Interfacial bonding of Co3O4 and oxygen vacancies engineering on ZnO induced efficient peroxymonosulfate activation and pollutants degradation.

A heterojunction of trace Co3O4 bonded on oxygen vacancies (OVs)-rich ZnO (OVs-ZnO/Co3O4) was synthesized via defect-assisted method to promote peroxymonosulfate (PMS) activation and pollutants degradation. Experiments and theoretical calculations demonstrated that electrons could efficiently transfer from OVs-ZnO to Co3O4. OVs-ZnO and Co3O4 played different roles in activating PMS. PMS was easily adsorbed on the OVs-ZnO to form PMS* complex and mediated electron transfer to oxide ciprofloxacin (CIP), whereas, Co3O4 facilitated breakup of peroxide bond to produce radicals. The optimal OVs-ZnO/Co3O4 with Co content of 1.34% exhibited good PMS decomposition ability (94.2% in 30 min) compared to unmodified ZnO (24.2%), stability and anti-interference feature in removing CIP, 96.9% CIP (10 ppm) and 79.6% of total organic carbon were removed in 30 min. Moreover, the OVs-ZnO/Co3O4 achieved 91.2% CIP removal ratio with 1.0 mM PMS via a flow-through device in 180 min. This study proposes a new strategy to enhance PMS activation of ZnO and provides new viewpoint in PMS activation way.

Efficient flocculation pretreatment of coal gasification wastewater by halophilic bacterium Halovibrio variabilis TG-5.

The isolated halophilic bacterial strain Halovibrio variabilis TG-5 showed a good performance in the pretreatment of coal gasification wastewater. With the optimum culture conditions of pH = 7, a temperature of 46 °C, and a salinity of 15%, the chemical oxygen demand and volatile phenol content of pretreated wastewater were decreased to 1721 mg/L and 94 mg/L, respectively. The removal rates of chemical oxygen demand and volatile phenol were over 90% and 70%, respectively. At the optimum salinity conditions of 15%, the total yield of intracellular compatible solutes and the extracellular transient released yield under hypotonic conditions were increased to 6.88 g/L and 3.45 g/L, respectively. The essential compatible solutes such as L-lysine, L-valine, and betaine were important in flocculation mechanism in wastewater pretreatment. This study provided a new method for pretreating coal gasification wastewater by halophilic microorganisms, and revealed the crucial roles of compatible solutes in the flocculation process.

Structure and function of the periostracum in the bivalve Perna viridis.

The periostracum is an outermost coating of all shelled-molluscs such as bivalves, corresponding to the interfacial layer separating the calcareous shells from the environment. It therefore plays a key role in the growth and survival of bivalves. Nevertheless, the periostracum has attracted little attention. Here, using the optical microscope (OM) and field-emission scanning electron microscope (FE-SEM), we investigate the structure and variation of the periostracum in the green mussel Perna viridis. We find that this periostracum has a novel sandwich structure with an outer (ODL) and inner dense layer (IDL) interleaved with a middle fibrous layer (MFL). The latter consists of locally parallel fibers (57-112 nm wide) and exhibits rich iridescent colors with a reversible hydrochromic behavior. Moreover, we find that this periostracum shows a significant variation in individual shells. Impressively, its thickness varies continuously along the shell edge. In addition, the periostracum at the ventral region is not only the thickest in a shell but also reinforced with the inorganic phosphate. We assume that this unusual variation in a same shell probably originates form defensive adaptations to predation and abrasion. Although many questions remain unanswered, this work reveals a new structure model of the periostracum, which not only advances our understanding of the periostracal formation mechanism, but also provides a natural prototype for design and synthesis of biomimetic coating and photonic materials.

A novel metallic silvery color caused by pointillistic mixing of disordered nano-to micro-pixels of iridescent colors.

Rich iridescent structural colors in nature, such as peacock feathers, butterfly wings, beetle scales, and mollusc nacre, have attracted extensive attention for a long time and they generally result from the interaction between light and periodic structures. However, non-iridescent structural colors, such as silvery structural colors, have received relatively little attention, and they usually result from non-periodic structures. Here, using optical microscopy, fiber-optic spectrometry, field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and laser Raman spectroscopy, we investigate the origin of a novel structural color occurring at the edge of a bivalve shell (i.e., an otter shell). We find that: (1) the structural colors are observed to be uniform metallic silvery when viewed with the naked eye; (2) they are surprisingly multicolored with various colorful pixels juxtaposed together when viewed with an optical microscope; (3) each individual pixel shows a single color originating from a periodic, multilayered organic film with definite spacing (d); and (4) different pixels vary significantly in size, shape, and color with different d values (202-387 nm). Finally, we confirm that the macroscopic silvery color results from the pointillistic mixing of nano-to microscale iridescent pixels. We also discuss the special photonic structure responsible for the silvery color. We hope that this work can not only accelerate our comprehension of photonic materials, but also provide new inspiration for the synthesis of silvery white materials.

Perceptual influence of auditory pitch on motion speed.

There is a cross-modal mapping between auditory pitch and many visual properties, but the relationship between auditory pitch and motion speed is unexplored. In this article, the ball and baffle are used as the research objects, and an object collision experiment is used to explore the perceptual influence of auditory pitch on motion speed. Since cross-modal mapping can influence perceptual experience, this article also explores the influence of auditory pitch on action measures. In Experiment 1, 12 participants attempted to release a baffle to block a falling ball on the basis of speed judgment, and after each trial, they were asked to rate the speed of the ball. The speed score and baffle release time were recorded and used for analysis of variance. Since making explicit judgments about speed can alter the processing of visual paths, another group of participants in Experiment 2 completed the experiment without making explicit judgments about speed. Our results show that there is a cross-modal mapping between auditory pitch and motion speed, and high or low tones cause perception shift to faster or slower speeds.

Natural Antireflective Microstructure of Blue Mussel Shells and Biomimetic Replication.

Nature provides various exquisite photonic structures of antireflection. Here, we investigate the color and structure of the inner surface of the shell edge (ISSE) of blue mussel shells, using a fiber optical spectrometer, scanning electron microscope (SEM), and X-ray diffraction (XRD). We demonstrate that the structurally assisted black color of the ISSE is produced by a pyramidal microstructure. Furthermore, we use the two-step biotemplate (TSBT) method to successfully replicate this microstructure. Particularly, we modify this method by using a poly(vinyl alcohol) (PVA) film as the negative replica and an epoxy resin film as the positive replica both fabricated without vacuum treatment. We show that the natural and replicated structures show a reflectivity of ∼4% and of ∼3% in the visible wavelength. Finally, we hope our investigation can provide basic data for the study of the bioinspired antireflective structures, which have a promising application in smart windows and optical devices.

Natural gradient composite made of aragonite nanofibers: the ligament of bivalve Acesta marissinica.

Here we investigate the nanostructure of the fibrous ligament (FL) in bivalve Acesta marissinica, using scanning electron microscopy (SEM) and an image processing method. We find this FL is mirror symmetrical in its transverse section and consists of aragonite nanofibers and organic materials, the former of which are generally arranged in a featherlike pattern along the mirror plane. Further, we find this FL has a unique graded architecture. From its inner (near the mirror plane) to lateral part (near the ligament-shell junction), the nanofiber angle gradually increases from about 20° to 45°, the nanofiber volume fraction remarkably decreases from 70% to 14%, and the nanofiber diameter also changes from about 137 nm to 85 nm. This novel design allows this FL to be both resilient and strong to meet the biofunctional requirements. We expect the present findings may help us to develop new functionally graded materials (FGMs) and further understand bivalve life processes.

Direct observation of the crystallographic relationship between interlamellar membranes and aragonite tablets in bivalve nacre.

Nacre is one of the most attractive models for understanding the fundamental principles of biomineralization and for designing bio-inspired materials due to its simple structure but with unusual mechanical properties. It is made up of lamellae of aragonite tablets bonded together by the organic interlamellar membranes (ILMs), of which the latter occupy less than 5wt% of nacre. For a long time, previous authors failed to directly observe the crystallographic relationship between the ILM and aragonite tablet in bivalve shells. Here, using high resolution transmission electron microscope (HRTEM), we investigate the interfacial structure of the domed tablets that coexist with the flat ones in green mussels. We directly observed that the ILMs are oriented with the underlying tablets and connected with the latter via a superlattice region. The finding advances our current knowledge of nacre biomineralization and may help to design novel nacre-like materials.

Biomineralization on the wavy substrate: Shape transition of nacreous tablets from pyramids of amorphous nanoparticles to dome-capped prisms of single crystals.

UNLABELLED: Nacre has long served as a model for understanding the biomineralization process and designing bio-inspired materials. However, our current knowledge about nacre is essentially based on the investigation of the flat nacre, where its building blocks, the aragonite tablets, grow on the flat substrate. Here, using field-emission scanning (SEM) and transmission electron microscopy (TEM), we investigate a new type of nacre, where the tablets grow on the wavy substrate. We first show that: (1) with growth, the tablet undergoes a shape transition from a pyramid to a frustum and finally to a dome-capped prism; (2) the shape transition occurs earlier at the downslope side of the tablet than at the upslope due to the slope effect; and (3) the shape of the top and base facet of the mature tablet depends on that of the substrate surface. In addition, we report that the tablet initially consists of amorphous calcium carbonate (ACC) nanoparticles, which gradually transforms into a single crystal of aragonite with time. Finally, we propose that the shape transition is induced by the crystal lattice mismatch between the tablet and substrate. We conclude that the topography and strain of the substrate play key roles in the biomineralization process of nacre. STATEMENT OF SIGNIFICANCE: Nacre is the iridescent inner lining of many mollusk shells, consisting of more than 95wt% aragonite tablets and minor biopolymers. Owing to its superior mechanical properties, nacre has been extensively studied. However, nearly all previous works focused on the flat tablets. Here, we focus on the curved tablets grown on the wavy substrate. The main finding is that the topography and strain of the substrate play key roles in the growth process of the tablets. They not only induce the shape transition of the tablets from pyramids to dome-capped prisms, but also control the final shape of the tablets. The finding advances our understanding of the biomineralization process of nacre.

A humidity sensitive two-dimensional tunable amorphous photonic structure in the bivalve ligament of Meretrix linnaeus.

A humidity sensitive two-dimensional tunable amorphous photonic structure (2D TAPS) in the bivalve ligament of Meretrix linnaeus (LML) was reported in this paper. The structural color and microstructure of LML were investigated by reflection spectra and scanning electron microscopy, respectively. The results indicate that the LML has complex structural colors from blue to orange in the wet state from ventral to dorsal, which are derived from the aragonite fiber diameter increases continuously from ventral to dorsal of the ligament. The reflection peak wavelength of the wet LML can blue-shift from 522 nm to 480 nm with the air drying time increased from 0 to 60 min, while the reflectivity decreases gradually and only a weak reflection peak at last, relevant color changes from green to light blue. The structural color in the LML is produced by a two-dimensional amorphous photonic structure consists of aligned aragonite fibers and proteins, in which the diameters of the aragonite fiber and the inter-fiber spacing are 104±11 nm and 126±16 nm, respectively. Water can reversibly tune the reflection peak wavelength and reflectivity of this photonic structure, and the regulation achieved through dynamically tune the degree of order and lattice constant of the ligament in the different wet states.

A humidity sensitive two-dimensional tunable amorphous photonic structure in the outer layer of bivalve ligament from Sunset Siliqua.

A humidity sensitive two-dimensional tunable amorphous photonic structure (2D TAPS) in the outer layer of bivalve ligament from Sunset Siliqua (OLLS) was reported in this paper. The structural color and microstructure of OLLS were investigated by reflection spectra and scanning electron microscopy, respectively. The results indicate that the reflection peak wavelength of the wet OLLS blue-shifts from 454 nm to 392 nm with the increasing of air drying time from 0 to 40 min, while the reflectivity decreases gradually and vanishes at last, relevant color changes from blue to black background color. The structural color in the OLLS is produced by a two-dimensional amorphous photonic structure consisting of aligned protein fibers, in which the diameter of protein fiber and the inter-fiber spacing are 101 ± 12 nm. Water can reversibly tune the reflection peak wavelength and reflectivity of this photonic structure, and the regulation achieved through dynamically tuning the interaction between inter-fiber spacing and average refractive index.

Unique morphology and gradient arrangement of nacre's platelets in green mussel shells.

Nacre has long served as a classic model in biomineralization and the synthesis of biomimetic materials. However, the morphology and arrangement of its basic building blocks, the aragonite platelets, are still under hot debate. In this study, using a field emission scanning electron microscope (SEM), a high-resolution transmission electron microscope (HRTEM), and an X-ray diffractometer (XRD), we investigate the platelets at the edges and centers of green mussel shells. We find that 1) flat and curved platelets coexist in green mussel shells; 2) the immature platelets at the shell edge are aggregates of aragonite nanoparticles, whereas the immature ones at the shell center are single crystals; and 3) the morphology and thickness of the platelets exhibit a gradient arrangement. Based on these findings, we hypothesize that the gradient in the thickness and curvature of the platelets may probably result from the difference in growth rate between the edge and the center of the shell and from the gradient in compressive stress imposed by the closing of the shells by the adductor muscles or the withdrawal of the periostracum by the mantle. We expect that the presented results will shed new light on the formation mechanisms of natural composite materials.

Biogenic nanospheres of amorphous carbonated Ca-Mg phosphate within the periostracum of the green mussel Perna viridis.

Recently there is increasing evidence that the shell biomineralization proceeds via an amorphous precursor route. Therefore, the search for and investigation of amorphous biominerals in bivalve shells are of great importance and interest. Here, using a scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), and Fourier transform infrared spectrometer (FTIR), we investigate the microstructure and mineralogy of the periostracum in Perna viridis. We find that: (1) the periostracum has three layers, of which the inner and outer layer are of proteins, while the middle layer is mineralized with nanospheres of amorphous biominerals; (2) the nanospheres are of amorphous carbonated Ca-Mg phosphate (ACCP), where the CO3(2)(-)/PO4(3)(-) weight ratio is estimated to be ∼0.3, and the Ca/P and Ca/Mg atomic ratio is ∼1.4 and 1.6, respectively; (3) the nanospheres, with a diameter of 43-106nm, are found to assemble into spherules with a diameter of 160-500nm, which are further organized into parallel microlayers separated by the proteins; and (4) the nanospheres are assumed to function as the pH stabilizer to facilitate the shell's initial mineralization. Finally, we expect that these findings will advance our understanding of the shell's biomineralization process.

From colloidal nanoparticles to a single crystal: new insights into the formation of nacre's aragonite tablets.

Nacre has long served as a model for understanding the biomineralization mechanism and designing bio-inspired materials. However, its basic building blocks, the aragonite tablets, are still under debate in terms of their fine structure at the nanoscale and corresponding formation mechanism. Here, using a field emission scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), and X-ray diffractometer, we comparatively investigate the immature and mature tablet from the green mussel's nacre. We find that: (1) the early immature tablet consists of closely-packed colloidal nanoparticles, which contain nanocrystals surrounded by the amorphous calcium carbonate (ACC) phase. Moreover, these nanocrystals are generally different in shape, size, and orientation; (2) the immature tablet can grow via oriented attachment besides via transformation of the ACC phase; and (3) with growth, the colloidal nanoparticles gradually increase in crystallinity and size until fully crystallized and fused together, leading to a mature tablet that is a monolithic single crystal of aragonite. Based on these findings, we propose a new model showing how the mature tablet evolves from the primary colloidal ACC nanoparticles. We expect this work will provide new insights into the formation of single crystal biominerals via the amorphous precursor route.

Identification and secondary structure analysis of a keratin-like fibrous protein discovered in ligament of the bivalve Siliqua radiata.

A novel keratin-like fibrous protein K58 with molecular weight of about 58 kDa was discovered in bivalve Siliqua radiata ligament and identified by amino acid composition and MALDI-TOF-TOF analysis. We found that the protein is composed of cylindrical fibers (~160 nm in diameter) and contains high glycine (27.4%) and phenylalanine (10.5%) contents. Furthermore, it is homologous to keratin type II cytoskeletal 1, with repeat motifs of SGGG and SYGSGG. FTIR and secondary structure analysis indicate that K58 is composed of 46.2% ß-sheet, 33.4% ß-turn, 13.1% α-helix, and 4.7% disordered structure. This structure feature is closely related to the superior tensile strength, elasticity, and solvent resistance property of K58. These discoveries provide some evidence for evolution of keratin and fibrous proteins and prompt further studies of ligament fibrous proteins.

[Unique optical reflection spectra of bivalve nacre and its origin].

The structural color and microstructure of nacre in bivalve shells of Pinctada maxima were investigated by optical reflection spectra, scanning electron microscopy and theoretical simulation. The following results are obtained: (1) The thickness of aragonite tablets decreased significantly from growing to central region of nacre, which leads to a blue-shift of reflection peak wavelength with the same reflection order obviously; (2) The structural color of nacre in bivalve shells of Pinctada maxima is derived from the combination effects of aragonite-protein multilayer structure and yellow pigments in nacre.

[XRD and FTIR spectra characteristics of nacreous layer in perna viridis].

The XRD and FTIR of aragonites in nacreous and prismatic layer of perna viridis were systematically measured, and the frequency variations of v1, v2 and v4 band of aragonites were especially analyzed. The results showed that both of them were aragonite and the frequency of v2 band differed in them, but the frequencies of other two bands were not altered and had the same values with cavernous aragonite. In the same specie of shell, the frequency of v2 band in nacreous layers was greater than that in prismatic layers, and there was a frequency shift of v2 band between them. For the first time, the phase transformation of biogenic aragonite was detected. After nacreous aragonite was heated at 300 degrees C, the frequency shift of v2 band was found. So it is concluded that the biogenic aragonite is related to the thermal effects in crystallizing process, meanwhile it stores excess energy. All of these can provide experiential basis for studying biomineralization theory.

[In situ resonance Raman spectra of organic pigments in freshwater cultured pearls].

In situ resonance Raman spectra of Chinese freshwater pearls were collected and analysed systematically with three different excitation wavelengths at lambda = 514, 633 and 785 nm. At the same time, the Raman spectra of eggshells of Pomacea canaliculata were also collected under the same experimental conditions in order to compare with pearls' Raman spectra. The conclusions were as follows: (1) Frequency dispersions of Raman spectra of organic pigments were obviously observed in Raman spectra of pearls. In contrast, Raman spectra of organic pigments in eggshells of Pomacea canaliculata showed no frequency dispersion phenomena; (2) It was considered that the organic pigments in pearls were polyacetylenic materials but not carotenoids which was proposed by previous researchers, and the organic pigments in eggshells of Pomacea canaliculata were carotenoids; (3) The conjugated (>=C number of polyacetylenic material in pearls was calculated to be about 10 and 16, and the conjugated C[double bond]C number of carotenoid in eggshells of Pomacea canaliculata was about 13 based on the Raman shifts caused by conjugated C[double bond]C double bonds.

[FTIR spectroscopic study on natural aragonitic ceramics-bivalve shells of Hyriopsis cumingii].

The two shell layers, i. e. , the ligament (HCL) and the inner nacreous layers (HCN) from bivalve shells of Hyriopsis cumingii, both composed of aragonite by powder XRD analysis, w ere comparatively analyzed by FT IR spectrometry. The results show that: (1) the features of vz and v3 bands of aragonite are clearly different between the two shell layers, as the v2 band of HCN aragonite shows a 6. 5 cm(-1) blue-shift, but the vs band shows a 22. 7 cm(-1) red-shift compared to that of HCL aragonite; (2) the full width at half maximum of v1 and v3 bands of HCN aragonite is nearly doubled compared to that of HCL aragonite; (3) however, the features of v1 and v4 bands are independent on shell layers. It is suggested that the anisotropic frequency shifts of the aragonite in HCN and HCL perhaps result from the size effects of aragonite crystals.

[Characteristics of FTIR spectra of biogenic aragonite in mollusk shells].

The FTIR spectra of aragonites in outer and inner layers of thirteen species of mollusk shells were systematically measured, and the frequency variations of frequency 1, frequency 2 and frequency 4 bands of the aragonites with the positions of shell layers were analyzed. The results showed that the frequency of v2 band differed in different species of shells and the positions of shell layers, but the frequencies of the other two bands were not altered, and had the same values with synthetic aragonites. In the same species of shells, the frequency of frequency 2 band in inner layers was greater than that in outer layers, and the frequency shift of frequency 2 band between inner and outer layers was in the range of 0.5 x 4.5 cm(-1) in all studied samples. The detection of frequency shift of frequency 2 band in different layers of aragonitic mollusk shell was first reported in this paper.