NH4OH tunes silica dots from 20 to 500 nm
Varying ammonia in a Stöber synthesis sizes silica nanoparticles from 20 to 200 nm (then 500 nm with extra TEOS), enabling core–shell TAMRA–BHQ2 quenching studies over unusually long distances.
Source
Enhanced distance-dependent fluorescence quenching using size tuneable core shell silica nanoparticles
Inspect source passages
NH4OH tunes silica dots from 20 to 500 nm
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Raising NH4OH from 0.3 to 5.0 mL increased diameters from 20 nm to 200 nm.
In contrast, increasing the volumes of NH 4 OH (28–30% v/v) from 0.3 to 5.0 mL (2.3 to 38.5 mmol L −1 ), whilst keeping the quantities of all other reactants constant (optimised TEOS of 500 μL, 2.2 mmol L −1 , and 16.75 mL of ethanol), gradually increased nanoparticle diameters from 20 nm to 200 nm, .
Varying TEOS left diameters centred at 145 ± 14 nm.
The results showed that different volumes of TEOS did not significantly ( p > 0.05) influence the mean nanoparticle diameter, which were centred at 145 ± 14 nm (polydispersity index, (PDI) ≤ 1.04), .
What they did
Authors mapped SNP diameter versus NH4OH, TEOS and ethanol, covalently doped dyes via APTES, grew silica shells, conjugated BHQ2, and recorded TAMRA quenching versus quencher loading and shell thickness.
What they found
NH4OH (0.3–5.0 mL) sizes particles 20–200 nm; extra TEOS grows them to 500 nm. TEOS or ethanol volume barely changes diameter (~145 or 70 nm). Quenching extends farther than classical Förster expectations.
The limits
What it doesn't show
The ‘greater than expected’ distance is not turned into a calibrated molecular ruler for a biological analyte.
Key terms
- Stöber synthesis
- Base-catalysed hydrolysis/condensation of TEOS in ethanol to make silica spheres.
- BHQ2
- Black-hole quencher paired with TAMRA in the quenching models.
- APTES
- Aminosilane linker used to attach dyes to the silica matrix.
- PDI
- Polydispersity index of the nanoparticle size distribution.
- Core–shell SNP
- Dye-doped core with a plain silica spacer then surface quencher.
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The main size-control reagent for 20–200 nm SNPs is:
Common questions
Which reactant mainly sets 20–200 nm size?
NH4OH volume.
How are >200 nm particles made?
Seed growth with extra 1.5 mL TEOS.
Does TEOS volume change size at fixed NH4OH?
Not significantly; ~145 ± 14 nm.
What dye/quencher pair was used?
TAMRA and BHQ2.
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