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Diverse Nanoassemblies of Graphene Quantum Dots and Their Mineralogical Counterparts
摘要： Complex structures from nanoparticles are found in rocks, soils, and sea sediments but the mechanisms of their formation are poorly understood, which causes controversial conclusions about their genesis. Here we show that graphene quantum dots (GQDs) can assemble into complex structures driven by coordination interactions with metal ions commonly present in environment and serve a special role in Earth’s history, such as Fe3+ and Al3+. GQDs self-assemble into mesoscale chains, sheets, supraparticles, nanoshells, and nanostars. Specific assembly patterns are determined by the effective symmetry of the GQDs when forming the coordination assemblies with the metal ions. As such, maximization of the electronic delocalization of p-orbitals of GQDs with Fe3+ leads to GQD-Fe-GQD units with D2 symmetry, dipolar bonding potential, and linear assemblies. Taking advantage of high electron microscopy contrast of carbonaceous nanostructures in respect to ceramic background, the mineralogical counterparts of GQD assemblies are found in mineraloid shungite. These findings provide insight into nanoparticle dynamics during the rock formation that can lead to mineralized structures of unexpectedly high complexity.
关键词： self-assembly,nanoscale mineralogy,nanoparticles,graphene quantum dots,electronic conjugation
更新于2025-09-19 17:13:59
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Direct molecular-level near-field plasmon and temperature assessment in a single plasmonic hotspot
摘要： Tip-enhanced Raman spectroscopy (TERS) is currently widely recognized as an essential but still emergent technique for exploring the nanoscale. However, our lack of comprehension of crucial parameters still limits its potential as a user-friendly analytical tool. The tip’s surface plasmon resonance, heating due to near-field temperature rise, and spatial resolution are undoubtedly three challenging experimental parameters to unravel. However, they are also the most fundamentally relevant parameters to explore, because they ultimately influence the state of the investigated molecule and consequently the probed signal. Here we propose a straightforward and purely experimental method to access quantitative information of the plasmon resonance and near-field temperature experienced exclusively by the molecules directly contributing to the TERS signal. The detailed near-field optical response, both at the molecular level and as a function of time, is evaluated using standard TERS experimental equipment by simultaneously probing the Stokes and anti-Stokes spectral intensities. Self-assembled 16-mercaptohexadodecanoic acid monolayers covalently bond to an ultra-flat gold surface were used as a demonstrator. Observation of blinking lines in the spectra also provides crucial information on the lateral resolution and indication of atomic-scale thermally induced morphological changes of the tip during the experiment. This study provides access to unprecedented molecular-level information on physical parameters that crucially affect experiments under TERS conditions. The study thereby improves the usability of TERS in day-to-day operation. The obtained information is of central importance for any experimental plasmonic investigation and for the application of TERS in the field of nanoscale thermometry.
关键词： surface plasmon resonance,nanoscale thermometry,Tip-enhanced Raman spectroscopy (TERS),spatial resolution,near-field temperature rise
更新于2025-09-19 17:13:59
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Effective Preparation of Nanoscale CH <sub/>3</sub> NH <sub/>3</sub> PbI <sub/>3</sub> Perovskite Photosensitizers for Mesoporous TiO <sub/>2</sub> ‐Based Solar Cells by Successive Precursor Layer Adsorption and Reaction (SPLAR) Process
摘要： Nanoscale CH3NH3PbI3 perovskite sensitizers are grown step-by-step by delivering each precursor successively onto the surface of mesoporous (meso) TiO2 electrode. Using Pb(NO3)2 ions as a lead(II) source and CH3NH3I (MAI) for methylammonium and iodide sources, repetitive cycles of the two dipping steps are successful in growing few nanometer-sized MAPbI3 gradually on the TiO2 surface inside the meso-TiO2 film. However, some aggregates are observed on the top-surface of meso-TiO2 film due to slight dissolution of PbI2 and its accumulation/reaction with MAI at the top-surface of meso-TiO2 film. To solve this inhomogeneity during the course of the deposition, a nondestructive multiple deposition route for nanoscale MAPbI3 is suggested as a successive precursor layer adsorption and reaction (SPLAR) process where, from the second cycle of deposition, PbI2 is delivered with the help of an ionic liquid compound dissolved in dichloromethane. With this new Pb-precursor in less-polar solvents by spin-coating process, nanoscale MAPbI3-sensitizers are grown step-by-step without dissolution of pre-formed perovskites back to PbI2 or formation of some aggregates at the top-surface. After the third cycle of SPLAR deposition, about 7.0 nm-size MAPbI3-sensitizers are prepared and they display enhanced photovoltaic performance (7.18± 0.31 %) compared to devices obtained from only one cycle (5.74± 0.30 %).
关键词： solid-state dye-sensitized solar cells,nanoscale perovskite,successive adsorption and reaction,photosensitizer
更新于2025-09-16 10:30:52
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High-efficiency non-halogenated solvent processable polymer/PCBM solar cells <i>via</i> fluorination-enabled optimized nanoscale morphology
摘要： PNTz4T-based polymers have been extensively employed in high-efficiency fullerene-based polymer solar cells (PSCs) with a power conversion efficiency (PCE) of approximately 10.0% due to the high crystallinity of these polymers. The introduction of two fluorine atoms into PNTz4T to synthesize the PNTz4T-2F polymer has boosted the PCE to 10.6%, but the introduction of four fluorine atoms to synthesize the PNTz4T-4F polymer negatively affects the efficiency (PCE ? 6.5%), implying that the number of fluorine atoms is not yet optimized. We have developed a new synthetic route for a novel monofluoro-bithiophene monomer and successfully synthesized a novel PNTz4T-1F polymer. The fullerene-based PSCs based on our novel PNTz4T-1F polymer processed using a halogen-free solvent system demonstrated an outstanding PCE of 11.77% (11.67% certified), representing the highest PCE reported thus far in the literature. Due to the optimum molecular ordering/packing, improved interaction with PC71BM and interconnectivity between photoactive material domains, PNTz4T-1F-based PSCs exhibit lower charge carrier recombination and enhanced charge carrier mobility levels, leading to a substantially high photocurrent density (20.37 mA cm(cid:2)2). These results create new means to tune the structural properties of polymers, ultimately leading to the realization of this class of solar cells for practical applications.
关键词： polymer solar cells,nanoscale morphology,halogen-free solvent,power conversion efficiency,fluorination
更新于2025-09-16 10:30:52
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Characteristics of quasi-unipolar electromagnetic pulses formed in the interaction of high-power laser pulses with nanoscale targets
摘要： A new method is suggested for generating quasi-unipolar electromagnetic IR and terahertz pulses. The method is based on synchronous acceleration of electrons combined to a dense bunch with a charge of up to several tens nanocoulombs, which are forced out from a nanoscale target under an action of a high-power, sharp-leading edge laser pulse. The electromagnetic bunch moving in a field of laser radiation can generate high-power electromagnetic pulses with various spectral composition including terahertz and IR ranges. A physical mechanism underlying the formation of generated quasi-unipolar pulses of electromagnetic radiation is determined and numerically studied. The pulse characteristics are found by numerical simulation, such as amplitude and duration dependences on the angle between the pulse propagation direction and laser beam axis. It is established that in modern laser installations, the amplitudes of quasi-unipolar pulses may reach relativistic values. Reflection of a unipolar pulse from an ideally reflecting surface is numerically analysed. It is shown that the pulse retains its unipolar profile in this case.
关键词： nanoscale targets,generation of terahertz and IR radiation,interaction of high-power laser pulses with matter,electron acceleration by laser pulses
更新于2025-09-16 10:30:52
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Ferroelectric ordering and energy storage capacity in lead-free Ba(Zr <sub/>0.2</sub> Ti <sub/>0.8</sub> )O <sub/>3</sub> nanoscale film capacitors fabricated using pulsed laser deposition technique
摘要： Dielectric thin film capacitors, storing large charge density, are useful in electric energy storing devices. Highly oriented lead-free BaZr0.20Ti0.80O3 (BZT20) thin films were grown on a conducting bottom layer La0.7Sr0.3MnO3 deposited on a MgO (100) substrate under an oxygen atmosphere using a pulsed laser deposition technique. X-ray diffraction studies indicate that BZT20 films were stabilized in a (100) oriented tetragonal phase. Microstructural studies on thin films indicate a smooth film (a roughness of ～1.25 nm) with a thickness of around 320 nm. The structural sensitive A1(TO2) Raman band exhibits a discontinuous change across the tetragonal-cubic phase transition temperature Tc ～ 275 K. The appearance of the broad Raman band in the cubic (Pm?3m) phase at an elevated temperature suggests the activation of symmetry forbidden Raman active bands. The temperature dependent band frequency and integrated intensity of the structural sensitive A1(TO2) band show anomaly across Tc. Temperature dependent dielectric studies (100–650 K) carried out in a wide range of frequencies 102–106 Hz on a fabricated Pt/BZT20/LSMO metal-insulator-metal capacitor suggest a broad dispersive peak of around 290 K. The polarization relaxation follows the Vogel-Fulcher relation with an activation energy of Ea = 0.047 eV and a freezing temperature of Tf = 246 K. The slim polarization P-E loops with a remanent polarization of ～89.6 μC/cm2 and an EC value of ～0.29 MV/cm were observed, suggesting its local ferroelectric ordering in corroboration with Raman and dielectric findings. From the P-E loop analysis, a large energy storage density of 31.9 J/cm3 and an energy storage efficiency of 56% were obtained. Our experimental results revealed that the BZT20 thin film capacitors have potential for energy storage device applications.
关键词： Ferroelectric ordering,Ba(Zr0.2Ti0.8)O3,energy storage capacity,nanoscale film capacitors,lead-free,pulsed laser deposition technique
更新于2025-09-16 10:30:52
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Manipulating Light–Matter Interactions in Plasmonic Nanoparticle Lattices
摘要： Rationally assembled nanostructures exhibit distinct physical and chemical properties beyond their individual units. Developments in nanofabrication techniques have enabled the patterning of a wide range of nanomaterial designs over macroscale (>in.2) areas. Periodic metal nanostructures show long-range diffractive interactions when the lattice spacing is close to the wavelength of the incident light. The collective coupling between metal nanoparticles in a lattice introduces sharp and intense plasmonic surface lattice resonances, in contrast to the broad localized resonances from single nanoparticles. Plasmonic nanoparticle lattices exhibit strongly enhanced optical fields within the subwavelength vicinity of the nanoparticle unit cells that are 2 orders of magnitude higher than that of individual units. These intense electromagnetic fields can manipulate nanoscale processes such as photocatalysis, optical spectroscopy, nonlinear optics, and light harvesting. This Account focuses on advances in exciton?plasmon coupling and light?matter interactions with plasmonic nanoparticle lattices. First, we introduce the fundamentals of ultrasharp surface lattice resonances; these resonances arise from the coupling of the localized surface plasmons of a nanoparticle to the diffraction mode from the lattice. Second, we discuss how integrating dye molecules with plasmonic nanoparticle lattices can result in an architecture for nanoscale lasing at room temperature. The lasing emission wavelength can be tuned in real time by adjusting the refractive index environment or varying the lattice spacing. Third, we describe how manipulating either the shape of the unit cell or the lattice geometry can control the lasing emission properties. Low-symmetry plasmonic nanoparticle lasing responses, and multiscale plasmonic superlattices—finite patches of lattices can show polarization-dependent nanoparticles grouped into microscale arrays—can support multiple plasmon resonances for controlled multimodal nanolasing. Fourth, we discuss how the assembly of photoactive emitters on the nanocavity arrays behaves as a hybrid materials system with enhanced exciton?plasmon coupling. Positioning metal?organic framework materials around nanoparticles produces mixed photon modes with strongly enhanced photoluminescence at wavelengths determined by the lattice. Deterministic coupling of quantum emitters in two-dimensional materials to plasmonic lattices leads to preserved single-photon emission and reduced decay lifetimes. Finally, we highlight emerging applications of nanoparticle lattices from compact, fully reconfigurable imaging devices to solid-state emitter structures. Plasmonic nanoparticle lattices are a versatile, scalable platform for tunable flat optics, nontrivial topological photonics, and modified chemical reactivities.
关键词： nanoscale lasing,surface lattice resonances,exciton?plasmon coupling,light?matter interactions,plasmonic nanoparticle lattices
更新于2025-09-16 10:30:52
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Parabolic two-step model and accurate numerical scheme for nanoscale heat conduction induced by ultrashort-pulsed laser heating
摘要： Simulation of nanoscale heat transfer phenomena has attracted great attention, particularly the nano-scale heat conduction induced by ultrashort-pulsed laser heating. In this article, we propose a nanoscale parabolic two-step model and an accurate numerical scheme for thermal analysis of the nanoscale heat conduction induced by ultrashort-pulsed laser heating. To this end, we first introduce the Knudsen number (Kn) into the original parabolic two-step heat conduction equations and couple them with the Kn-dependent and temperature-jump boundary condition. We then develop a fourth-order accurate compact finite difference method for solving the nanoscale model. Stability and convergence of the obtained numerical scheme are analyzed theoretically. We finally test the accuracy and applicability of the nanoscale model and the obtained numerical scheme in three examples. By choosing various values of the Kn and the parameter α in the boundary condition, the simulation could be a tool for analyzing the nanoscale heat conduction induced by ultrashort-pulsed laser heating.
关键词： Nanoscale heat conduction,Convergence,Compact finite difference scheme,Stability,Ultrashort-pulsed laser heating
更新于2025-09-12 10:27:22
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-Ga2O3 substrate enabled by self-assembled SiO2 nanospheres
摘要： To obtain high-quality GaN epitaxial ?lm on (?2 0 1) β-Ga2O3 substrate, periodic SiO2 nanosphere monolayer was self-assembled followed by inductively coupled plasma (ICP) etching. This periodic SiO2 nanosphere patterned Ga2O3 substrate (SiO2-NPGS) enables nanoscale epitaxial lateral overgrowth (NELOG) of GaN ?lm. Compared to planar Ga2O3 substrate, SiO2-NPGS shows great potential for epitaxial GaN with (0 0 0 2) and (1 0 ?1 2) full-width at half-maximum (FWHM) reduced from 555 to 388 arcsec, and 634 to 356 arcsec, respectively. Raman spectra also con?rm that the as-grown GaN ?lm on SiO2-NPGS is almost stress-free. The dislocation reduction is also observed by cross-sectional transmission electron microscope (TEM). The embedded SiO2-nanosphere blocks the dislocations and induces the GaN lateral overgrowth, thus leading to the signi?cant reduction of the threading dislocation densities. These ?ndings provide a new way for high quality stress-free GaN ?lm epitaxial growth on Ga2O3 substrate.
关键词： A3 Metal organic chemical vapor deposition,B1 SiO2 nanosphere,B1 Ga2O3,B1 GaN,A1 Nanoscale epitaxial lateral overgrowth
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - XUV Coherence Tomography with Nanoscale Resolution Driven by High Harmonic Generation
摘要： Optical coherence tomography (OCT) is a well-established method to retrieve three-dimensional, cross-sectional images of biological samples in a non-invasive way using near-infrared radiation. The axial resolution of OCT is on the order of the coherence length lc ∝ λ 2 /Δλ which depends on the central wavelength λ0 and the spectral width Δλ of the light source. As a consequence, the axial resolution only depends on the spectrum rather than the geometrical properties of the radiation. OCT with broadband visible and near-infrared sources typically reaches axial (depth) resolutions on the order of a few micrometers [1]. Here we present extreme ultra violet (XUV) coherence tomography (XCT) [2], which takes advantage of the fact that the coherence length can be signi?cantly reduced if broadband XUV and soft X-ray (SXR) radiation is used. XCT can display its full capabilities when used in the spectral transmission windows of the sample materials. For instance, the silicon transmission window (30-99 eV) corresponds to a coherence length of about 12 nm, thus suggesting applications for semiconductor inspection. In the water window at 280-530 eV, a coherence length as short as 3 nm can be achieved and highlights possible applications of XCT for life sciences. XCT utilizes a variant of the Fourier-domain OCT scheme that completely avoids a beam splitter. In the experiment, broadband XUV from a lab-based high-harmonic generation light source [3] is focused onto the surface of the sample. The re?ected spectrum is measured with a grating spectrometer (see Fig. 1 left side). The top layer re?ection assumes the role of a reference beam. Previously, this simpli?cation led to artifacts [2]. Here we show a novel one-dimensional phase retrieval algorithm (PR) to mitigate such disadvantages and enable artifact-free so-called PR-XCT [4]. The right side of Fig. 1 shows a 3D-tomogram of a nondestructive XCT scan of two nanometer thin laterally structured gold layers embedded in silicon. An axial resolution of 24 nm could be reached in the silicon transmission window with the table-top system. Another remarkable result is the high material sensitivity of XCT. At a depth of about 160 nm, a Silicon dioxide layer (blue) was detected which developed during the production process of the sample and has a thickness of a few nanometers only. This layer could not be detected with a SEM in a thin slice cut out of the sample, and even in a TEM image it is only barely visible. Furthermore, the PR-XCT algorithm is capable of extracting material information about the materials inside of the sample. We will present ?rst results on material-resolved XCT.
关键词： optical coherence tomography,high harmonic generation,XUV coherence tomography,nanoscale resolution,life sciences,semiconductor inspection
更新于2025-09-12 10:27:22