Laser Controlled Synthesis of Noble Metal Nanoparticle Arrays for Low Concentration Molecule Recognition

Nanostructured gold and silver thin films were grown by pulsed laser deposition. Performing the process in an ambient gas (Ar) leads to the nucleation and growth of nanoparticles in the ablation plasma and their self-organization on the substrate. The dependence of surface nanostructuring of the films on the deposition parameters is discussed considering in particular the number of laser pulses and the ambient gas nature and pressure. The performance of the deposited thin films as substrates for surface-enhanced Raman spectroscopy (SERS) was tested against the detection of molecules at a low concentration. Taking Raman maps on micrometer-sized areas, the spatial homogeneity of the substrates with respect to the SERS signal was tested

Topographical coloured plasmonic coins

The use of metal nanostructures for colourization has attracted a great deal of interest with the recent developments in plasmonics. However, the current top-down colourization methods based on plasmonic concepts are tedious and time consuming, and thus unviable for large-scale industrial applications. Here we show a bottom-up approach where, upon picosecond laser exposure, a full colour palette independent of viewing angle can be created on noble metals. We show that colours are related to a single laser processing parameter, the total accumulated fluence, which makes this process suitable for high throughput industrial applications. Statistical image analyses of the laser irradiated surfaces reveal various distributions of nanoparticle sizes which control colour. Quantitative comparisons between experiments and large-scale finite-difference time-domain computations, demonstrate that colours are produced by selective absorption phenomena in heterogeneous nanoclusters. Plasmonic cluster resonances are thus found to play the key role in colour formation.Comment: 9 pages, 5 figure

Layer by Layer Silver Acetate based Coating on Glass and Cement Substrates to Tailor Reflectance and Conductance

Tailoring reflectance and conductance was achieved through layer by layer assembly of a silver acetate based multilayer coating. The coating was applied over glass and cement substrates by sol-gel spin coating and by brush painting, respectively. The structural, optical and electrical characteristics and the composition of the coating were studied. The diffraction peaks for all films revealed that the face-centered cubic lattice of the silver crystal structure and the films with more layers had a higher degree of crystallinity. The optical characteristics showed that having more layers leads to decreasing transmittance and increasing reflectance. The I-V characteristics of all samples showed typical ohmic contacts in a voltage range of -1 to 1 V. The conductance increased drastically as the coating developed into multiple layers. The eight-layer coated glass and cement based substrates had very low surface resistance, at 4 Ω and 2 Ω at 1 V, respectively. The study also revealed that the resistance behavior of a multilayered film generally is thermally stable for annealing up to 400 °C. The coating resistance was significantly increased by further increasing the post-annealing beyond 500 °C. The studied multilayered coating can be used to tailor the reflectance and conductance of dielectric substrate surfaces for various optoelectronics and sensor device applications

바이오 응용을 위한LSPR과 SERS 동시측정방법: 광학 시스템과 센서 기판에 대해서

바이오 분자의 검출을 위해, 다양한 방법을 이용한 바이오 센서들이 개발되어 왔으며 각각의 바이오 센서들은 기기 적인 측면에서 다양한 장점과 차이점 들을 가지고 있다. 그러한 연구 속에서, 본 연구에서는 광섬유 기반의 바이오 센서를 개발하고자 한다. 광섬유 기반의 바이오센서는 다양한 장점들을 가지고 있으며 특히 광섬유 기반의 바이오센서는 항원-항체 반응의 국소 표면 플라즈몬 (localized surface plasmon resonance, LSPR)과 표면 증강 라만 산란 (Surface-enhanced Raman scattering, SERS) 동시 측정 및 실시간 측정이 가능하며 이를 기반으로 본 연구에서는 표적 물질 없이 인터페론-감마(IFN-γ)의 항원-항체 반응을 바이오 분야의 응용을 위한 개념 증명 형태로 성공적인 실험 수행을 진행하였다. 챕터 1 에서는 본 연구의 간단한 이론, 기본 법칙 및 연구 목적에 대해서 간략하게 제시하였다. 또한 최근 기술 중에서 바이오 분자 검출을 위해 널리 사용되는 것들에 대한 예시와 함께 간단한 논의를 첨부하였다. 챕터 2 에서는 광섬유 기반의 바이오 분자 검출을 위한 LSPR 및 SERS 동시 측정 시스템의 개발에 대해서 기술하였다. 우선 광섬유 말단 표면에 50 nm 정도 크기를 가지는 금 나노 입자를 표면 화학 처리를 이용하여 고정시켰으며 LSPR 및 SERS 동시 측정을 위해 분광학적 시스템을 개발하였다. 개발한 시스템을 이용하여 금 나노 입자가 도입된 광섬유의 LSPR 신호의 민감도 및 재현 가능성을 살펴보기 위해 굴절률에 따른 신호 변화를 측정하였으며 또한 SERS 신호의 민감도 및 재현 가능성 여부를 확인하기 위해 4-aminothiophenol (4-ATP)를 도입하여 SERS 신호의 여부를 확인하였다. 이를 기반으로 IFN-γ 의 실시간 LSPR 신호 변화 및 4-ATP의 SERS 스펙트럼의 변화를 동시 측정 하였으며 이를 통해 생물학적 응용의 가능성을 확인하였다. 바이오 분자 검출을 위한 SPR 및 SERS 센서를 구현하기 위해서는 유리 기판 혹은 광섬유 표면에 귀금속 나노 입자가 도입되어야 한다. 현재 대부분의 용액 기반의 연구에서는 기판 표면의 나노 입자 배열의 불균일성으로 인해 신호의 민감도나 재현성이 낮은 경우가 많으며 이를 극복하기 위해 도입하는 전자빔을 이용한 리소그래피 방법이나 진공 스퍼터링 등을 이용하여 기판 표면을 처리하는 방법들은 가격적인 측면에서 비싸고 복잡한 기기들이 필요한 경우가 대부분이다. 이러한 표면 기판의 나노 입자의 처리하는 방법들이 가지고 있는 여러 단점을 극복하는 대안으로 기판 표면에 직접적으로 나노 입자를 광 유도 반응을 이용해 만드는 것이 제시되었으나 이러한 방법 역시 현재 연구 수준에서는 여전히 균일도가 낮은 모습들을 보이고 있다. 이를 극복하기 위해 챕터 3 에서는 유리 기판 표면에 은 나노 입자를 단 분산 시킬 수 있는 간단한 방법 개발에 대해서 기술하였다. 우선 균일한 유리 기판 표면처리를 위하여 유리 기판 표면에 아민 작용기와 알킬 그룹을 일정한 비율로 도입하였다. 또한 빛을 조명하는 시간 역시 조절하였으며 성장 용액 속의 질산은과 시트르산 나트륨의 농도를 조절하여 기판 표면에서 성장하는 나노 입자의 크기 및 단 분산성을 조절하였다. 이러한 단 분산성은 전계 방출 주사 전자 현미경(Field-emission scanning electron microscopy) 과 암시야(Dark-field) 현미경을 이용하여 확인하였다. 이를 기반으로 실험 결과에 대한 광 유도 반응에 대한 이론적인 메커니즘을 규명하였다.In a field of bio-molecular analysis, various kinds of biosensors have been developed extensively. Each of them has many benefits and variations in the instrument designs. In this study proposed is a fiber optic (FO) sensor which has many advantages such as utilization of localized surface Plasmon resonance (LSPR) and surface enhanced Raman scattering (SERS) simultaneously and real time detection of antibody-antigen reaction. The fiber optic sensors were successfully utilized as label-free LSPR and SERS simultaneous detection of antibody-antigen reaction interferon-gamma (IFN-γ) as a proof-of-concept for bio-related applications. Chapter I, as an introductory chapter, aims to provide a brief theoretical information, basic principles and research objective of this study. Also modern techniques that are broadly used in field of bio-molecular detection and its examples are discussed. In Chapter II, fabrication of the FO LSPR and SERS sensor and its simultaneous detection system for bio-applications were described. First, an FO sensor was fabricated by immobilizing gold nanoparticles (Au NPs, ca. 50±5nm diameter) on one end of a fiber optic by chemical reaction. And simultaneous detection system of the LSPR and SERS was assembled. Then, for checking the FO sensor quality, sensitivity, and also simultaneous detection system reliability, LSPR and SERS signals were measured using various refractive indices solutions and SERS reporter molecule of 4-aminothiphenol (ATP). Finally, the sensor was applied to observe real-time LSPR sensor-gram and SERS spectra of the reporter molecule of ATP during the antibody-antigen reaction of interferon-gamma (IFN-γ) as experiment of biological applications. In a variety of practical applications, including surface plasmon resonance (SPR) sensors and surface-enhanced Raman scattering (SERS) sensors for bio-detection, noble metal nanoparticles attached to a glass slide or optical fiber are required for increased sensitivity. In addition to sensitivity, reproducibility is important for practical applications. In this aspect, many approaches such as e-beam lithography, vacuum sputtering, and wet chemical methods have usually been used for deposition of NPs onto the substrate [1-3]. However, issues such as cost of e-beam method and morphological non-uniformity of wet chemical methods hindered sensitive and reproducible fabrication of the sensor substrate. Recently, several photo-induced methods have been demonstrated to grow silver or gold NPs directly on a glass substrate or fiber optic surface from their aqueous solution. Until now, the morphologies of the photo-induced grown nanoparticles on the substrate have not reached enough uniformity. In Chapter III, a simple method which grows mono-disperse and uniform silver nanoparticles (Ag NPs) directly onto a silica substrate by light irradiation of silver nitrate solution in a presence of sodium citrate was described. Changing the mixed ratio of amine and non-amine functional groups on the substrate as well as photo-illumination time and concentration of growth solutions, mono-disperse growing of Ag NPs was able to control. After photo-induced growing, substrates are characterized by field emission scanning electron microscopy (FE-SEM) and dark field (DF) microscopy. Finally, mechanism of the photo-induced growing process was described on the basis of the experimental results.Chapter 1. Introduction 1 1. Surface Plasmon Resonance Spectroscopy for Bio-detection 2 2. Surface Enhanced Raman Spectroscopy for Bio-molecular Detection 10 3. Fiber optic and its Application for Bio-detection 12 4. Noble metal Nanoparticles for Bio-molecular Detection 15 5. Photo Chemical Method of the Noble metal Nanoparticles ynthesize and Growing 18 6. Research Objective 21 Chapter 2. Fiber Optic Sensor Simultaneously Detecting Localized Surface Plasmon Resonance and Surface-Enhanced Raman Scattering 24 1. Experimental Section 25 2. Results and Discussion 42 Chapter 3. Mono-disperse Growth Control of Silver Nanoparticles on Glass Substrate using Photo-reduction and Mixed Self-assembly 52 1. Experimental Section 53 2. Results and Discussion 64 Conclusions 99 References 102 Abstract in Korean 113Docto