Influence of Halides on the Optical Properties of Silicon Quantum Dots

Silicon quantum dots (Si-QDs) have received substantial attention over the last two decades owing to their abundance, biocompatibility, and optical properties. Similar to their group II−VI and III−V quantum dot counterparts, hydride-terminated Si-QDs with diameters smaller than 5 nm can exhibit size-dependent photoluminescence (PL) in the visible spectral region. However, the hydride surface is highly susceptible to oxidation and requires further modification to passivate it and render the QDs soluble in common solvents

Investigation of Silicon Nanoparticle-Polystyrene Hybrids

Current LED lights are created with quantum dots made of metals like selenium, tellurium, and cadmium which can be toxic. Silicon is used as a non-toxic substance and is the second most abundant element in the earth's crust. When silicon is prepared at a nanometer size, unique luminesce optical properties emerge that can be tuned using sized surface chemistry. Therefore, silicon nanoparticles can be used as an alternative emitter for LED lights. To produce hydride-terminated silicon nanoparticles we must synthesize the particles. Hydrogen silsesquioxane (HSQ) is processed at 1100 °C for one hour causing Si to cluster and form a SiO2 matrix, also known as the composite. The composite is then manually crushed in ethanol. The solution is further ground using glass beads, then filtered to get the composite powder. The final step is the HF etching. The hydride-terminated particles are then functionalized using three different methods to synthesize silicon nanoparticle-polystyrene hybrids, which determine the magnitude of luminosity and the quality of the hybrids. We spin coat each method and results were analyzed. Method 1 uses heat to functionalize hydride-terminated silicon nanoparticles with styrene. This process also causes styrene to attach to styrene to form a polystyrene chain. Method 1 gave a homogeneous mixture which yielded a consistent, bright and homogenous film. In method 2, dodecyl-terminated silicon nanoparticles are mixed with premade polystyrene. While this method gave better control of the amount of silicon nanoparticles inside the polymer hybrid, a homogeneous mixture was not created due to the different structures of polystyrene and dodecyl chains. Method 3 has dodecyl-terminated silicon with in-situ styrene polymerization. It generated a homogeneous mixture. The in-situ polymerization stabilizes the particles, allowing for brighter luminescence. Because of the stability and lower molecular weight, the mixture was easier to dissolve. We concluded that the different methods resulted in different polymer molecular weights and this created distinct properties between the polymer hybrids when spin-coating.   &nbsp

Charge transfer state emission dynamics in blue-emitting functionalized silicon nanocrystals

We explore the dynamics of blue emission from dodecylamine and ammonia functionalized silicon nanocrystals (Si NCs) with average diameters of ∼3 and ∼6 nm using time-resolved photoluminescence (TRPL) spectroscopy. The Si NCs exhibit nanosecond PL decay dynamics that is independent of NC size and uniform across the emission spectrum. The TRPL measurements reveal complete quenching of core state emission by a charge transfer state that is responsible for the blue PL with a radiative recombination rate of ∼5 × 10^7 s^(−1). A detailed picture of the charge transfer state emission dynamics in these functionalized Si NCs is proposed

Metal Nanoparticle-Decorated Germanane for Selective Photocatalytic Aerobic Oxidation of Benzyl Alcohol

Two dimensional materials such as germanane have attracted substantial research interest due to their unique chemical, optical, and electronic properties. A variety of methods for introducing diverse functionalities to their surfaces have been reported and these materials have been exploted as photocatalysts. Herein, we report the preparation of metal nanoparticle (Au, Ag, Cu, Pd, Pt) decorated germanane (M@GeNSs) via a facile surface mediated reduction and investigate their structure, composition, as well morphology using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). These functional materials were subsequently explored as photocatalysts for selective visible light-induced oxidation of benzyl alcohol to benzaldehyde as freestanding nanosystems and thin films and a reaction mechanism of the photocatalytic oxidation of benzyl alcohol is proposed

Understanding the Formation of Elemental Germanium by Thermolysis of Sol-Gel Derived Organogermanium Oxide Polymers

Thermolysis of organogermanium oxide sol-gel polymers yields germanium oxide-embedded germanium nanocrystals. In the present study, we investigate the influence of different organic substituents, R, on the sol-gel chemistry of organotrichloro- and organotrialkoxygermane precursors and the thermal behavior of the resulting organogermanium oxides (RGeO_1.5)_n. The organic substituent affects the structure of the sol-gel product, with bulky R groups hindering network polymer formation. Cage-like sol-gels formed in the presence of bulky substituents are volatile, while network polymers experience thermolytic cleavage of the Ge–C bond. This cleavage produces a Ge-rich oxide (GeO_1.5)_n, that undergoes thermally induced disproportionation into GeO₂ and elemental Ge. The onset temperature of the disproportionation reaction is profoundly influenced by the nature of the organic substituent. We propose the change in onset temperature arises from a shift in R-group cleavage pathways from radical to β-hydride elimination