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In this research, a novel manganese dioxide nanorod-anchored graphene oxide (MnO2 NRs/GO) composite was synthesized by a simple hydrothermal method for electrochemical sensing application. A highly sensitive electrochemical sensor for dopamine (DA) was constructed by modifying glassy carbon electrode (GCE) with MnO2 NRs/GO. The morphology and performance of the composite material and modified GCEs were investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV), respectively. The resultant MnO2 NRs/GO composite has a large electroactive area and shows excellent electrochemical activity toward DA. Under the optimal conditions, the DA sensor shows a linear response in the DA concentration ranges of 0.1 μM–0.08 mM and 0.08–0.41 mM with a low detection limit of 0.027 μM and a high sensitivity of 602.4 μA·mM−1·cm−2. The MnO2 NRs/GO composite provides a promising platform for the construction of a highly sensitive and selective sensor of DA.

In this research, we reported effective streptavidin-functionalized tin disulfide nanoflakes (SnS2 NFs) to develop an ultrasensitive electrochemical immunosensor for the bioanalysis of tumor markers. The streptavidin-functionalized SnS2 platform and immunosensor were characterized by scanning electron microscopy, electrochemical impedance spectroscopy, static water contact angle measurements and cyclic voltammetry. Biofunctionalized SnS2 NFs displayed a large specific surface area and outstanding hydrophilicity. These characteristics enhanced the loading efficiency and capacity of antibodies on the biosensing platform and ensured the biological activity of the immobilized protein biomolecules. Carcinoembryonic antigen (CEA) was chosen as the model analyte, and a wide linear range of 0.006–3.0 ng mL−1 with a low detection limit of 5 pg mL−1 for CEA was exhibited by the immunosensor. Human serum sample analysis was achieved through the CEA immunosensor with satisfactory results. Streptavidin-functionalized SnS2 NFs offer a potential platform for the expansion of electrochemical immunosensor applications.

A titanium dioxide functionalized SnS2 nanocomposite was synthesized for the immobilization of glucose oxidase (GOx) to develop an enzymatic electrochemical glucose biosensor. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry were used to characterize the nanocomposite and the glucose biosensor. The TiO2–SnS2 composite shows a larger surface area and GOx entrapped in this matrix maintains excellent bioactivity and stability. The constructed glucose biosensor responds to glucose linearly over two concentration ranges of 0.008 to 1.13 mM and 1.13 to 5.53 mM at a working potential of −0.45 V. The biosensor exhibits a high sensitivity (18.9 mA M−1 cm−2), low detection limit (1.8 × 10−6 M) and good repeatability. The present biosensor has excellent selectivity and can be successfully applied for the detection of glucose in serum samples. The advantages of the glucose biosensor show that a TiO2–SnS2 nanocomposite provides a new avenue for immobilizing proteins and fabricating excellent biosensors.

The cracking and iridescence properties of photonic crystals (PCs) greatly limit their availability, especially in the realms of color displays and optical devices. Herein, crack-free amorphous PCs with enhanced color contrast and low angle dependence were fabricated by the co-assembly of polydopamine-coated polystyrene core–shell nanoparticles (PS@PDA NPs) and 3-aminopropyltriethoxysilane (APTES) via a thermal-assisted self-assembly method. The covalent bonds, generated from Schiff base reaction or Michael addition between polydopamine (PDA) and APTES, successfully counteract the tensile stress that is initiated from latex shrinkage during drying, thereby enabling the formation of crack-free PCs. Moreover, thanks to the light-absorbing nature of PDA, a mussel-inspired melanin, and the amorphous arrays, these as-prepared crack-free PCs miraculously exhibit high visibility and low angle dependent structural colors. This facile, low-cost and environmentally friendly approach for preparing crack-free amorphous PCs can be employed in diverse colloidal sphere systems and may boost the promising applications of PCs.

Poly(2-oxazoline)-supported bifunctional organocatalysts have been prepared through a bottom-up protocol, which involves synthesis of well-defined poly(2-oxazoline) precursors bearing amino groups in the side-chains followed by amide coupling with N-Boc-L-proline then deprotection. The resultant L-prolinamido-functionalized polymers have proven to be significantly more active than their monomeric counterparts for the aldolisation of cyclic ketones with several substituted benzaldehydes under neat conditions. By using 15 mol% of the polymer as a catalyst, the direct aldol reaction products were isolated in high yields and with good diastereo- and enantioselectivity. Based on circular dichroism spectrum analysis, the enhancement in catalytic activity is probably related to the conformational changes of the pseudo-peptide scaffold of poly(2-oxazoline)s. In addition, these soluble polymeric catalysts can be recovered and reused by precipitation in ether for five catalytic cycles without significantly diminishing their efficiency.