| 1. |
- Alves Machado Filho, Manoel, et al.
(författare)
-
Self-Induced Core–Shell InAlN Nanorods: Formation and Stability Unraveled by Ab Initio Simulations
- 2023
-
Ingår i: ACS Nanoscience Au. - : American Chemical Society (ACS). - 2694-2496. ; 3:1, s. 84-93
-
Tidskriftsartikel (refereegranskat)abstract
- By addressing precursor prevalence and energetics using the DFT-based synthetic growth concept (SGC), the formation mechanism of self-induced InAlN core–shell nanorods (NRs) synthesized by reactive magnetron sputter epitaxy (MSE) is explored. The characteristics of In- and Al-containing precursor species are evaluated considering the thermal conditions at a typical NR growth temperature of around 700 °C. The cohesive and dissociation energies of In-containing precursors are consistently lower than those of their Al-containing counterparts, indicating that In-containing precursors are more weakly bonded and more prone to dissociation. Therefore, In-containing species are expected to exhibit lower abundance in the NR growth environment. At increased growth temperatures, the depletion of In-based precursors is even more pronounced. A distinctive imbalance in the incorporation of Al- and In-containing precursor species (namely, AlN/AlN+, AlN2/AlN2+, Al2N2/Al2N2+, and Al2/Al2+ vs InN/InN+, InN2/InN2+, In2N2/In2N2+, and In2/In2+) is found at the growing edge of the NR side surfaces, which correlates well with the experimentally obtained core–shell structure as well as with the distinctive In-rich core and vice versa for the Al-rich shell. The performed modeling indicates that the formation of the core–shell structure is substantially driven by the precursors’ abundance and their preferential bonding onto the growing edge of the nanoclusters/islands initiated by phase separation from the beginning of the NR growth. The cohesive energies and the band gaps of the NRs show decreasing trends with an increment in the In concentration of the NRs’ core and with an increment in the overall thickness (diameter) of the NRs. These results reveal the energy and electronic reasons behind the limited growth (up to ∼25% of In atoms of all metal atoms, i.e., InxAl1–xN, x ∼ 0.25) in the NR core and may be qualitatively perceived as a limiting factor for the thickness of the grown NRs (typically <50 nm).
|
|
| 2. |
- Cardoch, Sebastian, et al.
(författare)
-
Distinguishing between Similar Miniproteins with Single-Molecule Nanopore Sensing : A Computational Study
- 2022
-
Ingår i: ACS Nanoscience Au. - : American Chemical Society (ACS). - 2694-2496. ; 2:2, s. 119-127
-
Tidskriftsartikel (refereegranskat)abstract
- A nanopore is a tool in single-molecule sensing biotechnology that offers label-free identification with high throughput. Nanopores have been successfully applied to sequence DNA and show potential in the study of proteins. Nevertheless, the task remains challenging due to the large variability in size, charges, and folds of proteins. Miniproteins have a small number of residues, limited secondary structure, and stable tertiary structure, which can offer a systematic way to reduce complexity. In this computational work, we theoretically evaluated sensing two miniproteins found in the human body using a silicon nitride nanopore. We employed molecular dynamics methods to compute occupied-pore ionic current magnitudes and electronic structure calculations to obtain interaction strengths between pore wall and miniprotein. From the interaction strength, we derived dwell times using a mix of combinatorics and numerical solutions. This latter approach circumvents typical computational demands needed to simulate translocation events using molecular dynamics. We focused on two miniproteins potentially difficult to distinguish owing to their isotropic geometry, similar number of residues, and overall comparable structure. We found that the occupied-pore current magnitudes not to vary significantly, but their dwell times differ by 1 order of magnitude. Together, these results suggest a successful identification protocol for similar miniproteins.
|
|
| 3. |
- Haddadi, Sara, et al.
(författare)
-
From Attraction to Repulsion to Attraction: Non-Monotonic Temperature Dependence of Polymer-Mediated Interactions in Colloidal Dispersions
- 2021
-
Ingår i: ACS Nanoscience AU. - : American Chemical Society (ACS). - 2694-2496. ; 1:1, s. 69-80
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we have synthesized polystyrene particles that carry short end-grafted polyethylene glycol (PEG) chains. We then added dissolved 100 kDa PEG polymers and monitored potential flocculation by confocal microscopy. Qualitative predictions, based on previous theoretical developments in this field (Xie, F.; et al. Soft Matter 2016, 12, 658), suggest a non-monotonic temperature response. These theories propose that the “free” (dissolved) polymers will mediate attractive depletion interactions at room temperature, with a concomitant clustering/flocculation at a sufficiently high polymer concentration. At high temperatures, where the solvent is poorer, this is predicted to be replaced by attractive bridging interactions, again resulting in particle condensation. Interestingly enough, our theoretical framework, based on classical density functional theory, predicts an intermediate temperature regime where the polymer-mediated interactions are repulsive! This obviously implies a homogeneous dispersion in this regime. These qualitative predictions have been experimentally tested and confirmed in this work, where flocs of particles start to form at room temperature for a high enough polymer dosage. At temperatures near 45 °C, the flocs redisperse, and we obtain a homogeneous sample. However, samples at about 75 °C will again display clusters and eventually phase separation. Using results from these studies, we have been able to fine-tune parameters of our coarse-grained theoretical model, resulting in predictions of temperature-dependent stability that display semiquantitative accuracy. A crucial aspect is that under “intermediate” conditions, where the polymers neither adsorb nor desorb at the particle surfaces, the polymer-mediated equilibrium interaction is repulsive.
|
|
| 4. |
- Lei, Yu, et al.
(författare)
-
Graphene and Beyond: Recent Advances in Two-Dimensional Materials Synthesis, Properties, and Devices
- 2022
-
Ingår i: ACS Nanoscience Au. - : American Chemical Society (ACS). - 2694-2496. ; 2:6, s. 450-485
-
Forskningsöversikt (refereegranskat)abstract
- Since the isolation of graphene in 2004, two-dimensional (2D) materials research has rapidly evolved into an entire subdiscipline in the physical sciences with a wide range of emergent applications. The unique 2D structure offers an open canvas to tailor and functionalize 2D materials through layer number, defects, morphology, moiré pattern, strain, and other control knobs. Through this review, we aim to highlight the most recent discoveries in the following topics: theory-guided synthesis for enhanced control of 2D morphologies, quality, yield, as well as insights toward novel 2D materials; defect engineering to control and understand the role of various defects, including in situ and ex situ methods; and properties and applications that are related to moiré engineering, strain engineering, and artificial intelligence. Finally, we also provide our perspective on the challenges and opportunities in this fascinating field.
|
|
| 5. |
- Mårtensson, Erik K., et al.
(författare)
-
Simulating Vapor-Liquid-Solid Growth of Au-Seeded InGaAs Nanowires
- 2022
-
Ingår i: ACS Nanoscience AU. - : American Chemical Society (ACS). - 2694-2496. ; 2:3, s. 239-249
-
Tidskriftsartikel (refereegranskat)abstract
- Ternary III-V nanowires are commonly grown using the Au-seeded vapor-liquid-solid method, wherein the solid nanowires are grown from nanoscale liquid seed particles, which are supplied with growth species from the surrounding vapor phase. A result of the small size of these seed particles is that their composition can vary significantly during the cyclical layer-by-layer growth, despite experiencing a constant pressure of growth species from the surrounding vapor phase. Variations in the seed particle composition can greatly affect the solid nanowire composition, and these cyclical dynamics are poorly understood for ternary nanowire growth. Here, we present a method for simulating nanowire growth which captures the complex cyclical dynamics using a kinetic Monte Carlo framework. In the framework, a nanowire grows through the attachment or detachment of one III-V pair at the time, with rates that are based on the momentary composition of the seed particle. The composition of the seed evolves through the attachment and detachment of III-V pairs to the solid nanowire and through the impingement or evaporation of single atoms to the surrounding vapor. Here, we implement this framework using the As-Au-Ga-In materials system and use it to simulate the growth of Au-seeded InGaAs nanowires with an average solid Ga/III ratio around 0.5. The results show that nucleation preferentially occurs via clusters of InAs and that the compositional hierarchy of the liquid seed (XAs < XGa < XIn) determines much of the dynamics of the system. We see that imposing a constraint on the simulation, that only the most recently attached III-V pair can be detached, resulted in a significant narrowing of the compositional profile of the nanowire. In addition, our results suggest that, for ternary systems where the two binaries are heavily mismatched, the dynamics of the seed particle may result in an oscillating compositional profile.
|
|
| 6. |
- Sjökvist, Robin, et al.
(författare)
-
Observation of the Multilayer Growth Mode in Ternary InGaAs Nanowires
- 2022
-
Ingår i: ACS Nanoscience AU. - : American Chemical Society (ACS). - 2694-2496. ; 2:6, s. 539-548
-
Tidskriftsartikel (refereegranskat)abstract
- Au-seeded semiconductor nanowires have classically been considered to only grow in a layer-by-layer growth mode, where individual layers nucleate and grow one at a time with an incubation step in between. Recent in situ investigations have shown that there are circumstances where binary semiconductor nanowires grow in a multilayer fashion, creating a stack of incomplete layers at the interface between a nanoparticle and a nanowire. In the current investigation, the growth behavior in ternary InGaAs nanowires has been analyzed in situ, using environmental transmission electron microscopy. The investigation has revealed that multilayer growth also occurs for ternary nanowires and appears to be more common than in the binary case. In addition, the size of the multilayer stacks observed is much larger than what has been reported previously. The investigation details the implications of multilayers for the overall growth of the nanowires, as well as the surrounding conditions under which it has manifested. We show that multilayer growth is highly dynamic, where the stack of layers regularly changes size by transporting material between the growing layers. Another observation is that multilayer growth can be initiated in conjunction with the formation of crystallographic defects and compositional changes. In addition, the role that multilayers can have in behaviors such as growth failure and kinking, sometimes observed when creating heterostructures between GaAs and InAs ex situ, is discussed. The prevalence of multilayer growth in this ternary material system implies that, in order to fully understand and accurately predict the growth of nanowires of complex composition and structure, multilayer growth has to be considered.
|
|
| 7. |
- Surendiran, Pradheebha, et al.
(författare)
-
Solving Exact Cover Instances with Molecular-Motor-Powered Network-Based Biocomputation
- 2022
-
Ingår i: ACS Nanoscience Au. - : American Chemical Society (ACS). - 2694-2496 .- 2694-2496.
-
Tidskriftsartikel (refereegranskat)abstract
- Information processing by traditional, serial electronic processors consumes an ever-increasing part of the global electricity supply. An alternative, highly energy efficient, parallel computing paradigm is network-based biocomputation (NBC). In NBC a given combinatorial problem is encoded into a nanofabricated, modular network. Parallel exploration of the network by a very large number of independent molecular-motor-propelled protein filaments solves the encoded problem. Here we demonstrate a significant scale-up of this technology by solving four instances of Exact Cover, a nondeterministic polynomial time (NP) complete problem with applications in resource scheduling. The difficulty of the largest instances solved here is 128 times greater in comparison to the current state of the art for NBC.
|
|
| 8. |
- Thyr, Jakob, 1979-, et al.
(författare)
-
Energy Alignment of Quantum-Confined ZnO Particles with Copper Oxides for Heterojunctions with Improved Photocatalytic Performance
- 2022
-
Ingår i: ACS Nanoscience Au. - : American Chemical Society (ACS). - 2694-2496. ; 2:2, s. 128-139
-
Tidskriftsartikel (refereegranskat)abstract
- The ability to control electronic states by utilizing quantum confinement of one of the material components in heterojunctions is a promising approach to perform energy-level matching. In this work, we report the possibility to achieve optimum energy alignment in heterojunctions made from size-controlled quantum dots (Q-dots) of ZnO in combination with three copper oxides: Cu2O, Cu4O3, and CuO. Quantum confinement effects on the ZnO nanoparticles in the diameter range 2.6–7.4 nm showed that the direct optical band gap decreased from 3.99 to 3.41 eV, with a dominating shift occurring in the conduction band (CB) edge, and thus the possibility to obtain close to 0.6 eV CB edge shift by controlling the size of ZnO. The effect was utilized to align the electronic bands in the ZnO Q-dot/copper oxide heterojunctions to allow for charge transfer between the materials and to test the ability to improve the photocatalytic performance for the system, evaluated by the transformation of a dye molecule in water. The catalyst materials were investigated by X-ray diffraction, scanning electron microscopy, ultraviolet–visible (UV–vis), photoluminescence, and Raman spectroscopy. The most promising material combination was found to be the Cu2O copper oxide in combination with an energy aligned ZnO Q-dot system with approximately 7 nm diameter, showing strong synergy effects in good agreement with the energy-level analysis, outperforming the added effect of its individual components, ZnO-Q-dots and Cu2O, by about 140%. The results show that utilization of a heterojunction with controllable energy alignment can provide a drastically improved photocatalytic performance. Apart from increased photocatalytic activity, specific surface states of ZnO are quenched when the heterojunction is created. It is anticipated that the same approach can be utilized in several material combinations with the added benefit of a system with controllable overpotential and thus added specificity for the targeted reduction reaction.
|
|
| 9. |
- Tornberg, Marcus, et al.
(författare)
-
Direct Observations of Twin Formation Dynamics in Binary Semiconductors
- 2022
-
Ingår i: ACS Nanoscience AU. - : American Chemical Society (ACS). - 2694-2496. ; 2:1, s. 49-56
-
Tidskriftsartikel (refereegranskat)abstract
- With the increased demand for controlled deterministic growth of III–V semiconductors at the nanoscale, the impact and interest of understanding defect formation and crystal structure switching becomes increasingly important. Vapor–liquid–solid (VLS) growth of semiconductor nanocrystals is an important mechanism for controlling and studying the formation of individual crystal layers and stacking defects. Using in situ studies, combining atomic resolution of transmission electron microscopy and controlled VLS crystal growth using metal organic chemical vapor deposition, we investigate the simplest achievable change in atomic layer stacking–single twinned layers formed in GaAs. Using Au-assisted GaAs nanowires of various diameters, we study the formation of individual layers with atomic resolution to reveal the growth difference in forming a twin defect. We determine that the formation of a twinned layer occurs significantly more slowly than that of a normal crystal layer. To understand this, we conduct thermodynamic modeling and determine that the propagation of a twin is limited by the energy cost of forming the twin interface. Finally, we determine that the slower propagation of twinned layers increases the probability of additional layers nucleating, such that multiple layers grow simultaneously. This observation challenges the current understanding that continuous uniform epitaxial growth, especially in the case of liquid-metal assisted nanowires, proceeds one single layer at a time and that its progression is limited by the nucleation rate.
|
|
| 10. |
- Unksov, Ivan N., et al.
(författare)
-
Through the Eyes of Creators: Observing Artificial Molecular Motors : ACS Nanoscience Au
- 2022
-
Ingår i: ACS Nanoscience AU. - : American Chemical Society (ACS). - 2694-2496.
-
Tidskriftsartikel (refereegranskat)abstract
- Inspired by molecular motors in biology, there hasbeen significant progress in building artificial molecular motors, usinga number of quite distinct approaches. As the constructs become moresophisticated, there is also an increasing need to directly observe themotion of artificial motors at the nanoscale and to characterize theirperformance. Here, we review the most used methods that tacklethose tasks. We aim to help experimentalists with an overview of theavailable tools used for different types of synthetic motors and tochoose the method most suited for the size of a motor and the desiredmeasurements, such as the generated force or distances in the movingsystem. Furthermore, for many envisioned applications of syntheticmotors, it will be a requirement to guide and control directed motions.We therefore also provide a perspective on how motors can be observed on structures that allow for directional guidance, such asnanowires and microchannels. Thus, this Review facilitates the future research on synthetic molecular motors, where observations ata single-motor level and a detailed characterization of motion will promote applications.
|
|
