Mussel-Inspired Polydopamine-Functionalized Graphene as a

Subscriber access provided by ORTA DOGU TEKNIK UNIVERSITESI KUTUPHANESI

Article

Mussel-inspired Polydopamine Functionalized Graphene as a Conductive Adhesion Promoter and Protective Layer for Silver Nanowire Transparent Electrodes Jinlei Miao, Haihui Liu, Wei Li, and Xingxiang Zhang Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.6b00796 • Publication Date (Web): 03 May 2016 Downloaded from http://pubs.acs.org on May 6, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Langmuir is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Mussel-inspired Polydopamine Functionalized Graphene as a Conductive Adhesion Promoter and Protective Layer for Silver Nanowire Transparent Electrodes Jinlei Miao, Haihui Liu, Wei Li, and Xingxiang Zhang1

State Key Laboratory of Separation Membranes and Membrane Processes, Tianjin Municipal Key Lab of Advanced Fiber and Energy Storage, School of Material Science and Engineering, Tianjin Polytechnic University, Tianjin, 300387, China

ABSTRACT: For scalable fabrication of transparent electrodes and optoelectronic devices, excellent adhesion between the conductive films and the substrates is essential. In this work, a novel mussel-inspired polydopamine-functionalized graphene/silver nanowire hybrid nanomaterial for transparent electrodes was fabricated in a facile manner. Graphene oxide (GO) was functionalized and reduced by polydopamine while remaining stable in water without precipitation. It is shown that the polydopamine-functionalized GO (PFGO) film adhered to the substrate is much more easily and more uniformly than GO film. The PFGO film had a sheet

1

Corresponding author: Tel/Fax: +86-22-83955054

E-mail address: [email protected] (X.X. Zhang). 1 ACS Paragon Plus Environment

Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 31

resistance of ~3.46×108 Ω/sq and a transparency of 78.2%, with excellent thermal and chemical stability; these characteristics are appropriate for antistatic coatings. Further reduced PFGO (RPFGO) as a conductive adhesion promoter and protective layer for Ag nanowire (AgNW) significantly enhanced the adhesion force between AgNW networks and the substrate. The RPFGO-AgNW electrode was found to have a sheet resistance of 63 Ω/sq and a transparency of 70.5%. Moreover, the long-term stability of the RPFGO-AgNW electrode was greatly enhanced via the effective protection of the AgNW by RPFGO. These solution-processed antistatic coatings and electrodes have tremendous potential in the applications of optoelectronic devices due to their low production cost and facile processing.

Keywords: silver nanowire, polydopamine functionalized graphene, adhesion promoter, protective layer, optoelectronic devices

INTRODUCTION

Transparent conductive films (TCF) are essentially required in the applications of optoelectronic devices, such as solar cells, electrochromic devices, organic light-emitting diodes (OLED), and touch screens1-4. Recently, flexible optoelectronic devices have received increasing interest5. However, conventional indium tin oxide (ITO) cannot fulfill the requirements of flexible optoelectronic devices due to its brittleness and the scarcity of indium6-8. Therefore, it is urgently required to find alternative materials for ITO; towards this end, several substrates have emerged, 2 ACS Paragon Plus Environment

Page 3 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

including metallic nanowires9-10, conducting polymers11-12, carbon nanotubes 13-14, and graphene

15-16

. Among these materials, one-dimensional (1D) Ag nanowire (AgNW)

and 2D graphene-based films have attracted considerable attention due to their good optoelectronic characteristics and outstanding mechanical flexibility

17

. However, a

few challenges remain in the practical application of AgNW and graphene-based TCF. AgNW-based TCF encounter issues of weak adhesion to substrates and low stability in harsh environments18-20. The drawbacks of graphene-based TCF include the relatively high sheet resistance of reduced graphene oxide (RGO) and the topological defects of chemical vapor deposition-grown graphene21-23. These disadvantages of single AgNW or graphene-based TCF can be overcome by using them together. Tien et al. argued that AgNW not only inhibited the aggregation of graphene but also increased electrical conductivity among graphene sheets

24

.

Zhang et al. reported that graphene could be an effective protective layer for AgNW; the hybrid TCF showed a high optoelectronic property with great oxidation resistance 25

. Kwan et al. found that the composite electrodes of AgNW and RGO exhibited

increased robustness and stability; the electrodes showed a sheet resistance of 5.3 Ω/sq and an optical transparency of 64.9% 26. Recent studies of the graphene-AgNW hybrid TCF demonstrated that the fabrication of such hybrid films is a promising approach to complement the disadvantages of the single AgNW or graphene-based TCF 27-28.

3 ACS Paragon Plus Environment

Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 31

The graphene-AgNW hybrid TCF could be fabricated via several techniques, such as spray coating

29

, spin coating

30

, dip coating

31

, and vacuum filtration25. Vacuum

filtration is a widely used method due to its facile processing. However, transfer of the hybrid film from filter membrane to the substrate is required. The film tends to break during the transfer process due to the weak adhesion force between the hybrid film and the substrate. Excellent adhesion between the TCF and the substrate is essential for scalable fabrication of transparent electrodes and optoelectronic devices, which would guarantee the TCF undamaged during the post-treatment process

32

. To date,

few studies have been focused on the study of adhesion issue 33. Dopamine contains catechol and amine groups, which are the crucial functionalities for mimicking the adhesive proteins of mussels

34

. Under weak alkaline pH conditions, dopamine

undergoes self-polymerization to produce adherent polydopamine (PDA). PDA can adhere to virtually all types of inorganic and organic surfaces, regardless of the substrate’s chemistry35-37. Recently, Akter et al. fabricated a polydopamine layer on the elastomeric substrate to facilitate the subsequent spraying of AgNW; the obtained AgNW TCF demonstrated excellent adhesion to the substrate

38

. Jin et al. reported

that the PDA and alginic acid as a nonconductive binder induced AgNW networks contacted tighter and provided good adhesion to the substrate 39. However, graphene and PDA in previous studies act merely as a conducting protective layer or adhesive layer for AgNW TCF, respectively25, 39, they could not overcome the problematic issues of weak adhesion and low stability simultaneously. Recent studies showed that 4 ACS Paragon Plus Environment

Page 5 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

dopamine could reduce GO during its polymerization40, 41. Herein, a novel design of reduced PDA-functionalized graphene oxide (RPFGO) as a conductive adhesion promoter and protective layer for AgNW TCF is developed by incorporating mussel-inspired PDA. The procedure for preparing RPFGO-AgNW hybrid TCF is illustrated in Figure 1. GO was reduced via a two-step process, it was reduced and functionalized by PDA firstly and then further reduced by hydrazine vapor. To the best of our knowledge, RPFGO as a conductive adherent promoter and protective layer for AgNW TCF has not been described before.

Figure 1. Schematic illustration of the preparation process of RPFGO-AgNW hybrid TCF.

EXPERIMENTAL SECTION

Materials


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Natural graphite powders (NGP) (325 mesh) were kindly provided by Qingdao Laixi Graphite Co., Ltd. Sulfuric acid (H2SO4, 98%), potassium permanganate (KMnO4, 99.3%), hydrogen peroxide (H2O2, 30%), hydrochloric acid (HCl, 37%), hydrazine hydrate (N2H4, 80%), silver nitrate (AgNO3, 99.8%), polyvinylpyrrolidone (PVP), sodium chloride (NaCl), and ethylene glycol (EG) were provided by Tianjin Guangfu Fine Chemical Research Institute and used as received. Dopamine hydrochloride (98%) and tris(hydroxymethyl)aminomethane (Tris) (99.9%) were purchased from Aladdin and used as received. Fabrication of GO and PFGO

GO powders were prepared from natural graphite powders via a modified Hummers’ method, as reported in our previous work 42. PFGO was fabricated as follows: 160 mg of GO and 80 mg of dopamine hydrochloride were dispersed in 400 mL of 10 mM Tris-HCl (pH=8.5) buffer and then sonicated for 30 min. Afterwards, the mixture was stirred at 60 °C for 24 h. The as-prepared PFGO was filtered through a 0.22 µm membrane and then washed with distilled water. Finally, the PFGO was dispersed into water at a concentration of ~0.008 mg/mL. Fabrication of AgNW The 1D AgNW were synthesized using a solvothermal method 25. First, 3.53 g of PVP and 11.3 mg of NaCl were dissolved in 60 mL of EG at 120 °C for 30 min. Next, the mixture was added to AgNO3/EG (0.01 M, 90 mL) solution slowly under vigorous stirring. The combined solution was then transferred into three 100-mL autoclaves. 6 ACS Paragon Plus Environment

Page 6 of 31

Page 7 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

The autoclaves were kept at 160 °C for 7 h to yield AgNW. The as-prepared AgNW were washed repeatedly with acetone and ethanol via centrifugation at 5000 rpm. The obtained AgNW were dispersed into water at a concentration of ~0.009 mg/mL. Fabrication of PFGO Antistatic Coatings

The glass slides used as substrates for antistatic coatings were washed in fresh piranha solution (3:7, v:v, 30% H2O2 and concentrated H2SO4. Caution: piranha solution is strongly oxidant and may detonate upon contact with organic material) and then rinsed with deionized water. PFGO films were prepared on cellulose acetate (CA) filter membranes with a pore size of 0.22 µm via the vacuum filtration method. The thicknesses of the PFGO antistatic coatings were controlled by varying the filtration volumes at 8, 10, 12, 14, and 16 mL. The membranes with captured PFGO films were then cut to the desired size when they were still wet, and the cut pieces were transferred onto glass slides. To remove the air trapped between the PFGO film and the substrate, the membrane was pressed with a glass rod and moved from one side to the other side slowly several times with increasing pressure, and then a glass slide of the same size was placed on the CA and pressed for 30 min under 0.4 kPa pressure. Next, the glass/CA/PFGO/glass was dried in an oven at 100 ºC for several minutes. To verify the adhesion of PFGO films, the CA filter membrane was peeled off from the glass slides slowly instead of using the conventional approach of dissolving using acetone. Finally, the PFGO films were dried in a vacuum oven at 100 ºC for 60 min. As a comparison, GO films not functionalized by PDA were also fabricated. 7 ACS Paragon Plus Environment

Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Fabrication of RPFGO-AgNW TCF

For RPFGO-AgNW TCF, different amounts of AgNW solution (2 mL - 14 mL) were mixed with the PFGO solution (4.5 mL). The glass slides were also used as substrates for TCF, and the PFGO-AgNW films were transferred to the substrates using nearly the same process as described above. Because the films are somewhat damaged when the CA is peeled off the substrate, for high-performance hybrid TCF, the CA was dissolved by acetone. Next, the PFGO-AgNW films were further reduced by hydrazine vapor at 100 ºC for 5 h. Finally, the hybrid films were heated at 200 ºC for 30 min to form connecting junctions between AgNW, as the junction resistance between AgNW is very high. Characterization

The sheet resistances of PFGO and RPFGO-AgNW films were measured using the four-point probe method (Keithley 2700 multi-meter), and the transmittances were measured using a UV–vis spectrophotometer (TU-1901). The surface morphologies of the RPFGO-AgNW films were characterized by field-emission scanning electron microscopy (FE-SEM) (Hitachi S-4800). Transmission electron microscopy (TEM) was performed using a Hitachi H-800 electron microscope operating at an accelerating voltage of 120 kV. X-ray photoelectron spectroscopy (XPS) was conducted on a 60 (GENESIS EDAX, US) instrument equipped with an Al Kα radiation source (hν = 1486.4 eV). X-ray diffraction (XRD) was performed using a Rigaku D/MAX-gA diffractometer with filtered Cu Kα radiation (λ=0.15406 nm). 8 ACS Paragon Plus Environment

Page 8 of 31

Page 9 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Linear and 2D micro-Raman mapping spectra were measured on a Renishaw InVia Raman microscope equipped with a 532 nm laser and a Horiba Jobin Yvon Xplora confocal Raman microscope equipped with a 532 nm laser. Fourier transform infrared (FT-IR) spectroscopy (TENSOR37) was performed to detect the functional groups of GO and PFGO. Thermogravimetric analysis (TGA; NETZSCH STA 409, Germany) was performed in the temperature range of room temperature to 800 ºC under a nitrogen atmosphere at a heating rate of 5 ºC/min. The adhesion was investigated using the tape test, in which a 12 mm-wide piece of 3M scotch tape was attached each of the PFGO and RPFGO-AgNW films and then peeled off from the samples. RESULTS AND DISCUSSION

PFGO was fabricated by mixing the GO aqueous suspension with dopamine hydrochloride at pH=8.5. During the self-polymerization of dopamine, the color of the mixture changed from light brown to black (inset of Figure 2a). This color change suggested the reduction of GO

40

. The conversion of GO to PFGO via reduction by

PDA was first monitored by UV-vis spectroscopy. As shown in Figure 2a, GO exhibits a characteristic absorption peak at 230 nm

43

. As time went on, the

absorbance peak disappeared and a broad peak with an absorption maximum at ~260 nm was observed. The shift in the absorption peak of PFGO is due to the restoration of the п-network in the graphene sheets 44. The reduction of GO is possibly due to the release of electrons during the oxidative polymerization of dopamine-hydrochloride


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 31

45

. However, no obvious aggregate formation was observed when PFGO was

dispersed in water, which is attributed to the stabilization by PDA 46. The simultaneous surface functionalization and reduction of GO were also confirmed by FTIR and XPS spectroscopy. As illustrated in Figure 2b, the GO characteristic bands are present at 1730 cm-1 (C=O stretching), 1407 cm-1 (C-OH stretching) and 1055 cm-1 (C-O of epoxy stretching)

47

. For PFGO, new bands are

observed at 2918 and 2850 cm-1 (C–H stretching of methylene groups in PDA), which confirms success in achieving PFGO 48. Moreover, the characteristic absorption bands of oxygen functionalities in GO decreased dramatically.

Figure 2. UV-vis absorption (a) and FTIR (b) spectra of GO and PFGO.

The XPS spectra of GO and PFGO are shown in Figure 3a. The GO spectrum shows C 1s and O 1s peaks at 286 and 534 eV, respectively. The spectrum of PFGO exhibited an additional peak at 399 eV, which is attributed to the N 1s peak 40. The N 1s peak originated from amine groups of PDA. The C 1s XPS spectra of GO and PFGO are shown in Fig. 3c and 3d. The XPS C1s core-level spectrum of GO can be 10 ACS Paragon Plus Environment

Page 11 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

curve-fitted into three peak components with binding energies at approximately 284.7, 286.8, and 287.9 eV, which are attributable to C=C/C-C, C-O, and C=O species, respectively

49-50

. For PFGO, four different peaks at 284.6, 285.6, 286.7, and 287.8

eV are related to the C=C/ C-C, C-N, C-O, and C=O groups, respectively. The appearance of the C-N peak at a binding energy of 285.6 eV is consistent with the presence of a surface functionalized PDA layer. The intensities of all C 1s peaks of the carbon binding to oxygen decreased obviously, which confirmed that GO was simultaneously reduced by PDA.

Figure 3. The full-scale XPS spectra of GO and PFGO (a), N 1s of PFGO (b), C 1s of GO (c) and PFGO (d).


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 31

The thermal stability of GO and PFGO were also examined by TGA (Figure S1); PFGO exhibited approximately 4.6 wt % loss below 100 °C due to the absorbed water, and approximately 15.9 wt % loss at 200 °C due to the pyrolysis of the labile oxygen-containing functional groups. The value was much lower than that of the GO, confirming the chemical reduction of GO by the PDA 45.

The electrical conductivity of PFGO films improved as the oxygen-containing functional groups were partially removed. Figure 4 shows the sheet resistance and transmittance at 550 nm of PFGO films. The performance of the TCF varied according to the volume of PFGO coated on the glass substrates. It is shown that the sheet resistance and transmittance of PFGO films decreases with the PFGO contents increased. The sheet resistance of PFGO films ranged from ~107 to 109 Ω/sq. For comparison, the same content of GO films were insulating. More interestingly, PFGO films adhered to the glass substrate much more easily and more uniformly than the GO films (Figure 5). 3M Scotch tape applied with finger pressure was also unable to detach a significant amount of PFGO from the surface (Figure S2a). This result is probably due to the catechol groups of PFGO serving as an anchor enhancing the adhesion force between the films and the glass substrates

51

. Furthermore, the

positively charged amine groups (–NH3+) of PFGO could also interact electrostatically with the hydroxyl groups of the substrate 33. For 8 mL of PFGO, the film has a sheet resistance ~3.46×108 Ω/sq and a transparency of 78.2% at a typical wavelength of 550 nm. The conductivity and transparency of PFGO coating with 12 ACS Paragon Plus Environment

Page 13 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

excellent thermal and chemical stability, strong adhesion ability is sufficient for antistatic applications52. Whereas most previous researches on PFGO focused on further functional studies, rarely pay attention to its optoelectronic properties44, 48. This work may lead to the practical use of graphene for new generation of antistatic coatings.

Figure 4. Sheet resistance versus optical transmittance of PFGO films as a function of the PFGO

content.

Figure 5. Photograph and schematic of PFGO antistatic coatings adherent to the glass substrates.


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 31

Figure 6a shows the plasmon peaks of the AgNW. Two plasmon peaks at 380 and 350 nm are attributed to the transverse and longitudinal surface plasmon resonances of AgNW, respectively 53. This result confirms that the 1D AgNW were successfully fabricated. As shown in Figure 6b and 6c, the lengths of the AgNW reach up to tens of micrometers and the diameters range from 70 to 110 nm. TEM images of the 1D AgNW also confirmed the results, as revealed in Figure 6d and 6e.

Figure 6. (a) UV–visible absorption peaks, (b) low and (c) high-magnification SEM micro-images,

and (d) low and (e) high-magnification TEM images of AgNW.

High-performance RPFGO-AgNW

transparent conductive electrodes

were

prepared using a vacuum filtration method. Figure 7a shows the XPS C1s spectra of RPFGO, which clearly indicates that the oxygen-containing functional groups, such as C-O and C=O in RPFGO, decreased significantly. This result demonstrates the 14 ACS Paragon Plus Environment

Page 15 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

successful reduction of PFGO. A higher degree of reduced GO provides a higher electrical conductance. Figure 7b displays the XRD patterns of AgNW, GO, PFGO and RPFGO-AgNW. Four diffraction peaks observed from the XRD spectra of AgNW are indexed to the (111), (200), (220), and (311) planes of face-centered-cubic silver crystals, respectively 54. The XRD patterns of GO exhibits an interlayer distance of 0.80 nm corresponding to 11.1º (2θ) due to the introduction of oxygenated functional groups on graphene sheets 47. After GO was reduced and functionalized by PDA, the characteristic peak of GO disappeared and interlayer spacing between graphene sheets decreases to 0.51 nm (2θ=17.2°) owing to the oxygenated functional groups were partially removed. For RPFGO-AgNW TCF, the XRD pattern shows the characteristic peaks of AgNW, and no peaks attributed to silver oxide are observed, indicating the high quality of AgNW. The XRD peak of RPFGO changed to 20-25º (2θ). However, due to its low intensity compared to AgNW and the overlap with the pattern of the glass, the broad graphite-like peak is not apparent 55.


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 31

Figure 7. (a) XPS C1s spectra of RPFGO; (b) XRD patterns of Ag, GO/glass, PFGO/glass, and RPFGO-AgNW/glass.

Micro-Raman spectroscopy was used to investigate the structural disorder and homogeneity of PFGO with the relative intensities of the D and G bands (ID/IG) ratio before and after reduction. Figure 8a presents the µ-Raman spectra of GO, PFGO, and RPFGO-AgNW. All samples exhibit a strong D-band at ~1357 cm-1 and a G-band at ~1590 cm-1, corresponding to the structural disorder and the graphitized structure, respectively

56

. Changes in the ID/IG ratio indicate the changes in the electronic

conjugation state of the GO during reduction. The ID/IG ratios of GO, PFGO and RPFGO are 0.92, 0.97 and 1.02, respectively. The increase in the ID/IG ratio indicates that sp2 domains were formed and that GO was reduced during the reduction

57

. To

assess the homogeneity of the material, µ-Raman mapping was performed over 20×20 µm2 areas in samples. Figure 8b, 8c and 8d illustrate the mapping of the ID/IG ratio across the different samples, which indicate the high homogeneity of the material.


Page 17 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Figure 8. (a) Raman spectra of GO, PFGO, and RPFGO-AgNW, (b, c, and d) µ-Raman mapping of GO, PFGO, and RPFGO-AgNW showing the ID/IG ratios.

The RPFGO-AgNW hybrid film on the glass substrate is optically transparent, as shown in the inset of Figure 9a. As seen from the SEM image of RPFGO-AgNW TCF (Figure 9a), AgNW and the hollow spaces between AgNW networks were covered by RPFGO, as also demonstrated by the cross-sectional SEM of the film in Figure 9b. RPFGO as a protective layer for AgNW networks and they can efficiently improve the oxidation resistance of AgNW.


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 31

Figure 9. (a) SEM micro-images of RPFGO-AgNW TCF; inset (a) is the photograph of the TCF, (b) is the cross-sectional SEM image of the TCF.

The 3M scotch tape test applied with finger pressure was performed to monitor the adhesion of RPFGO-AgNW to the substrate; no obvious amount of RPFGO-AgNW was found to be peeled off the surface (Figure S2b), and no significant increase in the sheet resistance of the TCF was observed after the taping test. An adhesion factor incorporating transmittance was used to quantitatively characterize the adhesion, which can be easily measured from absorption spectroscopy 32: f = 1

T T0

100-T0

= 1

∆T

100T0

(1)

where f is the adhesion factor, Tn and T0 are transmittance of the detached film after trial and pristine samples, respectively. Tn = T0, f = 1, and no AgNW are detached demonstrate perfect adhesion and cohesion. Tn = 100% (base substrate without AgNW), f =0, and no AgNW are left on the film demonstrate no adhesion. The adhesion factor of RPFGO-AgNW(10 mL) and pure AgNW(10 mL) TCF are 0.91 and 0.17, respectively. RPFGO-AgNW TCF exhibit excellent adhesion property. The strong adhesion guarantee the film undamaged during the post-treatment process, especially for the large scalable fabrication of TCF and optoelectronic devices. This result may be due to the strong electrostatic interactions between the positively charged –NH3+ on RPFGO and the negatively charged substrate surface and oxo- and 18 ACS Paragon Plus Environment

Page 19 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

hydroxo-groups on AgNW surfaces

33

in addition to the reason that we discussed

above. As a conductive adhesion promoter and protective layer, RPFGO would be much more conductive than GO and PDA 29, 39 and adhesion than RGO 25, 26. XPS was used to investigate the changes in the chemical states induced by the interactions between the RPFGO and AgNW (Figure S3). The XPS signature of the Ag 3d doublet for the AgNW Ag 3d5/2 and 3d3/2 peaks appeared at 368.2 and 374.2 eV, respectively. For RPFGO-AgNW, the Ag 3d5/2 and 3d3/2 peaks shifted to the lower binding energies and appeared at 368.0 and 374.0 eV, respectively. A similar phenomenon was also observed in the study of Sun et al. They attributed the negative shift to the electron transfer from metallic Ag to the positively charged protonated amine groups

33

. The XPS results indicate the movement of the electrons from the

surfaces of the AgNW to the RPFGO58. The optoelectronic properties of RPFGO-AgNW TCF are shown in Figure 10a. The performance of the TCF varied according to the AgNW contents. The sheet resistance and transmittance of RPFGO-AgNW TCF decreased as the AgNW content increased. The sheet resistance of RPFGO-AgNW (8 mL) is 225 Ω/sq, which is significantly lower than the sheet resistance of RPFGO-AgNW (6 mL). This reduction may be due to the AgNW content being sufficiently high to overcome the percolation threshold 55. The RPFGO-AgNW (10 mL) TCF have a sheet resistance of 63 Ω/sq and a transparency of 70.5%, which is sufficient for many applications in optoelectronic devices. The sheet resistance could reach 37 Ω/sq as the content of AgNW continues to increase. The sheet resistance and transmittance of AgNW TCF were also 19 ACS Paragon Plus Environment

Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 31

evaluated. The AgNW films tend to break during the transfer process due to the weak adhesion force between AgNW films and the substrates. For low content AgNW, such as 2 mL, 4 mL, and 6 mL AgNW, the AgNW films were severely damaged. So we take typical 10 mL AgNW TCF for comparison. The sheet resistance and transmittance of AgNW (10 mL) TCF is 31 Ω/sq and 74.8%, which is better than RPFGO-AgNW(10 mL) TCF. However, the long-term stability of the AgNW electrode is worse. The sheet resistance of AgNW (10 mL) TCF increased from 31 Ω/sq to 117 Ω/sq after being placed at 100 ºC for 72 h (Figure S4). The increase of sheet resistance is due to the oxidation of AgNW25. The direct current electrical conductivity to optical conductivity ratio (σDC/σOP) was used to compare the opto-electrical property of TCF. The transmittance (T) and sheet resistance (Rs) can be linked by Equation (2)59:

σDC = σOP

Z0 2 Rs T

1 - 2

- 1

(2)

where Z0 = 377 Ω/sq is the impedance of free space. A high σDC/σOP ratio indicates a high transmittance and a low sheet resistance, and high opto-electrical property of TCF. The σDC/σOP of AgNW (10mL) and RPFGO-AgNW(10 mL) TCF is 38.92 and15.67, respectively. However, the σDC/σOP of AgNW (10mL) TCF decreased to 8.44 after being placed at 100 ºC for 72 h. The long-term stability of RPFGO-AgNW TCF is better, as observed in Figure 10b. The sheet resistance value of RPFGO-AgNW TCF is nearly constant after being placed at 100 ºC for 72 h. The good stability of RPFGO-AgNW TCF is due to RPFGO protecting the surface of 20 ACS Paragon Plus Environment

Page 21 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

AgNW from oxidation as its impermeable barrier property 60. The sheet resistance and transmittance of GO-AgNW TCF were also measured. However, the sheet resistance of GO-AgNW TCF was very large as the insulating GO between AgNW networks prevented AgNW from fusing with one another 61.

Figure 10. (a) Sheet resistance and optical transmittance of RPFGO-AgNW TCF as a function of the AgNW content. (b) Changes in the sheet resistance of RPFGO-AgNW hybrid films kept at 100 ºC for 72 h.

CONCLUSIONS

Solution-processable mussel-inspired RPFGO-AgNW hybrid TCF were successfully prepared. RPFGO acts as a conductive adhesive promoter and protective layer for the AgNW transparent electrodes, significantly enhanced the adhesion force between the AgNW networks and substrate. The strong adhesion guarantee the TCF undamaged during the post-treatment process. The long-term stability of RPFGO-AgNW TCF was also improved due to the protection effect of the RPFGO over-coating layer. It is believed that RPFGO-AgNW hybrid TCF could be used for various optoelectronic devices, such as solar cells, electrochromic devices, OLED, and touch panels. 21 ACS Paragon Plus Environment

Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 31

ASSOCIATED CONTENT Supporting Information TGA curves of GO and PFGO, 3M scotch tape tests of PFGO and RPFGO-AgNW films, Ag3d XPS spectra of AgNW, RPFGO-AgNW, and changes in the sheet resistance of AgNW (10 mL) TCF. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author * Tel/Fax: +86-22-83955054. E-mail address: [email protected] (X.X. Zhang). Notes The authors declare no completing financial interest. ACKNOWLEDGMENTS

This study was financially supported by the National Natural Science Foundation of China (Grant No.51573135) and Science and Technology Development Plan of Tianjin Municipal (Grant No.13JCZDJC32100). REFERENCES 1.

Bryant, D.; Greenwood, P.; Troughton, J.; Wijdekop, M.; Carnie, M.; Davies, M.;

Wojciechowski, K.; Snaith, H. J.; Watson, T.; Worsley, D. A Transparent Conductive Adhesive Laminate Electrode for High-Efficiency Organic-Inorganic Lead Halide Perovskite Solar Cells. Adv. Mater. 2014, 26, 7499-7504.


Page 23 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

2.

Khaligh, H. H.; Liew, K.; Han, Y.; Abukhdeir, N. M.; Goldthorpe, I. A. Silver

Nanowire Transparent Electrodes for Liquid Crystal-based Smart Windows. Sol. Energy Mater. Sol. Cells 2015, 132, 337-341. 3.

Han, T.-H.; Lee, Y.; Choi, M.-R.; Woo, S.-H.; Bae, S.-H.; Hong, B. H.; Ahn,

J.-H.; Lee, T.-W. Extremely Efficient Flexible Organic Light-emitting Diodes with Modified Graphene Anode. Nat. Photonics 2012, 6 , 105-110. 4.

Bae, S.; Kim, H.; Lee, Y.; Xu, X.; Park, J. S.; Zheng, Y.; Balakrishnan, J.; Lei,

T.; Kim, H. R.; Song, Y. I.; Kim, Y. J.; Kim, K. S.; Ozyilmaz, B.; Ahn, J. H.; Hong, B. H.; Iijima, S. Roll-to-roll Production of 30-inch Graphene Films for Transparent Electrodes. Nat. Nanotechnol. 2010, 5 , 574-578. 5.

Hu, M.; Gao, J.; Dong, Y.; Li, K.; Shan, G.; Yang, S.; Li, R. K.-Y. Flexible

Transparent PES/Silver Nanowires/PET Sandwich-Structured Film for High-Efficiency Electromagnetic Interference Shielding. Langmuir 2012, 28, 7101-7106. 6.

Zhu, Y.; Hill, C. M.; Pan, S. Reductive-Oxidation Electrogenerated

Chemiluminescence (ECL) Generation at a Transparent Silver Nanowire Electrode. Langmuir 2011, 27, 3121-3127. 7.

Li, Y.-A.; Chen, Y.-J.; Tai, N.-H. Fast Process To Decorate Silver Nanoparticles

on Carbon Nanomaterials for Preparing High-Performance Flexible Transparent Conductive Films. Langmuir 2013, 29, 8433-8439. 8.

Tai, Y. L.; Yang, Z.-G. Flexible, Transparent, Thickness-Controllable

SWCNT/PEDOT:PSS Hybrid Films based on Coffee-Ring Lithography for Functional Noncontact Sensing Device. Langmuir 2015, 31, 13257-13264. 9.

Chang, Y.; Lye, M. L.; Zeng, H. C. Large-Scale Synthesis of High-Quality

Ultralong Copper Nanowires. Langmuir 2005, 21, 3746-3748. 23 ACS Paragon Plus Environment

Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 31

10. Ko, Y.; Song, S. K.; Kim, N. H.; Chang, S. T. Highly Transparent and Stretchable Conductors Based on a Directional Arrangement of Silver Nanowires by a Microliter-Scale Solution Process. Langmuir 2016, 32, 366-373. 11. Mengistie, D. A.; Ibrahem, M. A.; Wang, P.-C.; Chu, C.-W. Highly Conductive PEDOT:PSS Treated with Formic Acid for ITO-Free Polymer Solar Cells. ACS Appl. Mater. Interfaces 2014, 6 , 2292-2299. 12. Vosgueritchian, M.; Lipomi, D. J.; Bao, Z. Highly Conductive and Transparent PEDOT:PSS Films with a Fluorosurfactant for Stretchable and Flexible Transparent Electrodes. Adv. Funct. Mater.2012, 22, 421-428. 13. Sung, S. J.; Kim, T.; Yang, S. J.; Oh, J. Y.; Park, C. R. New Insights Into the Oxidation of Single-walled Carbon Nanotubes for the Fabrication of Transparent Conductive Films. Carbon 2015, 81, 525-534. 14. Patole, A.; Lubineau, G. Carbon Nanotubes with Silver Nanoparticle Decoration and Conductive Polymer Coating for Improving the Electrical Conductivity of Polycarbonate Composites. Carbon 2015, 81, 720-730. 15. Jo, K.; Lee, T.; Choi, H. J.; Park, J. H.; Lee, D. J.; Lee, D. W.; Kim, B.-S. Stable Aqueous Dispersion of Reduced Graphene Nanosheets via Non-Covalent Functionalization with Conducting Polymers and Application in Transparent Electrodes. Langmuir 2011, 27, 2014-2018. 16. Lim, S.; Son, D.; Kim, J.; Lee, Y. B.; Song, J.-K.; Choi, S.; Lee, D. J.; Kim, J. H.; Lee, M.; Hyeon, T.; Kim, D.-H. Transparent and Stretchable Interactive Human Machine Interface Based on Patterned Graphene Heterostructures. Adv. Funct. Mater. 2015, 25, 375-383.


Page 25 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

17. Kim, J.; Lee, M. S.; Jeon, S.; Kim, M.; Kim, S.; Kim, K.; Bien, F.; Hong, S. Y.; Park, J. U. Highly Transparent and Stretchable Field-Effect Transistor Sensors Using Graphene-Nanowire Hybrid Nanostructures. Adv. Mater. 2015, 27,3292-3297. 18. Huang, Q.; Shen, W.; Fang, X.; Chen, G.; Yang, Y.; Huang, J.; Tan, R.; Song, W. Highly Thermostable, Flexible, Transparent, and Conductive Films on Polyimide Substrate with an AZO/AgNW/AZO Structure. ACS Appl. Mater. Interfaces 2015, 7, 4299-4305. 19. Lee, M.-S.; Lee, K.; Kim, S.-Y.; Lee, H.; Park, J.; Choi, K.-H.; Kim, H.-K.; Kim, D.-G.; Lee, D.-Y.; Nam, S. High-performance, Transparent, and Stretchable Electrodes Using Graphene–metal Nanowire Hybrid Structures. Nano Lett. 2013, 13, 2814-2821. 20. Jiang, Y.; Xi, J.; Wu, Z.; Dong, H.; Zhao, Z.; Jiao, B.; Hou, X. Highly Transparent, Conductive, Flexible Resin Films Embedded with Silver Nanowires. Langmuir 2015, 31, 4950-4957. 21. Kholmanov, I. N.; Domingues, S. H.; Chou, H.; Wang, X.; Tan, C.; Kim, J.-Y.; Li, H.; Piner, R.; Zarbin, A. J. G.; Ruoff, R. S. Reduced Graphene Oxide/Copper Nanowire Hybrid Films as High-Performance Transparent Electrodes. ACS Nano 2013, 7, 1811-1816. 22. Kholmanov, I. N.; Magnuson, C. W.; Aliev, A. E.; Li, H.; Zhang, B.; Suk, J. W.; Zhang, L. L.; Peng, E.; Mousavi, S. H.; Khanikaev, A. B. Improved Electrical Conductivity of Graphene Films Integrated with Metal Nanowires. Nano Lett. 2012, 12, 5679-5683. 23. Du, J.; Pei, S.; Ma, L.; Cheng, H. M. 25th Anniversary Article: Carbon Nanotube- and Graphene-based Transparent Conductive Films for Optoelectronic Devices. Adv. Mater. 2014, 26, 1958-1991. 25 ACS Paragon Plus Environment

Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 31

24. Tien, H.W.; Hsiao; S.T.; Liao, W.H.; Yu, Y.H.; Lin, F.C.; Wang, Y.S.; Li, S.M.; Ma, C. C. M. Using Self-assembly to Prepare a Graphene-Silver Nanowire Hybrid Film that is Transparent and Electrically Conductive. Carbon 2013, 58, 198-207. 25. Zhang, X.; Yan, X.; Chen, J.; Zhao, J. Large-size Graphene Microsheets as a Protective Layer for Transparent Conductive Silver Nanowire Film Heaters. Carbon 2014, 69, 437-443. 26. Kwan, Y. C. G.; Le, Q. L.; Huan, C. H. A. Time to Failure Modeling of Silver Nanowire Transparent Conducting Electrodes and Effects of a Reduced Graphene Oxide Over Layer. Sol. Energy Mater. Sol. Cells 2016, 144, 102-108. 27. Chen, R.; Das, S. R.; Jeong, C.; Khan, M. R.; Janes, D. B.; Alam, M. A. Co-Percolating Graphene-Wrapped Silver Nanowire Network for High Performance, Highly Stable, Transparent Conducting Electrodes. Adv. Funct. Mater.2013, 23, 5150-5158. 28. Jeong, C.; Nair, P.; Khan, M.; Lundstrom, M.; Alam, M. A. Prospects for Nanowire-doped Polycrystalline Graphene Films for Ultratransparent, Highly Conductive Electrodes. Nano Lett. 2011, 11, 5020-5025. 29. Moon, I. K.; Kim, J. I.; Lee, H.; Hur, K.; Kim, W. C.; Lee, H. 2D Graphene Oxide Nanosheets as an Adhesive Over-coating Layer for Flexible Transparent Conductive Electrodes. Sci. Rep. 2013, 3. 30. Kholmanov, I. N.; Stoller, M. D.; Edgeworth, J.; Lee, W. H.; Li, H.; Lee, J.; Barnhart, C.; Potts, J. R.; Piner, R.; Akinwande, D.; Barrick, J. E.; Ruoff, R. S. Nanostructured Hybrid Transparent Conductive Films with Antibacterial Properties. ACS Nano 2012, 6, 5157-5163. 31. Hsiao, S.-T.; Tien, H.-W.; Liao, W.-H.; Wang, Y.-S.; Li, S.-M.; Mma, C.-C.; Yu, Y.-H.; Chuang, W.-P. A Highly Electrically Conductive Graphene-silver Nanowire 26 ACS Paragon Plus Environment

Page 27 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Hybrid Nanomaterial for Transparent Conductive Films. J. Mater. Chem. C 2014, 2, 7284-7291. 32. Wang, Y.; Yang, H.-J.; Geng, H.-Z.; Zhang, Z.-C.; Ding, E.-X.; Meng, Y.; Luo, Z.-J.; Wang, J.; Su, X.-M.; Da, S.-X. Fabrication and Evaluation of Adhesion Enhanced Flexible Carbon Nanotube Transparent Conducting Films. J. Mater. Chem. C 2015,3,3796-1802. 33. Sun, Q.; Lee, S. J.; Kang, H.; Gim, Y.; Park, H. S.; Cho, J. H. Positively-charged Reduced Graphene Oxide as an Adhesion Promoter for Preparing a Highly-stable Silver Nanowire Film. Nanoscale 2015, 7 , 6798-6804. 34. Lee, H.; Dellatore, S. M.; Miller, W. M.; Messersmith, P. B. Mussel-inspired Surface Chemistry for Multifunctional Coatings. Science 2007, 318, 426-430. 35. Yu, X.; Fan, H.; Liu, Y.; Shi, Z.; Jin, Z. Characterization of Carbonized Polydopamine Nanoparticles Suggests Ordered Supramolecular Structure of Polydopamine. Langmuir 2014, 30, 5497-5505. 36. Ku, S. H.; Lee, J. S.; Park, C. B. Spatial Control of Cell Adhesion and Patterning through Mussel-Inspired Surface Modification by Polydopamine. Langmuir 2010, 26, 15104-15108. 37. Zangmeister, R. A.; Morris, T. A.; Tarlov, M. J. Characterization of Polydopamine Thin Films Deposited at Short Times by Autoxidation of Dopamine. Langmuir 2013, 29, 8619-8628. 38. Akter, T.; Kim, W. S. Reversibly Stretchable Transparent Conductive Coatings of Spray-Deposited Silver Nanowires. ACS Appl. Mater. Interfaces 2012, 4, 1855-1859. 39. Jin, Y.; Deng, D.; Cheng, Y.; Kong, L.; Xiao, F. Annealing-free and Strongly Adhesive Silver Nanowire Networks with Long-term Reliability by Introduction of a Nonconductive and Biocompatible Polymer Binder. Nanoscale 2014, 6, 4812-4818. 27 ACS Paragon Plus Environment

Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 31

40. Hwang, S.-H.; Kang, D.; Ruoff, R. S.; Shin, H. S.; Park, Y.-B. Poly (vinyl alcohol) Reinforced and Toughened with Poly (dopamine)-Treated Graphene Oxide, and Its Use for Humidity Sensing. ACS Nano 2014, 8, 6739-6747. 41. Lee, W.; Lee, J. U.; Jung, B. M.; Byun, J.-H.; Yi, J.-W.; Lee, S.-B.; Kim, B.-S. Simultaneous Enhancement of Mechanical, Electrical and Thermal Properties of Graphene Oxide Paper by Embedding Dopamine. Carbon 2013, 65, 296-304. 42. Liu, H.; Hou, L.; Peng, W.; Zhang, Q.; Zhang, X. Fabrication and Characterization of Polyamide 6-functionalized Graphene Nanocomposite Fiber. J Mater. Sci. 2012, 47, 8052-8060. 43. Li, D.; Mueller, M. B.; Gilje, S.; Kaner, R. B.; Wallace, G. G. Processable Aqueous Dispersions of Graphene Nanosheets. Nat. Nanotechnol. 2008, 3, 101-105. 44. Xu, L. Q.; Yang, W. J.; Neoh, K.-G.; Kang, E.-T.; Fu, G. D. Dopamine-Induced Reduction and Functionalization of Graphene Oxide Nanosheets. Macromolecules 2010, 43, 8336-8339. 45. Liu, H.; Xi, P.; Xie, G.; Shi, Y.; Hou, F.; Huang, L.; Chen, F.; Zeng, Z.; Shao, C.; Wang, J. Simultaneous Reduction and Surface Functionalization of Graphene Oxide for Hydroxyapatite Mineralization. J. Phys. Chem. C 2012, 116, 3334-3341. 46. Liu, Y.; Ai, K.; Lu, L. Polydopamine and Its Derivative Materials: Synthesis and Promising Applications in Energy, Environmental, and Biomedical Fields. Chem. Rev. 2014, 114, 5057-115. 47. Ramphal, I. A.; Hagerman, M. E. Water-Processable Laponite/Polyaniline/Graphene Oxide Nanocomposites for Energy Applications. Langmuir 2015, 31, 1505-1515.


Page 29 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

48. Tian, Y.; Cao, Y.; Wang, Y.; Yang, W.; Feng, J. Realizing Ultrahigh Modulus and High Strength of Macroscopic Graphene Oxide Papers Through Crosslinking of Mussel-Inspired Polymers. Adv. Mater. 2013,25,280-2983. 49. Stathi, P.; Gournis, D.; Deligiannakis, Y.; Rudolf, P. Stabilization of Phenolic Radicals on Graphene Oxide: An XPS and EPR Study. Langmuir 2015, 31, 10508-10516. 50. He, H.; Wang, H.; Li, K.; Zhu, J.; Liu, J.; Meng, X.; Shen, X.; Zeng, X.; Cai, W. Green and Tunable Decoration of Graphene with Spherical Nanoparticles Based on Laser Ablation in Water: A Case of Ag Nanoparticle/Graphene Oxide Sheet Composites. Langmuir 2016, 32, 1667-1673. 51. Lee, B. P.; Messersmith, P. B.; Israelachvili, J. N.; Waite, J. H. Mussel-Inspired Adhesives and Coatings. Annu. Rev. Mater. Res. 2011, 41, 99-132. 52. Kirchmeyer, S.; Reuter, K. Scientific Importance, Properties and Growing Applications of Poly(3,4-ethylenedioxythiophene). J. Mater. Chem. 2005, 15, 2077-2088. 53. Sun, Y.; Gates, B.; Mayers, B.; Xia, Y. Crystalline Silver Nanowires by Soft Solution Processing. Nano Lett. 2002, 2, 165-168. 54. Chen, J.; Bi, H.; Sun, S.; Tang, Y.; Zhao, W.; Lin, T.; Wan, D.; Huang, F.; Zhou, X.; Xie, X.; Jiang, M. Highly Conductive and Flexible Paper of 1D Silver-nanowire-doped Graphene. ACS Appl. Mater. Interfaces 2013, 5, 1408-1413. 55. Liu, B.-T.; Kuo, H.-L. Graphene/silver Nanowire Sandwich Structures for Transparent Conductive Films. Carbon 2013, 63, 390-396. 56. Chen, Z.; Yu, D.; Xiong, W.; Liu, P.; Liu, Y.; Dai, L. Graphene-Based Nanowire Supercapacitors. Langmuir 2014, 30, 3567-3571.


Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 31

57. Zhao, J.; Liu, Z.; Li, H.; Hu, W.; Zhao, C.; Zhao, P.; Shi, D. Development of a Highly Active Electrocatalyst via Ultrafine Pd Nanoparticles Dispersed on Pristine Graphene. Langmuir 2015, 31, 2576-2583. 58. Choo, D. C.; Kim, T. W. Conducting Transparent Thin Films Based on Silver Nanowires and Graphene-Oxide Flakes. J. Electrochem. Soc. 2015, 162, H419-H421. 59. Shi L, Yang J, Yang T, Qiu H, Li J, Zheng Q. Molecular Level Controlled Fabrication of Highly Transparent Conductive Reduced Graphene Oxide/Silver Nanowire Hybrid Films. RSC Adv. 2014, 4: 43270-43277. 60. Chen, S.; Brown, L.; Levendorf, M.; Cai, W.; Ju, S.-Y.; Edgeworth, J.; Li, X.; Magnuson, C. W.; Velamakanni, A.; Piner, R. D. Oxidation Resistance of Graphene-coated Cu and Cu/Ni Alloy. ACS Nano 2011, 5, 1321-1327. 61. Naito K, Yoshinaga N, Tsutsumi E, Akasaka Y. Transparent Conducting Film Composed of Graphene and Silver Nanowire Stacked Layers. Synthetic Met. 2013, 175: 42-46.


Page 31 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

Insert Table of Contents Graphic and Synopsis Here


Mussel-Inspired Polydopamine-Functionalized Graphene as a

Recommend Documents