Photoassisted Tuning of Silicon Nanocrystal Photoluminescence

Abstract

Silicon is a rather inefficient light emitter due to the indirect band gap electronic structure, requiring a phonon to balance the electron momentum during the interband transition. Fortunately, momentum requirements are relaxed in the 1-5 nm diameter Si crystals as a result of quantum confinement effects, and bright photoluminescence (PL) in the UV-vis range is achieved. Photoluminescent Si nanocrystals along with the C- and SiC-based nanoparticles are considered bioinert and may lead to the development of biocompatible and smaller probes than the well-known metal chalcogenide-based quantum dots. Published Si nanocrystal production procedures typically do not allow for the fine control of the particle size. An accepted way to make the H-terminated Si nanocrystals consists of anodic Si wafer etching with the subsequent breakup of the porous film in an ultrasound bath. Resulting H-termination provides a useful platform for further chemical derivatization and conjugation to biomolecules. However, a rather polydisperse mixture is produced following the ultrasonic treatment, leading to the distributed band gap energies and the extent of surface passivation. From the technological point of view, a homogeneous nanoparticle size mixture is highly desirable. In this study, we offer an efficient way to reduce the H-terminated Si nanocrystal diameter and narrow size distribution through photocatalyzed dissolution in a HF/HNO3 acid mixture. Si particles were produced using the lateral etching of a Si wafer in a HF/EtOH/H2O bath followed by sonication in deaerated methanol. Initial suspensions exhibited broad photoluminescence in the red spectral region. Photoassisted etching was carried out by adding the HF/HNO3 acid mixture to the suspension and exposing it to a 340 nm light. Photoluminescence and absorbance spectra, measured during dissolution, show the gradual particle size decrease as confirmed by the photoluminescence blue shift. The simultaneous narrowing of the photoluminescence spectral bandwidth suggests that the dissolution rate varies with the particle size. We show that the Si nanoparticle dissolution rate depends on the amount of light adsorbed by the particle and accounts for the etching rate variation with the particle size. Significant improvement in the PL quantum yield is observed during the acid treatment, suggesting improvement in the dangling bond passivation.

Comparison of cytotoxic and inflammatory responses of photoluminescent silicon nanoparticles with silicon micron‐sized particles in RAW 264.7 macrophages

“…SNs were synthesized using electrochemical etching of silicon wafers followed by ultrasound treatment (Yamani et al, 1998;Choi et al, 2007Choi et al, , 2008a. To prepare SNs for use in cell culture experiments, a suspension of SNs was delivered to a glass, sterile Petri dish for a thermal sterilization treatment.…”

Фотолюминесценция Аморфных И Кристаллических Кремниевых Нанокластеров В Сверхрешетках Из Нитрида И Оксида Кремния

“…Оптические свойства кремниевых нанокластеров в различных диэлектрических матрицах представляют значительный интерес для оптоэлектроники, посколь-ку в таких структурах, в отличие от объемного кремния, наблюдается эффективная фотолюминесцен-ция (ФЛ) [1][2][3][4][5][6][7][8][9][10][11][12][13]. В частности, перспективным является создание светоизлучающих элементов на основе кремни-евых нанокристаллов в кремнийсодержащей матрице и последующее их интегрирование в устройства нанофото-ники [1,3].…”

Silicium‐Nanokristalle und Silicium‐Polymer‐Hybridmaterialien: Synthese, Oberflächenmodifikation und Anwendungen

“…Die am häufigsten verwendeten Methoden kçnnen generell in verschiedene Reaktionen, wie die Reduktion von Siliciumhalogeniden, [16] Oxidation von Metallsiliciden, [17] thermische Disproportionierung von siliciumreichen Oxiden [18] und Zersetzung von Silan oder Disilan [19] unter Verwendung von Plasma oder Wärme eingeteilt werden (Schema 1). Andere Verfahren, wie die magnesiotherme Reduktion, [20] die thermische Zersetzung von Silicium-Vorstufen in überkritischem Fluid [21] und ¾tzen [22] oder mechanochemisches Mahlen von Bulk-Silicium zu SiNanokristallen mit einer Kugelmühle [23] wurden ebenfalls berichtet. Diese Methoden sowie ihre Vor-und Nachteile wurden vor kurzem in einem Artikel zusammengefasst und werden hier daher nicht weiter behandelt.…”