pH 감응형 센서용 형광 야누스 입자의 설계 및 제조 = Design and Fabrication of Fluorescent Janus Particles for pH-Responsive Sensing

다국어 초록 (Multilingual Abstract)

Organic fluorescent dyes are widely utilized in pH sensing and bioimaging; however, their intrinsic limitations, such as low fluorescence intensity, insufficient photostability, and short fluorescence lifetimes, restrict their effectiveness in long-term and quantitative measurements. To overcome these drawbacks, strategies involving the encapsulation or immobilization of dyes within inorganic matrices have been proposed. Among these, silica nanoparticles have gained significant attention as promising matrices due to their high chemical stability, excellent biocompatibility, and ease of surface functionalization. Nevertheless, single-dye-based systems remain highly susceptible to external factors, including fluctuations in excitation intensity, dye concentration, and photobleaching, which compromise quantitative reliability.
To address these limitations, this study presents a dual-dye system incorporating two pH-responsive dyes that exhibit complementary fluorescence responses at distinct wavelengths. This approach enables robust pH evaluation while minimizing the influence of external variables. Unlike conventional dual-dye systems based on core–shell or mesoporous structures, where undesired fluorescence resonance energy transfer (FRET) or mutual quenching often occur, the Janus architecture spatially separates the two dyes onto opposite hemispheres of a single nanoparticle. This structural asymmetry effectively suppresses signal interference and ensures high signal stability even in complex biological environments, making Janus nanoparticles a highly promising platform for biosensing.
Janus particles are asymmetric colloids possessing two distinct surface regions with differing physicochemical properties. In this work, silica nanoparticles synthesized via the Stöber method were adsorbed at the interface between molten paraffin wax and water, facilitated by a cationic surfactant, and subsequently cooled to form wax–silica colloidosomes. By employing a masking strategy, selective silane coupling reactions were performed exclusively on the exposed silica surfaces. After the wax template was removed, a different silane coupling agent was introduced to the previously shielded hemisphere, yielding Janus silica nanoparticles with dual functional surfaces. The selectivity of this modification was verified through zeta potential measurements, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and Pickering emulsion stability tests.
One hemisphere of the Janus silica nanoparticles was functionalized with fluorescein 5(6)-isothiocyanate (FITC), while the opposite hemisphere was modified with Rhodamine B hydrazide. Confocal laser scanning microscopy and fluorescence spectroscopy revealed two well-resolved emission peaks at approximately 520 nm (FITC) and 580 nm (Rhodamine B hydrazide). FITC exhibited enhanced fluorescence under alkaline conditions, whereas Rhodamine B hydrazide showed strong emission in acidic environments. By monitoring the ratiometric fluorescence responses over a pH range of 2–10, stable and precise pH evaluation was achieved. These results demonstrate that the Janus silica nanoparticles developed in this study serve as a superior platform for high-precision pH sensing applications

목차 (Table of Contents)

• I. 서론 1
• 1. 연구 배경 1
• 1) pH 센서 6
• 2. 피커링 에멀션 8
• 3. 가리움법 9
• 4. 형광 염료 10
• 1) Fluorescein 5(6)-isothiocyanate (FITC) 10
• 2) Rhodamine B hydrazide 12
• 5. 연구 목표 14
• II. 실험 16
• 1. 시약 및 재료 16
• 2. 단분산 실리카 입자 제조 17
• 3. 실리카-왁스 콜로이도좀 제조 20
• 4. 형광 염료의 기능화 23
• 1) FITC 실란화 23
• 2) Rhodamine B hydrazide 합성 25
• 5. pH 감응형 형광 야누스 입자 합성 27
• 6. 피커링 에멀션 제조 32
• 7. 분석 34
• III. 결과 및 고찰 36
• 1. 단분산 실리카 입자 합성 36
• 2. 콜로이도좀 39
• 3. 실리카 입자의 반구 선택적 표면개질 검증 44
• 1) XPS 분석 44
• 2) TGA 분석 46
• 3) 제타 전위 분석 48
• 4) 피커링 에멀션 분석 50
• 4. 형광 염료의 pH 감응 특성 분석 53
• 5. 형광 야누스 입자 분석 55
• 1) pH 변화에 따른 야누스 입자의 광학적 응답 특성 55
• 2) pH 변화에 따른 야누스 입자의 형광 강도 분석 58
• 3) UV-Vis 측정 60
• 4) 시간 의존성 평가 62
• 5) pH 가역성 평가 64
• IV. 결론 66
• 참고문헌 69