Colloidal solutions of luminescent porous silicon clusters with different cluster sizes

Abstract

Silicon nanocrystals (Si-ncs) are promising for biological studies due to their supposed low cytotoxicity, good biocompatibility and biodegradability in living organisms. However, the bioresearchers' focus on Si-ncs has lasted only for a few recent years, and detailed studies of the interaction of various types of Si-ncs with biological environment are still rare. Suitable size and solubility of the Si-ncs in water-based isotonic solutions are important towards bringing the nanocrystals inside the living cells. We have prepared colloidal solutions of luminescent porous silicon of different cluster sizes in methanol, water and phosphate-buffered saline (PBS). By combination of ultrasonic treatment with filtration, we have obtained two different silicon cluster sizes in methanol (120 and 525 nm) and three different cluster sizes (85, 210 and 1,500 nm) in PBS. Nanoclusters of heavily oxidized porous silicon are hydrophilic and well soluble in water and/or PBS. They can be further used for studies on the biocompatibility of these materials and may be potentially employed as luminescent markers in living cells in biological research.PACS78.67.Rb; 78.67.-n; 87.85.Qr; 87.85.Rs; 81.07.-b

Agglomeration of Luminescent Porous Silicon Nanoparticles in Colloidal Solutions

“…For biological in vivo studies, perhaps even for the use of silicon nanoparticles for controlled drug delivery, suitable samples are colloidal solutions in water-based (non-toxic) or isotonic solvents such as phosphate-buffered saline (PBS); alcohol solutions in methanol or ethanol must be strongly diluted because of their toxicity for living cells. Further requirement is that the nanoparticles must have suitable size of the order of units, tens or maximally couple of hundreds nanometers [ 16 ] in order to easily penetrate into the cells via endocytosis process. Last but not least, the Si-ncs have to be hydrophilic (easily soluble in water) and stable in time, without any agglomeration tendency.…”

Structural and luminescence properties of silicon nanocrystals in colloidal solutions for bio applications

“…b show red photoluminescence of all colloidal solutions, the BSA spectrum is blue shifted due to the luminescence of the solvent itself. It should be noted that the clusters of electrochemically etched highly porous silicon are composed of interconnected nanometer‐sized luminescent nanocrystals, so the quantum confinement effect is responsible for the red luminescence . The photoluminescence intensity varies slightly from solution to solution, however, the overall photoluminescence intensity is for all the solutions roughly of the same order of magnitude and comparable.…”

“…In this paper, we report on structural and optical properties of Si‐ncs prepared by low‐pressure plasma synthesis and compare them with porous silicon obtained by standard electrochemical etching . Electrochemical etching is a top‐down technique producing highly porous luminescent silicon nanoclusters of hundreds nanometer size and their surface modification by methyl groups is known to lead to interesting properties such as increased luminescence quantum yield, accelerating luminescence decay , direct band gap behavior , and luminescence blinking caused by trions . Surface modification of Si‐ncs in colloidal solutions by methyl groups was carried out in plasma‐synthesized Si‐ncs, too, and the attempt to avoid agglomeration by steric stabilization of the Si‐ncs by simple organic compounds is presented (see also Ref.…”

Functionalization of Biomolecules With Nanostructured Porous Silicon for Biomedical Application

“…5,6 Recently Herynkova et al, have prepared colloidal solutions of luminescent porous silicon of di®erent cluster sizes and studied their biocompatibility as luminescent markers in living cells in biological research. 7 Rodriguez et al, have designed porous silicon (PS) Bloch surface wave (BSW) and Bloch sub-surface wave (BSSW) composite biosensor and used for the size-selective detection of both small and large molecules. 8 Kafshgari et al, have investigated the ability of porous silicon nanoparticles (PS NPs) to entrap and deliver nitric oxide (NO) as an e®ective antibacterial agent against di®erent Gram-positive and Gram-negative bacteria.…”