Hydrophilicity and carbon chain length effects on the gas sensing properties of chemoresistive, self-assembled monolayer carbon nanotube sensors

• Juan Casanova-Cháfer,
• Carla Bittencourt and
• Eduard Llobet

Beilstein J. Nanotechnol. 2019, 10, 565–577, doi:10.3762/bjnano.10.58

• attributed to the interaction, via strong hydrogen bonding, of the polar molecules tested to the polar surface of hydrophilic thiols. The approach discussed here could be extended further by combining hydrophilic and hydrophobic thiol SAMs in Au-MWCNT sensor arrays as a helpful strategy for tuning sensor

• ); self-assembled monolayer (SAM); thiol; Introduction Carbon nanotubes were first observed by Sumio Iijima in 1991 [1] and since then, this nanostructure has been widely used in chemoresistive gas sensors [2][3][4][5] due to the possibility to engineer its sensitivity towards chemicals present in a

• approach, carbon nanotubes act as support and charge transport transducing elements while the recognition function is performed by grafted molecules. Two examples of this have consisted of obtaining thiol-functionalized carbon nanotube buckypapers [27] or self-assembled monolayers (SAMs) of thiol molecules

Targeting strategies for improving the efficacy of nanomedicine in oncology

• Gonzalo Villaverde and
• Alejandro Baeza

Beilstein J. Nanotechnol. 2019, 10, 168–181, doi:10.3762/bjnano.10.16

• techniques as carbodiimide coupling chemistry [28]. An alternative is the introduction of certain functional groups on specific positions of the antibody, which allows the utilization of bio-orthogonal chemical strategies, such as azide-strained alkyne or thiol–maleimide reaction, for carrying out the

• specifically designed for binding to the epidermal growth factor receptors (EGFR) have been anchored on the surface of hollow gold nanospheres [39]. The thiolated version of these aptamers was anchored on the gold surface through the thiol groups producing an average anchorage yield of 250 aptamers per

Colloidal chemistry with patchy silica nanoparticles

• Pierre-Etienne Rouet,
• Cyril Chomette,
• Laurent Adumeau,
• Etienne Duguet and
• Serge Ravaine

Beilstein J. Nanotechnol. 2018, 9, 2989–2998, doi:10.3762/bjnano.9.278

• , i.e., well-calibrated silica nanospheres or core–shell nanoparticles, were obtained according to a seeded-growth protocol [22] and a method using methoxy poly(ethylene glycol)-thiol as a coupling agent [23], respectively. Their surface functionalization with carboxylic acid groups was performed by a

High-throughput micro-nanostructuring by microdroplet inkjet printing

• Hendrikje R. Neumann and
• Christine Selhuber-Unkel

Beilstein J. Nanotechnol. 2018, 9, 2372–2380, doi:10.3762/bjnano.9.222

• [9], titania [10], and hybrid nanoparticles [11][12]. If the nanoparticles are intended to provide a chemical contrast for further functionalization, gold nanoparticles are an appropriate choice as they are easily functionalized using thiol chemistry [13]. For example, gold nanoparticles prepared by

Dumbbell gold nanoparticle dimer antennas with advanced optical properties

• Janning F. Herrmann and
• Christiane Höppener

Beilstein J. Nanotechnol. 2018, 9, 2188–2197, doi:10.3762/bjnano.9.205

• . Utilizing the capabilities of an AFM to manipulate such structures with sub-nanometer precision in space enables to add a smaller 40 nm AuNP to the larger one. Even though, shorter linker thiol molecules could be used instead, in principle, the high mobility of these linker molecules on the AuNP surface

• expected cascade of the electromagnetic field towards the intermediate points of these gap structures. Figure 2D indicates that the CB[8] antenna provides similar light confinement capabilities than the thiol trimer. Most strikingly, the electromagnetic field enhancement of this dimer antenna reaches the

• a high reproducibility of these antennas and a low influence of deviations from the sphere geometry on the enhancement factor. The enhancement factor is further increased by utilizing the gap mode. In this case the average fluorescence enhancement factor for the thiol-mediated gap antennas is

Self-assembled quasi-hexagonal arrays of gold nanoparticles with small gaps for surface-enhanced Raman spectroscopy

• Emre Gürdal,
• Simon Dickreuter,
• Fatima Noureddine,
• Pascal Bieschke,
• Dieter P. Kern and
• Monika Fleischer

Beilstein J. Nanotechnol. 2018, 9, 1977–1985, doi:10.3762/bjnano.9.188

• features. To measure the SERS signal, the gold nanoparticles were covered with a self-assembled monolayer of 4-MBA. Because the thiol-group of the 4-MBA molecules has a very high affinity for gold [27], and the samples were rinsed thoroughly with ethanol to remove any unbound molecules, we can assume that

Tuning adhesion forces between functionalized gold colloidal nanoparticles and silicon AFM tips: role of ligands and capillary forces

• Sven Oras,
• Sergei Vlassov,
• Marta Berholts,
• Rünno Lõhmus and
• Karine Mougin

Beilstein J. Nanotechnol. 2018, 9, 660–670, doi:10.3762/bjnano.9.61

• ) equipped with PeakForce QNM (Quantitative Nanoscale Mechanics) module. Au NPs were synthesized by a seed-mediated process and then functionalized with thiols containing different functional groups: amino, hydroxy, methoxy, carboxy, methyl, and thiol. Adhesion measurements showed strong differences between

• (–COOH), methyl (–CH3), methoxy (–OCH3) or thiol (–SH). The adhesion was measured by atomic force microscope (AFM) equipped with a PeakForce QNM module. The results were also compared to additional adhesion measurements performed on flat Au films functionalized with the same molecular thin film to

• organosulfur (thiol) molecules having different tail groups ranging from a highly hydrophilic (–OH, –COOH, –SH, –NH2) to a partially hydrophilic (–O–CH3) and to a more hydrophobic group (–CH3). A covalent bond between the sulfur head group (–SH) and the Au atoms ensured the strong anchorage of the organosulfur

Facile phase transfer of gold nanorods and nanospheres stabilized with block copolymers

• Yaroslav I. Derikov,
• Georgiy A. Shandryuk,
• Raisa V. Talroze,
• Alexander A. Ezhov and
• Yaroslav V. Kudryavtsev

Beilstein J. Nanotechnol. 2018, 9, 616–627, doi:10.3762/bjnano.9.58

• the use of strong thiol and amine surfactants. Keywords: Au nanorods; block copolymers; optical absorbance spectroscopy; phase transfer; seeded growth method; Introduction The size effects that determine the functional characteristics of nanoparticles are no less important than their precise

• or cetyl trimethylammonium bromide-stabilized Au nanorods with a solution of thiol- [18] or amine-terminated [19] surfactants in organic solvent. With a strong affinity to gold, thiols and amines replace nanoparticle shells via ligand exchange, while the tails of these molecules provide miscibility

• propose that P2VP blocks wrap around nanoparticles preventing their aggregation, while PS blocks form an organophilic corona that provides dispersability of the nanoparticles in organic media. Compared to thiol- and amine-functionalized stabilizers that form strong covalent bonds with Au, the interaction

Wafer-scale bioactive substrate patterning by chemical lift-off lithography

• Chong-You Chen,
• Chang-Ming Wang,
• Hsiang-Hua Li,
• Hong-Hseng Chan and
• Wei-Ssu Liao

Beilstein J. Nanotechnol. 2018, 9, 311–320, doi:10.3762/bjnano.9.31

• -arrangement of silane or thiol molecules on silica or Au surfaces, which has been proven as a convenient route for the fabrication of functional surfaces toward versatile targets [12][13][14][15][16]. In addition to direct surface modification, the versatility of anchoring molecule tail groups provides

• washed with ethanol to remove excess thiol molecules, and blown dry with nitrogen gas. Polydimethylsiloxane (PDMS) stamps with various patterns were fabricated by standard photolithography-created masters. A 10:1 mass ratio of SYLGARD 184 silicone elastomer base and curing agent (Dow Corning, Midland, MI

• TRIS buffer (150 mM NaCl, pH 7.4) in advance. Target DNA solutions in 25 mM TRIS buffer (150 mM NaCl, pH 7.4) was thereafter dropped onto the target DNA-specific probe-modified substrates for a 5 min incubation period. For sandwich-like array signal reporting, biotinylated thiol-patterned substrates

Patterning of supported gold monolayers via chemical lift-off lithography

• Liane S. Slaughter,
• Kevin M. Cheung,
• Sami Kaappa,
• Huan H. Cao,
• Qing Yang,
• Thomas D. Young,
• Andrew C. Serino,
• Sami Malola,
• Jana M. Olson,
• Stephan Link,
• Hannu Häkkinen,
• Anne M. Andrews and
• Paul S. Weiss

Beilstein J. Nanotechnol. 2017, 8, 2648–2661, doi:10.3762/bjnano.8.265

• found to be consistent with molecular dynamics simulations that predicted the removal of no more than 1.5 Au atoms per thiol, thus presenting a monolayer-like structure. Keywords: chemical patterning; hybrid material; monolayer; soft lithography; two-dimensional material; Introduction Chemical lift

• orientation and each thiol removes one Au atom. Nonetheless, we know that the Au–alkanethiolate monolayers on PDMS resulting from typical CLL experiments are indicative of incomplete lift-off [1][10][31]. Moreover, the dimensions of the Au–alkanethiol complexes that compose the lifted-off monolayer on PDMS

• structures that are still able to bond to additional Au atoms. Before complete separation, a chain consisting of two or three Au atoms between each thiol and the Au surface is formed and finally ruptures, usually after the first or second Au atom has attached to each sulfur atom. As a consequence of lift-off

The role of ligands in coinage-metal nanoparticles for electronics

• Ioannis Kanelidis and
• Tobias Kraus

Beilstein J. Nanotechnol. 2017, 8, 2625–2639, doi:10.3762/bjnano.8.263

• substituents (Me, MeO, Cl, or Br) in para-position to the thiol group reduced the conductivity compared to films of triphenylphosphine (PPh3) (Figure 3) and thiophenol (H)-capped gold nanocrystals. The electron-withdrawing nitro group (NO2) caused an increase in conductivity from 30 S/cm (PPh3-capped Au NPs

• transformation temperatures (Tp) are desirable for applications on plastic films with low glass-transition temperatures (Tg) [33][44]. The required annealing temperature is correlated with the length of the capping agents as reported by Gupta and co-workers. Inks of thiol-functionalized gold nanoparticles having

• thiols with eight, six, or four carbon atoms in their alkyl chains exhibited descending sintering temperatures from the longer thiol (204 °C) to the shorter (155 °C). The layer prepared from the C4-thiol-functionalized gold nanoparticles could be annealed at 160 °C, a temperature sufficiently low to

Inelastic electron tunneling spectroscopy of difurylethene-based photochromic single-molecule junctions

• Youngsang Kim,
• Safa G. Bahoosh,
• Dmytro Sysoiev,
• Thomas Huhn,
• Fabian Pauly and
• Elke Scheer

Beilstein J. Nanotechnol. 2017, 8, 2606–2614, doi:10.3762/bjnano.8.261

• switched to either the open or the closed form in ethanol and are subsequently assembled on gold-patterned MCBJ samples [14]. The acetyl (COCH3, denoted as Ac) groups are cleaved off by adding a droplet of ammonium hydroxide (NH4OH), resulting in a thiol (SH) group, before assembly on the metal surfaces of

• C5F-ThM molecules [14]. The overall magnitude of the conductance of both the open and the closed form is rather small. This can be attributed to the presence of sp3 hybridized methylene groups, isolating the π-system and the thiol anchor groups. These act as efficient tunneling barriers for the

Amplified cross-linking efficiency of self-assembled monolayers through targeted dissociative electron attachment for the production of carbon nanomembranes

• Sascha Koch,
• Christopher D. Kaiser,
• Paul Penner,
• Michael Barclay,
• Lena Frommeyer,
• Daniel Emmrich,
• Patrick Stohmann,
• Tarek Abu-Husein,
• Andreas Terfort,
• D. Howard Fairbrother,
• Oddur Ingólfsson and
• Armin Gölzhäuser

Beilstein J. Nanotechnol. 2017, 8, 2562–2571, doi:10.3762/bjnano.8.256

• -biphenyls, where the DEA channel is exothermic, we expect significant cross sections at 0 eV. Similarly, from the DEA threshold energy, we expect C–H cleavage through DEA to be present but inefficient. In fact, Houplin et al. [32] recently showed that for terphenyl-thiol (TPT) SAMs, which should behave

• . In a control experiment, DEA to 2-bromobiphenyl-4-thiol was also studied. The effect of the 4-thiol group was found to be insignificant. For comparison, we have recorded positive ion mass spectra at 70 eV (not shown here), and we find that these agree well with those available in the NIST database

• that the radical sites generated in the DEA process substantially stimulate the cross-linking process and that the very effective iodine loss in the DEA process should thus be reflected in the cross-linking efficiency. The decrease of the intensity maximum of the thiol sulfur S 2p3/2 peak at a binding

Synthesis of metal-fluoride nanoparticles supported on thermally reduced graphite oxide

• Alexa Schmitz,
• Kai Schütte,
• Vesko Ilievski,
• Juri Barthel,
• Laura Burk,
• Rolf Mülhaupt,
• Junpei Yue,
• Bernd Smarsly and
• Christoph Janiak

Beilstein J. Nanotechnol. 2017, 8, 2474–2483, doi:10.3762/bjnano.8.247

• Scheme S2 in Supporting Information File 1). Thiol-functionalized TRGO-SH [62] was additionally used to support metal-fluoride nanoparticles. The morphology, crystalline phase (MFx-NPs), size and size dispersion of the nanoparticles was analyzed by powder X-ray diffraction (PXRD) and transmission

Expanding the molecular-ruler process through vapor deposition of hexadecanethiol

• Alexandra M. Patron,
• Timothy S. Hooker,
• Daniel F. Santavicca,
• Corey P. Causey and
• Thomas J. Mullen

Beilstein J. Nanotechnol. 2017, 8, 2339–2344, doi:10.3762/bjnano.8.233

• iterative deposition of bifunctional organic molecules and metal ions. Note that the use of a thiol as one of the two functionalities ensures that deposition and growth of the multilayer only occurs on the surface of the metal, not the exposed substrate. By using molecules of discrete length, the thickness

• apply this strategy to other bifunctional thiol molecules are ongoing. Key steps for the molecular-ruler process. (A) A metal is patterned on a substrate via conventional lithography. (B) A molecular-ruler, consisting of alternating layers of thiol molecules and metal ions, is created only on the first

Application of visible-light photosensitization to form alkyl-radical-derived thin films on gold

• Rashanique D. Quarels,
• Xianglin Zhai,
• Neepa Kuruppu,
• Jenny K. Hedlund,
• Ashley A. Ellsworth,
• Amy V. Walker,
• Jayne C. Garno and
• Justin R. Ragains

Beilstein J. Nanotechnol. 2017, 8, 1863–1877, doi:10.3762/bjnano.8.187

• cursor profiles and for a head-to-head comparison of the chemical and mechanical stability of a polynitrophenylene multilayer to a thiol thin film on Au(111) [17]. In the work described herein, visible-light-photosensitized deposition of alkyl radicals was combined with particle lithography to generate

• radical contains a 10 carbon chain which has a theoretical chain length of 1.5 nm, however, the observed film thickness is probably coincidental. It is likely that the upright conformations and surface assembly seen with thiol SAMs [55][56][57][58] is not operative with our method, and water contact

• force applied by an AFM tip readily removed ω-functionalized thiol SAMS from Au [59] whereas 10 nN could not remove Au–Me or Au–NHBoc films. In considering the process 11→12 (Scheme 3), the rate of hydrogen atom abstraction by a primary, carbon-centered radical from a relatively strong bond between an

A biofunctionalizable ink platform composed of catechol-modified chitosan and reduced graphene oxide/platinum nanocomposite

• Peter Sobolewski,
• Agata Goszczyńska,
• Małgorzata Aleksandrzak,
• Karolina Urbaś,
• Joanna Derkowska,
• Agnieszka Bartoszewska,
• Jacek Podolski,
• Ewa Mijowska and
• Mirosława El Fray

Beilstein J. Nanotechnol. 2017, 8, 1508–1514, doi:10.3762/bjnano.8.151

• . Printed patterns utilizing ink prepared with thiol-modified chitosan instead or no chitosan, just rGO–Pt dispersed in EG, were washed off during the course of the functionalization/hybridization process. Importantly, we observed no strong non-specific binding between the non-complementary PCR product and

Deposition of exchange-coupled dinickel complexes on gold substrates utilizing ambidentate mercapto-carboxylato ligands

• Martin Börner,
• Laura Blömer,
• Marcus Kischel,
• Peter Richter,
• Georgeta Salvan,
• Dietrich R. T. Zahn,
• Pablo F. Siles,
• Maria E. N. Fuentes,
• Carlos C. B. Bufon,
• Daniel Grimm,
• Oliver G. Schmidt,
• Daniel Breite,
• Bernd Abel and
• Berthold Kersting

Beilstein J. Nanotechnol. 2017, 8, 1375–1387, doi:10.3762/bjnano.8.139

• (Scheme 1), L’ an ambidentate coligand, and M is a paramagnetic transition metal ion, usually MnII, FeII, CoII, or NiII [37]. The ambidentate phosphane-carboxylato [38] and thiol-carboxylato coligands H2L2 and H1L3 (Figure 1) were found to bind selectively via their carboxylate function to form the

• carboxylato-bridged complexes [Ni2L(HL2)](ClO4) (2) and [Ni2L(L3)](ClO4) (3) [39][40] such that an exposed thiol or phosphane group is available for further functionalization. Indeed, 2 dimerizes via a disulphide bond upon oxidation in air to generate a tetranuclear [{Ni2L}2(O2CC6H4S)2]2+ complex, while

• according to a protocol developed for the preparation of self-assembled thiol monolayers [59] as the complexes cannot be deposited via the gas phase. They decompose without melting. Thus, clean gold-coated Si wafers were immersed in a 1 × 10−3 M solution of the respective complex in MeCN or CH2Cl2 for 24 h

Micro- and nano-surface structures based on vapor-deposited polymers

• Hsien-Yeh Chen

Beilstein J. Nanotechnol. 2017, 8, 1366–1374, doi:10.3762/bjnano.8.138

• microstructures of PEG hydrogels [22]. In a separate report, this photodefinable polymer was used to pattern protein molecules using a photomask-assisted lithographical approach [23]. Recently, surface patterns were enabled via light-induced thiol-ene/thiol-yne reactions on a poly(4-vinyl-p-xylylene-co-p-xylylene

• initiated CVD system [75]. The route-controlled click reactions, including a thiol-yne reaction and a copper-free alkyne/azide click reaction, were enabled to create continuous and reverse gradients on a CVD deposited poly[(4-methylpropiolate-p-xylylene)-co-(p-xylylene)] surface. The two-click reactions

Triptycene-terminated thiolate and selenolate monolayers on Au(111)

• Jinxuan Liu,
• Martin Kind,
• Björn Schüpbach,
• Daniel Käfer,
• Stefanie Winkler,
• Wenhua Zhang,
• Andreas Terfort and
• Christof Wöll

Beilstein J. Nanotechnol. 2017, 8, 892–905, doi:10.3762/bjnano.8.91

• selenoacetate Trp1SeAc (compare Scheme S1 in the Supporting Information File 1). Selenoacetate compounds can be used to form selenolate SAMs on gold surfaces [8]. Earlier work on homologous sulfur compounds revealed that free thiol groups are incompatible with benzyne [28]. Yet, it could be shown that formation

• of the triptycene group by reaction of anthracene moieties with benzyne is possible if the sulfur atom is protected, e.g., with an acyl group [28]. We suspected the selenol group to be similarly unstable towards benzyne as the thiol group and thus aimed to protect it. For this purpose, 9

Selective detection of Mg²⁺ ions via enhanced fluorescence emission using Au–DNA nanocomposites

• Tanushree Basu,
• Khyati Rana,
• Niranjan Das and
• Bonamali Pal

Beilstein J. Nanotechnol. 2017, 8, 762–771, doi:10.3762/bjnano.8.79

• modifications in the plasmonic spectra. The biophysical properties of DNA make it compatible for linkage with metals, which are useful in a variety of applications such as biosensor development. They can also be stabilized with a wide variety of molecules because of the alkyl thiol adsorption phenomena [3

• . Here, MPA helps both in the stabilization as well as thiol functionalization. MPA can easily stabilize the AuNPs due to the strong affinity of sulphur groups for gold. Also, the thiolated-DNA can directly bind to the surface of AuNPs by thiol–Au interactions [39][40]. Before use, DTT (0.1 M DTT, 10 mM

α-((4-Cyanobenzoyl)oxy)-ω-methyl poly(ethylene glycol): a new stabilizer for silver nanoparticles

• Jana Lutze,
• Miguel A. Bañares,
• Marcos Pita,
• Andrea Haase,
• Andreas Luch and
• Andreas Taubert

Beilstein J. Nanotechnol. 2017, 8, 627–635, doi:10.3762/bjnano.8.67

• metal nanoparticles that is based on a cyano rather than a thiol or thiolate anchor group. The silver particles used to evaluate the effectiveness of the new stabilizer typically have a bimodal size distribution with hydrodynamic diameters of ca. 13 and ca. 79 nm. Polymer stability was evaluated as a

• suggesting that α-((4-cyanobenzoyl)oxy)-ω-methyl poly(ethylene glycol) is a good stabilizer for metal nanoparticles in aqueous media unless very high pH conditions are present in the system. The study thus demonstrates that cyano groups can be viable alternatives to the more conventional thiol/thiolate

• oligomeric or polymeric stabilizer is attached to the particle surface without a specific anchor group [26][27][28][29][30]. The current gold standard for anchoring an organic moiety on the NP surface is the thiol or thiolate group [3][24][31][32][33]. There are, however, cases where the thiol group may not

Gas sensing properties of MWCNT layers electrochemically decorated with Au and Pd nanoparticles

• Elena Dilonardo,
• Michele Penza,
• Marco Alvisi,
• Riccardo Rossi,
• Gennaro Cassano,
• Cinzia Di Franco,
• Francesco Palmisano,
• Luisa Torsi and
• Nicola Cioffi

Beilstein J. Nanotechnol. 2017, 8, 592–603, doi:10.3762/bjnano.8.64

• that a high gold content enhances the gas sensor response, thanks to the great affinity between gold and sulfur atoms of thiol groups [50]. Therefore, the increase in the Au NP density enhances the amount of the adsorption sites for H2S, resulting in a higher sensitivity and selectivity towards H2S gas

Comparison of four methods for the biofunctionalization of gold nanorods by the introduction of sulfhydryl groups to antibodies

• Xuefeng Wang,
• Zhong Mei,
• Yanyan Wang and
• Liang Tang

Beilstein J. Nanotechnol. 2017, 8, 372–380, doi:10.3762/bjnano.8.39

• methods for the introduction of thiol groups onto the surface of GNRs by using Traut’s reagent, dithiotreitol (DTT), dithiolaromatic PEG6-CONHNH2, and thiol-polyethylene glycolamine (SH-PEG-NH2) combined with EDC reaction. We showed that the four above-mentioned thiolation methods can efficiently

• EDC reaction may affect the amount of functionalized GNRs because of the efficiency of thiol moiety linkage to antibodies, thereby affecting the sensitivity of the GNR sensor. The introduction of a thiol group to antibodies by using Traut’s reagent, DTT, and PEG6-CONHNH2 allowed for direct

• solution and the CTAB bilayer density [15]. The common ligand exchange is the replacement of the CTAB of GNR with thiol-terminated ligands, such as thiolated poly(ethylene glycol) and mercaptoundecanoic acid [10][11]. These agents can link the amino groups of biomolecules with the carboxylic group from

Comparison of four functionalization methods of gold nanoparticles for enhancing the enzyme-linked immunosorbent assay (ELISA)

• Paula Ciaurriz,
• Fátima Fernández,
• Edurne Tellechea,
• Jose F. Moran and
• Aaron C. Asensio

Beilstein J. Nanotechnol. 2017, 8, 244–253, doi:10.3762/bjnano.8.27

• ). Afterwards, the appropriated amount of Ab-linker and HRP-linker were mixed with 1 mL of AuNPs and incubated for 20 min. Thereafter, 100 μg of m-PEG thiol were added and mixed again for 20 min. Subsequently, 100 µL of 1 mg/mL of BSA were incubated for 10 min more. Samples were centrifuged (5,000g 30 min) and

• complex concentration was measured by absorption at 520 nm and kept at 4 °C until use. Covalent functionalization was achieved using hetero-bifunctional linkers of polyethyleneglycol (PEG). In this case, AuNPs were incubated overnight with methyl-PEG-thiol (mPEG thiol, n = 6) and PEG-thiol acid (n = 7) in

• order to create a mixed monolayer of linker on the nanoparticle. 1 mL containing 0.075 M of mPEG thiol and 0.025 M of PEG-thiol acid was added to 100 mL of synthetized AuNPs and maintained overnight under stirring. Subsequently, the AuNPs were washed by centrifugation at 18,000g for 30 min and the