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--- o2_sensor [2025/01/17 02:45] – kenson
+++ o2_sensor [2025/01/30 20:43] (current) – kenson
@@ Line 3: / Line 3: @@
   * {{ :ocr60.pdf | Whitepaper describing use of 9,10-Diphenylanthracene for oxygen detection}}
   * The oxygen quenching is predicted by the Stern-Volmer equation, and changes in intensity or lifetime of the fluorescence can be monitored
+  * Ruthenium complex
+    * [[https://www.cyanagen.com/products/rubp3-pf62-ruthenium-complexes/]]
+    * [[https://www.cyanagen.com/cyanacontent/uploads/Products/RuBP3-PF62/Documents/SDS/EN-IS_RuBP3-PF62-F3R050X_rev01.pdf]]
+    * [[https://www.ruixibiotech.com/pts/ru-bpy3-pf6-2]] CAS: 60804-74-2 $400/g
+    * {{:rubp3-pf62_transient_absorption.png?direct&400|}}
+  * [[https://www.eevblog.com/forum/projects/accurate-pulse-width-measurement/]]
+  * [[https://www.ti.com/product/TDC7200]]
+    * Datasheet: [[https://www.ti.com/lit/ds/symlink/tdc7200.pdf]]
+    * [[https://github.com/Yveaux/TDC7200]]
+  * {{ :quenching_of_the_fluorescence_of_tris_2_2_bipyridine_ruthenium.pdf |Quenching of the Fluorescence of Tris (2,2’-Bipyridine) Ruthenium(II),
+[Ru(bipy)3]2+, by a Dimeric Copper(II) Complex}}
 ==== 390nm LED ====
@@ Line 49: / Line 60: @@
 {{:photodiodespectra.png?direct&600|}}
-==== Making samples ====
+===== Making Rubene Samples =====
-= Regarding doping rubrene into PDMS =
+==== Doping rubrene into PDMS ====
 (e.g., Sylgard 184 or a similar PDMS variant like Sylcap 284).
@@ Line 63: / Line 74: @@
 === Why This Range? ===
   - **Fluorescence Brightness vs. Self-Quenching**
     * Rubrene is highly fluorescent, so even a small concentration can yield significant emission.
     * Above roughly **0.1–0.2 wt%**, many organic dyes (including rubrene) begin to exhibit “concentration quenching,” where the emission drops due to exciton–exciton annihilation or dye aggregation.
   - **Cost and Solubility**
-   - Rubrene can be expensive, and it’s only moderately soluble in typical organic solvents. Over-saturating the mix will result in precipitates, optical scattering, or inhomogeneous films.
+    * Rubrene can be expensive, and it’s only moderately soluble in typical organic solvents. Over-saturating the mix will result in precipitates, optical scattering, or inhomogeneous films.
-. **Oxygen Diffusion**
+  - **Oxygen Diffusion**
-   - PDMS is highly oxygen-permeable, which is great for oxygen sensing but also means the dye gets quenched quickly. Going too high in dye content doesn’t necessarily improve sensitivity—it may just cause more self-quenching without improving the sensor’s performance.
+    * PDMS is highly oxygen-permeable, which is great for oxygen sensing but also means the dye gets quenched quickly. Going too high in dye content doesn’t necessarily improve sensitivity—it may just cause more self-quenching without improving the sensor’s performance.
----
+==== 2. Practical Mixing Tips ====
-## 2. Practical Mixing Tips
+  - **Pre-Dissolve the Rubrene**
+    * Dissolve rubrene in a small volume of an organic solvent (toluene or chloroform) at a known concentration (e.g., 1–10 mg/mL).
+    * Slowly add this solution to the PDMS base resin while stirring. This helps achieve more uniform dispersal.
-. **Pre-Dissolve the Rubrene**
+  - **Degas**
-   - Dissolve rubrene in a small volume of an organic solvent (toluene or chloroform) at a known concentration (e.g., 1–10 mg/mL).
+    * After mixing, place the solution under vacuum to remove both solvent and air bubbles.
-   - Slowly add this solution to the PDMS base resin while stirring. This helps achieve more uniform dispersal.
+    * If you have a two-part system (base + curing agent), you might do a preliminary degassing before adding the curing agent, then a final degassing after thoroughly mixing in the catalyst.
-. **Degas**
+  - **Curing**
-   - After mixing, place the solution under vacuum to remove both solvent and air bubbles.
+    * Many PDMS systems can cure at room temperature in 24–48 hours or at 60–70 °C for a few hours.
-   - If you have a two-part system (base + curing agent), you might do a preliminary degassing before adding the curing agent, then a final degassing after thoroughly mixing in the catalyst.
+    * Try not to exceed 120 °C or keep the mixture at high temperature for too long—rubrene will degrade over time if both heat and oxygen are present.
-. **Curing**
+==== 3. Considerations for a 450 nm LED ====
-   - Many PDMS systems can cure at room temperature in 24–48 hours or at 60–70 °C for a few hours.
-   - Try not to exceed 120 °C or keep the mixture at high temperature for too long—rubrene will degrade over time if both heat and oxygen are present.
----
+  - **Absorption Spectrum of Rubrene**
+    * Rubrene absorbs sufficiently at ~450 nm to fluoresce orange.
+    * Verifying the absorbance in your final PDMS film to ensure you’re not “under-absorbing.”
-## 3. Considerations for a 450 nm LED
+  - **Film Thickness**
+    * If the film is too thick or dye concentration is too high, inner regions might not be excited properly due to light attenuation.
+    * A thickness of **~0.1–1 mm** is typical for sensor films, but this depends on optical design and the LED intensity.
-. **Absorption Spectrum of Rubrene**
+  - **Sensor Calibration**
-   - Rubrene has a primary absorption peak around ~495–530 nm. However, it still absorbs sufficiently at ~450 nm to fluoresce orange. You won’t be hitting its absolute peak absorption, but in practice, 450 nm can still excite rubrene decently.
+    * Once cured, measure the fluorescence intensity (and/or lifetime) under different known oxygen concentrations to build a calibration curve using the Stern–Volmer relationship.
-   - You may consider verifying the absorbance in your final PDMS film to ensure you’re not “under-absorbing.”
-. **Film Thickness**
-   - If the film is too thick or dye concentration is too high, inner regions might not be excited properly due to light attenuation.
-   - A thickness of **~0.1–1 mm** is typical for sensor films, but this depends on optical design and the LED intensity.
-. **Sensor Calibration**
+==== 4. Adjusting the Ratio Over Time ====
-   - Once cured, measure the fluorescence intensity (and/or lifetime) under different known oxygen concentrations to build a calibration curve using the Stern–Volmer relationship.
----
+  * **If the Film Is Too Dark (Self-Absorbing)**
+    * Lower the dye percentage. Even going from 0.1 wt% down to 0.02 wt% can make a big difference in clarity and reduce self-quenching.
+  * **If the Signal Is Too Dim**
+    * Increase the dye content in small increments (e.g., from 0.02 wt% up to 0.05 wt%), but watch for diminishing returns due to concentration quenching.
-## 4. Adjusting the Ratio Over Time
+==== Bottom Line ====
-- **If the Film Is Too Dark (Self-Absorbing)**
-  - Lower the dye percentage. Even going from 0.1 wt% down to 0.02 wt% can make a big difference in clarity and reduce self-quenching.
-- **If the Signal Is Too Dim**
-  - Increase the dye content in small increments (e.g., from 0.02 wt% up to 0.05 wt%), but watch for diminishing returns due to concentration quenching.
----
-### Bottom Line
 A good **starting point** is **0.01–0.1 wt% rubrene** relative to the PDMS base. Begin on the lower side (e.g., **0.02–0.05 wt%**) to avoid aggregation, see how bright the sensor is at 450 nm excitation, and adjust accordingly. Once you have a homogeneously dispersed rubrene-PDMS film, you can calibrate its oxygen response using the Stern–Volmer equation and fine-tune the formulation to optimize fluorescence intensity versus oxygen quenching sensitivity.
-==== pH ====
+==== pH optode sensor notes ====
   * {{ :nandi-amdursky-2022-the-dual-use-of-the-pyranine-_hpts_-fluorescent-probe-a-ground-state-ph-indicator-and-an-excited_1_.pdf | Pyranine (HPTS) Fluorescent Probe}}
   * Pyranine Solvent Green 7 CAS 6358-69-6 aka HPTS aka Pyranine