Paper
Here, we report on the preparation and characterization of
RSC Advances
Preparation of diacetylene containing ligand molecules (7)
the tailored ligand, DA-COOH and the respective DA-COOH–
AuNP, before (DA-COOH–AuNP) and aer photoinduced poly-
merization (clDA-COOH–AuNP) (Scheme 1a). We applied AuNP
in the size range of 12–13 nm.
Hept-6-yn-1-ol (2). Ethylenediamine (43 mL, distilled) and
NaH (8.565 g 0.2141 mol, 60% on mineral oil) were stirred at 10
ꢁC for 1 h and Hept-3-yn-1-ol (4.825 g, 0.0430 mol) was added
dropwise. The resulting slurry was stirred overnight. While the
reaction mixture was cooled in an ice bath water (40 mL) was
added and the mixture was extracted three times with ether. The
combined organic extracts were washed with 1 N HCl solution,
sat. sodium bicarbonate and brine, and then dried over Na2SO4.
The product was obtained as a light yellow oil (4.525 g, 0.0403
mol, 93%). 1H NMR (400 MHz, CDCl3) d (ppm): 3.66 (t, 2H, J ¼
6.5 Hz), 2.21 (td, 2H, J ¼ 6.8 Hz, 2.7 Hz), 1.95 (t, 1H, J ¼ 2.7 Hz),
1.75 (s, OH), 1.62–1.43 (m, 7H). 13C NMR (100 MHz, CDCl3)
d (ppm): 84.4 (–C^CH), 68.3 (–C^CH), 62.8 (–CH2–OH), 32.2
(–CH2–CH2–OH), 28.2 (–CH2–(CH2)3–OH), 24.9 (–CH2–(CH2)2–
OH), 18.4 (–CH2–C^CH).
7-Iodohept-6-yn-1-ol (3). To a solution of 2 (0.555 g, 4.95
mmol) and potassium iodide (1.236 g, 7.446 mmol) in meth-
anol (15 mL), aqueous TBHP (1.28 mL, 9.94 mmol, 70%) was
added dropwise and stirred at room temperature overnight.
The reaction mixture was quenched with sat. aqueous Na2S2O3
and extracted with ethyl acetate. The combined extracts were
washed with brine and dried over Na2SO4. The crude residue
was puried by ash chromatography (ethyl acetate/hexane, 1/
2, v/v) and dried in vacuum which gave 3 as a dark yellow oil
(0.725 g, 3.045 mmol, 62%). 1H NMR (400 MHz, CDCl3)
d (ppm): 3.65 (t, 2H, J ¼ 6.5 Hz), 2.39 (t, 2H, J ¼ 6.8 Hz), 1.63 (s,
OH), 1.62–1.43 (m, 6H). 13C NMR (100 MHz, CDCl3) d (ppm):
97.45 (I-C^C–), 62.71 (HO–CH2–), 60.22 (I–C^C–), 32.13 (HO–
CH2–CH2), 28.22 (HO–(CH2)3–CH2), 24.92 (HO–(CH2)2–CH2),
20.76 (–CH2–C^C–).
12-Hydroxydodeca-4,6-diynoic acid (4). Methanol (2 mL) was
added to a mixture of pent-4-ynoic acid (0.138 g, 1.41 mmol) and
10% aqueous potassium hydroxide (1.5 mL). Hydroxylamine
hydrochloride (0.0098 g, 0.1410 mmol) was added followed by
a solution of freshly puried copper(I) chloride (0.035 g, 0.354
mmol) in 70% aqueous ethylamine (0.5 mL). The solution was
cooled down to ꢀ20 ꢁC and a solution of 3 (0.336 g, 1.41 mmol)
in THF was added dropwise and stirred overnight at room
temperature. The reaction mixture was quenched with 10%
sulfuric acid and extracted with ether. The combined extracts
were washed with brine and dried over Na2SO4. The crude
residue was puried by ash chromatography (ethyl acetate/
hexane, 2/3, v/v) and dried in vacuum which gave 4 as a light
yellow solid (0.158 g, 0.759 mmol, 54%). 1H NMR (400 MHz,
CDCl3) d (ppm): 5.35 (s, OH), 3.67 (t, 2H, J ¼ 6.5 Hz), 2.65–2.55
(m, 4H), 2.28 (t, 2H, J ¼ 6.8 Hz), 1.68–1.42 (m, 6H). 13C NMR (100
MHz, CDCl3) d (ppm): 176.15 (–COOH), 78.05 (–C^C–(CH2)2–
COOH), 74.79 (HO–(CH2)5–C^C–), 66.13 (–C^C–(CH2)2–
COOH), 65.19 (HO–(CH2)5–C^C–), 62.73 (–CH2–OH), 32.73
(–CH2–COOH), 32.01 (–CH2–CH2–OH), 27.97 (HO–(CH2)3–CH2–),
24.94 (HO–(CH2)2–CH2–), 19.13 (HO–(CH2)4–CH2–), 14.91
(–CH2–CH2–COOH).
The particles were characterized by UV-vis spectroscopy,
infrared reection absorption spectroscopy (IRRAS), surface
enhanced Raman scattering, z-potential as well as scanning
electron microscopy in transmission mode (SEM-T) measure-
ments. Stability investigations were performed including
stability towards NaCl, ligand displacement against dithio-
threithol (DTT) and heating. As the SPR is sensitive to changes
in the ligand shell, particle size and interparticle distance,26
these investigations involve mainly UV-vis measurements.
Particle aggregation upon decreasing nanoparticle stabilization
is reected by a red-shi and signicant broadening, or inten-
sity lost, of the SPR. Transport characteristics of individual
clDA-COOH–AuNP were investigated applying the same nano-
electrode setup used in our investigations reported previously
(Scheme 1b).15
Experimental
All reagents were purchased either from Acros, Fisher Scientic
or Sigma Aldrich and if not mentioned otherwise used without
further purication. Ultrapure water with a conductivity < 55 nS
cmꢀ1 was used for all procedures.
UV-vis absorption spectra were recorded with a JASCO V-630
spectrophotometer using quartz glass cuvettes.
Dynamic light scattering (DLS) measurements and z-poten-
tial measurements were performed with a Malvern Zetasizer
Nano S, He–Ne laser, l ¼ 633 nm, P ¼ 4 mW, q ¼ 173ꢁ.
IRRAS measurements were performed on a FT-IR spectro-
scope Vertex 70, Bruker Optics equipped with a MCT detector at
a spectral resolution of 4 cmꢀ1
.
Scanning electron microscopy (SEM) in transmission mode
was conducted with a high-resolution eld emission scanning
electron microscope (FE-SEM, LEO/ZEISS Supra 35 VP, Ober-
kochen, Germany). For sample preparation 5 mL of the particle
solution were dropped on a carbon-coated copper grid and
incubated for 30 min. The remaining solution was removed
with a tissue.
Raman and SERS spectra were obtained using a Horiba–
Jobin–Yvon Raman spectrometer equipped with Olympus
objectives and used at 50 fold magnication and a laser wave-
length of 633 nm at 180ꢁ backscattering arrangement. The
spectral resolution was 7 cmꢀ1 and the power on the sample was
12 mW. Particle solution was dropped and dried on a sputtered
Au layer on silicon wafer with a thickness of 100 nm.
TGA measurements were conducted on a Mettler STARe SW
9.20 instrument. 4–5 mg of dried AuNP and pure DA-COOH ligand
were weighed in standard alumina pans, and the measurements
were carried out between 25 and 600 ꢁC at a heating rate of 10 ꢁC
minꢀ1 under a nitrogen ow of 60 mL minꢀ1
.
12-(Tosyloxy)dodeca-4,6-diynoic acid (5). Compound 4 (0.503
mg, 2.41 mmol) was dissolved in chloroform (10 mL) and cooled
to approx. 3 ꢁC. Pyridine (0.78 mL, 9.7 mmol) was added
NMR measurements were performed with a Bruker Avance
II-400 and Bruker II-HD and referenced to solvent residual
signal.
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 102981–102992 | 102983