In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films

Summary

Here, we present a protocol for the in situ synthesis of gold nanoparticles (AuNPs) within the interlayer space of layered titanate films without the aggregation of AuNPs. No spectral change was observed even after 4 months. The synthesized material has expected applications in catalysis, photo-catalysis, and the development of cost-effective plasmonic devices.

Abstract

Combinations of metal oxide semiconductors and gold nanoparticles (AuNPs) have been investigated as new types of materials. The in situ synthesis of AuNPs within the interlayer space of semiconducting layered titania nanosheet (TNS) films was investigated here. Two types of intermediate films (i.e., TNS films containing methyl viologen (TNS/MV²⁺) and 2-ammoniumethanethiol (TNS/2-AET⁺)) were prepared. The two intermediate films were soaked in an aqueous tetrachloroauric(III) acid (HAuCl₄) solution, whereby considerable amounts of Au(III) species were accommodated within the interlayer spaces of the TNS films. The two types of obtained films were then soaked in an aqueous sodium tetrahydroborate (NaBH₄) solution, whereupon the color of the films immediately changed from colorless to purple, suggesting the formation of AuNPs within the TNS interlayer. When only TNS/MV²⁺ was used as the intermediate film, the color of the film gradually changed from metallic purple to dusty purple within 30 min, suggesting that aggregation of AuNPs had occurred. In contrast, this color change was suppressed by using the TNS/2-AET⁺ intermediate film, and the AuNPs were stabilized for over 4 months, as evidenced by the characteristic extinction (absorption and scattering) band from the AuNPs.

Introduction

Various noble metal nanoparticles (MNPs) exhibit characteristic colors or tones due to their localized surface plasmon resonance (LSPR) properties; thus, MNPs can be used in various optical and/or photochemical applications^1-4. Recently, combinations of metal oxide semiconductor (MOS) photocatalysts, such as titanium oxide (TiO₂) and MNPs, have been thoroughly investigated as new types of photocatalysts^5-14. However, in many cases, very small amounts of MNPs exist on the MOS surface, because most MOS particles have relatively low surface areas. On the other hand, layered metal oxide semiconductors (LMOSs) exhibit photocatalytic propert....

Protocol

Caution: Always use caution when working with chemicals and solutions. Follow the appropriate safety practices and wear gloves, glasses, and a lab coat at all times. Be aware that nanomaterials may have additional hazards as compared to their bulk counterpart.

1. Preparation of Regents

1. Prepare the methyl viologen aqueous solution by dissolving 0.0012 g of 1,1'-dimethyl-4,4'-bipyridinium dichloride (methyl viologen; MV²⁺) in 20 ml of water to give 0.2 mM MV²⁺.
2. Prepare the gold(III) chloride aqueous solution by dissolving 0.1050 g of gold(III) tetrachloride trihydrate (HAuCl₄• 3H₂O) i....

Results

Two types of precursor films were used in this study (i.e., with and without the protective reagent (2-AET⁺) within the interlayer of TNS). In the absence of 2-AET⁺, 1,1'-dimethyl-4,4'-bipyridinium dichloride (methyl viologen; MV²⁺) was used as an expander of the interlayer space, because MV²⁺-containing LMOSs have been frequently used as intermediates in the guest exchange method for preparing LMOSs^{16,17,21,33-36}.

Discussion

This manuscript provides a detailed protocol for the in situ synthesis of gold nanoparticles (AuNPs) within the interlayer space of TNS films. This is the first report of the in situ synthesis of AuNPs within the interlayer space of TNS. Moreover, we found that the 2-AET⁺ works as an effective protective reagent for AuNPs within the interlayer of TNS. These methods hybridized AuNPs and TNS transparent films. TNS films with good optical transparency²¹ were synthesized through sinter.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Methyl viologen dichloride	Aldrich Chemical  Co., Inc.	1910-42-5
Tetrabutylammonium hydroxide	TCI	T1685
cesium carbonate	Kanto Chemical Co., Inc.	07184-33
anatase titanium dixoide	Ishihara Sangyo Ltd.	ST-01
hydrochloric acid	Junsei Chemical Co., Ltd.	20010-0350
sodium hydroxide	Junsei Chemical Co., Ltd.	195-13775
Tetrachloroauric(III) acid trihydrate	Kanto Chemical Co., Inc.	17044-60
sodium tetrahydroborate	Junsei Chemical Co., Ltd.	39245-1210
2-ammoniumethanethiol hydrochloride	TCI	A0296
Ultrapure water (0.056 µS/cm)			Milli-Q water purification system (Direct-Q® 3UV, Millipore)
Microscope slide (Thickness: 1.0–1.2 mm)	Matsunami glass Co., Ltd.