Natural Seashells Research Articles

The Production and Characterization of Seashell Reinforced Epoxy Composite Material

In this study, it was aimed to examine the production, characterization and mechanical properties of epoxy matrix composites added with seashells collected from different coastal locations of the Mersin Region, which is a natural raw material. Natural seashells with different mass ratios were ground into different sizes and added into epoxy, the matrix material. By performing physical and chemical characterization of the produced composites, the next step is to analyze and produce the product with the best and most superior properties.

Cold sintering of calcium carbonate derived from seashells

The cold sintering process (CSP) densifies ceramics powder at significantly lower temperatures (<300 °C) than used in conventional sintering. This is enabled with the application of a uniaxial pressure of several hundred mega pascals and a small amount of transient solvent that derives chemo-mechanical mechanisms. Therefore, by using this method, carbonates can be densified below their decomposition temperature. Since natural seashells are composed of more than 95% calcium carbonate (calcite and/or aragonite) along with organic components, most of them can be densified by CSP. In this study, two types of shells (clam and oyster) with different crystal phases of calcite and aragonite were used as starting materials and the mechanism of their densification by CSP was investigated. Differences in densification behavior between the two kinds of shells with and without heating pretreatment were also examined. Hardened bodies formed by CSP from seashells have potential uses as construction materials.

Bioinspired synthesis of thermally stable and mechanically strong nanocomposite coatings

An innovative biomimetic method has been developed to synthesize layered nanocomposite coatings using silica and sugar-derived carbon to mimic the formation of a natural seashell structure. The layered nanocomposites are fabricated through alternate coatings of condensed silica and sugar. Sugar-derived carbon is a cost-effective material as well as environmentally friendly. Pyrolysis of sugar will form polycyclic aromatic carbon sheets, i.e., carbon black. The resulting final nanocomposite coatings can survive temperatures of more than 1150 °C and potentially up to 1650 °C. These coatings have strong mechanical properties, with hardness of more than 11 GPa and elastic modulus of 120 GPa, which are 80% greater than those of pure silica. The layered coatings have many applications, such as shielding in the form of mechanical barriers, body armor, and space debris shields.Graphical abstract

Natural Seashell Waste as an Efficient and Low‐Cost Catalyst for the Synthesis of Arylmethylenemalonitriles

AbstractIn this work, four kinds of natural seashells (clam shell, oyster shell, scallop shell, and conch shell) are investigated as catalysts for the Knoevenagel reaction to produce arylmethylenemalonitriles, among which conch shells show the highest catalytic activity due to their mixed phases of calcite and aragonite, resulting in the relatively weak base strength and fewer number of basic sites. Solvent effect and catalyst usage are systematically investigated, and conch shells show high universality for nine aromatic aldehydes to produce the desired products with high yield in short time under optimized conditions. In addition, this catalyst possesses good recyclability and could be used four times without obvious deactivation. In all, conch shell is an efficient, low‐cost, green, and recyclable catalyst for the Knoevenagel reaction.

Bio-Inspired Stable Lithium-Metal Anodes by Co-depositing Lithium with a 2D Vermiculite Shuttle.

Progress in lithium-metal batteries is severely hindered by lithium dendrite growth. Lithium is soft with a mechanical modulus as low as that of polymers. Herein we suppress lithium dendrites by forming soft-hard organic-inorganic lamella reminiscent of the natural sea-shell material nacres. We use lithium as the soft segment and colloidal vermiculite sheets as the hard inorganic constituent. The vermiculite sheets are highly negatively charged so can absorb Li+ then be co-deposited with lithium, flattening the lithium growth which remains dendrite-free over hundreds of cycles. After Li+ ions absorbed on the vermiculite are transferred to the lithium substrate, the vermiculite sheets become negative charged again and move away from the substrate along the electric field, allowing them to absorb new Li+ and shuttling to and from the substrate. Long term cycling of full cells using the nacre-mimetic lithium-metal anodes is also demonstrated.

Antibody-modified hydroxyapatite surfaces for the efficient capture of bladder cancer cells in a patient's urine without recourse to any sample pre-treatment.

In this study, we describe a sensitive protocol for the detection of bladder cancer cells in a patient's urine without pre-treatment of the urine sample using antibody-modified hydroxyapatite (HAp) micro/nanostructured surfaces converted from natural seashells under mild biomineralization conditions. The mechanism based on fractal dimension-crystalline phase interactions was utilised for the enhancement of cell capture capabilities that has been verified by application in the determination of 22 urine samples from bladder cancer patients. We have established a facile and economical yet biocompatible and bioactive surface with a topography consisting of micro and nano features that provide useful binding sites for antibodies permitting the rapid identification of cancer cells during urine cytology via fluorescence observation with the naked eye.

A fluorescence-quenching platform based on biomineralized hydroxyapatite from natural seashell and applied to cancer cell detection.

As a typical biomineral, hydroxyapatite (HAp) is widely applied in bone implants and other related fields. However, the inherent nature of HAp can potentially be altered through restricting its fabrication conditions. Here, HAp fabricated by a hydrothermal treatment of pieces of natural seashell is demonstrated to have the capability of fluorescence quenching. To the best of the author's knowledge, this is the first time that this new property of HAp has been reported. Consequently, we assembled a fluorescence-quenching platform based on the biomineralized HAp substrate following a hydrothermal treatment and associated with a DNA molecular beacon and applied to cancer cell detection by the transformation from “OFF state” (fluorescence quenching) to “ON state” (fluorescence recovery). Herein, we found that the outer surface of HAp material after hydrothermal biomineralization for 5 days has considerable capability for both fluorescence quenching and recovery. These results may also have implications in the further detection of various targets such as cancer cells with other special surface antigens, significant biological small molecules or disease related microRNA, just by changing the sequence of the nucleic acid beacon according to the corresponding aptamer.