techniques using electron beams, such as direct electron beam lithography. In the present study, the methodology is applied to the IDMD simulation of the FEBID of Pt(PF3)4, a widely studied precursor molecule, on a SiO2 surface. The simulations reveal the processes driving the initial phase of nanostructure formation during FEBID, including the nucleation of Pt atoms and the formation of small metal clusters on the surface, followed by their aggregation and the formation of dendritic platinum nanostructures. The analysis of the simulation results provides spatially resolved relative metal content, height, and growth rate of the deposits, which represents valuable reference data for the experimental characterization of the nanostructures grown by FEBID.
Beilstein Journal of Nanotechnology, Volume 12, pp 1140-1150; https://doi.org/10.3762/bjnano.12.85
Biomolecules, such as proteins and peptides, can be self-assembled. They are widely distributed, easy to obtain, and biocompatible. However, the self-assembly of proteins and peptides has disadvantages, such as difficulty in obtaining high quantities of materials, high cost, polydispersity, and purification limitations. The difficulties in using proteins and peptides as functional materials make it more complicate to arrange assembled nanostructures at both microscopic and macroscopic scales. Amino acids, as the smallest constituent of proteins and the smallest constituent in the bottom-up approach, are the smallest building blocks that can be self-assembled. The self-assembly of single amino acids has the advantages of low synthesis cost, simple modeling, excellent biocompatibility and biodegradability in vivo. In addition, amino acids can be assembled with other components to meet multiple scientific needs. However, using these simple building blocks to design attractive materials remains a challenge due to the simplicity of the amino acids. Most of the review articles about self-assembly focus on large molecules, such as peptides and proteins. The preparation of complicated materials by self-assembly of amino acids has not yet been evaluated. Therefore, it is of great significance to systematically summarize the literature of amino acid self-assembly. This article reviews the recent advances in amino acid self-assembly regarding amino acid self-assembly, functional amino acid self-assembly, amino acid coordination self-assembly, and amino acid regulatory functional molecule self-assembly.
Beilstein Journal of Nanotechnology, Volume 12, pp 1127-1139; https://doi.org/10.3762/bjnano.12.84
Nanoparticle deployment in drug delivery is contingent upon controlled drug loading and a desired release profile, with simultaneous biocompatibility and cellular targeting. Iron oxide nanoparticles (IONPs), being biocompatible, are used as drug carriers. However, to prevent aggregation of bare IONPs, they are coated with stabilizing agents. We hypothesize that, zwitterionic drugs like norfloxacin (NOR, a fluoroquinolone) can manifest dual functionality – nanoparticle stabilization and antibiotic activity, eliminating the need of a separate stabilizing agent. Since these drugs have different charges, depending on the surrounding pH, drug loading enhancement could be pH dependent. Hence, upon synthesizing IONPs, they were coated with NOR, either at pH 5 (predominantly as cationic, NOR+) or at pH 10 (predominantly as anionic, NOR−). We observed that, drug loading at pH 5 exceeded that at pH 10 by 4.7–5.7 times. Furthermore, only the former (pH 5 system) exhibited a desirable slower drug release profile, compared to the free drug. NOR-coated IONPs also enable a 22 times higher drug accumulation in macrophages, compared to identical extracellular concentrations of the free drug. Thus, lowering the drug coating pH to 5 imparts multiple benefits – improved IONP stability, enhanced drug coating, higher drug uptake in macrophages at reduced toxicity and slower drug release.
Beilstein Journal of Nanotechnology, Volume 12, pp 1115-1126; https://doi.org/10.3762/bjnano.12.83
The open-loop (OL) variant of Kelvin probe force microscopy (KPFM) provides access to the voltage response of the electrostatic interaction between a conductive atomic force microscopy (AFM) probe and the investigated sample. The measured response can be analyzed a posteriori, modeled, and interpreted to include various contributions from the probe geometry and imaged features of the sample. In contrast to this, the currently implemented closed-loop (CL) variants of KPFM, either amplitude-modulation (AM) or frequency-modulation (FM), solely report on their final product in terms of the tip–sample contact potential difference. In ambient atmosphere, both CL AM-KPFM and CL FM-KPFM work at their best during the lift part of a two-pass scanning mode to avoid the direct contact with the surface of the sample. In this work, a new OL AM-KPFM mode was implemented in the single-pass scan of the PeakForce Tapping (PFT) mode. The topographical and electrical components were combined in a single pass by applying the electrical modulation only in between the PFT tip–sample contacts, when the AFM probe separates from the sample. In this way, any contact and tunneling discharges are avoided and, yet, the location of the measured electrical tip–sample interaction is directly affixed to the topography rendered by the mechanical PFT modulation at each tap. Furthermore, because the detailed response of the cantilever to the bias stimulation was recorded, it was possible to analyze and separate an average contribution of the cantilever to the determined local contact potential difference between the AFM probe and the imaged sample. The removal of this unwanted contribution greatly improved the accuracy of the AM-KPFM measurements to the level of the FM-KPFM counterpart.
Beilstein Journal of Nanotechnology, Volume 12, pp 1101-1114; https://doi.org/10.3762/bjnano.12.82
Tin selenide (SnSe) has thermoelectric (TE) and photovoltaic (PV) applications due to its exceptional advantages, such as the remarkable figure of merit (ZT ≈ 2.6 at 923 K) and excellent optoelectronic properties. In addition, SnSe is nontoxic, inexpensive, and relatively abundant. These aspects make SnSe of great practical importance for the next generation of thermoelectric devices. Here, we report structural, optoelectronic, thermodynamic, and thermoelectric properties of the recently experimentally identified binary phase of tin monoselenide (π-SnSe) by using the density functional theory (DFT). Our DFT calculations reveal that π-SnSe features an optical bandgap of 1.41 eV and has an exceptionally large lattice constant (12.2 Å, P213). We report several thermodynamic, optical, and thermoelectric properties of this π-SnSe phase for the first time. Our finding shows that the π-SnSe alloy is exceptionally promising for the next generation of photovoltaic and thermoelectric devices at room and high temperatures.
Beilstein Journal of Nanotechnology, Volume 12, pp 1093-1100; https://doi.org/10.3762/bjnano.12.81
Most of the technically important properties of nanomaterials, such as superparamagnetism or luminescence, depend on the particle size. During synthesis and handling of nanoparticles, agglomeration may occur. Agglomeration of nanoparticles may be controlled by different mechanisms. During synthesis one observes agglomeration controlled by the geometry and electrical charges of the particles. Additionally, one may find agglomeration controlled by thermodynamic interaction of the particles in the direction of a minimum of the free enthalpy. In this context, one may observe mechanisms leading to a reduction of the surface energy or controlled by the van der Waals interaction. Additionally, the ensemble may arrange in the direction of a maximum of the entropy. Simulations based on Monte Carlo methods teach that, in case of any energetic interaction of the particles, the influence of the entropy is minor or even negligible. Complementary to the simulations, the extremum of the entropy was determined using the Lagrange method. Both approaches yielded identical result for the particle size distribution of an agglomerated ensemble, that is, an exponential function characterized by two parameters. In this context, it is important to realize that one has to take care of fluctuations of the entropy.
Beilstein Journal of Nanotechnology, Volume 12, pp 1078-1092; https://doi.org/10.3762/bjnano.12.80
Light-emitting diodes (LED) are widely employed in display applications and lighting systems. Further research on LED that incorporates carbon nanostructures and metal nanoparticles exhibiting surface plasmon resonance has demonstrated a significant improvement in device performance. These devices offer lower turn-on voltages, higher external quantum efficiencies, and luminance. De facto, plasmonic nanoparticles, such as Au and Ag have boosted the luminance of red, green, and blue emissions. When combined with carbon nanostructures they additionally offer new possibilities towards lightweight and flexible devices with better thermal management. This review surveys the diverse possibilities to combine various inorganic, organic, and carbon nanostructures along with plasmonic nanoparticles. Such combinations would allow an enhancement in the overall properties of LED.
Beilstein Journal of Nanotechnology, Volume 12, pp 1063-1077; https://doi.org/10.3762/bjnano.12.79
Viscoelastic characterization of materials at the micro- and the nanoscale is commonly performed with the aid of force–distance relationships acquired using atomic force microscopy (AFM). The general strategy for existing methods is to fit the observed material behavior to specific viscoelastic models, such as generalized viscoelastic models or power-law rheology models, among others. Here we propose a new method to invert and obtain the viscoelastic properties of a material through the use of the Z-transform, without using a model. We present the rheological viscoelastic relations in their classical derivation and their z-domain correspondence. We illustrate the proposed technique on a model experiment involving a traditional ramp-shaped force–distance AFM curve, demonstrating good agreement between the viscoelastic characteristics extracted from the simulated experiment and the theoretical expectations. We also provide a path for calculating standard viscoelastic responses from the extracted material characteristics. The new technique based on the Z-transform is complementary to previous model-based viscoelastic analyses and can be advantageous with respect to Fourier techniques due to its generality. Additionally, it can handle the unbounded inputs traditionally used to acquire force–distance relationships in AFM, such as ramp functions, in which the cantilever position is displaced linearly with time for a finite period of time.
Beilstein Journal of Nanotechnology, Volume 12, pp 1047-1062; https://doi.org/10.3762/bjnano.12.78
Curcumin (CUR) is a phenolic compound that is safe for human consumption. It exhibits chemopreventive, antiproliferative, antiangiogenic, and antimetastatic effects. However, these benefits can be hampered due to the lipophilic nature, rapid metabolism, low bioavailability, and fast elimination of the molecule. Considering this, the present work reviews the use of CUR-based nanosystems as anticancer agents, including conventional nanosystems (i.e., liposomes, nanoemulsions, nanocrystals, nanosuspensions, polymeric nanoparticles) and nanosystems that respond to external stimuli (i.e., magnetic nanoparticles and photodynamic therapy). Previous studies showed that the effects of CUR were improved when loaded into nanosystems as compared to the free compound, as well as synergist effects when it is co-administrated alongside with other molecules. In order to maximize the beneficial health effects of CUR, critical factors need to be strictly controlled, such as particle size, morphology, and interaction between the encapsulating material and CUR. In addition, there is an area of study to be explored in the development of CUR-based smart materials for nanomedical applications. Imaging-guided drug delivery of CUR-based nanosystems may also directly target specific cells, thereby increasing the therapeutic and chemopreventive efficacy of this versatile compound.
Beilstein Journal of Nanotechnology, Volume 12, pp 1034-1046; https://doi.org/10.3762/bjnano.12.77
Microneedle-based microdevices promise to expand the scope for delivery of vaccines and therapeutic agents through the skin and withdrawing biofluids for point-of-care diagnostics – so-called theranostics. Unskilled and painless applications of microneedle patches for blood collection or drug delivery are two of the advantages of microneedle arrays over hypodermic needles. Developing the necessary microneedle fabrication processes has the potential to dramatically impact the health care delivery system by changing the landscape of fluid sampling and subcutaneous drug delivery. Microneedle designs which range from sub-micron to millimetre feature sizes are fabricated using the tools of the microelectronics industry from metals, silicon, and polymers. Various types of subtractive and additive manufacturing processes have been used to manufacture microneedles, but the development of microneedle-based systems using conventional subtractive methods has been constrained by the limitations and high cost of microfabrication technology. Additive manufacturing processes such as 3D printing and two-photon polymerization fabrication are promising transformative technologies developed in recent years. The present article provides an overview of microneedle systems applications, designs, material selection, and manufacturing methods.