Preparation of hexagonal GeO₂particles with particle size and crystallinity controlled by peptides, silk and silk-peptide chimeras

Abstract

We demonstrate the use of silk based proteins to control the particle/crystallite size during GeO 2 formation, using a bio-mimetic approach at circumneutral pH and ambient temperature. Multicrystalline GeO 2 was prepared from germanium tetraethoxide (TEOG) in the presence of different silk-based proteins: Bombyx mori silk (native silk) and two chimeric proteins prepared by linking a germania binding peptide (Ge28: HATGTHGLSLSH) with Bombyx mori silk via chemical coupling at different peptide loadings (silk-Ge28 10% and silk-Ge28 50%). The mineralisation 10 activity of the silk-based proteins was compared with that of peptide Ge28 as a control system. GeO 2 mineralisation was investigated in water and in citric acid/bis-tris propane buffer at pH 6. Morphology, particle size, crystallinity, water and organic content of the materials obtained were analysed to study the effect of added biomolecules and mineralisation environment on material properties. In the presence of silk additives well-defined cube-shape hybrid materials composed of hexagonal germania and up to ca. 5 wt% organic content were obtained. The cubic particles 15 ranged from 0.4 to 1.4 m in size and were composed of crystalline domains in the range 35-106 nm depending on the additive used and synthesis conditions. The organic material incorporated in the mineral did not appear to affect the unit cell dimensions. The silk and chimeric proteins in water promote material formation and crystal growth, possibly via an effective ion-channelling mechanism. The germania binding peptide alone did not have any significant effect on reaction rate, yield or the material's properties compared to the blank. Interestingly, the peptide 20 content in the silk chimeras tested did not affect mineralisation. The presence of buffer inhibited mineral condensation rate and yield. The use of silk-based biomolecules allows control of crystallite/particle size of hybrid materials opening up opportunities for bio-inspired approaches to be applied for the synthesis of functional germania based devices and materials.

Extreme biomimetic approach for developing novel chitin-GeO2 nanocomposites with photoluminescent properties

“…The chitin spectrum shows bands characteristic of the α-chitin polymorph and corresponds to previously published data [50,51]. The triplet band, characteristic of the GeO 2 hexagonal phase, is clearly visible between 588 and 520 cm -1 and is attributed to the Ge-O-Ge υ4 vibrational mode [24,27,45,[52][53][54][55]. The low-frequency bands around 555 cm -1 are equivalent with the longitudinal optic (LO) bending mode observed in the Raman spectrum at ~589 cm -1 (Fig.…”

“…It was reported that these organic materials incorporated into the mineral did not appear to affect the unit-cell dimensions. Moreover, the germania-binding peptide alone did not have any significant effect on reaction rate, yield, or the material's properties in comparison with the control reference [45].…”

“…7). Furthermore, peaks assigned to Ge-O-Ge (the antisymmetric stretching mode of hexagonal GeO 2 ) were found at 892 and 960 cm -1 [25,45,56] (Fig. 6); these peaks are equivalent to Nano Res.…”

“…On the other hand, Sewell et al [44] claimed that poly(amidoamine) (PAMAM) dendrimers can be used for the synthesis of germanium-oxide nanoparticles under ambient conditions. Very recently, multicrystalline GeO 2 was prepared from germanium tetraethoxide (TEOG) in the presence of different silk-based peptides [45]. It was reported that these organic materials incorporated into the mineral did not appear to affect the unit-cell dimensions.…”

Synthesis of SiO2 based nanocomposite of Agar and its characterization

“…FTIR spectrum of pure Agar confirmed by in the wavelength range of 950 and 1200 cm -1 are considered as the 'finger print' region for carbohydrates as it allows the identification of major chemical groups in polysaccharides [25]. This region is dominated by ring vibrations overlapped with stretching vibrations of (C-OH) side groups and the (C-O-C) glycosidic bond vibration.…”