Critical assessment of wet-chemical oxidation synthesis of silicon quantum dots

ABSTRACTSilicon nanocrystals with diameters of less than 5 nm show efficient room temperature pho-toluminescence (PL). Previous reports of PL quantum yields for ensembles of silicon quantum dots have usually been in the few percent range, and generally less than 30%. Here we report the plasma synthesis of silicon quantum dots and their subsequent wet-chemical surface passivation with organic ligands while strictly excluding oxygen. Photoluminescence quantum yields as high as 62% have been achieved at peak wavelengths of about 789 nm.

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Effects of Wet Chemical Oxidation on Surface Functionalization and Morphology of Highly Oriented Pyrolytic Graphite

10.26434/chemrxiv.12907604.v1 ◽

2020 ◽

Author(s):

Mikhail Trought ◽

Isobel Wentworth ◽

Timothy Leftwich ◽

Kathryn Perrine

Keyword(s):

Surface Functionalization ◽

Functional Group ◽

Pyrolytic Graphite ◽

Surface Oxidation ◽

Chemical Oxidation ◽

Synthesis Methods ◽

Acid Solutions ◽

Highly Oriented Pyrolytic Graphite ◽

Wet Chemical ◽

Surface Morphologies

The knowledge of chemical functionalization for area selective deposition (ASD) is crucial for designing the next generation heterogeneous catalysis. Surface functionalization by oxidation was studied on the surface of highly oriented pyrolytic graphite (HOPG). The HOPG surface was exposed to with various concentrations of two different acids (HCl and HNO3). We show that exposure of the HOPG surface to the acid solutions produce primarily the same -OH functional group and also significant differences the surface topography. Mechanisms are suggested to explain these strikingly different surface morphologies after surface oxidation. This knowledge can be used to for ASD synthesis methods for future graphene-based technologies.

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Communication: Photoinduced Carbon Dioxide Binding with Surface-Functionalized Silicon Quantum Dots

10.26434/chemrxiv.5944273.v1 ◽

2018 ◽

Author(s):

Oscar A. Douglas-Gallardo ◽

Cristián Gabriel Sánchez ◽

Esteban Vöhringer-Martinez

Keyword(s):

Carbon Dioxide ◽

Quantum Dots ◽

Atmospheric Carbon Dioxide ◽

Density Functional ◽

Tight Binding ◽

Carbon Dioxide Concentration ◽

Research Area ◽

Silicon Quantum Dots ◽

Dependent Model ◽

Photoinduced Charge

<div> <div> <div> <p>Nowadays, the search of efficient methods able to reduce the high atmospheric carbon dioxide concentration has turned into a very dynamic research area. Several environmental problems have been closely associated with the high atmospheric level of this greenhouse gas. Here, a novel system based on the use of surface-functionalized silicon quantum dots (sf -SiQDs) is theoretically proposed as a versatile device to bind carbon dioxide. Within this approach, carbon dioxide trapping is modulated by a photoinduced charge redistribution between the capping molecule and the silicon quantum dots (SiQDs). Chemical and electronic properties of the proposed SiQDs have been studied with Density Functional Theory (DFT) and Density Functional Tight-Binding (DFTB) approach along with a Time-Dependent model based on the DFTB (TD-DFTB) framework. To the best of our knowledge, this is the first report that proposes and explores the potential application of a versatile and friendly device based on the use of sf -SiQDs for photochemically activated carbon dioxide fixation. </p> </div> </div> </div>

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