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Journal of Materials Chemistry B
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Synthesis and characterisation of 3: Compound 5 (3.67 g, 10 Preparation of Au@ONPs
mmol) was refluxed for 8 h with ethylenediamine (2) (10
DOI: 10.1039/D0TB01195A
mmol) using ethanol as reaction solvent. On completion of
Gold based organic – inorganic nanohybrid particles have
unique synthetic properties. The gold nanoparticles have an
absorption maximum near 530 nm, and TEM and DLS
experiments were performed for the size and shape of the
nanohybrids. Common method used for the fabrication of the
nanohybrid35 uses heating of the solution of ligand and HAuCl4
under rapid stirring, followed by addition of reducing agent
like trisodium citrate, sodiumborohydride and ascorbic acid. In
present work, we have prepared Au@ONPs via wet chemical
method to prepare using ascorbic acid as reducing agents.
TEM analysis was further used to study the size and shape of
the Au@ONPs. Ascorbic acid solution (0.1 mM) was prepared
by dissolving ascorbic acid in type 1 water. Gold solution (0.1
mM) was prepared by dissolving HAuCl4 in water. The required
Au@ONPs were prepared by mixing the gold solution, ONPs
and ascorbic acid in a ratio of 9:1:9, respectively. Appearance
of pink colour confirmed the formation of Au@ONPs. The
prepared Au@ONPs were characterized using DLS and TEM
analysis.
reaction, reaction mixture was allowed to cool to room
temperature naturally. Yellow coloured compound
3
precipitated out and was filtered and dried. Yield = 82%. mp =
159-161 °C; 1H NMR (400 MHz, CDCl3) δ 8.63 (m, 2H, ArH), 8.53
(dd, J = 1.6 Hz, 2H, ArH), 8.26 (dd, J = 1.6 Hz, 2H, ArH), 7.80 (t, J
= 8 Hz, 2H, ArH), 7.34 (dd, J = 8 Hz, 1H, ArH), 5.37 (s, 2H,
picolylamine-CH2), 3.90 (t, J = 4 Hz, 2H, ethylenediamine-CH2),
3.44 (t, J = 4 Hz, 2H, ethylenediamine-CH2). 13C NMR (100 MHz,
DMSO-d6) δ 164.43, 163.43, 151.71, 150.15, 147.26, 135.04,
131.69, 129.53, 127.90, 125.05, 122.60, 122.16, 108.03,
104.72, 42.74, 42.38, 38.36. MS (EI) : m/z 347.20 (M++1).
Synthesis and characterisation of 1:
Compound 3 (0.346 g, 1 mmol) was dissolved in dry DCM and
to this solution, 2-fluorophenyl isothiocyanate (2) (0.153 g, 1
mmol) was added and reaction mixture was stirred at room
temperature for 8 h. On completion of reaction, solvent was
evaporated under vacuum. The crude product was then
purified using column chromatography to get yellow coloured Chemosensing response of materials:
solid as product 1. Yield = 78%. mp = 187-189 °C. 1H NMR (400
MHz, DMSO-d6) δ 9.45 (s, 1H, -NH), 8.69 (d, J = 8 Hz, 1H, ArH),
1mM stock solutions of ONPs and Au@ONPs were prepared in
8.43 (dd, J = 1.6 Hz, 1H, ArH), 8.24 (d, J = 8 Hz, 1H, ArH), 8.01
(s, 1H, ArH), 7.95 (s, 1H, ArH), 7.70 (t, J = 8 Hz, 1H, ArH), 7.52 (t,
J = 8 Hz, 1H,ArH), 7.23 (dd, J = 8 Hz, 3H, ArH), 7.13 (m, 1H,
ArH), 6.95 (d, 1H, ArH), 5.19 (s, 2H, picolylamine-CH2), 3.82 (t, J
= 4 Hz, 2H, ethylenediamine-CH2), 3.59 (t, J = 4 Hz, 2H,
ethylenediamine-CH2). 13C NMR (100 MHz, DMSO-d6) δ 182.10,
164.37, 163.38, 151.60, 150.15, 147.31, 135.07, 131.61,
130.18, 129.51, 128.93, 127.89, 124.97, 122.58, 122.15,
120.76, 116.45, 108.02, 104.68, 55.45, 42.92, 42.72, 42.36. MS
(EI) : m/z 500.19 (M++1).
water. A composite solution of ONPs and Au@ONPs was
prepared with varied ratios of both materials and the most
suitable are achieved with the solution where ONPs:Au@ONPs
has ratio of 4:6 by v/v was chosen for further studies. All
solutions were shaken properly for a sufficient time and kept
undisturbed for 30 min to confirm the homogeneity of
solutions, before recording the spectra. The spectroscopic
studies were executed at 25 ± 1 ◦C. ONPs, Au@ONPs and their
composite were studies for their interaction with various
toxins in aqueous medium. Composite of ONPs and Au@ONPs
exhibited tremendous change in the UV-Vis absorption spectra
on interaction with Okadaic Acid (OA) as comparative to ONPs
and Au@ONPs. Titrations of OA with the composite were done
by the addition of successive amounts of OA solution to the
composite solution in a 10 mL flask and recording of UV-Vis
absorption spectra incremental addition. Similarly, titration
experiments of OA with composite were performed in using
fluorescence spectroscopy and cyclic voltametery.
Preparation of organic nanoparticles (ONPs)
There are various methods to develop organic nanoparticles;
researchers use the method according to their usage.
Depending on the fabrication method the properties of the
nanoparticles such as size and morphology may vary. The
choice of the solvents, temperature and pH govern the
fabrication process of the nanomaterials. In present work we
have fabricated the ONPs using bottom – up strategy. 1mM
solution of the synthesized receptor was prepared in DMSO.
The solution was then slowly injected into the water using
microsyringe under ultrasonication. The solution was further
sonicated for 30 minutes to assure the formation of stable
ONPs. This technique is the single step process called re-
precipitation. The formation of ONPs was monitored using
external probe of a particle size analyzer. Different solvents
and concentrations were used to optimize the desirable result.
Size distribution of the ONPs was continuously monitored
using DLS analysis. TEM analysis was further used to study the
size and morphology of the ONPs.
Results and discussion
Synthesis and Characterization of materials:
Receptor 1 has been designed with excellent fluorescent
properties to target the desired analyte. The synthesis of
desired receptor was achieved through the bromination of 1,8-
naphthalic anhydride using a method reported in literature.30
Compound 5 was synthesized by reacting 7 with 1 equivalent
of picolylamine in ethanol. After 8 h of refluxing, the reaction
mixture was cooled to room temperature, which yielded the
brown precipitates of compound 5 (Figure S1-3).
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