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Synthesis of Cu2O/CuO Nanocrystals and Their Application to H2S Sensing
摘要： Semiconducting metal oxide nanocrystals are an important class of materials that have versatile applications because of their useful properties and high stability. Here, we developed a simple route to synthesize nanocrystals (NCs) of copper oxides such as Cu2O and CuO using a hot-soap method, and applied them to H2S sensing. Cu2O NCs were synthesized by simply heating a copper precursor in oleylamine in the presence of diol at 160 °C under an Ar flow. X-ray diffractometry (XRD), dynamic light scattering (DLS), and transmission electron microscopy (TEM) results indicated the formation of monodispersed Cu2O NCs having approximately 5 nm in crystallite size and 12 nm in colloidal size. The conversion of the Cu2O NCs to CuO NCs was undertaken by straightforward air oxidation at room temperature, as confirmed by XRD and UV-vis analyses. A thin film Cu2O NC sensor fabricated by spin coating showed responses to H2S in dilute concentrations (1–8 ppm) at 50–150 °C, but the stability was poor because of the formation of metallic Cu2S in a H2S atmosphere. We found that Pd loading improved the stability of the sensor response. The Pd-loaded Cu2O NC sensor exhibited reproducible responses to H2S at 200 °C. Based on the gas sensing mechanism, it is suggested that Pd loading facilitates the reaction of adsorbed oxygen with H2S and suppresses the irreversible formation of Cu2S.
关键词： CuO,H2S,gas sensor,Cu2O,nanocrystal
更新于2025-09-23 15:22:29
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Changes of the absorption cross section of Si nanocrystals with temperature and distance
摘要： The absorption cross section (ACS) of silicon nanocrystals (Si NCs) in single-layer and multilayer structures with variable thickness of oxide barriers is determined via a photoluminescence (PL) modulation technique that is based on the analysis of excitation intensity-dependent PL kinetics under modulated pumping. We clearly demonstrate that roughly doubling the barrier thickness (from ca. 1 to 2.2 nm) induces a decrease of the ACS by a factor of 1.5. An optimum separation barrier thickness of ca. 1.6 nm is calculated to maximize the PL intensity yield. This large variation of ACS values with barrier thickness is attributed to a modulation of either defect population states or of the efficiency of energy transfer between confined NC layers. An exponential decrease of the ACS with decreasing temperature down to 120 K can be explained by smaller occupation number of phonons and expansion of the band gap of Si NCs at low temperatures. This study clearly shows that the ACS of Si NCs cannot be considered as independent on experimental conditions and sample parameters.
关键词： silicon nanocrystals,average lifetime,absorption cross section,photoluminescence decay,nanocrystal distance
更新于2025-09-23 15:22:29
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Integrable all-optical pass switch
摘要： A completely new design for an all-silicon all-optical pass switch has been proposed based on the stimulated Raman scattering (SRS) in silicon nanocrystal embedded slotted photonic crystal waveguide (SPCW). Substantial miniaturisation in the device footprint and operating power has been attained by merging the benefits of the giant SRS gain and the ultra-high optical confinement of the SPCW. The proposed switch offers a tremendously high contrast ratio of (cid:1) 27 dB between the logic levels and an extraordinary bit rate of 125 Gbps.
关键词： high bit rate,stimulated Raman scattering,high contrast ratio,slotted photonic crystal waveguide,silicon nanocrystal,all-optical pass switch
更新于2025-09-23 15:21:21
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Tellurium Precursor for Nanocrystal Synthesis: Tris(dimethylamino)phosphine Telluride
摘要： Preparations of CdTe quantum platelets, magic-size (CdTe)13 nanoclusters, and CdTe quantum wires are described using (Me2N)3PTe (with (Me2N)3P) as a Te precursor. The (Me2N)3PTe/(Me2N)3P precursor mixture is shown to be more reactive than mixtures of trialkylphosphine tellurides and the corresponding trialkylphosphines, R3PTe/R3P, which are commonly employed in nanocrystal syntheses. For syntheses conducted in primary amine solvents, (Me2N)3PTe and (Me2N)3P undergo a transamination reaction, affording (Me2N)x(RHN)3?xPTe and (Me2N)x(RHN)3?xP (R = n-octyl or oleyl). The transaminated (Me2N)x(RHN)3?xPTe derivatives are shown to be the likely Te precursors under those conditions. The enhanced reactivities of the tris(amino)phosphine tellurides are ascribed to increased nucleophilicity due to the amino-N lone pairs.
关键词： tris(dimethylamino)phosphine telluride,tellurium precursor,CdTe quantum wires,nanocrystal synthesis,CdTe nanoplatelets,(CdTe)13
更新于2025-09-23 15:21:21
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Magnetic and optical behaviors of SnO2-x thin films with oxygen vacancies prepared by atomic layer deposition
摘要： SnO2-x thin films with different concentration oxygen vacancies were prepared by Atomic Layer Deposition (ALD). Specifically, the oxygen vacancy concentration was controlled by the oxidation pulse time during the ALD process. The crystal structure of the as-prepared thin films was determined by XRD, and the magnetic properties were measured by VSM, while the optical properties were measured by optical transmittance spectrum. The results showed that the oxygen vacancy concentration of the SnO2-x could be controlled by the oxidation pulse time, and the crystal structures, magnetic properties, and optical properties were largely impacted by the concentration of oxygen vacancy.
关键词： microstructure,thin film,magnetic,diffraction,nanocrystal,oxygen vacancy
更新于2025-09-23 15:21:21
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Improved Models for Metallic Nanoparticle Cores From Atomic Pair Distribution Function (PDF) Analysis
摘要： X-ray atomic pair distribution functions (PDFs) were collected from a range of canonical metallic nanomaterials, both elemental and alloyed, prepared using different synthesis methods and exhibiting drastically different morphological properties. Widely applied shape-tuned attenuated crystal (AC) fcc models proved inadequate, yielding structured, coherent, and correlated fit residuals. However, equally simple discrete cluster models could account for the largest amplitude features in these difference signals. A hypothesis testing based approach to nanoparticle structure modelling systematically ruled out effects from crystallite size, composition, shape, and surface faceting as primary factors contributing to the AC misfit. On the other hand, decahedrally twinned cluster cores were found to be the origin of the AC structure misfits for a majority of the nanomaterials reported here. It is further motivated that the PDF can readily differentiate between the arrangement of domains in these multiply-twinned motifs. Most of the nanomaterials surveyed also fall within the sub-5 nm size regime where traditional electron microscopy cannot easily detect and quantify domain structures, with sampling representative of the average nanocrystal synthesized. The results demonstrate that PDF analysis is a powerful method for understanding internal atomic interfaces in small noble metallic nanomaterials. Such core cluster models, easily built algorithmically, should serve as starting structures for more advanced models able to capture atomic positional disorder, ligand induced or otherwise, near nanocrystal surfaces.
关键词： decahedrally twinned cluster cores,PDF analysis,metallic nanomaterials,nanocrystal surfaces,X-ray atomic pair distribution functions
更新于2025-09-23 15:21:21
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Heterojunction Incorporating Perovskite and Microporous Metala??Organic Framework Nanocrystals for Efficient and Stable Solar Cells
摘要： In this paper, we present a facile approach to enhance the efficiency and stability of perovskite solar cells (PSCs) by incorporating perovskite with microporous indium-based metal–organic framework [In12O(OH)16(H2O)5(btc)6]n (In-BTC) nanocrystals and forming heterojunction light-harvesting layer. The interconnected micropores and terminal oxygen sites of In-BTC allow the preferential crystallization of perovskite inside the regular cavities, endowing the derived films with improved morphology/crystallinity and reduced grain boundaries/defects. Consequently, the In-BTC-modified PSC yields enhanced fill factor of 0.79 and power conversion efficiency (PCE) of 20.87%, surpassing the pristine device (0.76 and 19.52%, respectively). More importantly, over 80% of the original PCE is retained after 12 days of exposure to ambient environment (25 °C and relative humidity of ~ 65%) without encapsulation, while only about 35% is left to the pristine device.
关键词： Light-harvesting layer,Metal–organic framework,Heterojunction,Perovskite solar cell,Nanocrystal
更新于2025-09-23 15:21:01
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Silicon Nanoparticle Films Infilled with Al <sub/>2</sub> O <sub/>3</sub> using Atomic Layer Deposition for Photosensor, Light Emission and Photovoltaic Applications
摘要： Solution-processed thin films of crystalline silicon nanoparticles (Si NPs) have a great potential for a wide variety of electronic and optoelectronic applications. However, such films are inherently unstable due to their huge surface-to-volume ratios and high surface energies, making them prone to degradation associated to spontaneous oxidation in ambient conditions. In this work, we explore the use of atomic layer deposition (ALD) as a means to stabilize and potentially functionalize solution-processed thin films of Si NPs for (opto)electronics e.g. thin-film transistors, photosensors, light-emitting devices, and photovoltaics. We prepared films of randomly distributed Si NPs with ultrashort surface ligands (Si-H termination) using wet-chemistry and spray-coating and then use ALD to infill the films with Al2O3. Through microscopy and optical structural/morphological analysis, we demonstrate the achievability of ALD infilling of films of Si NPs and probe the stability of these films against oxidation. Moreover, we show that the ALD infilling leads to changes in the light emission properties of the Si NP films, including a relative quenching of disorder-related emission features and variations in surface-related dielectric confinement effects. Our studies reveal ALD as a relevant technique toward manufacturing de facto robust, functional nanomaterials based on Si NPs and on nanoscale silicon materials more generally.
关键词： Photoluminescence properties,Nanoparticle film infilling,Silicon nanocrystal films,Air stability,Atomic layer deposition
更新于2025-09-23 15:21:01
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Nanoplatelet-Based Light-Emitting Diode and Its Use in All-Nanocrystal LiFi-like Communication
摘要： Since colloidal nanocrystals (NCs) were integrated as green and red sources for LCD displays, the next challenge for quantum dots has been their use in electrically driven light emitting diodes (LEDs). Among various colloidal nanocrystals, nanoplatelets (NPLs) appeared as promising candidates for light emitting devices because their two-dimensional shape allows a narrow luminescence spectrum, directional emission and high light extraction. To reach high quantum efficiency it is critical to grow core/shell structures. High temperature growth of the shells seems to be a better strategy than previously reported low temperature approaches to obtain bright NPLs. Here, we synthesize CdSe/CdZnS core/shell NPLs whose shell alloy content is tuned to optimize the hole injection in the LED structure. The obtained LED has exceptionally low turn-on voltage, long-term stability (>3100 h at 100 Cd.m-2), external quantum efficiency above 5% and luminance up to 35000 cd.m-2. We study the low-temperature performance of the LED and find that there is a delay of droop in terms of current density as temperature decreases. In the last part of the paper, we design a large LED (56 mm2 emitting area) and test its potential for LiFi-like communication. In such approach, the LED is not only a lightning source but also used to transmit a communication signal to a PbS quantum dot solar cell used as a broad band photodetector. Operating conditions compatible with both lighting and information transfer have been identified. This work paves the way toward an all nanocrystal-based communication setup.
关键词： efficiency droop,nanoplatelets,electronic transport,light emitting diode,nanocrystal-based communication
更新于2025-09-23 15:19:57
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Colloidal Synthesis and Charge-Carrier Dynamics of Cs2AgSb1-yBiyX6 (X: Br, Cl; 0 ≤y ≤ 1) Double Perovskite Nanocrystals
摘要： A series of lead-free double perovskite NCs: Cs2AgSb1-yBiyX6 (X: Br, Cl; 0≤y≤1) NCs are synthesized. In particular, Cs2AgSbBr6 NCs is a new double perovskite material that has not been reported for the bulk form. Mixed Ag-Sb/Bi NCs exhibit enhanced stability in colloidal solution compared to Ag-Bi or Ag-Sb NCs. Femtosecond transient absorption studies indicate the presence of two prominent fast trapping processes in the charge carrier relaxation. The two fast trapping processes are dominated by intrinsic self-trapping (1~2 ps) due to giant exciton-phonon coupling and surface defects trapping (50~100 ps), respectively. Slow hot-carrier relaxation is observed at high pump fluence, and the possible mechanisms for the slow hot-carrier relaxation are also discussed.
关键词： nanocrystal,double perovskite,carrier-phonon coupling,hot-carrier cooling,trap state
更新于2025-09-23 15:19:57