Self‐Assembly of Atomically Precise Silver Nanoclusters in Crowded Colloids into Ultra‐Long Ribbons with Tunable Supramolecular Chirality

Abstract Atomically precise metal nanoclusters (NCs) emerge as fascinating synthons in self‐assembled materials. The self‐assembly of metal NCs are highly sensitive to the environment because they have an inorganic‐organic hybridized structure and a relatively complicated conformation. Here, it is shown that when confined in crowded colloids, a water‐soluble Ag9‐cored nanocluster (Ag9‐NC) can self‐ assemble into ultra‐long (up to millimeters) and photoluminescent ribbons with high flexibility. The ribbon contains rectangularly organized columns of Ag9‐NCs and can undergo secondary self‐assembly to form bundled and branched structures. Formation of ribbons is observed in all the tested colloids, including lyotropic liquid crystals and disordered, three‐dimensional network. The high viscosity/elasticity of the crowded colloids weakens gravity‐induced sedimentation of the ribbons, leading to the formation of an interesting class of inorganic‐organic composite materials where the hard Ag‐containing skeleton strengthens the soft matter. The simultaneously occurring symmetry breaking during the self‐assembly of Ag9‐NCs gives uncontrolled supramolecular chirality, which can be tuned through the majority rule and soldier‐and‐sergeant rule by the introduction of chiral seeds. The regulated chirality and the intrinsic photoluminescence of the Ag9‐NCs ribbons impart the composite material circularly polarized luminescence, opening the door for a variety of potential applications.


Introduction
Atomically precise metal nanoclusters (NCs) are constituted by a few to hundreds of metal atoms with a ligand shell and sizes which provides a good opportunity for deep studying the structure-property relationship of the self-assemblies.To date, various metal NCs have been synthesized, which were covered by diversified ligands.For metal NCs with precise structures confirmed by single crystal analysis, the ligands used are normally small molecules.As the active part (typically polar groups) will be consumed by coordination with metal atoms/ions, the so-obtained metal NCs are typically hydrophobic.12][13][14] To enrich the noncovalent interaction among the clusters and increase the sensitivity of the metal NCs toward the environment during self-assembly, it would be necessary to impart the metal NCs surplus functional groups.For this purpose, the selection of polydentate ligands is necessary.For example, we have demonstrated that silver NC containing six silver atoms (Ag 6 -NC) could be obtained by using mercaptonicotinic acid as a ligand, which has six peripheral carboxylic groups surrounding the cluster. [15][18] Another example is silver NC containing nine silver atoms (Ag 9 -NC, Scheme 1a) with thiosalicylic acid as ligands, which have three peripheral carboxy groups.Compared to Ag 6 -NC, Ag 9 -NC has a lower water solubility due to the decreased number of the peripheral carboxylic groups while increased number of the silver atoms in the core.Thus, it can be dissolved only in an alkaline solution, which makes it highly sensitive to the perturbation of the environment.[23][24] CISA could also be induced by the modification of the solvent by the introduction of a protonic solvent (ethanol, EtOH), [25] or by coordination of the peripheral carboxylic groups with secondary metal ions (such as Ba 2+ ). [26]hese preliminary results proved that Ag 9 -NC is a powerful building block in self-assembly.Structural analysis of the selfassemblies revealed that the internal organization is highly dependent on the environment and the aggregation pathway of Ag 9 -NCs.In a solvent-free state, the crystallized self-assemblies have quite a similar organization to that of the lyophilized stock solution of Ag 9 -NCs. [24]In the gels induced by EtOH, the selfassemblies exhibit a high degree of crystallization but a poor phase purity. [25]In Ba 2+ -based gel, a well-defined chiral cubic (I*) phase was observed with a space group of I4132 (Q214), but the degree of order is not high seen from the relatively large peak width at half-height. [26]o get a deep understanding of the self-assembly of metal NCs and to further expand the applications of the self-assemblies, in this work, we created a new environment to tune the self-assembly of Ag 9 -NCs.When confined in highly concentrated aqueous solutions of polyether-based surfactants (C 12 E 4 , Tyloxapol, and F127, Scheme 1b) or macromolecule (PEG, Scheme 1b), the hydrophilic part of Ag 9 -NC was dehydrated and the local concentration of Ag 9 -NC was increased, which success-fully triggered CISA.The highly viscous colloids not only provided an ideal microenvironment for the elongation of the selfassemblies but also weakened the gravity-induced sedimentation, leading to the formation of ultralong (up to millimeters) and photoluminescent (PL) ribbons with high flexibility.Importantly, the rather slow kinetics aided by the highly viscous microenvironment give enough time for the self-assembly of Ag 9 -NCs, leading to the formation of a columnar rectangular (Col r ) phase.By applying the majority rule and soldier-and-sergeant rule, the spontaneously-occurred supramolecular chirality during the self-assembly, which is irregular and hard to control, was made homochiral by the introduction of chiral seeds (Fmoc-Val-ONa and Fmoc-Ala-ONa, abbreviated to Val and Ala, respectively, Scheme 1b).Combining the intrinsic photoluminescence of the self-assembled Ag 9 -NCs, inorganic-organic hybrid materials with circularly polarized luminescence (CPL) were finally obtained (see Scheme 1c for the illustration of the whole selfassembly process).

Results and Discussion
We first investigated the self-assembly of Ag 9 -NCs in aqueous solution of C 12 E 4 with a concentration of 50 wt.%.At this concentration, C 12 E 4 itself forms a lyotropic liquid crystal (LLC) phase with lamellar organization proved by polarized optical microscopy (POM) observations and small-angle X-ray scattering (SAXS) measurements (Figure S1, Supporting Information).After Ag 9 -NCs were introduced and the sample was aged for a sufficiently long time (over one week), elongated nanostructures formed which were evenly distributed inside the LLC phase.As seen from the optical microscopy image in Figure 1a, the nanostructures occupy the whole area of the image with a length of up to millimeters.Entanglement and bending were noticed, indicating their high flexibility.Optical anisotropy was noticed when crossed  and c) fluorescent images of the self-assemblies embedded inside the LLC phase.d) 3D CLSM image of the self-assemblies embedded in the LLC phase.The voids will be occupied by surfactant and water molecules, which are invisible under the microscope.e) SAXS patterns of the self-assemblies before and after washing.Results from lyophilized Ag 9 -NCs are also given for comparison.The dashed line is a guide for the eyes.f-i) SEM images of the self-assemblies after washing.polarizers were applied, especially for the thick nanostructures (Figure 1b).Ag 9 -NCs exhibit aggregation-induced emission (AIE) with intrinsic red emission, which makes the nanostructures visible under a fluorescence microscope (Figure 1c).More structural details of the nanostructures were obtained from 3D reconstructed confocal laser scan microscopy (CLSM) images.As presented in Figure 1d and the supporting movie, the diameters of the nanostructures are polydisperse.They have a solid structure with tabular cross-sections, indicating that they are actually ribbons.Among them, furcation of a thick ribbon into smaller ones and coalesce of thin ribbons into a big one occurred quite often.This feature, combining the bending of individual ribbons, led to the formation of a 3D network.The internal structure of the ribbons was probed by SAXS measurements (Figure 1e).Four peaks were observed in addition to those of the lamellar phase (marked by the stars), which can be assigned to the (11), (20), (30), and (40) planes of a columnar rectangular (Col r ) phase [27] with a lattice parameter of a r = 2.63 nm and b r = 1.97 nm.
In our previous work, we have shown that Ba 2+ -induced selfassemblies of Ag 9 -NCs underwent a structural transition during the post-treatment by washing and drying. [26]In the current study, the same phenomenon was noticed.As seen in Figure 1e, the SAXS curve of the ribbons lost the feature of the Col r phase once they were washed out of the LLC phase followed by drying.The curve became quite similar to that of the lyophilized Ag 9 -NCs with only a slight peak shift toward small q values (< 0.1 nm −1 ), indicating that Ag 9 -NCs are the main components of the dried ribbons.This conclusion gained further support from the rather similar curves of the washed ribbons and lyophilized Ag 9 -NCs from X-ray photoelectron spectroscopy (XPS) measurements (Figure S2, Supporting Information), as well as energy dispersive spectroscopy (EDS) analysis on the ribbons where elements of Ag and S were detected besides C and O (Figure S3, Supporting Information).However, from Fourier transform infrared (FTIR) measurements, we realized that the spectrum of the washed ribbons also contained signals from C 12 E 4 (Figure S4, Supporting Information), indicating that C 12 E 4 also attended in the self-assembly of Ag 9 -NCs, which could not be fully removed by washing.In addition, the peaks ≈1457, 1282, and 1236 cm −1 , which originated from C 12 E 4 , and those in between 768-616 cm −1 , which came from lyophilized Ag 9 -NCs, shift to lower wavenumbers.These observations indicate that noncovalent interaction exists between C 12 E 4 and Ag 9 -NCs, which led to better thermal stability of the washed ribbons compared to that of the lyophilized Ag 9 -NCs confirmed by thermogravimetric analysis (TGA, Figure S5, Supporting Information).
Despite the internal structural transition induced by washing and drying, the ribbons basically retained their morphologies.From the scanning electron microscopy (SEM) image shown in Figure 1f, ribbons were clearly observed.A typical one with a width of ≈1.31 μm has been marked between the arrowheads.Also marked is a thin one with a width of only ≈0.17 μm (between the arrows).SEM observation with a higher magnification shows the twisting of a small ribbon, with the widest and narrowest places to be ≈145 and ≈77 nm, respectively (Figure 1g).Examination of thick ribbons showed that they are formed by the secondary self-assembly of smaller ones.Two typical images exhibiting this situation are given in Figure 1h,i.The structural features of the ribbons were also proved by atomic force microscopy (AFM) and transition electron microscopy (TEM) observations (Figures S6 and S7, Supporting Information).
Formation of the ribbons is influenced by the concentrations of both Ag 9 -NCs (c Ag9-NCs ) and C 12 E 4 (c C12E4 ).At a fixed concentration of c C12E4 of 50 wt.%,lowering c Ag9-NCs from 2.0 wt.% to 1.5 wt.% caused an obvious decrease in the number density of the ribbons proved by polarized optical microscopy (POM) observations (Figure S8, Supporting Information).From SAXS patterns, peaks from the Col r phase could hardly be detected (Figure S9, Supporting Information).The less pronounced self-assembly of Ag 9 -NCs at lower concentrations caused obvious changes in the optical properties of the composite materials.As seen in Figure 2a, the sample of 2.0 wt.% Ag 9 -NCs/50 wt.% C 12 E 4 showed absorbance across the UV and visible regions with a shoulder peak ≈265 nm.When c Ag9-NCs decreased to 1.5 wt.%, a hypochromatic shift of the peak (by ≈4 nm) was observed together with an obvious decrease in absorption.When c Ag9-NCs further decreased to 1.0 wt.%, the peak underwent a further hypochromatic shift (by ≈1 nm) and the sample became optically transparent above 400 nm.From PL measurements, the sample of 2.0 wt.% Ag 9 -NCs/50 wt.% C 12 E 4 exhibited an optimized excitation at ≈420 nm with a broad emission covering the yellow and red regions (Figure 2b, Figure S10, Supporting Information).When c Ag9-NCs decreased, the intensity in the long wavelengths weakened and the emission transferred to the blue region, which was assigned to the emission from the peripheral ligands. [26]The influence of c C12E4 on the self-assembly of Ag 9 -NCs is also obvious.At a fixed c Ag9-NCs of 2.0 wt.%, ribbons could not be observed by POM if c C12E4 was below 40 wt.%.Examination of other compositions showed that the self-assembly of Ag 9 -NCs was heavily dependent on c C12E4 .A sample matrix could be obtained by POM observations, which are given in Figure 2c (also see Figure S11, Supporting Information, which contains typical images).One can see that a larger c C12E4 corresponded to a lower critical c Ag9-NCs for the formation of ribbons, indicating that a more crowded colloidal environment is beneficial for the self-assembly of Ag 9 -NCs.
The kinetics involved in the self-assembly were tracked by time-dependent POM observations using the sample with c C12E4 = 50 wt.%and c Ag9-NCs = 2.0 wt.% as an example.The image obtained 1 day after sample preparation showed only quite a limited number of anisotropic, short ribbons (Figure 2d).During aging, both the number and length of the ribbons increased (Figure 2e,f).The growth of ribbons induced a continuous change of the photoluminescence, with the emission gradually shifting from the blue region to the red region (Figure 2g).Compared to EtOH-induced [25] and Ba 2+ -induced gels, [26] the time scales noticed in the self-assembly of Ag 9 -NCs in the LLC phase of C 12 E 4 are significantly longer.Probably, the high viscosity of the system and the presence of the surfactant bilayers set barriers and retarded the self-assembly.In this case, Ag 9 -NCs have sufficient time to tune their conformation to better fit in the selfassemblies, accounting for the formation of ribbons with high internal order.
The formation of hard nanostructures (ribbons) embedded in the soft matters (LLC phase) enhances the mechanical strength of the LLC phase has been reinforced by the presence of the ribbons.At c Ag9-NCs of 2.0 wt.%, the elastic modulus (G') of the LLC phase of 50 wt.%C 12 E 4 was improved by ≈3.6 folds (Figure 2h, Figure S12, Supporting Information), and the complex viscosity (|h*|) was increased by ≈4.3 folds (Figure S13, Supporting Information).Further examination revealed that both G' and |h*| increased steadily with increasing c Ag9-NCs (Figure 2i).
Thus, reinforcement also occurred at low cAg9-NCs, despite the fact that the ribbons were hard to capture by imaging studies under such circumstances.
[30] Next issue is whether or not the self-assembly of Ag 9 -NCs into ribbons is specific to the LLC phase of C 12 E 4 .To figure it out, other two LLC phases formed also by nonionic surfactants were selected, including the hexagonal phase formed by Tyloxapol (Figure S14, Supporting Information) and the cubic phase formed by Pluronic F127 (Figure S15, Supporting Information).An amorphous phase formed by PEG, which is a nonionic, fully hydrophilic polymer lacking amphiphilicity, was also selected.Comparison between the rheological properties of the four samples with a concentration of 50 wt.%revealed big differences in their mechanical strength, as seen in Table 1.The hexagonal phase shows the highest elastic modulus while the cubic phase has the largest viscosity.The amorphous phase formed by PEG has the smallest viscosity and lacks elasticity.However, it exhibits a less   pronounced shear-thinning behavior with ≈24% loss of viscosity when the shear rate was increased from 0.1 to 100 s −1 .The self-assembly of Ag 9 -NCs in the above three colloids was fully investigated.At a fixed concentration of the colloids of 50 wt.%and a fixed c Ag9-NCs of 2.0 wt.%, imaging studies showed that ribbons formed within all of them (Figure 3a-d, Figure S16, Supporting Information).Morphological analysis of these structures revealed two more assembly modes of the ribbons, i.e., stacking (inset of Figure 3b) and cross-joining (inset of Figure 3d).Further investigations on other concentrations showed that ribbon formation was easier in these three colloids compared to the system of C 12 E 4 .For example, at c Tyloxapol = 50 wt.%, the formation of ribbons was already obvious at c Ag9-NCs = 1.5 wt.% (Figure S17, Supporting Information).Even at c Ag9-NCs = 1.0 wt.%, the presence of ribbons could be distinguished despite the low number density (Figure S18, Supporting Information).For another example, when c Ag9-NCs are fixed at 2.0 wt.%, a considerable amount of ribbons was observed in 30 wt.% F127 (Figure S19, Supporting Information), which is not the case for C 12 E 4 (see Figure 2c).For PEG solutions, formation of ribbons was also obvious when c PEG reached 40 wt.% at c Ag9-NCs = 2.0 wt.% (Figure S20, Supporting Information).Time-dependent studies on F127-based system revealed that the ribbon formation exhibited relatively fast kinetics.As shown in Figure 3e-h, large amount of ribbons appeared only 8 h after sample preparation for F127-based system, which is much shorter than the time scale noticed in the lamellar phase of C 12 E 4 .These observations showed that although the formation of ribbons is equally successful for Ag 9 -NCs, the parameters of each colloid could also modify the process of self-assembly.The character of each colloid also influenced the organization of Ag 9 -NCs within the self-assemblies.Examination of the Col r phases by SAXS measurements showed that the ribbons formed in the hexagonal and cubic phases shared quite similar lattice parameters with those observed in the lamellar phase (Figure 3i).In F127-based system, the shoulder peak assigned to the averaged distance between adjacent Ag 9 -NCs within the column of the Col r phase was also detected (marked by the arrowhead).For ribbons formed in PEG solution, a shrunken lattice was detected with four extra peaks which could hardly assigned to the Col r phase (Figure 3i, marked by stars), which indicates that the organization of Ag 9 -NCs within the column is more complicated.Of course, the presence of a concomitant unknown phase in addition to the Col r phase could not be fully excluded at the moment.PL measurements showed that the emission from the colloids of C 12 E 4 , F127, and PEG almost superpose when excited at 420 nm (Figure S21, Supporting Information).Examination of the optimized excitation on the F127-based system (Figure S22, Supporting Information) only revealed quite a limited difference (≈10 nm smaller) compared to the C 12 E 4 -based system.For Tyloxapol-based system, the emission was heavily intervened by the strong blue-emission from Tyloxapol (Figure S23, Supporting Information).Rheological measurements showed that the degree of mechanical reinforcement for the hexagonal LLC phase caused by the self-assembly of Ag 9 -NCs is similar to that observed in the lamellar LLC phase formed by C 12 E 4 , while it is not obvious for the cubic LLC phase formed by F127 as the mesophase itself already has an extremely large viscosity (Figure S24, Supporting Information).For the low viscous PEG solutions, the mechanical reinforcement is the most obvious.As seen from Figure 3j,k, the viscosity of the composite solution increased significantly with a much more pronounced shear-thinning behavior, and the intrinsically only viscous sample became viscoelastic.
Further extension showed that in the LLC phase formed by an anionic surfactant (sodium dodecyl sulfate, SDS), the ribbons could form without obvious macroscopic phase separation (Figure S25, Supporting Information).However, this is not the case for cationic surfactant (cetyltrimethylammonium bromide, CTAB) where precipitation formed driven by the electrostatic attraction between negatively-charged Ag 9 -NCs and the positivelycharged aggregates of CTAB.It should also be noted that the usage of Ag 9 -NCs is necessary for the formation of the ribbons.In control experiment, no ribbon was found when Ag 9 -NCs were replaced by AgNO 3 , even with a higher content (5.0 wt.%, Figure S26, Supporting Information).
Thus, our results showed that by introducing Ag 9 -NCs into nonionic as well as anionic crowded colloids, formation of ribbons will be triggered regardless of the spatial organization of the colloids.When trapped within these colloidal matrixes, the originally soluble Ag 9 -NCs will be pushed into the confined water channels, leading to an abrupt increase in their local concentration.The hydrophilic polyether will compete with the peripheral carboxylic groups of Ag 9 -NCs in hydration.These two effects synergistically triggered the crystallization of Ag 9 -NCs followed by an axial growth, leading to the formation of 1D stacks of Ag 9 -NCs which further assemble parallelly into ribbons.During this process, the peripheral ligands of Ag 9 -NCs were forced to adopt an uneven distribution due to the crowded microenvironment, making the originally circular cross-section of Ag 9 -NCs (see Scheme 1a) elliptical and accounting for the rectangular organization of the stacks.As the crystallized Ag 9 -NCs are hard and sharp with decreased hydrophilicity, they can cross the soft hydrophobic domains formed by surfactants.With the continuous growth of the ribbons, adjacent ribbons can join together to form bundles, which can undergo dissociation and branching.Finally, a 3D network is formed (for an intuitive impres-sion, see the supporting movie).The process of the self-assembly and models of ribbons embedded in the three LLC phases as well as the entangled PEG network are illustrated in Scheme 2. Considering that the LLC phases formed by Tyloxapol and F127 have large viscoelasticity, we suppose that the space confinement will become more obvious, accounting for the easier self-assembly of Ag 9 -NCs.In the case of PEG, the easier formation of the ribbons might be ascribed to the more pronounced dehydration effect of the peripheral carboxylic groups of Ag 9 -NCs induced by PEG which is fully composed of hydrophilic groups (see Table 1).
Appending specific properties, such as chirality, to the composite materials is beneficial for their practical applications.Consistent with our previous observations on self-assembled Ag 9 -NCs, the colloids with embedded ribbons of Ag 9 -NCs presented in the current study also showed chiral signals despite the lack of any chiral centers of the building blocks.We have previously demonstrated that when viewed along the C 3 axis, Ag 9 -NC looks like a triskelion with either clockwise or anticlockwise conformation due to the referentially unidirectional arrangement of the peripheral ligands. [26]During self-assembly, the transient chirality caused by the vibration of the peripheral ligands could be fixed and amplified.As the formation of 1D stacks has been unambiguously confirmed by SAXS in the current study, another possibility for the chirality could be proposed.As seen in Scheme 1a, Ag 9 -NC can be viewed as an analog of a C 3 -symmetric organic molecule [31][32][33][34] where a tabular triangular prism was surrounded by organic ligands.37] Taking Ag 9 -NCs/C 12 E 4 system as an example, during multiple measurements, both positive and negative signals were obtained from circular dichroism (CD) measurements.Recently, we showed that the uncontrolled supramolecular chirality of crystallized Ag 9 -NCs could be manipulated by the introduction of small organic molecules with defined chirality, such as L-or D-tartaric acid (TrA). [24]Applying a similar strategy, herein the supramolecular chirality of the self-assembled Ag 9 -NCs (taking the lamellar LLC phase as an example) was tuned by Fmocprotected amino acid sodium salts (Val, Scheme 1a).The introduction of these chiral seeds did not destroy the morphology of the nanostructures.Imaging studies on typical samples showed that long and flexible nanostructures are present after the addition of chiral seeds (Figure 4b, Figure S27, Supporting Information).The ribbons retained their morphologies after washing and drying, where bending and twisting of the ribbons were again observed (Figure 4c, d), and magnifications on typical ribbons redisplayed the secondary self-assembly of individual ribbons into larger ones (Figure S28, Supporting Information).CD measurements showed that enantiomeric selectivity was successful, with only one sign of the CD signal obtained for the sample containing a specific amino acid salt (Figure 4e).The regulated chirality, combined with the intrinsic photoluminescence of the ribbons, led to well-defined CPL signals (Figure 4f), which were otherwise chaotic in the absence of the amino acid salt.Normally, the seed effect in controlling overall chirality of selfassembled systems contains majority rule which stands for the induced chirality by the major or lesser component respectively.During the self-assembly of Ag 9 -NCs into ribbons, the chiral seed could be entrapped inside the 1D matrix via physical immobilization and/or noncovalent forces.As both Ag 9 -NC and the chiral seed bear carboxylate moieties, formation of assemblies was expected, which induced the emergence of helical ribbons with homochirality determined by the absolute chirality of the chiral seed.This seeding effect is consistent with the soldier-andsergeant rule, which to date has rarely been clarified in selfassemblies with metal NCs as the main component. [24]Although further details might be needed to fully reveal the mechanisms behind the transfer and amplification of the chirality, the current study provided a novel protocol to produce chiral soft materials from achiral metal NCs, where the chiral behavior and chiroptical effects are under rational control.

Conclusion
In summary, we have presented for the first time the selfassembly of metal NCs in crowded colloids, using the negatively charged Ag 9 -NC as an example.The competitive hydration of the hydrophilic groups and the exclusion effect induced by the colloids triggered the CISA of Ag 9 -NCs.The high viscosity/elasticity of the colloidal solution retarded the self-assembly of Ag 9 -NCs and provided the self-assemblies resistance against gravity-induced sedimentation, leading to the formation of ultralong ribbons with Col r organization, photoluminescence, and hierarchical structure.Embedded with a network of ribbons, the mechanical strength of the colloids has been improved.By tuning with chiral seeds, the uncontrolled supramolecular chirality of the system was regulated to give homochiral signals.Combined with the AIE of Ag 9 -NCs, CPL was achieved for the composite materials.Current study deepens our understanding of the selfassembly of metal NCs, and the marriage between cluster science and colloid science opens a new frontier for engineering hard/soft hybrid materials with potential applications in fields of chiral optics, chiral separation, and chiral catalysis.

Scheme 1 .
Scheme 1. a) Top (left) and side (right) view of Ag 9 -NC, obtained from single crystal analysis.Values of typical distances are given.The dashed circle in a is a guide for the eyes.Blue: Ag, yellow: S, red: O, grey: C. green: H. b) Structures of the polyethers and chiral seeds adopted in the current study.c) Schematic representation of the self-assembly of Ag 9 -NCs in crowded colloids and the subsequent chiral regulation by seeds.

Figure 1 .
Figure 1.Morphologies and structures of the self-assembled Ag 9 -NCs (2.0 wt.%) in the lamellar LLC phase of C 12 E 4 (50 wt.%).a) Optical microscopy, b) POM, and c) fluorescent images of the self-assemblies embedded inside the LLC phase.d) 3D CLSM image of the self-assemblies embedded in the LLC phase.The voids will be occupied by surfactant and water molecules, which are invisible under the microscope.e) SAXS patterns of the self-assemblies before and after washing.Results from lyophilized Ag 9 -NCs are also given for comparison.The dashed line is a guide for the eyes.f-i) SEM images of the self-assemblies after washing.

Figure 2 .
Figure 2. UV-vis absorption a) and emission at an optimized excitation wavelength of 420 nm b) of the lamellar LLC phase of C 12 E 4 (50 wt.%) containing varying amounts of Ag 9 -NCs as indicated.Inset in a are the statistics of the optical density (O.D.) at 550 nm and insets in b are photos of the three selected samples under 365 nm UV irradiation.c) A sample matrix for C 12 E 4 /Ag 9 -NCs/H 2 O ternary system.The intertwined symbols denote the nanoribbons.d-f) POM images recorded at different times after sample preparation for Ag 9 -NCs (2.0 wt.%) in C 12 E 4 (50 wt.%).The images were recorded with the same magnification (the scale is given in image d).g) Time-dependent emission of Ag 9 -NCs (2.0 wt.%) in C 12 E 4 (50 wt.%).The two arrows are guides for the eyes.h) Variations of the elastic modulus G' and viscous modulus G" as a function of the angular frequency  for Ag 9 -NCs (2.0 wt.%) in C 12 E 4 (50 wt.%).For comparison, data from the sample without Ag 9 -NCs are also given.i) Statistics of G' and complex viscosity |h*| recorded at 0.1 rad•s −1 for the C 12 E 4 (50 wt.%) containing varying amount of Ag 9 -NCs.

Figure 3 .
Figure 3. a-d) Typical results from imaging studies on the self-assembled Ag 9 -NCs (2.0 wt.%) in 50 wt.% of Tyloxapol (a, CLSM image), F127 (b, c, SEM images) and PEG (d.SEM image).Inset of b highlights the stacking of the nanoribbons to form a bigger one, while that of d highlights the joint of four nanoribbons to form a wider one.In both cases, the scale bar corresponds to 1 mm.e-h) Optical microscopy images recorded at different times show the evolution of the self-assemblies of Ag 9 -NCs (2.0 wt.%) in F127 (50 wt.%).i) Comparison of the scattering peaks in the range of 3.5-5.5 nm −1 , which contains the (11) and (20) planes of the Col r phase, for Ag 9 -NCs (2.0 wt.%) in aqueous solutions formed by the three polyethers as indicated (50 wt.%).j) Variation of the apparent viscosity as a function of shear rate for the sample containing 2.0 wt.% Ag 9 -NCs and 50 wt.%PEG.For comparison, data from the sample without Ag 9 -NCs are also given.k) Variations of G', G'', and |*| as a function of  for the sample containing 2.0 wt.% Ag 9 -NCs and 50 wt.%PEG.

Scheme 2 .
Scheme 2. Illustration of the composite materials where ribbons from self-assembly of Ag 9 -NCs are embedded in various soft mesophases.The ribbon contains highly ordered Ag 9 -NCs organized in a Col r phase, which can undergo secondary self-assembly into bundles.

Figure 4 .
Figure 4. a) Proposed chirality origination from the spiral organization of Ag 9 -NCs within the 1D stack.b) A typical optical microscopy image for the self-assembled Ag 9 -NCs (2.0 wt.%) in 50 wt.%C 12 E 4 at the presence of LVal (1.5 wt.%).c) SEM image for the washed sample shown in b. d) SEM image of the sample with the same amount of Dval.Insets in c and d highlight the twisting of the nanoribbons.e) CD spectra of the two samples containing Val.For comparison, data from samples only containing Val but without Ag 9 -NCs are also given.f) Variation of glum value as a function of wavelength for the two samples containing Val.Data with no doping is also given for comparison.

Table 1 .
Parameters for C 12 E 4 , Tyloxapol, F127, and PEG as well as their aqueous solutions (at a fixed concentration of 50 wt.%).