A review on photothermal conversion of solar energy with nanomaterials and nanostructures: from fundamentals to applications. - In: Advanced sustainable systems, ISSN 2366-7486, Bd. 6 (2022), 9, 2200115, S. 1-19
Solar energy is a green, sustainable, and de facto inexhaustible energy source for mankind. The conversion of solar energy into other forms of energy has attracted extensive research interest due to climate change and the energy crisis. Among all the solar energy conversion technologies, photothermal conversion of solar energy exhibits unique advantages when applied for water purification, desalination, high-temperature heterogeneous catalysis, anti-bacterial treatments, and deicing. In this review, the various photothermal conversion mechanisms based on different forms of heat release are summarized and some of the latest examples are presented. In addition, the necessary prerequisites for solar-driven photothermal materials toward their practical applications are also discussed. Further, the latest advances in photothermal conversion of solar energy are discussed, focusing on different types of photothermal applications. Finally, a summary is given and the challenges and opportunities in the photothermal conversion of solar energy are presented. This review aims to give a comprehensive understanding of emerging solar energy conversion technologies based on the photothermal effect, especially by using nanomaterials and nanostructures.
https://doi.org/10.1002/adsu.202200115
Evaluating the optical response of heavily decorated black silicon based on a realistic 3D modeling methodology. - In: ACS applied materials & interfaces, ISSN 1944-8252, Bd. 14 (2022), 31, S. 36189-36199
Combining black silicon (BS), a nanostructured silicon containing highly roughened surface morphology with plasmonic materials, is becoming an attractive approach for greatly enhancing light-matter interactions with promising applications of sensing and light harvesting. However, precisely describing the optical response of a heavily decorated BS structure is still challenging due to the increasing complexity in surface morphology and plasmon hybridization. Here, we propose and fully characterize BS-based multistacked nanostructures with randomly distributed nanoparticles on the highly roughened nonflat surface. We demonstrate a realistic 3D modeling methodology based on parametrized scanning electron microscopy images that provides high-precision morphology details, successfully linking the theoretical analysis with experimental optical response of the complex nanostructures. Far-field calculations very nicely reproduce experimental reflectance spectra, revealing the dependency of light trapping on the thickness of the conformal reflector and the atop nanoparticle size. Near-field analysis clearly identifies three types of stochastic “hotspots”. Their contribution to the overall field enhancement is shown to be very much sensitive to the nanoscale surface morphology. The simulated near-field property is then used to examine the measured surface-enhanced Raman scattering (SERS) response on the multistacked structures. The present modeling approach combined with spectroscopic characterizations is expected to offer a powerful tool for the precise description of the optical response of other large-scale highly disordered realistic 3D systems.
https://doi.org/10.1021/acsami.2c05652
Plasma-assisted fabrication of molecularly imprinted NiAl-LDH layer on Ni nanorod arrays for glyphosate detection. - In: ACS applied materials & interfaces, ISSN 1944-8252, Bd. 14 (2022), 31, S. 35704-35715
An inorganic-framework molecularly imprinted NiAl layered double hydroxide (MI-NiAl-LDH) with specific template molecule (glyphosate pesticide, Glyp) recognition ability was prepared on Ni nanorod arrays (Ni NRAs) through electrodeposition followed by a low-temperature O2 plasma treatment. The freestanding Ni/MI-NiAl-LDH NRA electrode had highly enhanced sensitivity and selectivity. The electrocatalytic oxidation of Glyp was proposed to occur at Ni3+ centers in MI-NiAl-LDH, and the current response depended linearly on the Glyp concentration from 10.0 nmol/L to 1.0 μmol/L (R2 = 0.9906), with the limit of detection (LOD) being 3.1 nmol/L (S/N = 3). An exceptional discriminating capability with tolerance for other similar organophosphorus compounds was achieved. Molecular imprinting (N and P residues) affected the electronic structure of NiAl-LDH, triggering the formation of highly active NiOOH sites at relatively lower anodic potentials and substantially enhancing the electrocatalytic oxidation ability of the NiAl-LDH interface toward the C-N bonds in Glyp. In combination with the surface enrichment effect of MI-NiAl-LDH toward template molecules, the electrochemical oxidation signal intensity of Glyp increased significantly, with a greater peak separation from interfering molecules. These results challenge the common belief that the excellent performance of inorganic-framework molecularly imprinted interfaces arises from their specific adsorption of template molecules, providing new insight into the development of high-performance organic-pollutant-sensing electrodes.
https://doi.org/10.1021/acsami.2c08500
Improving silicon photocathode performance for water reduction through dual interface engineering and integrating ReS2 photocatalyst. - In: ACS applied energy materials, ISSN 2574-0962, Bd. 5 (2022), 7, S. 8222-8231
Photoelectrochemical (PEC) water splitting for H2 production is a possible alternative for fossil energy in the future. However, there exists three problems in PEC water splitting with the silicon (Si) photocathode: poor light absorption of the untreated Si substrate, bad stability in strong acid solution, and poor photocatalytic activity of Si. Here, a strategy of dual interface engineering and photocatalyst deposition is proposed to improve the PEC performance, which consists of fabricating black Si (b-Si) by reactive ion etching, depositing of TiO2 on the b-Si by atomic layer deposition, and growing ReS2 on top of the TiO2 by chemical vapor deposition. Owing to the suitable band alignment of b-Si, TiO2, and ReS2, the ReS2/TiO2/b-Si shows obviously enhanced PEC performance compared to b-Si, TiO2/b-Si, and ReS2/b-Si photocathodes. Results of electrochemical impedance spectroscopy and Mott-Schottky plot analysis demonstrate that the TiO2 layer plays an important role and the charge-transfer kinetics of the system is clearly improved. Transient photocurrent measurements indicate that the ReS2/TiO2/b-Si photocathode has the most remarkable photocurrent response. In addition, the ReS2/TiO2/b-Si photocathode also shows excellent stability after being operated for 25 h.
https://doi.org/10.1021/acsaem.2c00761
Grundlagenuntersuchung zur ultraschallunterstützten Aufbautechnik für Elektronik. - Ilmenau, 2022. - 121 Blätter
Technische Universität Ilmenau, Dissertation 2022
Die Einpresstechnik ist ein gut entwickelter Prozess, um eine elektrische Kontaktierung zwischen Pin und Leiterplatte herzustellen. Ein Vorteil der Einpresstechnik ist das Herstellen der Verbindung ohne weitere Hilfsmittel wie Lotpaste oder Wärme. Nachteile des Verfahrens sind zum Teil hohe Einpresskräfte, die zu Beschädigungen an der Leiterplatte führen können oder die Verwendung von zusätzlichen Beschichtungen, um ausreichend hohe Festigkeiten zu erzielen. Im Rahmen der vorliegenden Arbeit wird ein neuer Prozess, ultraschallunterstützte Einpresstechnik, untersucht. Dabei wird die Leiterplatte während oder nach dem Einpressen mit Ultraschall angeregt. Das verwendete Materialsystem Kupfer- bzw. Aluminium-basierter Pin und Kupfer-Hülse weist keine zusätzliche metallische Beschichtung auf. Es werden verschiedene Einflussfaktoren des Prozesses auf Einpresskraft, Festigkeit und Qualität der Verbindungen untersucht. Der Prozess wird weiterentwickelt, um eine Reproduzierbarkeit der Ergebnisse zu gewährleisten und die Prozessparameter werden optimiert. Weiterhin wird eine neue geeignete Pingeometrie entwickelt und ihr Verhalten mit einer flexiblen Pingeometrie verglichen. Der Wirkmechanismus des Ultraschalls wird anhand der Verformung der Fügezone und Veränderungen im Werkstoff erläutert. Zu weiteren Erklärung werden statistische und thermische Modelle aufgestellt. Damit ist eine Voraussage der Auspresskraft und der Temperatur in der Fügezone möglich.
Anisotropy of the electric field gradient in two-dimensional α-MoO3 investigated by 57Mn(57Fe) emission Mössbauer spectroscopy. - In: Crystals, ISSN 2073-4352, Bd. 12 (2022), 7, 942, S. 1-13
Van der Waals α-MoO3 samples offer a wide range of attractive catalytic, electronic, and optical properties. We present herein an emission Mössbauer spectroscopy (eMS) study of the electric-field gradient (EFG) anisotropy in crystalline free-standing α-MoO3 samples. Although α-MoO3 is a two-dimensional (2D) material, scanning electron microscopy shows that the crystals are 0.5-5-µm thick. The combination of X-ray diffraction and micro-Raman spectroscopy, performed after sample preparation, provided evidence of the phase purity and crystal quality of the samples. The eMS measurements were conducted following the implantation of 57Mn (t1/2 = 1.5 min), which decays to the 57Fe, 14.4 keV Mössbauer state. The eMS spectra of the samples are dominated by a paramagnetic doublet (D1) with an angular dependence, pointing to the Fe2+ probe ions being in a crystalline environment. It is attributed to an asymmetric EFG at the eMS probe site originating from strong in-plane covalent bonds and weak out-of-plane van der Waals interactions in the 2D material. Moreover, a second broad component, D2, can be assigned to Fe3+ defects that are dynamically generated during the online measurements. The results are compared to ab initio simulations and are discussed in terms of the in-plane and out-of-plane interactions in the system.
https://doi.org/10.3390/cryst12070942
Compositional dependence of epitaxial L10-Mnx Ga magnetic properties as probed by 57Mn/Fe and 119In/Sn emission Mössbauer spectroscopy. - In: Physica status solidi, ISSN 1521-3951, Bd. 259 (2022), 7, 2200121, S. 1-11
The magnetic properties of Mn x Ga alloys critically depend on composition x, and the atomic-scale origin of those dependences is still not fully disclosed. Molecular beam epitaxy has been used to produce a set of Mn x Ga samples (x = 0.7 ÷ 1.9) with strong perpendicular magnetic anisotropy, and controllable saturation magnetization and coercive field depending on x. By conducting 57Mn/Fe and 119In/Sn emission Mössbauer spectroscopy at ISOLDE/CERN, the Mn and Ga site-specific chemical, structural, and magnetic properties of Mn x Ga are investigated as a function of x, and correlated with the magnetic properties as measured by superconducting quantum interference device magnetometry. Hyperfine magnetic fields of Mn/Fe (either at Mn or Ga sites) are found to be greatly influenced by the local strain induced by the implantation. However, In/Sn probes show clear angular dependence, demonstrating a huge transferred dipolar hyperfine field to the Ga sites. A clear increase of the occupancy of Ga lattice sites by Mn for x > 1 is observed, and identified as the origin for the increased antiferromagnetic coupling between Mn and Mn at Ga sites that lowers the samples' magnetization. The results shed further light on the atomic-scale mechanisms driving the compositional dependence of magnetism in Mn x Ga.
https://doi.org/10.1002/pssb.202200121
Hydrogenated TiO2 nanoparticles loaded with Au nanoclusters demonstrating largely enhanced performance for electrochemical reduction of nitrogen to ammonia. - In: Energy technology, ISSN 2194-4296, Bd. 10 (2022), 7, 2200085, S. 1-9
Pristine TiO2/Au (P-TiO2/Au) is modified by hydrogen plasma (H-TiO2/Au) or hydrogen and oxygen plasma (H-O-TiO2/Au) treatment, and then used as electrochemical catalysts for nitrogen reduction reaction (NRR). H-TiO2/Au shows enhanced performance for the NRR process compared with both P-TiO2/Au and H-O-TiO2/Au. After hydrogenation treatment, some disordered regions on the surface of TiO2 nanoparticles are formed, and a large number of oxygen vacancies are incorporated into the TiO2 crystalline structures. When the samples are used as catalysts for electrochemical NRR, the yield of NH3 of H-TiO2/Au is about ten times compared to that of P-TiO2/Au and about three times that of H-O-TiO2/Au, while the highest Faradaic efficiency of 2.7% is also obtained at the potential of -0.1 V for the H-TiO2/Au catalyst. The density functional theory (DFT) calculation results confirm that H-TiO2/Au with oxygen vacancies and the disordered surface layer is much preferred energetically for the NRR process. It proves that enhanced adsorption of N2 molecules on the catalyst and reduced reaction barriers due to the presence of defects play an important role in improving catalysts’ performances. The results show that the plasma hydrogenation technique can be used as an efficient method to modify catalysts for electrochemical NRR processes.
https://doi.org/10.1002/ente.202200085
Anisotropy of the ΔE effect in Ni-based magnetoelectric cantilevers: a finite element method analysis. - In: Sensors, ISSN 1424-8220, Bd. 22 (2022), 13, 4958, S. 1-16
In recent investigations of magnetoelectric sensors based on microelectromechanical cantilevers made of TiN/AlN/Ni, a complex eigenfrequency behavior arising from the anisotropic ΔE effect was demonstrated. Within this work, a FEM simulation model based on this material system is presented to allow an investigation of the vibrational properties of cantilever-based sensors derived from magnetocrystalline anisotropy while avoiding other anisotropic contributions. Using the magnetocrystalline ΔE effect, a magnetic hardening of Nickel is demonstrated for the (110) as well as the (111) orientation. The sensitivity is extracted from the field-dependent eigenfrequency curves. It is found, that the transitions of the individual magnetic domain states in the magnetization process are the dominant influencing factor on the sensitivity for all crystal orientations. It is shown, that Nickel layers in the sensor aligned along the medium or hard axis yield a higher sensitivity than layers along the easy axis. The peak sensitivity was determined to 41.3 T−1 for (110) in-plane-oriented Nickel at a magnetic bias flux of 1.78 mT. The results achieved by FEM simulations are compared to the results calculated by the Euler-Bernoulli theory.
https://doi.org/10.3390/s22134958
Perturbed angular correlation technique at ISOLDE/CERN applied for studies of hydrogenated titanium dioxide (TiO2): observation of Cd-H Pairs. - In: Crystals, ISSN 2073-4352, Bd. 12 (2022), 6, 756, S. 1-10
Profound understanding of the local electronic and defect structure in semiconductors always plays a vital role in the further developing of applications of such materials. In the present work an investigation of the electronic structure in hydrogenated TiO2 (rutile) thin films is conducted by virtue of Time-Differential γ-γ Perturbed Angular Correlation spectroscopy (TDPAC or PAC) with 111mCd/Cd isotope, produced and implanted at ISOLDE/CERN. The measurements were performed at 581 K as a function of the temperature of the samples during hydrogenation. Despite the fact, that rutile single crystals usually show the presence of two local environments, when are studies with Cd/In isotopes, the current pristine thin films sample had a single electric field gradient. Upon various degrees of hydrogenation, Cd probe atoms showed underwent alterations, resulting in up to 3 different local surroundings, generally with high electric field gradients. Broad EFG distributions are likely due to randomly distributed point defects in the neighbourhood of Cd acceptors. Observed results suggest that hydrogenations performed at RT and 423 K are not able to promote unique defect configurations, while in the range of 473-573 K the formation of such configurations is observed. Therefore, one may assume that the formation of Cd-defect complexes (Cd-H pairs) is temperature enhanced. At higher levels of hydrogenation (663 K), the samples become partly amorphous that further hinders any atomistic studies with strong damped PAC spectra. Cd-H complexes seem to be stable up to annealing up to 581 K annealing. The obtained results give a deep insight into complex hydrogen defects, their interactions and bond formations with Cd acceptor.
https://doi.org/10.3390/cryst12060756