Nano Res.2016 Sep;9(9):2760-2771
Rapid identification of electricigens via silver-plated photonic crystal filters
Delong Wang1,2, Xiangwei Zhao1,2*, Xing Liu1,2, Zhongde Mu1,2, and Zhongze Gu1,2*
1State Key Laboratory of Bioelectronics, School of BiologicalScience and Medical Engineering, Southeast University, Nanjing 210096, China
2Suzhou Key Laboratory of Environment and Biosafety, Suzhou Research Institute of Southeast University, Suzhou 215123, China
Electricigens are usually isolated from environmental samples and play an important role in microbial fuel cells (MFCs), but the isolation process is cumbersome and time-cost. In this paper, we utilized a silver-plated photonic crystals (PCs) substrate for the filtration, capture and detection of electricigens in simple and complex bacteria samples (Fig. 1). With this functional plasmonic substrate, we could identify electricigens with 5 μL sample in 5 min. The Raman spectra results showed that we could discriminate not only different bacteria, different categories of electricigens, but also wild and mutant electricigens.
Figure 1. Schematic of the silver-plated PCs filter for identification of electricigens.
The identification and isolation of electricigens are very important for the study of MFCs, but the low efficiency of traditional tedious isolation process has been an obstacle for the development of MFCs. Hence, a high-efficient tool for the rapid identification of electricigens is bound to promote the study of MFCs. Herein, we reported a silver-plated PCs filter for the rapid identification of electricigens from simple and complex samples. As we know, PCs could benefit the Raman analysis due to the controllable “hot spots” and extra enhancement of local electromagnetic field. The Finite Difference Time Domain (FDTD) simulation results (Figure 2a and 2b) showed the distribution and intensity (|E|2) of electric field of this substrate at xy plane and xz plane. Compared with other SERS substrates reported before, this PCs-based biosensor could enhance the intensity of E-field more obviously. For example, the electric field intensity (|E|2) of the gold nanoparticles was 70-fold less than that of PCs biosensor 1. Besides, the |E|2 of gold-Raman probe-silica sandwiched nanoparticles reported by Li et al. was 5-fold less than that of PCs biosensor 2. Moreover, the “hot spots” were located at the gaps of silica nanoparticles, where bacteria were filtered and captured. It meant that hot spots were very close to bacteria, which was beneficial to enhance the Raman signals of bacteria.
Figure 2. The FDTD simulation results of silver-plated PCs substrate. a, the intensity (|E|2) of E-field of the substrate at xy plane; b, the intensity (|E|2) of E-field of the substrate at xz plane.
The advantages of the silver-plated PCs filter are presented as follows. First, the colloidal PCs substrate have ordered pores in nanoscale, acting as filters for bacteria in microns. Therefore the bacteria in solution could be captured onto the surface of PCs by filtration even if their concentration is very low, which is especially useful for pathogenic bacteria or rare bacteria detection. Second, the ordered nanostructure of PCs provides uniform SERS measurement in comparison with disordered structure of nanoparticle assemblies, which is desirable for repeatable and reliable SERS detection especially for SERS imaging. Third, the propagation of light could be modulated by PCs and the interaction of light and plasmonic material could be enhanced by PCs, resulting in boosted SERS signal.
(1) Zhang, Z.; Liao, F.; Ma, S.; Gao, S.; Shao, M. Surf. Interface Anal. 2015, 47, 398-402.
(2) Li, M.; Cushing, S. K.; Zhang, J.; Lankford, J.; Aguilar, Z. P.; Ma, D.; Wu, N. Nanotechnology 2012, 23, 115501.
This paper was supported by National Natural Science Foundation of China (Grants 21073033, 21373046 and 21327902), Jiangsu Science and Technology Department (Grant No.2014707), Suzhou Science and Technology Project (Grants ZXG2013036), the State Key Lab of Space Medicine Fundamentals and Application (SMFA12K11), Scientific Innovation Research of College Graduate in Jiangsu Province (CXZZ13_0126), Fundamental Research Funds for the Central Universities and the Program for New Century Excellent Talents in University. The authors thank Professor Derek Lovley from the Department of Microbiology at the University of Massachusetts, Amherst for providing electricigens.
Prof. Dr. Xiangwei Zhao & Zhongze Gu
State Key Laboratory of Bioelectronics
School of Biological Science and Medical Engineering, Southeast University
2 Si Pai Lou, Nanjing 210096, China
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