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Here is the situation that I have been tacking for weeks and I have still not understood.

We are trying to understand how to do this:

This mixture for the preparation of the "LI–PVC" was obtained from a batch of 80 mg of poly(vinyl chloride), 160 μl of tributylphosphate and 20 mg of Lophine dissolved in 2 ml of freshly distilled TetraHydrofuran (THF).

Paper: http://www.sciencedirect.com/science/article/pii/S014381661400089X which refers to :http://www.mdpi.com/1424-8220/8/2/847

We have no idea how to do this, since we dont have any step/by/step instruction, reaction time, environment we need to maintain for this.

How do we go about identifying this process and replicating this mixture. This is very critical to us. Any help on this matter would be of immense help, if you have a resource which may have be able to shed some light on this. It would be of help as well.

Many Thanks

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  • $\begingroup$ Can you explain what kind of educational background and laboratory you have? Perhaps you should hire a chemist if you want to produce chemical sensors. $\endgroup$ – Karl Nov 24 '16 at 21:14
  • $\begingroup$ I have bachelor in Eng., I'm not sure how this process works, so what health and safety hazard we should avoid when testing. This is for school project. Unfortunately, I don't have much background in chemical eng., we have a lab setup. $\endgroup$ – pozza Nov 24 '16 at 21:29
  • $\begingroup$ @Karl, would you be interested in consulting opportunity? - we have very limited budget. $\endgroup$ – pozza Nov 24 '16 at 21:31
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We have no idea how to do this, since we dont have any step/by/step instruction, reaction time, environment we need to maintain for this.

Let's redefine the general task:

  • How to deposit a layer of 2,4,5-triphenylimidazole (lophine) on the tip of an optical fibre?

Requirements:

  • The layer must be permanent/durable and does not wear or wash off during measurements of the nitrate concentration in drinking water.

The workflow therefore includes:

  1. How to prepare the fibre?
  2. How to deposit one (or several) layers of lophine?
  3. How to cure the layers to make sure that they do not wear/wash off?

As far as the preparation of the fibre is concerned, your primary paper (Optics and Lasers in Engineering, 2014, 60, 38-43) gives some hints on page 39:

To deposit the sensitive layer on the optical fiber, the coating was removed in a 1 cm section, and the exposed cladding was sterilized. Isopropyl Alcohol Level was used for cleaning the optical fiber in special cleaning cloths and immediately the LI–PVC was introduced [...].

Apparently, lophine is deposited on the fibre in a PVC matrix and you have cited the composition of the mixture used.

How is this actually done?

An earlier publication by the same authors gives some directions! It's reference 19 in the paper that you cited!

In Sensors, 2008, 8, 847-859, the describe authors describe the dipping method in chapter 2.2. and provide further references.

In summary, the prepared fibre is

  • dipped into the solution (lophine, PVC, TBP, THF) and then
  • cured by placing the fibre in an oven for 15 minutes at 80 °C.

These two steps are repeated as often as necessary to obtain the required total layer thickness.

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