Cartoon describing: (right) Chemical route töone-pot¨synthesizingpot¨synthesizing core-shell Au@polymer nanohybrids and (left) Structures of monomers used for polymer-shell coverage of AuNP. 

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... of Au@Polymer Core-shell Hybrids. The Au@polymer nanohybrids were synthesized through heterogeneous polymerization in water. Previously to the polymerization step, 1 mL of the as-synthesized AuNPs was centrifugated (4500 rpm, 30 min.) to remove the free citrate ligand. A typical procedure for the shell synthesis is described below for sample Au@pMEO 2 MA-G1 (Table 1). In a tube equipped with a stirrer and a N 2 gas inlet, reactive were added in the following order: 4.75 μL of a solution of AcSEO 2 MA monomer in Supplementary Fig. S1). After above 10 min, the solution became cloudy, indicating that polymerization started, and the solution was left to react for 2 h. To stop the reaction, the solution was cooling down in an ice bath while the tube was opened to air. Finally, after water dilution, the sample was four times centrifuged (4600 rpm, 30 min.) and resuspended in water until complete removal of empty polymer-particles and excess of ...

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... further demonstrate the adaptability and robustness of the method, the somewhat hydrophilic mono- mers (MEO 2 MA and NIPAM) were swapped for other more hydrophobic ones (MMA, Fig. 3a and St, Fig. 4a). Preliminary experiments with similar SDS concentration and water/ethanol ratio, as used for MEO 2 MA and NIPAM, resulted in lower pSt shell growth onto AuNP (data shown in Supplementary Fig S3). Note that pNI- PAM and pMEO 2 MA, as water containing polymers, have swelling capability, not exhibited by pSt and pMMA. Then, since SDS controls nanohybrid size, at similar SDS concentration the nanohybrid´s polymer coverage for pNIPAM and pMEO 2 MA will be higher than for pSt and pMMA. In an attempt to overcome this limitation and to forge a broad-based coverage of the polymer, a lowered surfactant SDS concentration was added to the reac- tion mixture (Table 1) during the synthetic procedure (Fig. 1). The red-shift in extinction spectra (up to 579 and 549 nm, Au@pMMA-G6- Fig. 3d and Au@pSt-G8- Fig. 4d, respectively), due to the increase of the local dielectric constant surrounding the metal surface; and the particle size increase around 34%, Au@pSt-G8 and 300%, Au@ pMMA-G6 (DLS, Table 1 and Fig. 3c) were consistent with polymer-shell formation around the Au ...

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... to their distinct hydrophobicity character, four acrylic/vinyl monomers, namely N-isopropylacrylamide (NIPAM), diethylene glycol methyl ether methacrylate (MEO 2 MA), methyl methacrylate (MMA) and styrene (St) (Fig. 1) were chosen as model for the AuNP system to parse the viability and versatility of our one-pot syn- thetic protocol. As first validation of the method, MEO 2 MA and NIPAM monomer, and AuNPs were investigated (Fig. 2a). pMEO 2 MA and pNIPAM are well known smart temperature-responsive polymers in water 30,31 , with improved swelling performances, once crosslinked. They were initially used to explore the optimal reaction con- ditions too (Table 1). Au@p(MEO 2 MA)-G1 sample in Table 1 indicates the initial experimental conditions on the basis of previous work 7 ...

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... the basis of evidence presented above, as well as more detailed results below, ethanol appears to drive the polymer-shell assembly of hydrophobic monomer on metal NPs, as induced by the slow addition of a good solvent to the monomer solution in water. Basically, the ethanol controls the polymerization of pMMA shells onto Au spheres (Fig. 3b, Table 1). Thus, the floating MMA phase acts as monomer source for the pMMA shell formation (Fig. 3b-i); and, indeed, the shell thickness continues a uniform growth, until the whole MMA amount is consumed (that eventually ends up engulfing AuNPs, Fig. 3b-ii). Nevertheless, this will only happen if the inter- facial energies between the MMA droplets and aqueous phases, and surface ligands are quantitatively adjusted by the solvent (Fig. 3b-ii), at the initial stages of polymerization. Note that, from the point of view of interfacial energies, a key issue is to exchange the surface ligands on the core NPs, so that the subsequently formed shell can form a wetting layer around the core. From the TEM images ( Fig. 3b-i and ii), it can be clearly seen that the homogeneous nucleation (concentric shell) is promoted over the heterogeneous one (eccentric shell). So, whereas some AuNPs appeared not isotropi- cally covered (Fig. 3b-i); nevertheless, AuNPs resulted uniformly enclosed for growing polymer shells (Fig. 3b-ii) by the addition of 2.6× times of ethanol. As previously mentioned, these morphologies might represent¨laterepresent¨late or ineffectiveïnterfacial collisions/interactions in the residence ethanol volume ratio without ability for spreading of the monomer. The MMA monomer appears not to wet the AuNP completely, and, after the assembly, ethanol removal from the swollen polymer domain produces quizzical-aspheric pMMA shells by locking the resulting nanostructure (from hereafter emoji-N-hybrids, Fig. 3b-i). In fact, dense AuNP core inside swollen-like pMMA shell and compact pMMA, which ends forming a bump at the polymer-shell periphery, can be easily observed. Topological features in dark-field SEM image and electronic densities in the transmission electron beams in TEM picture reflect the distinct structural arrangements (porosities) of the components (Fig. ...

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... this point, we might say that lower ethanol concentration leads to thinner polymer shell (Au@pSt-G9); whereas higher concentration disturbs the proper functioning of coverage-boundary, and subsequently, a broader and red-shifter longitudinal plasmon band is defined (Au@pSt-G11, Fig. 4). This boundary distortion enables rapprochement among well-defined hybrids (Supplementary Fig. S4), which can be then disassembled by simple addition of water (Fig. 4b-iv). Hence, the summation of thëplasmonic couplingëffect to thësurrounding Scientific REpORtS | (2018) 8:5721 | DOI:10.1038/s41598-018-24078-8 refractive indexëffect should be taken into consideration. And, both the shifted Au absorption peak and the appearance of additional peak in longer wavelength range well support the symmetry breaking of the nanohy- brids during the polymer shell ...

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... we report on a one-pot synthesis of singular nanohybrid species with tunable anisotropic polymer cov- erage via interfacial energy and surfacëwetting/dewettingädjustment of the components in aqueous media. Interestingly, while the use of methacrylate-monomer tagged-AuNPs, as seeding system, for self-assembly of diverse selected acrylic/vinyl-monomers by precipitation-polymerization ( Fig. 1) generates, in one-step, Au@ polymer hybrid NPs with a wide sort of polymer shells; the fine-tuning of ethanol-water proportion efficiently yields morphologies ranging from core-shell-like to eccentric or Janus structures. Furthermore, this simple mod- ification of usual precipitation-polymerization reaction overcomes difficulties, inherent to time-lapse control for Au-seeds addition 16,17 , absence of shell-thickness tunability 18 , mixed bimodal patterned NP distribution 19 , and complexness 22,23 , reported in previous synthetic approaches. Even when the conceptual use of interfacial energy for nanohybrid syntheses with tunable morphology is not new; the reported works used enriched isopropanol media and are only applicable to highly hydrophilic polymers as polyacrylic acid (PAA) with suitable functional groups to interact with NPs surface 26,27 . Additionally, our method provides a controlled composition domain, since it is likely to be applicable to a large number of ...