Diatom Frustules Research Articles

Laser powder bed fusion of diatom frustule inspired bionic NiTi lattice structures: compressive behavior and shape memory effect

This work aimed to propose a feasible lattice structure to fully exploit the advantages of NiTi shape memory alloy, providing more options for the development of functional components such as micro-vibration isolators and smart actuators in the aerospace field. Inspired from the Campylodiscus diatom frustule, the novel NiTi-based truss lattice structures were designed and fabricated by laser powder bed fusion. Four lattice structures with different ratios of traditional sharp angle (TSA) number to bionic arc angle (BAA) number (ξ TSA/BAA) were designed and the effect of the ξ TSA/BAA on the compressive behaviors and shape memory effect (SME) was experimentally investigated and the failure mechanism was revealed using finite element (FE) simulation. Results showed that all components possessed a nearly dense microstructure (>98%) and high dimensional accuracy (size error < 2.5%). As the ratio of the number of TSA to BAA decreased, the maximum first peak force decreased by 31.5%, and the elastic modulus Eϵ =0.2% decreased from 1.81 GPa to 1.19 GPa. And the failure modes changed from layer-by-layer failure to shear failure. The simulation results were in agreement with the experimental results and revealed that the ξ TSA/BAA affected the compressive behaviors by controlling the stress value and distribution of components. Results of SME tests showed that the introduction of BAA design can improve the recovery performance, and the ξ 0/6 component exhibited the largest recoverable ratio and the lowest accumulated residual strain.

Sustainable treatment of dye wastewater by recycling microalgal and diatom biogenic materials: Biorefinery perspectives

Discharge of untreated or partially treated toxic dyes containing wastewater from textile industries into water streams is hazardous for environment. The use of heavy metal(s) rich dyes, which are chemically active in azo and sulfur content(s) has been tremendously increasing in last two decades. Conventional physical and chemical treatment processes help to eliminate the dyes from textile wastewater but generates the secondary pollutants which create an additional environmental problem. Microalgae especially the diatoms are promising candidate for dye remediation from textile wastewater. Nanoporous diatoms frustules doped with nanocomposites increase the wastewater remediation efficiency due to their adsorption properties. On the other hand, microalgae with photosynthetic microbial fuel cell have shown significant results in being efficient, cost effective and suitable for large scale phycoremediation. This integrated system has also capability to enhance lipid and carotenoids biosynthesis in microalgae while simultaneously generating the bioelectricity. The present review highlights the textile industry wastewater treatment by live and dead diatoms as well as microalgae such as Chlorella, Scenedesmus, Desmodesmus sp. etc. This review engrosses applicability of diatoms and microalgae as an alternative way of conventional dye removal techniques with techno-economic aspects.

Diatomaceous earth as a drug-loaded carrier in a glass-ionomer cement

The effect of a natural filler (diatomaceous earth [DE], a promising drug-delivery agent) and its content was investigated on the performance of a model glass-ionomer cement (GIC). Three sample series, differing in DE content (0, 2.5 and 5 wt%), were prepared using a commercial GIC as a matrix (3M Ketac Molar Easymix). The resultant surface microhardness and roughness, wear performance, and compressive strength of the samples were measured after the samples had been stored in deionized water at 37°C for a fixed time. Moreover, the film thickness was tested for the freshly mixed samples. The numerical data was subjected to statistical analysis, in order to test the null hypotheses of the equality of the measured properties between the reference and the DE-modified samples. According to the results, diatomaceous earth particles are uniformly distributed in the GIC matrix, and the cavities of frustules tend to be filled with the GIC. This translates into the observed performance of the DE-loaded GIC. Compared with the reference material (0 wt% DE), the surface microhardness (2.5 wt% DE, p = 0.014; 5 wt% DE, p = 0.005) and roughness (e.g. Ra; 2.5 wt% DE, p = 0.003; 5 wt% DE, p < 0.001) are increased. No effect on the wear performance (p = 0.530 and 0.256, respectively) or compressive strength (p = 0.514) was noticed in the case of DE partially substituting the glass phase. Based on the study results, it is evidenced that diatom frustules are a suitable filler for application in conventional glass-ionomer cements as the glass-substituting drug-loaded carrier. Notably, however, the surface finish method of the DE-filled materials needs development.

Further investigations towards luminescence dating of diatoms

Following up on previous attempts to date diatom frustules, further investigations were made on 1) extracting diatom frustules devoid of inorganic luminescent grains, 2) developing an equivalent dose estimating protocol based on the diatomite luminescence characterization, and 3) testing the applicability of this protocol on two lacustrine profiles. Diatom frustules were extracted in such a way that they are almost devoid of non-biogenic polymineral grains, confirmed by field emission scanning electron microscope (FE-SEM) observation and energy dispersive X-ray (EDX) analysis. The presence of opal was confirmed by X-ray diffraction (XRD) spectrometric analysis. The optimized luminescence signal that could be used for equivalent dose estimation was blue stimulated UV emission with a preheat temperature of 200 °C. The thermoluminescence glow curve peaking at 245 °C might be the source of this signal. In this study the characteristic dose was found to be ∼1500 Gy. Two sediment profiles were explored for luminescence dating, fading rates and a-values were found different between profiles. This discrepancy can be resolved 1) by measuring luminescence characteristics across different regions, or/and 2) by using species-specific luminescence measurements. This attempt has yielded an encouraging set of luminescence ages, with diatom frustule ages comparable to fine grain polymineral ages.

Gold Nanoparticle-Functionalized Diatom Biosilica as Label-Free Biosensor for Biomolecule Detection.

Diatom biosilica (DBs) is the cell wall of natural diatom called frustule, which is made of porous hydrogenated amorphous silica possessing periodic micro- to nanoscale features. In this study, a simple, sensitive, and label-free photoluminescence (PL) immune-detection platform based on functionalized diatom frustules was developed. Gold nanoparticles (AuNPs) deposited on poly-dopamine-coated diatom frustules via in situ deposition which considerably decreased the intrinsic blue PL intensity of diatom biosilica. Then, goat anti-rabbit immunoglobulin G (IgG) was added to functionalize diatom biosilica-poly-dopamine-AuNPs (DBs-PDA-AuNPs). PL studies revealed that the specific binding with antigen rabbit IgG increased the peak intensity of PL in comparison with the non-complimentary antigen (human IgG). The enhancement in PL intensity of DBs-PDA had a linear correlation with antigen (rabbit IgG) concentration, whose limit of detection (LOD) reached 8 × 10-6 mg/ml. Furthermore, PL detection based on DBs-PDA-AuNPs showed a high detection sensitivity with the LOD as low as 8 × 10-9 mg/ml and spread over almost eight orders of magnitude, making it suitable for the sensitive quantitative analysis of immune complex compared with traditional fluorescence immunoassay. Hence, the study proves that the AuNP-functionalized diatom frustules can serve as an effective biosensor platform for label-free PL-based immunoassay.

Ultrastructure of setae of a planktonic diatom, Chaetoceros coarctatus

Silica frustules of most planktonic diatoms have many shallow holes in which the length (L) is smaller than the width (W). The present study focuses on a silica ultrastructure of setae of a planktonic diatom having deep (L/W > 1) holes. Here, we characterized microscopically patterned nanoholes on the silica walls of thick, robust, and hollow setae of a colony of Chaetoceros coarctatus. Basically, tetragonal poroid arrangements with and without a costa pattern are observed on the inner and outer surfaces, respectively, for three kinds of curving hollow setae attached to the anterior, intercalary, and posterior parts of the colony. The seta structures including specific poroid arrangements and continuity of deep nanoholes depend on the location. The deep nanoholes ∼90 nm wide are elongated from 150 to 1500 nm (L/W ∼17) with an increase in the wall thickness of the polygonal tubes of the setae. The inside poroid array, with a period of 190 nm in the extension direction of setae, is lined by parallel plates of the costae. However, the poroid arrangement on the outer surface is disordered, with several holes obstructed with increasing wall thickness of the posterior terminal setae. According to the movement of a colony in a fluid microchannel, the thick curving terminal setae is suggested to involve attitude control and mechanical protection. Using an optical simulation, the patterned deep through-holes on the intercalary setae were suggested to contribute anti-reflection of blue light in the wavelength range of 400 to 500 nm for the promotion of photosynthesis in seawater.

Poly(lactic acid)/artificially cultured diatom frustules nanofibrous membranes with fast and controllable degradation rates for air filtration.

The worldwide pandemic, coronavirus COVID-19, has been posing a serious threat to the global economy and security in last 2 years. The monthly consumption and subsequent discarding of 129 billion masks (equivalent to 645,000 tons) pose a serious detrimental impact on environmental sustainability. In this study, we report a novel type of nanofibrous membranes (NFMs) with supreme filtration performance and controllable degradation rates, which are mainly composed of polylactic acid (PLA) and artificially cultured diatom frustules (DFs). In this way, the filtration efficiency of particular matter (PM) and the pressure drop were significantly improved in the prepared PLA/DFs NFMs as compared with the neat PLA NFM. In specific, with incorporation of 5% DFs into fibers, PM0.3 removal with a filtration efficiency of over 99% and a pressure drop of 109 Pa were achieved with a membrane thickness of only 0.1 mm. Moreover, the yield strength and crystallinity degree of the PLA/DFs5 NFMs were sharply increased from 1.88 Mpa and 26.37% to 2.72 Mpa and 30.02%. Besides those unique characters, the PLA/DFs5 presented excellent degradability, accompanied by the degradation of 38% in 0.01 M sodium hydroxide solution after 7 days and approximately 100% in natural condition after 42 days, respectively. Meanwhile, the environmentally friendly raw materials of the composite polylactic acid and artificially cultured diatom frustules could be extracted from corn-derived biomass and artificially cultivated diatoms, ensuring the conformance to carbon neutrality and promising applications in personal protection.Graphical abstract Supplementary informationThe online version contains supplementary material available at 10.1007/s42114-022-00474-7.

Ti3C2Tx-coated diatom frustules-derived porous SiO2 composites with high EMI shielding and mechanical properties

Effective electromagnetic interference (EMI) shielding materials have garnered substantial interest for their efficacy in attenuating electromagnetic wave energy, ensuring data confidentiality, ensuring the operational stability of fragile electronic systems. To begin, artificially cultured diatom frustules (DF)-derived porous silica (DFPS) skeletons were constructed as templates in this study. Porous ceramics hot-pressed at 800 °C displayed a high compressive strength with a high specific surface area due to their three-dimensional (3D) multilayered and porous structures. Then, mechanically robust Ti3C2Tx/DFPS composites with exceptional EMI shielding performance were fabricated by immersing porous DF-based ceramics into Ti3C2Tx solutions and annealing in an argon environment to increase the materials’ shielding efficiency (SE). The EMI SE of composites hot-pressed at 800 °C achieved the maximum EMI SE of 43.2 dB in the X-band and a compressive strength of 67.5 MPa, establishing a hitherto unreported balance of mechanical characteristics and shielding performance. Prolonged transmission paths, multiple dissipation, scattering and reflection of electromagnetic energy were achieved using a well-maintained hierarchical porous silica framework decorated with MXene, with adsorption caused by surface MXene serving as the primary shielding mechanism for the composites. Due to their superior overall performance, MXene/DFPS EMI shielding composites have a bright future in the aircraft sector as delicate electronic device components.

Antagonistically Functionalized Diatom Biosilica for Bio‐Triboelectric Generators

Although biomaterial-based triboelectric nanogenerators (Bio-TENGs) for use in wearable electronics and implantable sensors have been developed, power generation is not suitable for satisfying the basic requirements for practical applications. Here, to greatly enhance output performances of Bio-TENG devices, an antagonistic approach of diatom frustules (DFs) with amine and fluorine chemical functionalizations is reported. The DFs are treated with piranha solution to increase the density of hydroxyl groups and tribo-positive and tribo-negative composite films are designed with antagonistically functionalized DFs. The tribo-positive composites having electron donating functionality consist of aminated DFs and cellulose nanocrystals (CNCs), while the tribo-negative composite is composed of fluorinated DFs and polydimethylsiloxane (PDMS). An antagonistically and chemically functionalized TENG (ACF TENG) with an efficient contact area of 9.6 cm2 under a force of 8 N and a frequency of 5Hz exhibits an output voltage of 248V, a short-circuit current of 16.4 µA, and a power density of 2.01 W m-2 , which is 16.6 times higher than a reference (CNC:PDMS) TENG. This study shows a simple antagonistic approach for chemical functionalization as an efficient method to manipulate the tribo-polarity of bio-additives for enhancing power generation of Bio-TENGs.

Changes in phytoplankton and biomineral content of particles during episodic fluxes to abyssal depth

AbstractLarge episodic pulses of particulate organic carbon (POC) at the deep‐sea (~ 4000 m) time‐series Sta. M in the Northeast Pacific Ocean have increased in frequency and magnitude over the past 32 years. We inferred the ecological drivers of these events by quantifying the phytoplankton and biomineral composition within particles collected by bottom‐moored sediment traps immediately before, during, and after 14 high‐flux events. Samples collected during high‐flux events contained a significantly different phytoplankton community from other sampling periods. These particles contained relatively fewer intact phytoplankton cells and a sustained contribution from fragmented diatom frustules from species typical in coastal blooms. Biomineral fluxes did not appear to be driving high‐flux events. We suggest that most of the observed high‐flux events were generated by offshore transport of coastal diatom blooms, but that these particles were also highly transformed by deep‐sea pelagic food webs before reaching bathypelagic depths.

Ultrafast bulk degradation of polylactic acid by artificially cultured diatom frustules

In the field of governing our “Plastic Planet”, polylactic acid (PLA) has been considered to be a promising and ecologically friendlier alternative to traditional petroleum-based plastics. However, PLA-based products degrade slowly in the natural environment, likely resulting in a large accumulation of PLA waste worldwide in the near future. Herein, we have incorporated artificially cultured diatom frustules (DFs) into PLA, and found an improvement of more than eightfold on the degradation rate, from more than 24 months to 3 months or even less, as compared with the pure PLA. Mechanistic investigations illustrate that DFs change the degradation behavior of PLA from surface erosion to bulk erosion by the induced microfibril crystals. Simulation analysis verifies that the unstable crack propagation inside the PLA matrix greatly accelerates the degradation. The method developed in this work provides an efficient way to achieve rapid and adjustable degradation of biodegradable polymers for the urgent and widespread usage of green plastic productions.

Insecticidal and repellency effects of a Turkish diatomaceous earth formulation (Detech) on adults of three important pests of stored grain

In this study, laboratory experiments were conducted in order to assess the insecticidal and repellency effects of a novel Turkish diatomaceous earth (DE) formulation (Detech) on adults of the rice weevil, Sitophilus oryzae (L., 1763) (Coleoptera: Curculionidae), the confused flour beetle, Tribolium confusum du Val., 1863 (Coleoptera: Tenebrionidae), and the lesser grain borer, Rhyzopertha dominica (F., 1792) (Coleoptera: Bostrichidae). For the insecticidal activity, bioassays were conducted with soft wheat treated with 0, 600 and 900 ppm of Detech at 25 ± 1°C and 65 ± 5% RH and progeny production was assessed after 45 days. For the repellency tests, two-choice tests on mono-layer wheat were conducted at 1,000 ppm of Detech at 25 ± 1°C and 65 ± 5% RH. Overall, Detech was effective against T. confusum and S. oryzae adults in wheat, causing 82% to 100% mortality at 600 and 900 ppm after 7 and 14 days exposure. The complete, or almost complete, progeny inhibition of S. oryzae were found at both concentrations, whereas the highest reduction in R. dominica progeny (84%) was obtained at 900 ppm. Detech was highly and moderately repellent to T. confusum and S. oryzae adults, respectively, whereas it had no or low repellency effect on R. dominica adults. In conclusion, Detech, which consists of a mixture of three DE deposits with different diatom frustules has potential for use against stored-grain insect pests as a promising grain protectant. Experiments were conducted in 2020-2021 in Entomology Laboratory of Tekirdağ Namık Kemal University and Kahramanmaraş Sütçü İmam University.

The effect of ethanol or long-time reaction on the diatom test in water samples using sodium hypochlorite

BackgroundThe diatom test method using sodium hypochlorite (NaClO) was equivalent to the conventional method in water samples. However, the method using NaClO was inferior to the conventional method in lung samples, in which ethanol was used and the reaction with NaClO was longer compared with the method in water samples. Using water samples, we aimed to clarify whether these differences affect the diatom test result. Materials and methodsThirteen water samples from natural water sources were each divided into four parts corresponding to four (2 × 2) digestion methods: 3 “digestion” vs. 1 “digestion” and with ethanol vs. without ethanol. After the base-2 logarithmic transformation, the diatom counts were analyzed using three-way analysis of variance (ANOVA); factor 1 was “digestion times,” factor 2 was “ethanol,” and factor 3 was “sample number,” and the interaction between factors 1 and 2 was also analyzed. ResultsThe geometric means of the diatoms from the 3 “digestion” with ethanol method, the 3 “digestion” without ethanol method, the 1 “digestion” with ethanol method, and the 1 “digestion” without ethanol method were 373.5, 551.8, 436.6, and 522.0, respectively. ANOVA showed a significant difference in factor 2 (P = 1.7 × 10-4). There was no significant difference in factor 1 (P = 0.46), and no significant interaction between factors 1 and 2 (P = 0.13). ConclusionEthanol may decrease the diatom count in the diatom test using NaClO. In contrast, the diatom frustules do not dissolve through three-times digestion using NaClO.

Alterations of physical properties and microstructure of marine diatomite owing to variation of diatom content

Diatomite is a natural soil and comprises mainly clays and diatom frustules and is distributed generally in the marine environment. The presence of the diatom frustules imparts the diatomite physical properties different from those of common clays and sands, such as high Atterberg limits, low density, and high specific surface area. However, how the diatom frustules affect the physical properties of diatomite has yet to be established, especially from a microscopic perspective. This study linked the physical characteristics and microstructure of diatom frustules by performing laboratory tests on diatom–kaolin mixtures with different diatom contents. The results reveal the considerable influence of the diatom content on the physical characteristics of diatomite, with the feature alterations explained by microstructural investigation. The current understanding of diatomite in soil classification is also discussed based on the special physical behaviours and microstructure caused by the diatom frustules. This study provides a comprehensive description of the physical characteristics influenced by different diatom content associated with the microstructure, which reveals the essence of the physical behaviors of diatomite.

Thicker shells reduce copepod grazing on diatoms

AbstractThe diatom frustule provides partial protection against copepod grazing. Whether the defense is due to the cells being de‐selected or handled for so long that the grazers lose time for foraging is unknown. The mechanism has implications for the population dynamics of both defended and co‐occurring, undefended nutrient competitors. We use video‐observations to demonstrate that thick‐shelled diatoms captured by the copepod Temora longicornis were rejected more frequently than thin‐shelled diatoms, irrespective of cell size. The thick‐shelled cells of the larger diatoms were handled for much longer, and the time spent handling these limits the consumption of phytoplankton. This may be why many diatoms, even in the presence of dense grazer populations, reach bloom concentrations, and thus, facilitate aggregation and mass sedimentation. This has implications for both carbon sequestration and for securing a large population of cells at depth ready to colonize the pelagic, when growth conditions again become favorable.

Insights Into the Mn(VII) and Cr(VI) Adsorption Mechanisms on Purified Diatomite/MCM-41 Composite: Experimental Study and Statistical Physics Analysis.

In this study, a purified diatomite (PD) with a concentration of diatom frustules more than 92% SiO2 was utilized to synthesize a composite of MCM-41 silica under hydrothermal conditions. The as-synthesized PD/MCM-41 composite was characterized and tested as an adsorbent for the removal of Cr(VI) and Mn(VII) ions from aqueous solution. Results of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR) revealed that the diatom frustules of the PD were coated with MCM-41 mesoporous silica. Experimental isotherms of Cr(VI) and Mn(VII) adsorption were fitted to classical and advanced statistical physics models at 25°C–55°C and pH 3. The Langmuir model estimated monolayer adsorption capacities ranging from 144.1 to 162.2 mg/g for Cr(VI) and 166.2 to 177.0 mg/g for Mn(VII), which improved with increasing the solution temperature. Steric and energetic parameters obtained from a monolayer adsorption model with one adsorption site was utilized to explain the adsorption mechanism at a microscopic level. The number of Cr(VI) and Mn(VII) ions adsorbed on PD/MCM-41 active site (n) were 1.25–1.27 for Cr(VI) and 1.27–1.32 for Mn(VII), thus suggesting multi-interaction mechanisms. The density of PD/MCM-41 active sites (D M) was a key parameter to explain the adsorption of these heavy metals. The adsorbed quantities were maximum at 55°C, thus obtaining 102.8 and 110.7 mg/g for Cr(VI) and Mn(VII), respectively. Cr(VI) and Mn(VII) adsorption energies ranged from 18.48 to 26.70 kJ/mol and corresponded to an endothermic adsorption with physical forces. Entropy, free enthalpy, and internal energy associated to the adsorption of Cr(VI) and Mn(VII) ions were calculated, thus indicating that the removal of these pollutants was spontaneous. Overall, this article offers new interpretations for the Cr(VI) and Mn(VII) adsorption mechanisms on PD/MCM-41 composite, which are relevant to contribute to the development of effective water treatment processes.

Hydrogen economy and storage by nanoporous microalgae diatom: Special emphasis on designing photobioreactors

Storing multiple energy forms from microalgae is not only facile but also lowers the cost of culturing the microalgae. Among many microalgae, diatoms are microscopic glass menageries which are responsible for converting stored lipids and biomass into hydrogen, besides fixing 25% of global CO2. Besides this their silica frustules are also nature's naturally available bionanomaterials which have immense applications in nanotechnology for hydrogen production and other energy storage. The diatom frustules get hybridized with various chemical and biological components to generate or store hydrogen in various fuel cells. In laboratory these live diatoms can be allowed to culture in various designed solar panel photobioreactors better known as diatom solar panels for high and low value-added products essentially biofuel and fucoxanthin. The present review thus discusses about possible scope and approaches to produce hydrogen from live diatom and as well as from its biomass in specially designed photobioreactors. This truly has economic aspects of hydrogen production from diatoms in comparison to other microalgae which needs to be explored for its wide applications due to its robustness and abundance occurrence.

Molecular Evolution of Tubulins in Diatoms.

Microtubules are formed by α- and β-tubulin heterodimers nucleated with γ-tubulin. Tubulins are conserved eukaryotic proteins. Previously, it was shown that microtubules are involved in diatom silica frustule morphogenesis. Diatom frustules are varied, and their morphology is species-specific. Despite the attractiveness of the problem of elucidating the molecular mechanisms of genetically programmed morphogenesis, the structure and evolution of diatom tubulins have not been studied previously. Based on available genomic and transcriptome data, we analyzed the phylogeny of the predicted amino acid sequences of diatom α-, β- and γ-tubulins and identified five groups for α-tubulins, six for β-tubulins and four for γ-tubulins. We identified characteristic amino acids of each of these groups and also analyzed possible posttranslational modification sites of diatom tubulins. According to our results, we assumed what changes occurred in the diatom tubulin structures during their evolution. We also identified which tubulin groups are inherent in large diatom taxa. The similarity between the evolution of diatom tubulins and the evolution of diatoms suggests that molecular changes in α-, β- and γ-tubulins could be one of the factors in the formation of a high morphological diversity of diatoms.

Nature engineered metasurfaces: spin-to-orbital angular momentum conversion in diatom frustules

Evolution provided, through eras, several animal, vegetal, and protist species with sub-micrometric constituent structures able to manipulate light at the nanoscale in non trivial ways. In particular, diatoms are single-celled microalgae enclosed in a porous silica shell, the frustule, perforated by regular patterns of microand nano-pores and whose functionalities comprise mechanical stability, sorting of nutrients from harmful agents and optimization of sunlight harvesting. Photonic properties of frustules include focusing, photoluminescence, and optical activity, among others. In the present work we show preliminary results concerning the ability of single valves of Arachnoidiscus ehrenbergii diatom frustules to manipulate incoming, circularly polarized radiation in such a way to generate light beams provided with orbital angular momentum (optical vortices). The combination of cross-polarization imaging in different spectral ranges, polarization sensitive digital holographic imaging (PSDHI), and interferometry allowed characterizing the valves and detecting the presence of spin-orbit coupling induced by their ultrastructure.

Diatom Frustules Based Dissolved Oxygen Sensor with Superhydrophobic Surface

Diatom Frustules Based Dissolved Oxygen Sensor with Superhydrophobic Surface