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Cite This: ACS Appl. Nano Mater. XXXX, XXX, XXX−XXX

Phase and Dispersion Stability of Silver Nanocolloids for Nanoparticle-Chemisorption Printing Yuya Hirakawa, Keisuke Aoshima, Shunto Arai,* and Tatsuo Hasegawa* Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan

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S Supporting Information *

ABSTRACT: Here we investigated the unique phase and dispersion characteristics of alkylamine/alkylacid encapsulated silver nanocolloids (AgNCs) that allowed the production of ultrafine metal wiring using the nanoparticle chemisorption printing technique. We found that a polar methanol component, which was unintentionally involved during the synthesis of the AgNCs, promoted the instability of the colloidal phase and slightly accelerated the flocculation of the silver nanoparticles (AgNPs). We also investigated ternary phase diagram of a mixed solvent system of octane/butanol/methanol in the absence of AgNPs. The phase separation was observed at relatively large methanol content, and the feature was closely associated with the deterioration of AgNCs due to phase separation. In the unseparated AgNCs, the methanol component accelerated the selfaggregation of AgNPs, eventually triggering the phase separation that took place at lower methanol content as compared to the pure mixed-solvent system. Furthermore, the self-aggregation considerably affected the conductivity of the printed silver wires without undergoing the annealing process. We discuss that the compatibility of encapsulating ligands with polar/nonpolar solvent molecules is the key to understand the instability of AgNCs. KEYWORDS: silver nanocolloid, printed electronics, phase separation, dispersion stability, solvent mediated interactions, surface wetting

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INTRODUCTION Concentrated metal nanocolloids or dense suspensions of metal nanoparticles in dispersion media have attracted considerable attention from both basic science and the industries. 1−3 A recent study showed that a unique phenomenon of “nanoparticle chemisorption” is observed in a particular class of silver nanocolloids (AgNCs) having a combination of patterned activated perfluorinated polymer surfaces.4 This phenomenon resulted in the formation of ultrafine silver wiring on plastic substrates by extremely facile printing processes. These are frequently called “printed electronics” technology, where printing techniques are utilized to realize flexible, lightweight, and large-area electronics devices, substituting the conventional photolithographic patterning and vacuum-based thin-film processing techniques.5−18 Among the several printed electronics technologies, the above-mentioned technique, known as “surface photoreactive nanometal printing (SuPR-NaP)”, is quite promising as it allows the fabrication of ultrafine silver wiring with a line width as narrow as 800 nm under ambient pressure and temperature by a facile process. It involves only a masked vacuum ultraviolet light irradiation on a perfluorinated polymer surface and a subsequent blade coating of the AgNCs. In terms of the fundamental aspects of the metal nanocolloids, these AgNCs exhibit some unusual characteristics that are indispensable for the nanoparticle chemisorption phenomenon. The AgNCs are composed of silver nano© XXXX American Chemical Society

particles (AgNPs) of an average diameter of about 13 nm encapsulated by alkylamines and a small amount of oleic acid suspended in a 4:1 octane/butanol solution.19−21 The peculiarity is that the high dispersion stability of the AgNCs is maintained for several months at room temperature, although the AgNPs readily fuse with each other after the AgNCs are fully dried (i.e., the dispersant is evaporated). The dried deposits eventually exhibit metallic conductivity without any annealing at room temperature. This feature is in striking contrast to the several usual metal nanocolloids developed for the printing techniques of conductive metal wiring. This is because the removal of the ligands encapsulating the metal nanoparticles using laser light irradiation,5 addition of salt,6−8 high-temperature annealing,9−14 or other sintering treatments15−18 are indispensable post-printing. It is clear that the peculiarities, that is, the coexistence of the high dispersion stability and the self-aggregation, are seemingly incompatible in terms of the degree of ligand encapsulation of the AgNPs. To clarify the origin of the peculiarities, Aoshima and coworkers investigated the composition dependence of the dispersion stability of the AgNCs using confocal dynamic light scattering (c-DLS).22 They found that the dispersion stability was considerably affected by the change in ligand Received: April 28, 2019 Accepted: July 5, 2019

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DOI: 10.1021/acsanm.9b00795 ACS Appl. Nano Mater. XXXX, XXX, XXX−XXX

ACS Applied Nano Materials

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RESULTS AND DISCUSSION Phase Stability of Dispersion Media and AgNCs. We investigated miscibility of the ternary solvent mixture in the absence of AgNPs as shown in Figure 1b. Figure 1c shows the ternary phase diagram of the mixed solvent system of octane/ butanol/methanol. The light blue area indicates the miscible phase, and the pale-yellow area denotes the phase separation. It is clear from the diagram that octane and butanol are completely miscible with each other (along the right oblique side of the triangle), whereas octane and methanol are immiscible without butanol (along the base of the triangle). It was also found that the phase separation could occur in the ternary system if the butanol component was lower than about 5%, implying that butanol could act as a buffer between octane and methanol. If the octane component is dominant (>75%), the relative component ratio of methanol/butanol should be lower than 6 or 7 for miscibility, as seen from the phase diagram. In the AgNCs, although the 4:1 mixed dispersant of octane and butanol is utilized nominally,22 it should include a residual methanol component, which was inevitably involved during the washing of the AgNPs. This indicates that the actual composition of the ternary solvent should be positioned along the left oblique side. We found that the ternary system was miscible at all compositions along the side, while the phase boundary came closer with increasing methanol content. Nonetheless, the phase separation of AgNCs could not be explained simply by the phase behavior of the dispersant at a particular composition. To investigate the time-dependent phase separation of the AgNCs, we left the AgNCs for a while after their synthesis. After the phase separation, we identified the composition of the dispersion media of the respective phases by 1H NMR spectroscopy. For instance, the composition of the dispersion media of the lower phase was 88% octane, 7% butanol, and 5% methanol and that of the upper phase was 39% octane, 31% butanol, and 30% methanol. The AgNPs were mainly present in the octane-rich lower phase, indicating that the AgNPs should be more readily dispersed in the octane-rich phase rather than in the methanol-rich phase (we note, however, that the AgNPs were not dispersible in pure octane22). We also investigated the lifetimes of the AgNCs that contained methanol at volume fractions of 10%, 26%, and 35%. We found that phase separation occurs after 48 h only in the AgNC containing 35% methanol (Figure 1a). To study the relationship between the phase instability of the dispersant and that of the AgNCs, we also monitored the phase separation temperature for a mixed solvent in the absence of AgNPs. We used the ternary solvent with methanol volume fractions of 0.1, 0.2, 0.3, 0.4, and 0.5, whereas the ratio of octane to butanol was fixed at 4:1. Figure 2 presents the measured transition temperatures. It is clear that the addition of methanol promotes the phase instability, and this can be controlled by temperature. We also investigated the effect of temperature on the phase separation of the AgNCs containing around 30% methanol; we kept the AgNCs at 25 °C (room temperature), 30 °C, and 40 °C and checked the time dependence of the appearance of the phase separation. The phase separation in AgNCs was observed within 2 days at 25 and 30 °C, whereas no phase separation was observed at 40 °C for more than a month. However, it was promptly observed when the AgNCs were cooled to room temperature. Thus, we

formulation and the dispersant composition of the AgNCs. In particular, a small amount of oleic acid, which was used as a subsidiary encapsulating agent, played a critical role in the unique coexistence of the high dispersion stability and nanoparticle chemisorption. Additionally, the colloidal stability seemed to be optimum at a 4:1 mixed dispersant ratio of octane and butanol.22 However, the AgNPs do not disperse in either pure octane or butanol. These AgNCs also exhibit further intriguing (or often undesirable) properties in terms of the phase and dispersion stability, although the origin of these characteristics have not yet been understood. For example, in some of the AgNCs, phase separation may occur after a few days or a month after the synthesis of the AgNCs (Figure 1a), thereby substantially decreasing the long-term stability of the AgNCs; the origin of the phase behavior, however, remains unknown.

Figure 1. (a) Picture of the phase separated AgNCs. (b) Picture of the phase separation in ternary mixed solvent system of octane/ butanol/methanol in the absence of AgNPs and (c) its phase diagram at room temperature.

In this study, we investigated the origin of the long-term colloidal phase instability in the AgNCs, specially focusing on the composition of the dispersant media. Because the main dispersant media, octane and butanol, are compatible (or miscible) with each other at all compositions, we studied the effect of the residual solvent component, methanol, which was unintentionally involved during the synthesis of the AgNCs. We first investigated the ternary phase diagram of the pure mixed solvent system of octane/butanol/methanol in the absence of the AgNPs. We also investigated the component ratio of the media in each phase of the phase-separated AgNCs by nuclear magnetic resonance (NMR) spectroscopy. We concluded that the instability of the colloidal phases could be ascribed to the effect of the polar methanol component. On the basis of this, we investigated the effect of residual methanol in the AgNCs before phase separation by c-DLS and performed the conductivity measurement of the silver wires after printing. We discuss the phase and dispersion stability of the AgNCs in terms of the compatibility of the polar methanol molecules with the ligands encapsulating the AgNPs. B


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consistent with the c-DLS measurements, and indicate that methanol reduces the dispersion stability considerably. These results implied that the dispersion instability was caused by the high methanol content, which accelerated the aggregation of the AgNPs and eventually resulted in the phase instability, as mentioned before. We consider that the origin of the dispersion instability should be related to a class of solventmediated attractive interaction.24−27 There should be a concentration gradient of solvents around the AgNP surfaces because of the different affinity of the solvents toward the AgNP surfaces. This is schematically presented in Figure 5a (the solvent with higher (lower) affinity for the AgNP surfaces is denoted as solvent I (II)). The concentration gradient should generate an attractive force between the AgNPs, which is mediated by the liquid-bridging force with solvent I.24−27 The destabilization might also be enhanced by the effect of osmotic pressure for the encapsulating ligands as schematically shown in Figure 5b. The osmotic pressure for protecting the ligands can be represented by the Flory−Huggins theory,28−30

Figure 2. Phase diagram (temperature vs volume fraction of methanol) of the ternary mixed solvent system of octane/butanol/ methanol in the absence of AgNPs. The ratio of octane to butanol is fixed at 4:1.

Δπ =

2kBT ij 1 y jj − χ zzzϕ2 vm k 2 {

where vm is the volume of the solvent molecule, χ is the Flory− Huggins parameter, and ϕ is the volume fraction of the protecting ligands. χ represents the affinity between the protecting ligand and solvent. When the affinity is low, the parameter is high, and the osmotic pressure is not effective. Thus, attractive forces should be generated. A major portion of the protecting ligand is composed of a long alkyl chain, resulting in a poor affinity between the protecting ligands and methanol. Therefore, the repulsive forces of the protecting ligands should become weaker in dispersants that have high methanol contents. We conclude that the attractive forces induced by the concentration gradient due to methanol should promote the aggregation of AgNPs or the dispersion instability of the AgNCs (see Figure 5c). Self-Aggregation of AgNPs after Printing. To investigate the effect of methanol on the self-aggregation of the AgNPs, we characterized the printed electrodes fabricated with AgNCs containing different amounts of methanol using the SuPR-NaP technique.4 A typical micrograph of the printed electrodes is presented in Figure 6a. We found that the width of the printed electrodes depended on the methanol content in the AgNCs, while the predefined photoactivated width was fixed (50 μm). The widths of the printed electrodes as a function of the methanol content (5%, 18%, and 30%) in the AgNCs are plotted in Figure 6b. The widths of the printed electrodes became broader with increasing methanol content in the AgNCs. The result is consistent with the increased dispersion instability by polar methanol, as discussed in the previous section. Figure 6c shows the conductivity of the printed electrodes fabricated with AgNCs containing different amounts of methanol (5%, 18%, and 30%). Here the conductivity is shown for the printed electrodes that do not undergo any thermal treatment after the printing. We note that the ink becomes unstable and the phase separation easily takes place after the synthesis if the ink includes the larger amount of methanol. This feature makes it difficult to obtain printed silver electrodes. We also note that the enough high conductivity (∼104/Ωcm) can be achieved for all the printed electrodes through the relatively low-temperature (below 50 °C) thermal treatment as shown in Figure 6c and Figure S3.

conclude that the AgNCs become more stable when the dispersion media is farther from the phase boundary in the ternary phase diagram. The results also indicate that the phase instability of the dispersion media should promote the dispersion instability of the AgNPs. Dispersion Stability of AgNCs. To evaluate the effect of methanol on the dispersion stability by c-DLS23 (see Experimental Methods), we used AgNCs containing methanol at volume fractions of 15%, 25%, and 36% at a constant ratio (4:1) of octane to butanol. The autocorrelation functions of the backscattered light from the AgNCs were recorded immediately, at 2 and 4 h, and also 20 days after the syntheses, the results of which are shown in Figure 3b,c. It is to be noted that all the measurements were conducted before the phase separation. The autocorrelation functions for the AgNCs containing 15% or 25% methanol do not show appreciable change with time for 4 h (Figure 3c). Additionally, the AgNCs containing methanol at 16.9% exhibited long-term phase stability and were stable for at least 20 days after the synthesis (Figure 3b). In contrast, the autocorrelation function of the AgNC containing 36% methanol exhibits considerable variation with time with a delay time higher than 102 μs. The size distribution of the AgNPs was obtained from the analyses of the autocorrelation functions using the CONTIN method, the result of which is shown in Figure 3d. We also analyzed the average radius of clusters grown in AgNCs containing 36% methanol by using the cumulant method and found that the average radius exponentially grows with time as shown in Figure S2. The result are well fitted with an exponential function: f (t) = r0 exp(t /τ). The value of r0 and τ are determined as 10.2 nm and 1.4 h, respectively, by the fitting. The highest peak of Figure 3d of around a few nanometers in radius should correspond to the primary AgNPs, as observed by SEM (Figure 4a). Only in the AgNC containing 36% methanol, the amount of aggregates bigger than 100 nm increases drastically with time. The large aggregates with sizes around 100 nm and 1 μm were observed by SEM (Figure 4b− d) dipersion stability considerably. The results are clearly C


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Figure 3. (a) A schematic diagram of the c-DLS optical system. (b) Long-term stability of AgNCs. (Left) The c-DLS autocorrelation functions of the AgNCs containing 16.9% methanol at a fixed ratio (4:1) of octane to butanol. (Right) Size distribution functions calculated from the autocorrelation functions. The measurements were conducted immediately (red) and 20 days (blue) after the syntheses. (c) The c-DLS autocorrelation functions of the AgNCs containing 15% (left), 25% (middle), and 36% (right) methanol at a fixed ratio (4:1) of octane to butanol. The measurements were conducted immediately (red), 2 h (green), and 4 h (blue) after the syntheses. (d) Size distribution functions calculated from the autocorrelation functions in (b).

NaP technique. As the origin of the phase separation, we focused on the polar methanol component that was unintentionally involved during the synthesis of the AgNCs and investigated the effect of methanol on both the dispersion and phase stability of the AgNCs. First, we obtained the ternary phase diagram of the solvent-only system of octane/butanol/ methanol in the absence of AgNPs and found that although octane and methanol were not miscible with each other, butanol could act as a buffer between octane and methanol. We also found that the time-dependent phase separation of the AgNCs was promoted by increasing the polar methanol component, even if the dispersant was a miscible composition of the solvent-only system. From the c-DLS measurements, it was found that the methanol component accelerated the self-

The SEM images are also shown in Figure 6d. The conductivity (just after printing) increased with increasing methanol content in the AgNCs. It was also found that the well-sintered area of the printed AgNPs increased with increasing methanol content in the AgNCs, which is consistent with the change in conductivity. All the results clearly demonstrated that the polar methanol component accelerated the self-aggregation of the AgNPs.

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CONCLUSIONS We have investigated the origin and mechanism of the timedependent degradation in the alkylamine/alkylacid-encapsulated AgNCs owing to phase separation. The AgNCs allow the production of ultrafine metal wiring through the unique SuPRD



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EXPERIMENTAL METHODS

Synthesis of AgNCs. Silver nitrate (AgNO3) was purchased from Sigma-Aldrich; oxalic acid dihydrate ((COOH) 2·2H2O) was purchased from Kanto Chemical Co., Inc.; normal octane, normal butanol, and methanol were purchased from FUJIFILM Wako Pure Chemical Corporation; and oleic acid (C18H34O2), hexylamine (C6H15N), dodecylamine (C12H27N), and N,N-dimethyl-1,3-propanediamine (C5H14N2) were purchased from Tokyo Chemical Industry Co. Ltd. These materials were used without further purification. The ultrafine AgNPs were directly synthesized by a thermal decomposition reaction of oxalate-bridged silver complex, according to the procedure in literature.19 Silver nitrate and oxalic acid were first dissolved in deionized water to obtain silver oxalate (Ag2(C2O4)). After drying, silver oxalate (I) was mixed with two equivalents of alkylamines (R-NH2) (i.e., Ag/alkylamines = 1:1 mol/mol) and a trace amount of oleic acid to generate the oxalate-bridged silver complex ([(R-NH2)Ag(μ-C2O4)Ag(R-NH2)]). A mixture of N,Ndimethyl-1,3-propanediamine, hexylamine, and dodecylamine was used as the alkylamines. Heating the mixture at 110 °C led to thermal decomposition with the evolution of CO2, eventually producing the alkylamine-encapsulated AgNPs in an almost quantitative yield. The uniform radius (= 6.8 nm) of the ultrafine, monodisperse, and spherical AgNPs are obtained in the synthetic process. The obtained AgNPs were washed twice with methanol to reduce the excess amount of alkylamines, where a sufficient amount of methanol was poured on the AgNPs and then separated rapidly as the supernatant from the AgNPs by centrifugation. Finally, the AgNPs were suspended in a 4:1 mixed solvent of octane and butanol to obtain 40 wt % AgNCs (4.4 vol %), although they inevitably included the remaining component of methanol, which was used as the washing agent. To produce AgNCs with controlled amounts of methanol, we decreased the methanol concentration in the AgNCs by evaporating methanol from the AgNCs under atmospheric condition, or we intentionally added methanol to the mixed solvent that was used as the dispersant for the AgNCs. We used 1H NMR spectroscopy to identify the solvent composition of the AgNCs. We prepared diluted inks by adding 500 μL of deuterated chloroform (CDCl3) to 2 μL AgNCs, which was eventually set in an NMR spectrometer (Bruker AVANCE III). A typical NMR spectrum is shown in Figure S1. The peaks observed at around 1.26, 3.49, and 3.65 ppm correspond to octane, butanol, and methanol, respectively.

Figure 4. SEM images of (a) primary AgNPs and (b−d) selfaggregated AgNPs, as observed in the printed AgNPs by printing AgNCs containing 10% (a) and 36% (b−d) methanol. The sizes of the aggregated AgNPs are as big as about 100 nm (b) and 1 μm (c,d). SEM image of (d) is an enlarged image of the red square shown in (c). The scale bars correspond to 100 nm (a,b,d), and 1 μm (c).

aggregation of AgNPs, which eventually triggered the phase separation. We conclude that the concentration gradient around the AgNP surfaces generated attractive forces between the AgNPs and induced the self-aggregation. We believe that the alkylamine/alkylacid-encapsulated AgNCs could be a unique and important material in the basic colloid science as well as in the printed electronics applications.

Figure 5. Schematics for the (a) gradient of the dispersion media near the surface of AgNPs, (b) proposed chain states of oleic acid ligands in (left) methanol-poor and (right) methanol-rich dispersants, and (c) proposed mechanism of aggregation and precipitation of AgNPs for triggering the phase separation in the methanol-rich AgNCs. Stage 1 represents the aggregation of the AgNPs, stage 2 represents the promotion of aggregation, and stage 3 represents the precipitation of the aggregates. E


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Figure 6. (a) Picture of the printed silver electrode fabricated by the SuPR-NaP technique. The scale bar corresponds to 500 μm. (b) Width and (c) conductivity of the printed silver electrodes on the photoactivated surface with a width of 50 μm, plotted as a function of the volume fraction of methanol in the AgNCs. The open squares show the conductivity of printed electrodes after thermal annealing at relatively low temperature (50 °C), as presented in Figure 3S. (d) SEM images of the printed silver electrodes fabricated with the AgNCs containing 15%, 25%, and 36% methanol. The scale bars correspond to 100 nm The volume fraction of each solvent was calculated by integrating the area under the corresponding peak. Evaluation of Phase Stability. We investigated the phase behavior of the mixed solvent system of octane/butanol/methanol in the absence of AgNPs to obtain the ternary phase diagram at room temperature. We first poured the phase-separated mixed solvent of octane and methanol in a vessel at various ratios such that the total volume was 100 mL. Then, 20 μL butanol was continuously added every time into the vessel, and the occurrence of the transparent transition was checked by visual inspection. Additionally, we investigated the phase-separation transition at a low temperature for some compositions of the mixed solvents that are miscible at room temperature. For this, the mixed solvent was poured into a glass cell with inner thickness of about 200 μm, and the cell was sealed. The cell was set on a cooling stage, and the growth of the minor phase nucleus was inspected at a low temperature using a differential interference contrast microscope. Some of the AgNCs exhibited time-dependent phase separation, though their dispersants were miscible at that particular composition. We prepared several AgNCs with different methanol contents, maintaining the 4:1 ratio of octane and butanol, and we investigated the phase separation at a low temperature. We also investigated the time dependence of the appearance of the AgNCs (containing 30% methanol) at various temperatures by automatic photography. Evaluation of Dispersion Stability. c-DLS was used to evaluate the dispersion stability of the AgNCs23 (the optical system is schematically shown in Figure 3a). We used a semiconductor laser (λ = 638 nm, LuxX 638−100, Omicron) as the light source. The laser was focused on the AgNCs filled in a rectangular glass cuvette (inner dimensions 1 mm × 10 mm × 50 mm) placed into the sample holder of the focused optical system. The laser power was set below 5 mW to prevent the sample from damage due to irradiation heating. The backscattered light from the sample was collected and detected by an avalanche photodiode and a multiple-τ digital real-time correlator unit (ALV-7004/USB-FAST, ALV) for 90 s. The autocorrelation function of the backscattered light was calculated. The autocorrelation function of the detected scattered light intensity I(t) can be expressed as

g(2)(τ ) − 1 =

2 ⟨I(t )I(t + τ )⟩ = e−2Dq τ ⟨I(t )I(t )⟩

where τ is the delay time, q is the scattering vector, and D is the diffusion coefficient. The amplitudes of autocorrelation functions at τ = 1 μs were set to 1.0, and they were normalized by multiplying the appropriate constant for clarity. The particle radius a can be obtained from D using the Stokes−Einstein equation D=

kBT 6πηa

Here, kB is the Boltzmann constant, T is the absolute temperature, and η is the viscosity of the solvent. The CONTIN method was used to obtain the size distribution of the particles in the AgNCs.23 Evaluation of the Self-Aggregation in Printed Silver Wires. Printed silver electrodes were fabricated by the SuPR-NaP technique.4 As a substrate for silver electrodes, thin films of amorphous perfluorinated polymer, poly[perfluoro (4-vinyloxy-1-butene)] (Cytop, AGC Chemicals.) were produced by spin coating at 2000 rpm for 60 s at room temperature, followed by subsequent drying at 180 °C at 0.02 MPa for 60 min. A patterned photoactivated surface was produced by the masked irradiation of a 172 nm vacuum ultraviolet (VUV) light emitted by a Xe2 excimer lamp (VUS-3150, ORC Manufacturing Co., Ltd.). Then, the patterned photoactivated surface was wetted by blade-coating with the AgNCs at a sweep rate of 2 mm/s under ambient conditions. We fabricated printed silver electrodes, 2 mm in length, to investigate the self-aggregation of the AgNPs. The conductivity of the electrodes was measured just after the printing without any heating treatment. The surface morphology of the electrodes was observed by scanning electron microscopy (SEM, JSM-7000F, JEOL) with an acceleration voltage of 25 kV. The conductivity was also checked for the printed electrodes after thermal annealing at relatively low temperatures (50 °C). F


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of silver nanoparticles and electrolyte sintering solutions. J. Mater. Chem. 2012, 22, 14349. (8) Corsino, D. C.; Balela, M. D. L. Room temperature sintering of printer silver nanoparticle conductive ink. IOP Conf. Ser.: Mater. Sci. Eng. 2017, 264, No. 012020. (9) Zhang, Z.; Zhang, X.; Xin, Z.; Deng, M.; Wen, Y.; Song, Y. Controlled Inkjetting of a Conductive Pattern of Silver Nanoparticles Based on the Coffee-Ring Effect. Adv. Mater. 2013, 25, 6714. (10) Chou, K.-S.; Huang, K.-C.; Lee, H.-H. Fabrication and sintering effect on the morphologies and conductivity of nano-Ag particle films by the spin coating method. Nanotechnology 2005, 16, 779. (11) Kim, D.; Moon, J. Highly Conductive Ink Jet Printed Films of Nanosilver Particles for Printable Electronics. Electrochem. Solid-State Lett. 2005, 8, J30. (12) Xue, F.; Liu, Z.; Su, Y.; Varahramyan, K. Inkjet printed silver source/drain electrodes for low-cost polymer thin film transistors. Microelectron. Eng. 2006, 83, 298. (13) Kim, D.; Jeong, S.; Lee, S.; Park, B. K.; Moon, J. Organic thin film transistor using silver electrodes by the ink-jet printing technology. Thin Solid Films 2007, 515, 7692. (14) Sekitani, T.; Noguchi, Y.; Zschieschang, U.; Klauk, H.; Someya, T. Organic transistors manufactured using inkjet technology with subfemtoliter accuracy. Proc. Natl. Acad. Sci. U. S. A. 2008, 105, 4976. (15) Allen, M. L.; Aronniemi, M.; Mattila, T.; Alastalo, A.; Ojanperä, K.; Suhonen, M.; Seppä, H. Electrical sintering of nanoparticle structures. Nanotechnology 2008, 19, 175201. (16) Perelaer, J.; de Gans, B.-J.; Schubert, U. S. Microwave Flash Sintering of Inkjet-Printed Silver Tracks on Polymer Substrates. Adv. Mater. 2006, 18, 2101. (17) Magdassi, S.; Grouchko, M.; Berezin, O.; Kamyshny, A. Triggering the Sintering of Silver Nanoparticles at Room Temperature. ACS Nano 2010, 4, 1943. (18) Novara, C.; Petracca, F.; Virga, A.; Rivolo, P.; Ferrero, S.; Chiolerio, A.; Geobaldo, F.; Porro, S.; Giorgis, F. SERS active silver nanoparticles synthesized by inkjet printing on mesoporous silicon. Nanoscale Res. Lett. 2014, 9, 527. (19) Itoh, M.; Kakuta, T.; Nagaoka, M.; Koyama, Y.; Sakamoto, M.; Kawasaki, S.; Umeda, N.; Kurihara, M. Direct Transformation into Silver Nanoparticles via Thermal Decomposition of Oxalate-Bridging Silver Oleylamine Complexes. J. Nanosci. Nanotechnol. 2009, 9, 6655. (20) Fukuda, K.; Sekine, T.; Kobayashi, Y.; Takeda, Y.; Shimizu, M.; Yamashita, N.; Kumai, D.; Itoh, M.; Nagaoka, M.; Toda, T.; Saito, S.; Kurihara, M.; Sakamoto, M.; Tokito, S. Organic integrated circuits using room-temperature sintered silver nanoparticles as printed electrodes. Org. Electron. 2012, 13, 3296. (21) Fukuda, K.; Sekine, T.; Kobayashi, Y.; Kumaki, D.; Itoh, M.; Nagaoka, M.; Toda, T.; Saito, S.; Kurihara, M.; Sakamoto, M.; Tokito, S. Stable organic thin-film transistors using full solution-processing and low-temperature sintering silver nanoparticle inks. Org. Electron. 2012, 13, 1660. (22) Aoshima, K.; Hirakawa, Y.; Togashi, T.; Kurihara, M.; Arai, S.; Hasegawa, T. Unique coexistence of dispersion stability and nanoparticle chemisorption in alkylamine/alkylacid encapsulated silver nanocolloids. Sci. Rep. 2018, 8, 6133. (23) Hiroi, T.; Shibayama, M. Dynamic light scattering microscope: Accessing opaque samples with high spatial resolution. Opt. Express 2013, 21, 20260. (24) Beysens, D.; Narayanan, T. Wetting-Induced Aggregation of Colloids. J. Stat. Phys. 1999, 95, 997−1008. (25) Guo, H.; Narayanan, T.; Sztuchi, M.; Schall, P.; Wegdam, G. H. Reversible Phase Transition of Colloids in a Binary Liquid Solvent. Phys. Rev. Lett. 2008, 100, 188303. (26) Hopkins, P.; Archer, A. J.; Evans, R. Solvent mediated interactions between model colloids and interfaces: A microscopic approach. J. Chem. Phys. 2009, 131, 124704. (27) Labbé-Laurent, M.; Law, A. D.; Dietrich, S. Liquid bridging of cylindrical colloids in near-critical solvents. J. Chem. Phys. 2017, 147, 104701.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsanm.9b00795. Figures of typical NMR spectrum of the AgNCs, growth of average size of colloidal clusters, conductivity measurements of printed electrodes with low-temperature thermal treatment (PDF)

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (S.A.). *E-mail: [email protected] (T.H.). ORCID

Shunto Arai: 0000-0002-0055-3006 Tatsuo Hasegawa: 0000-0001-5187-7433 Author Contributions

S.A. and T.H. supervised the study. Y.H. and S.A. performed the experiments, and K.A. initially guided the experiments. All the authors discussed the results, and Y.H., S.A., and T.H. wrote the manuscript. All authors have given approval to the final version of the manuscript. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by Japan Science and Technology Agency (JST) through S-Innovation program (S-Innova), and JST CREST Grant JPMJCR18J2, Japan.

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ABBREVIATIONS AgNC: alkylamine/alkylacid-encapsulated silver nanocolloid; AgNP: silver nanoparticle; SuPR-NaP: surface photoreactive nanometal printing; c-DLS: confocal dynamic light scattering; NMR: nuclear magnetic resonance; VUV: vacuum ultraviolet; SEM: scanning electron microscopy

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REFERENCES

(1) Daniel, M.-C.; Astruc, D. Gold Nanoparticles: Assembly, Supramolecular Chemistry, Quantum-Size-Related Properties, and Applications toward Biology, Catalysis, and Nanotechnology. Chem. Rev. 2004, 104, 293. (2) Schlucker, S. SERS Microscopy: Nanoparticle Probes and Biomedical Applications. ChemPhysChem 2009, 10, 1344. (3) Lai, C. Y.; Cheong, C. F.; Mandeep, J. S.; Abdullah, H. B.; Amin, N.; Lai, K. W. Synthesis and Characterization of Silver Nanoparticles and Silver Inks: Review on the Past and Recent Technology Roadmaps. J. Mater. Eng. Perform. 2014, 23, 3541. (4) Yamada, T.; Fukuhara, K.; Matsuoka, K.; Minemawari, H.; Tsutsumi, J.; Fukuda, N.; Aoshima, K.; Arai, S.; Makita, Y.; Kubo, H.; Enomoto, T.; Togashi, T.; Kurihara, M.; Hasegawa, T. Nanoparticle chemisorption printing technique for conductive silver patterning with submicron resolution. Nat. Commun. 2016, 7, 11402. (5) Ko, S. H.; Pan, H.; Grigoropoulos, C. P.; Luscombe, C. K.; Fréchet, J. M.; Poulikakos, D. All-inkjet-printed flexible electronics fabrication on a polymer substrate by low-temperature high-resolution selective laser sintering of metal nanoparticles. Nanotechnology 2007, 18, 345202. (6) Grouchko, M.; Kamyshny, A.; Mihailescu, C. F.; Anghel, D. F.; Magdassi, S. Conductive Inks with a “Built-In” Mechanism That Enables Sintering at Room Temperature. ACS Nano 2011, 5, 3354. (7) Layani, M.; Grouchko, M.; Shemesh, S.; Magdassi, S. Conductive patterns on plastic substrates by sequential inkjet printing G


Article

ACS Applied Nano Materials (28) Fritz, G.; Schädler, V.; Willenbacher, N.; Wagner, N. J. Electrosteric Stabilization of Colloidal Dispersions. Langmuir 2002, 18, 6381. (29) Sariban, A.; Binder, K. Critical properties of the Flory−Huggins lattice model of polymer mixtures. J. Chem. Phys. 1987, 86, 5859. (30) Favre, E.; Nguyen, Q. T.; Clement, R.; Neel, J. Application of Flory-Huggins theory to ternary polymer-solvents equilibria: A case study. Eur. Polym. J. 1996, 32, 303.

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Phase and Dispersion Stability of Silver ... - ACS Publications

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