Abstract
Biomineralization in general is based on electrostatic interactions and molecular recognition of organic and inorganic phases. These principles of biomineralization have also been utilized and transferred to bio-inspired synthesis of functional materials during the past decades. Proteins involved in both, biomineralization and bio-inspired processes, are often piezoelectric due to their dipolar character hinting to the impact of a template’s piezoelectricity on mineralization processes. However, the piezoelectric contribution on the mineralization process and especially the interaction of organic and inorganic phases is hardly considered so far. We herein report the successful use of the intrinsic piezoelectric properties of tobacco mosaic virus (TMV) to synthesize piezoelectric ZnO. Such films show a two-fold increase of the piezoelectric coefficient up to 7.2 pm V−1 compared to films synthesized on non-piezoelectric templates. By utilizing the intrinsic piezoelectricity of a biotemplate, we thus established a novel synthesis pathway towards functional materials, which sheds light on the whole field of biomimetics. The obtained results are of even broader and general interest since they are providing a new, more comprehensive insight into the mechanisms involved into biomineralization in living nature.
Highlights
There are many examples for biomineralization processes in living nature leading to sophisticated functional materials, such as nacre, teeth or bones[1,2,3]
Some viruses possess the structural requirements for piezoelectricity. Virus templates such as tobacco mosaic virus (TMV)[9] and M13 phages[10] exhibit themselves electromechanical properties due to dipole formation within the protein structure, giving high effective piezoelectric response
Due to their low stiffness, flexoelectric effects can contribute to global piezoresponse as it was reported for single TMV via piezoresponse force microscopy (PFM) measurements[9], for which the piezoelectric constant d33 was found to be as high as 12 pm V−1
Summary
For carboxyl termination, cleaned silicon wafers were immersed in triethoxysilylpropyl succinic anhydride (TESPSA; 10% in toluene) for 16h and subsequently sonicated in toluene, N,N-dimethylformamide (DMF) and nanopure water (20 minutes each) before drying under an N2 stream. The substrate was horizontally positioned on a sample holder connected to a computer controlled linear motor (KSV Instruments, Espoo, Finland) ensuring continuous motion with constant withdrawal velocity. The functionalized substrates were subsequently immersed in the freshly prepared reaction solution and kept at 60 °C in an oil bath for 90 minutes. Piezoresponse force microscopy (PFM) was performed on a Digital Instruments MultiModeTM 8 from Bruker with a NanoScope V controller by applying an AC electric field (driving excitation) to the tip of the AFM while working in contact mode, and measuring the induced mechanical deformation of the sample at the same frequency due to the inverse piezoelectric effect. Detailed information on additional methods can be found in the Supplementary Methods: substrate preparation, purification of TMV, immobilization of single TMV, zeta potentials, SEM, and AFM
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