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Size-dependent phosphorus doping effect in nanocrystalline-Si-based multilayers
摘要： Doping in Si nanocrystalline (Si NCs) is currently an interesting issue since it can modulate electronic structures of Si NCs and consequently affect the electric and optical properties. However, it has been reported that doping in Si NCs is quite difficult due to the self-purification effect and the locations of dopants such as phosphorus (P) and boron (B), as well as the influences of dopants on physical properties is still unclear. In the present work, the P-doped Si NCs/SiO2 multilayers with various dot sizes (2–20 nm) were fabricated. It is found that the electronic properties are enhanced significantly after doping. However, for P-doped samples, the conductivity is size-dependent and reduces with decreasing the dot size, which can be attributed to the reduction of activated carrier concentration in the film with small dot size. Moreover, we find P dopants can induce deep-level for sample with small size of 2 nm, and a sub-band near infrared light emission near 1250 nm is detected. The possible mechanism are discussed briefly.
关键词： Si nanocrystals,Luminescence,Phosphorus doping,Electronic performance,Size dependence
更新于2025-09-11 14:15:04
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Stabilization of cubic phase in scandium-doped zirconia nanocrystals synthesized with sol-gel method
摘要： A new room-temperature synthesis of nanocrystals of scandium doped zirconium oxide by sol-gel method is reported. The structure of the obtained product is checked with standard structural analysis methods. The crystal phase of ZrO2-Sc2O3 nanocrystals changes from monoclinic to tetragonal and cubic with the increase in scandium concentration. The importance of the cubic phase, which appears at 10 mol% and refines at 16 mol% of Sc2O3 concentration, is emphasized. The UV-Vis absorption spectra of the product are measured, and its bandgap is evaluated from the fundamental absorption edge. The value of the bandgap was calculated as 5.65 eV for the cubic phase.
关键词： scandium-doped zirconia nanocrystals,UV-Vis spectra,sol-gel synthesis,stabilization of cubic phase
更新于2025-09-11 14:15:04
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Structural characterization determination of silicon nanocrystals embedded in amorphous silicon nitride matrix from the effect of the light scattering
摘要： In this work, we will study the elastic and inelastic light scattering by the silicon nanocrystals (Si-nc) embedded in amorphous silicon nitride matrix. Indeed, the photons are subjected to several modifications in terms of intensity, direction and wavelength when they interact with Si-ncs. The reflectance combined with photoluminescence (PL) and Raman spectroscopy are a very sensitive tool for probing the scattering light. Results show that the observed shift of the experimental PL peaks is attributed to the Raman scattering and the PL broadening peaks to the Rayleigh scattering. A novel method allowed the determination of both the core and the surface bond lengths of Si-nc was reported. The decrease of the Raman shift observed in structures containing Si-ncs is mainly due to the Si-nc curved surface, and it reflects the presence of silicon dangling bonds at the Si-nc interfaces.
关键词： Rayleigh scattering,Silicon nanocrystals,Silicon dangling bond,Raman scattering,Bond length,Silicon nanocrystal surface
更新于2025-09-10 09:29:36
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Design Principles for Trap-Free CsPbX <sub/>3</sub> Nanocrystals: Enumerating and Eliminating Surface Halide Vacancies with Softer Lewis Bases
摘要： We introduce a general surface passivation mechanism for cesium lead halide perovskite materials (CsPbX3, X = Cl, Br, I) that is supported by a combined experimental and theoretical study of the nanocrystal surface chemistry. A variety of spectroscopic methods are employed together with ab initio calculations to identify surface halide vacancies as the predominant source of charge trapping. The number of surface traps per nanocrystal is quantified by 1H NMR spectroscopy, and that number is consistent with a simple trapping model in which surface halide vacancies create deleterious under-coordinated lead atoms. These halide vacancies exhibit trapping behavior that differs between CsPbCl3, CsPbBr3, and CsPbI3. Ab initio calculations suggest that introduction of anionic X-type ligands can produce trap-free band gaps by altering the energetics of lead-based defect levels. General rules for selecting effective passivating ligand pairs are introduced by considering established principles of coordination chemistry. Introducing softer, anionic, X-type Lewis bases that target under-coordinated lead atoms results in absolute quantum yields approaching unity and monoexponential luminescence decay kinetics, thereby indicating full trap passivation. This work provides a systematic framework for preparing highly luminescent CsPbX3 nanocrystals with variable compositions and dimensionalities, thereby improving fundamental understanding of these materials and informing future synthetic and post-synthetic efforts towards trap-free CsPbX3 nanocrystals.
关键词： charge trapping,nanocrystals,surface passivation,ab initio calculations,halide vacancies,CsPbX3,ligand exchange,quantum yield
更新于2025-09-10 09:29:36
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Design principle of all-inorganic halide perovskite-related nanocrystals
摘要： All-inorganic halide perovskite (AIHP)-related (e.g., CsPbBr3, Cs4PbBr6, and CsPb2Br5) nanocrystals have attracted great research interest in the recent three years, owing to their unique optical properties. However, rational structural and compositional control of these nanocrystals is still challenging, particularly using the room temperature saturated recrystallization (RTSR) method. Here, we revealed that the structure and the composition of the nanocrystals fabricated by the RTSR approach are highly dependent not only on the previously thought concentration ratio of PbBr2 and CsBr in N-dimethylformamide (DMF), but the previously neglected absolute concentration and reaction time. This is the reason why pure AIHP-related nanocrystals are usually difficult to prepare using the RTSR method. Through a series of carefully designed experiments, we obtained the evolution trend of the precipitation rate of PbBr2 and CsBr within a wide concentration range in DMF. Based on the understanding of the growth mechanism, we achieved preparation of pure or a mixture of CsPbBr3, Cs4PbBr6, and CsPb2Br5 nanocrystals through either control of the concentration of PbBr2 and CsBr or the reaction time. This study deepens our understanding of the growth mechanism of AIHP-related nanocrystals, paving the way for future engineering of nanocrystals with desired structures and compositions. These structures with desired compositions will definitely have promising applications in optical and optoelectronic devices.
关键词： nanocrystals,All-inorganic halide perovskite,room temperature saturated recrystallization,optical properties,optoelectronic devices
更新于2025-09-10 09:29:36
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Preparation and optical characterization of PbWO4 nanocrystals from mechanical alloying process
摘要： This study presents the fabrication of PbWO4 nanoparticles using PbO and WO3 of designed molar ratio as the starting materials by mechanical alloying in atmospheric conditions. The impact energy of the SPEX ball milling machine provided the energy difference to form the PbWO4 through the mechanochemical process. The milled nanocrystals showcase single-phase product with particle sizes in the range of 3–10 nm. The UV–Vis-NIR spectra provide the direct band gap of 3.82 eV.
关键词： mechanical alloying,band gap,optical characterization,PbWO4 nanocrystals
更新于2025-09-10 09:29:36
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Alkaline-Earth Fluorohalide Nanocrystals for Upconversion Thermometry
摘要： The temperature-dependent luminescence response of SrFCl:Yb,Er and SrFBr:Yb,Er upconverting nanocrystals was investigated with an eye towards the expansion of the library of host materials for optical thermometry. Steady-state and luminescence decays of the 2H11/2 and 4S3/2 thermally coupled levels of the Er3+ activator were probed in the 100?450 K temperature range. Fluorescence intensity ratios and thermometric sensitivities were extracted in two temperature regimes. In the low-temperature regime, SrFCl:Yb,Er and SrFBr:Yb,Er displayed maximum sensitivities of 3.2 × 10?2 K?1 (125 K) and 2.1 × 10?2 K?1 (175 K), respectively. In the high-temperature regime, sensitivities were comparable to those observed in upconverting nanocrystals such as NaYF4:Yb,Er at room temperature, with values of 9.4 × 10?3 K?1 (325 K) for SrFCl:Yb,Er and 1.1 × 10?2 K?1 (300 K) for SrFBr:Yb,Er. The observed temperature-dependent responses resulted from long- and short-lived Er3+ emitters present in both fluorohalide hosts. For each type of emitter, radiative constants and activation energies for thermal quenching of the emission from the 4S3/2 level were estimated using a single-barrier quenching model. The local atomic environments of the long- and short-lived Er3+ emitters differed to a greater extent in SrFCl:Yb,Er than in SrFBr:Yb,Er.
关键词： SrFBr,Nanocrystals,Thermometry,SrFCl,Upconversion,Rare-earth
更新于2025-09-10 09:29:36
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Small lanthanide-doped Sr2YbF7 nanocrystals: Upconversion fluorescence and upconversion-driven photodegradation
摘要： A series of lanthanide-doped Sr2YbF7 nanocrystals were prepared conveniently via a solvothermal method using oleic acid as the stabilizing agent, which were about 15 nm of the average crystalline size at 200 °C and 24 h. Through screening the doped lanthanide ions and their concentrations, we found that the nanocrystals realized intense ultraviolet, visible and near-infrared upconversion emissions under 980 nm excitation. Based on the photo-physical property of the nanocrystals, we built the hybrid Sr2YbF7: Tm3+@TiO2 to successfully realize upconversion-driven photo-degradation of Rhodamine B, in which semiconducting TiO2 took advantage of the light emitted by Sr2YbF7: Tm3+ to produce the electron-hole pairs.
关键词： Upconversion,Photo-degradation,Sr2YbF7 nanocrystals
更新于2025-09-10 09:29:36
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Excitonic Luminescence Engineering in Tervalent Europium Doped Cesium Lead Halide Perovskite Nanocrystals and Their Temperature-Dependent Energy Transfer Emission Properties
摘要： Cesium lead halide (CsPbX3 (X=Cl, Br, I)) perovskite nanocrystals (NCs) have revealed brilliant prospect in lighting, display and lasing fields owing to their excellent photoluminescence properties. To dope rare earth ions into halide perovskite, CsPbX3 (X=Cl, Br, I) NCs hosts not only inherit the excellent narrow linewidth excitonic properties but also yield unique photoluminescence emission. Herein, engineering of such excitonic luminescence is achieved in Eu3+ doped CsPbCl3-xBrx (x=0, 1, 1.5, 2, 3) solid solution NCs for the first time. The single doped-NCs present wide color gamut emission covering whole visible spectrum. Blue to green range (400-520 nm) emission is taken on by tunable excitonic photoluminescence of CsPbX3 NCs. Besides, there is a broad red spectra (590-700 nm) originating from emission of the tervalent europium ions in NCs. Meanwhile, a noticeable spin-polarized 5D0→7F1-6 emission of Eu3+ ions is acquired owing to energy transfer from excitons to dopants. Moreover, the energy transfer is temperature-dependent which originating from the increase of nonradiative transition probability, leading to decrease for the NCs hosts’ PL intensity, but increase for the PL intensity of dopants.
关键词： Eu3+ doped,excitonic luminescence,Cesium lead halide,energy transfer,perovskite nanocrystals
更新于2025-09-10 09:29:36
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Energy Transfer from CdSe/ZnS Nanocrystals to Tetraphenyl Porphyrin
摘要： CdSe/ZnS nanocrystals (NCs) and Tetraphenyl Porphyrin (TPP) are mixed uniformly to prepare CdSe/ZnS NCs/TPP complex. TPP can quench the fluorescent signal of CdSe/ZnS NCs. UV-Vis absorption spectra and fluorescence spectra are employed to analysis the energy transfer. The mechanism of energy transfer is the F?rster resonance energy transfer from CdSe/ZnS to TPP.
关键词： Tetraphenyl Porphyrin,energy transfer,CdSe/ZnS nanocrystals,F?rster resonance energy transfer
更新于2025-09-10 09:29:36