Brilliant molecular nanocrystals emerging from sol–gel thin films: towards a new generation of fluorescent biochips

Abstract

To develop highly sensitive biosensors, we made directly available to biological aqueous solutions organic nanocrystals previously grown in the pores of sol-gel films. Through the controlled dissolution of the sol-gel surface, we obtained emerging nanocrystals that remained strongly anchored to the sol-gel coating for good mechanical stability of the final sensing device. We demonstrated that in the presence of a solution of DNA functionalized with a molecular probe, the nanocrystal fluorescence is strongly quenched by Förster resonance energy transfer thus opening the way towards very sensitive fluorescent biosensors through biomolecules grafted onto fluorescent nanocrystals. Finally, this controlled dissolution, involving weak concentrated NaOH solution, is a generic process that can be used for the thinning of any kind of sol-gel layer.

New core–shell hybrid nanoparticles for biophotonics: fluorescent organic nanocrystals confined in organosilicate spheres

“…To optimize the structure and porosity of silicate shells, different relative amounts were used, according to previously reported results obtained for the preparation of sol-gel thin films. [36][37][38][39][40] Most importantly, this was done to control the dye-shell interactions and the hydrophilic-hydrophobic balance of NPs. Indeed, the strength of chemical interactions between the dye molecules and the silicate or organosilicate shell can be highly detrimental to the confined nucleation and growth of the organic nanocrystals.…”

“…To produce linear silicate chains, weakly interconnected, the alkoxides were hydrolyzed under acid-catalyzed conditions (pH z 1, HCl) associated with the hydrolysis molar ratio h ¼ 1. On the other hand, based on previous works related to organic nanocrystals grown in sol-gel thin films, 36,[44][45][46][47][48] we used high solvent amounts: 50 # s # 500. These high amounts of solvent led to a better control of the hydrolysis and polycondensation reactions of the silicon alkoxides and to nanometre-sized particles after the solvent evaporation.…”

“…This process was previously demonstrated as very efficient to remove the silicate matrix surrounding organic nanocrystals without any damage. 35,36 NPs (100 mg) were dispersed by ultrasound for 30 min (bath, 150 W) in 10 mL of NaOH solution (10 À1 M). Then, the slow dissolution of silicate shells was prolonged at room temperature for one week in a closed vial.…”

“…This equimolar mixture of TMOS + MTMOS was chosen on the basis of previously optimized conditions of the confined nucleation and growth of organic nanocrystals in sol-gel thin films. 36,46,47 Involving this sol, three main physical parameters of the spray-drying process were first optimized: the drying temperature in the horizontal furnace (Scheme 2-( 4)), the N 2 pressure involved in the sol atomization (Scheme 2-( 2)) and the flow of vector gas (Scheme 2-(3)). The N 2 pressure and gas vector flow were initially fixed respectively at 2 bars and 2 L min À1 , referring to previous spraydrying works done with similar equipment.…”

Fluorescence Spectroscopy of AdamBODIPY Single Crystals

“…Fluorescent dyes have attracted great attention for decades due to their potential applications in the field of biological sensing and labeling . Solid‐state fluorescent dyes have also received increasing interest in various fields, such as bioanalysis, photocatalysis, photonics, and microelectronics . The recent enhanced interest in (solid state) fluorescent dyes research has coincided with continuing miniaturization in materials science, to the point that words such as “nanotechnology” and “nanoparticles” have become established terms .…”