화학 감지용 귀금속 나노입자로 장식된 전기방사 고분자 나노섬유

귀금속 나노입자로 장식된 전기방사 고분자 나노섬유의 응용 감지

귀금속 나노입자(예:Au 및 Ag NPs)로 장식된 전기방사 고분자 나노섬유를 기반으로 한 감지 응용 분야의 최근 몇 가지 예가 표 1에 나와 있습니다. 표 1에서 금속 입자/나노섬유 복합재는 단순성과 같은 많은 이점이 있음을 알 수 있습니다 , 고감도, 고선택성으로 다양한 생물학적, 화학적 시료를 검출합니다. 전기방사를 통해 금속 입자/나노섬유 복합재는 표면적이 큰 금속 입자/나노섬유 복합재를 쉽게 제작할 수 있어 검출 분자에 쉽게 접근할 수 있어 SERS에 대한 우수한 활성을 이끌어냅니다. 따라서 많은 금속 입자/나노섬유 복합재료가 낮은 검출 한계를 보입니다. 또한, 표 1의 결과를 바탕으로 금속 입자 사이에 핫스팟이 존재하여 라만 신호가 향상되기 때문에 금속 입자의 밀도와 크기가 SERS 활성/민감도에 중요한 영향을 미친다는 결론을 내릴 수 있습니다. .

SERS 기반 화학 감지용 귀금속 나노입자로 장식된 전기방사 고분자 나노섬유

표면 강화 라만 산란(SERS)은 단일 분자, 이온, 생체 분자를 조사하고 세포 연구를 위한 가장 유망하고 강력한 분석 도구 중 하나로 부상했습니다[105,106,107,108,109,110,111]. 1980년대 중반 이후로 더 많은 연구자들이 현상에 대한 근본적인 이해 대신 SERS의 유망한 분석적 응용에 대한 탐구에 집중하기 시작했습니다[112]. 조직화된 Au 또는 Ag 나노구조는 금속 나노구조에 의해 유도된 국부 전자기장 향상에 기인한 SERS 기판으로서의 신호 증폭 기능으로 인해 엄청난 주목을 받았습니다. SERS 향상 인자(나노구조가 있는 경우와 없는 경우에 주어진 수의 분자에서 나오는 라만 신호 사이의 비율)는 효과를 일으키는 나노구조의 크기 및 모양과 밀접한 관련이 있습니다[113]. Typically, the Au, Ag, or AuAg-mixed nanostructures are arranged on rigid materials as the SERS substrate and these methods are either complicated and time consuming in synthesis processes or require strict synthetic conditions.

Recently, a flexible substrate fabricated by combining electrospun nanofibers with Au, Ag, or AuAg-mixed nanostructures has become popular due to their excellent SERS performance and, compared with the rigid substrate, these flexible structures are adaptable to a rough substrate in terms of wrapping and bending [106, 114]. These metal/nanofiber composites demonstrated a 3D structure, which can provide high density of “hot spots”, which refers to the regions of highly enhanced local electromagnetic field [115]. In addition, the polymer outside the nanostructures can protect them from the surrounding environment especially for Ag nanostructures, which gives the composite long lifetime and high sensitivity [116].

Different polymers or ceramic nanofibers, such as PVA [100, 116, 117], cellulose [118], poly(methyl methacrylate) (PMMA) [119], chitosan [106], poly (acrylic acid) (PAA)/PVA [120], and silica [121] have been utilized to combine with different Ag or Au nanostructures to fabricate the flexible substrate for SERS. PVA is a nontoxic, biocompatible polymer, which has good electrospinability, and it is a popular material for electrospinning. When it is used as the supporting material for Ag nanostructures for SERS, it functions not only as the host matrix but also as an organic additive inducing the aggregation of individual Ag nanostructures [116]. In a typical process, the Au or Ag nanostructures are produced in specific morphologies first and these nanostructures are added into the polymer solution as the precursor solution. 그는 외. synthesized nearly monodispersed Ag NPs via a microwave-assisted method and then these as-prepared silver dimers and aggregates were mixed into a 7% aqueous PVA solution for electrospinning [116]. In order to reduce the specific surface area and the surface Gibbs free energy of individual nanofibers, Ag NPs were self-assembled inside the PVA nanofibers. The assembly of Ag dimers or aligned aggregates within PVA nanofibers was confirmed using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses. Moreover, Ag NPs tended to form a linear chain-like structure along the axial direction of fibers (Fig. 6) because when a high voltage was applied to the solution, Ag NPs became positively charged on one side and negatively charged on the other, leading to a self-alignment by electrostatic attraction in the direction of the electric field [116].

아 –d Typical TEM image of Ag/PVA nanofibers with the molar ratio of PVA/Ag 530:1 (a ), 530:2 (b ), 530:3 (c ), and 530:4 (d ). The increase of the molar ratio of Ag/PVA in the Ag/PVA solution led to stronger aggregation state and a larger distribution in the sizes of the aggregated Ag NPs. 이 Schematic representation of the formation of chain-like arrays of Ag NP aggregates within PVA nanofibers [116]. Reprinted with permission from ref. [116]. Copyright {2009} American Chemical Society

As the amount of Ag NPs increased in the PVA nanofibers, the enhancement factor did not increase accordingly, which indicated that different morphology of Ag NP aggregation had a great influence on the enhancement effects of SERS [116]. When 4-mercaptobenzoic acid (4-MBA) was used as a probing molecule to study the Raman enhancement effects, the Ag/PVA nanofibers showed excellent detection reproducibility (i.e., the average relative standard deviation values of the major Raman peak were less than 0.07). Taking advantage of the same nanoparticle alignment in the polymer nanofibers, Ag nanowires (NWs) were also synthesized and electrospun into PVA nanofibers [122]. The Ag NW/PVA nanofibers showed similar morphology and the NWs were “frozen-up” within the polymer fibers. In addition, the electrospun Ag NW/PVA nanofibers were arranged into different structures and stronger SERS intensities were obtained from the arranged samples [122]. Besides Ag nanostructures, Au nanostructures were also encapsulated into the PVA electrospun nanofibers as SERS substrates [100]. Zhang et al. used a seed-mediated surfactant-directed approach to synthesize Au nanorods (AuNRs), and these Au NRs exhibited good alignment along the axial direction of the nanofibers, which demonstrates that electrospinning is a powerful tool to assemble anisotropic nanorods on a large scale [100]. Ag and Au nanostructures can be co-assembled into the PVA nanofibers [117, 123]. Different SERS effects can be obtained by varying the Au/Ag ratio and the excitation wavelength due to the different activities of Au and Ag nanostructures under different wavelengths [124]. In spite of the different morphologies of Ag and Au nanostructures, both Au/PVA and Ag/PVA composites showed excellent SERS performance.

Electrospun Polymer Nanofibers Decorated with Noble Metal Nanoparticles for Chemical Sensing Based on Electrochemical Techniques

Nowadays, metal nanoparticles (such as Au, Ag, Cu, and Ni) have become widely utilized in electrochemical sensing applications, which can be attributed to their rich electronic properties, high surface area, and excellent chemical stability [125, 126]. Au NPs can decrease the overpotentials of many electroanalytical reactions and maintain the reversibility of redox reactions [41, 127]. The Au NP platform can be used for detection of different kinds of analytes including small molecules such as glucose [128, 129], dopamine [130,131,132,133], bisphenol A [134], toxic chemicals and drugs such as mercury [135,136,137,138], antimony [139], and hydrogen peroxide [140]. Au NPs hold great promise as substrates for designing electrochemical biosensors, which benefit from their ability to provide a stable immobilization of biomolecules retaining their bioactivity, ease of use in chemical synthesis, narrow size distribution, and their convenient labeling of biomolecules [141,142,143]. Furthermore, both Ag and Au NPs have good biocompatibility and large surface area which can help adsorb biomolecules strongly and play an important role in the immobilization of biomolecules [144]. Accordingly, combining Au or Ag NPs with large-surface-area polymer nanofibers, which provide a large loading capacity for nanoparticles, can further enhance the sensitivity of the sensors [145].

Sapountzi et al. decorated the PVA/poly(ethyleneimine) (PEI)/glucose oxidase nanofibers with Au NPs to further improve the conductivity of the mat and used these composites as electrochemical biosensors [146]. However, both PVA and PEI are water soluble polymers and it may weaken the stability of the composite. Therefore, the researchers conducted a post-electrospinning cross-linking step by exposing the NFs to glutaraldehyde (GA) vapors and the morphology of the fibers was still well retained, suggesting a successful chemical cross-linking reaction induced by GA vapors [146]. The same treatment was also performed by other researchers and the cross-linked PVA nanofiber mat maintained its morphology even after being soaked in water for 15 days [99]. After obtaining the water soluble PVA nanofiber mat, 3-mercaptopropyltrimethoxysilanes (MPTES) were first modified on the surface of electrospun PVA nanofibers. Then, the modified PVA nanofiber mat was immersed into the as-prepared Au NPs aqueous solutions and Au NPs were strongly bonded onto the surface of the modified PVA nanofibers due to the strong affinity between the thiol groups and Au NPs [99]. Au NPs were homogenously decorated on the surface of the modified PVA nanofibers for different Au NP concentrations, leading to highly sensitive detection of H₂ O₂ and the Au NPs/modified PVA also showed more advantages such as fast response, broad linear range, and low detection limit [99].