Up conversion nano capsules allow for the precise spatial generation of high energy photons from low energy photons. Their deployment enables to innovations in technologies such as Volumetric 3D printing. This protocol shows fabrication of durable silicone encapsulated nanocapsules.
Our procedure is very scalable and we highlight protocols for synthesis at two different scales. Begin by setting up a glove box with an inert atmosphere under red lighting. To prepare saturated solution of this sensitizer, add two milliliters of 99%oleic acid to 20 milligrams of the sensitizer in a vial with a stir bar.
Cover the vial with foil to protect it from ambient light. Then add two milliliters of 99%oleic acid to 25 milligrams of the annihilator in a vial with a stir bar. Stir the mixture at 600 RPM in room temperature for at least four hours.
Then, filter both solutions with a 0.45 micrometer PTFE syringe filter. Using a syringe, mix 0.7 milliliters of the filter denialator solution. 0.35 milliliters of the filtered sensitizer solution.
And 0.7 milliliters of oleic acid to prepare the up conversion material stock solution. Next, under ambient lighting, add 200 milliliters of ultrapure deionized water in a 250 milliliter Erlenmeyer flask sealed with a septum. Chill the flask in an ice bath for at least one hour to reach approximately five degrees Celsius.
And secure the septum using sealing film. Immediately before preparing the nanocapsules, bring the chilled water into the glove box. Ensure to only pull a light vacuum on the antechamber when bringing in the water by pulling 20%vacuum based on the measurement of the antechamber pressure gauge.
After bringing the water into the glove box, immediately turn on the glove box purge feature to bypass the column. Ensure all chemicals and consumables within reach, including syringes and needles for dispensing optus and tetraethyl orthosilicate. 10k mPEG-Saline and nylon cloth for cleaning.
Plug in the blender and cover the electrical sockets with a plastic bin or nylon cloth. Carefully pour the water into the blender. Add 1.45 milliliters of the upconversion material stock solution in one portion with a syringe into the center of the water of the blender.
Affix the lid and cover it with a nylon wipe. Blend at 22, 600 RPM for exactly 60 seconds while holding the blender lid to prevent small leaks. Transfer the emulsion to a 500 milliliter round bottom flask.
Secure the flask to a stir plate with a clamp. Add an egg-shaped stir bar and mix the emulsion vigorously at 1200 rpm. Using a syringe, add 0.75 milliliters of optus to the emulsion to generate a clear solution of micelles.
Add four grams of 10k mPEG-Silane to prevent capsule aggregation. Shake the flask to ensure it is dispersed. And stir at 1200 RPM for approximately 10 minutes.
After stirring, add 15 milliliters of tetraethyl orthosilicate in one portion using a 20 milliliter syringe. Add another 15 milliliters in one portion. Affix the septum to the flask and stir at 1200 RPM for 30 minutes.
Remove the flask and waste from the glove box. Affix the flask to a stir plate with a heating element and connect the flask to a schlenk line to hold the reaction at a constant pressure under an inert gas. Stir and heat the reaction at 1200 RPM for 40 hours at 65 degrees Celsius.
Then, disconnect the reaction from the schlenk line and add four grams of 10k mPEG-Silane. Reconnect the reaction to the schlenk line. Stir and heat the reaction for eight hours.
After eight hours, turn off the heat and allow the reaction to cool to room temperature while stirring at 1200 rpm. Then, centrifuge the suspension in centrifuge tubes at 8, 670 G for one hour at 22 degrees Celsius. Discard the pellet and retain the supernatant containing the nano capsules.
Again, centrifuge the supernatant for 14 to 16 hours. Discard the supernatant and collect the pellet containing upconversion nanocapsules. Using a pipette, carefully rinse the top surface of the nano capsule pellet twice with 10 milliliters of ultrapure deionized water.
With a spatula, transfer the nanocapsule paste into separate 20 milliliters scintillation vials. And immediately bring the vials into the glove box and characterize the nano capsule preparation. Plug in the vortex mixer and set the speed to the highest setting at 3, 200 rpm.
Using a micropipette, add 145 microliters of sensitizer annihilator stock solution to 20 milliliters of sparged water. Affix the lid with electrical tape or ceiling film. Vortex the solution for seven minutes by holding the vial close to the base.
Affix the vial to a stir plate and stir the emulsion at 1, 200 RPM with an octagon shaped stir bar. Using a micropipette, add 75 microliters of optus to generate a clear solution of micelles. And then, immediately add 400 milligrams of 10k mPEG-Silane.
Shake the vial to officially mix the reaction and return the vial to the stir plate. Using a syringe, add three milliliters of tetraethyl orthosilicate while the reaction is being stirred at 1200 rpm. Shake the vial and then stir the reaction at 1200 RPM until it is removed from the glove box.
Seal the vial with electrical tape or sealing film and remove the vial from the glove box. Heat the solution at 65 degrees Celsius while stirring it 1200 RPM for 40 hours. Then, add 400 milligrams of 10k mPEG-Silane and stir the reaction for eight hours.
A scanning electron microscopy image of the upconversion nanocapsule obtained using this protocol, showed monodispersed nanocapsules with a diameter of approximately 50 nanometers. Under the ultra high vacuum necessary for this measurement, the nanocapsules fuse after approximately 30 minutes. As seen by dynamic light scattering traces, similar upconversion nanocapsule diameters can be generated from large scale or small scale protocols.
With an average hydrodynamic diameter of 75 nanometers for the large batch and 66 nanometers for the small batch. Optical characterization showed that upon a radiation with a 635 nanometer laser The anthrosin upconversion emission was present. Signifying that the silica shell remained intact in the nano capsules.
There are small details that can make a big difference in the nanocapsule performance. Take care to protect the reaction from ambient oxygen and add the proper volume of app test. Researchers are able to maximize upconversion performance using these in analogous nanocapsules.
Additionally, using this technique researchers can make nanocapsules for incorporation into a light driven 3D printing resin.
