Cihan Baydaroglu

Dye Incorporation: Instead of directly mixing the dye into the reaction mixture, consider covalently binding the dye to the silica precursor prior to particle synthesis. This can be achieved by reacting the dye with a silane coupling agent, such as (3-aminopropyl)triethoxysilane (APTES), to create a dye-silane conjugate. This conjugate can then be integrated into the silica network during the formation of the particles.

Particle Size Control: The diameter of silica particles produced by the Stöber process is influenced by various factors, including the concentrations of reactants (such as TEOS, ammonia, and water), the temperature of the reaction, and the rate of stirring. To obtain smaller particle sizes, consider increasing the concentrations of ammonia or water, which can encourage quicker nucleation and result in smaller particles. Additionally, managing the temperature of the reaction and the rate of stirring can lead to a more consistent distribution of particle sizes.

Reducing Polydispersity: To lower the polydispersity index (PDI), it's crucial to maintain consistent reaction conditions throughout the synthesis. This can be accomplished by using a precise stirring system and ensuring that the reactants are thoroughly mixed before initiating the reaction. Using silica seeds with a narrow size distribution for the synthesis can also contribute to reducing the PDI.

Enhancing Dye Intensity: To boost the intensity of the dye in the particles, consider increasing the quantity of the dye-silane conjugate in the reaction mixture. However, it's important to balance this with the potential risks of aggregation or uneven dye distribution. Another strategy is to fine-tune the dye loading process by modifying the pH and ionic strength of the reaction mixture to optimize dye adsorption onto the silica surface.

Characterization: After the synthesis, it's essential to thoroughly characterize the particles using techniques such as dynamic light scattering (DLS) for measuring size and PDI, transmission electron microscopy (TEM) or scanning electron microscopy (SEM) for observing morphology, and fluorescence spectroscopy for assessing dye intensity.

You need reactive groups on both the silica particle and the dye for making dye loaded silica particle.

The Fluorescein dye tends to aggregates in non aqueous solvents. This kills their fluorescence because of intermolecular photoinduced charge transfer. You could try quinacridone of antracene whose cristals are fluorescent. But they are neutral.

A. S. Klymchenko has created fluorescent fluorescein crystals in polymer dots using bulky counter ions. DOI: 10.1038/s41566-017-0001-7

Thank you for the answers - I will try it as soon as possible.

Instead of making silica particles yourself you can purchase them in any particle size. Next, you can aminate the particles using triethoxy 3-aminopropylsilane. If you use 5- or 6-carboxyfluorescein in place of fluorescein, the former can be covalently attached to to the amino groups created on the surface of the particle in the previous step. To attach 5(6)-carboxyfluorescein, one first activates the carboxy group using, for instance N-hydroxysuccinimide plus N-ethyl-N'-dimethylaminopropylcarbodiimide or coupling agents such as HBTU, TBTU, HATU, and COMU plus N-ethyl-N,N-diisopropylamine (Hunig's Base). Once the dye is activated, it is mixed with a suspension of the particles in an organic solvent, e.c. acetonitrile. The loading of the particles with the dye takes 2 to 4 h at RT, and you can make particles loaded to a different degree. For experimental details, please see the attached file.

Hi Cihan,

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