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In this work, we present the combination of two different types of nanomaterials, 2D molybdenum disulfide nanosheets (MoS2-NS) and zero-dimensional carbon nanodots (CDs), for the development of a new electrochemiluminescence (ECL) platform for the early detection and quantification of the biomarker human epidermal growth factor receptor 2 (HER2), whose overexpression is associated with breast cancer. MoS2-NS are used as an immobilization platform for the thiolated aptamer, which can recognize the HER2 epitope peptide with high affinity, and CDs act as coreactants of the anodic oxidation of the luminophore [Ru(bpy)3]2+. The HER2 biomarker is detected by changes in the ECL signal of the [Ru(bpy)3]2+/CD system, with a low detection limit of 1.84 fg/mL and a wide linear range. The proposed method has been successfully applied to detect the HER2 biomarker in human serum samples. [ABSTRACT FROM AUTHOR]

Exfoliation of lamellar materials into their corresponding layers represented a breakthrough, owing to the outstanding properties arising from the nanometric thickness confinement. Among the cleavage techniques, liquid-phase exfoliation is now on the rise because it is scalable and leads to easy-to-manipulate colloids. However, all appropriate exfoliating solvents exhibit strong polarity, which greatly restricts the scope of feasible functionalization or processing of the resulting flakes. Here, this scope is extended: nanosheets exfoliated in a polar medium are demonstrated to properly disperse in a nonpolar solvent. To that purpose, suspensions of molybdenum disulfide flakes were prepared in isopropanol/water and a phase transfer of the nanosheets to chloroform was developed by flocculation and redispersion/centrifugation sequences, without any assisting surfactant. The colloidal stability of the nanosheets in chloroform was found to be governed by their lateral dimensions and, although lower than in polar media, proved to be high enough to open the way to subsequent functionalization or processing of the flakes in nonpolar media. [ABSTRACT FROM AUTHOR]

We present an easy noncovalent functionalization of MoS2-based photodetectors that results in an enhancement of the photoresponse by about four orders of magnitude, reaching responsivities up to 100 A W−1. The functionalization is technologically trivial, air-stable, fully reversible and reproducible, and opens the door to the combination of 2D-materials with molecular dyes for the development of high performance photodetectors. [ABSTRACT FROM AUTHOR]

In this work we present the development of an electrochemiluminescence aptasensor based on electrografting molybdenum disulphide nanosheets functionalized with diazonium salt (MoS 2 –N 2 +) upon screen-printed electrodes of graphene (SPEs GPH) for viral proteins detection. In brief, this aptasensor consists of SPEs GPH electrografted with MoS 2 –N 2 + and modified with a thiolated aptamer, which can specifically recognize the target protein analyte. In this case, we have used SARS-CoV-2 spike protein as model protein. Electrochemiluminescence detection was performed by using the [Ru(bpy) 3 ]2+/TPRA (tripropylamine) system, which allows the specific detection of the SARS-CoV-2 spike protein easily and rapidly with a detection limit of 9.74 fg/mL and a linear range from 32.5 fg/mL to 50.0 pg/mL. Moreover, the applicability of the aptasensor has been confirmed by the detection of the protein directly in human saliva samples. Comparing our device with a traditional saliva antigen test, our aptasensor can detect the spike protein even when the saliva antigen test gives a negative result. [Display omitted] • Covalent 2D MoS 2 /graphene heterostructure applied to an aptasensor development. • ECL behaviour of the [Ru(bpy) 3 ]2+/TPrA system upon the MoS 2 /graphene platform. • ECL aptasensor for rapid and sensitive viral protein detection. • Direct detection of SARS-CoV-2 spike protein in human saliva. [ABSTRACT FROM AUTHOR]

In this work we present the preparation of a 2D molybdenum disulphide nanosheets (2D-MoS 2) and tetrahedral DNA nanostructures (TDNs) bioconjugate, and its application to the development of a bioassay for rapid and easy virus detection. The bioconjugate has been prepared by using TDNs carrying the capture probe labelled with 6-carboxyfluoresceine (6-FAM). As case of study to assess the utility of the assay developed, we have chosen the SARS-CoV-2 virus. Hence, as probe we have used a DNA sequence complementary to a region of the SARS-CoV-2 ORF1ab gene (TDN-ORF-FAM). This 6-FAM labelled capture probe is located on the top vertex of the tetrahedral DNA nanostructure, the three left vertices of TDNs have a thiol group. These TDNs are bounded to 2D-MoS 2 surface through the three thiol groups, allowing the capture probe to be oriented to favour the biorecognition reaction with the analyte. This biorecognition resulting platform has finally been challenged to the detection of the SARS-CoV-2 ORF1ab gene sequence as the target model by measuring fluorescence before and after the hybridization event with a detection limit of 19.7fM. Furthermore, due to high sensitivity of the proposed methodology, it has been applied to directly detect the virus in nasopharyngeal samples of infected patients without the need of any amplification step. The developed bioassay has a wide range of applicability since it can be applied to the detection of any pathogen by changing the probe corresponding to the target sequence. Thus, a novel, hands-on strategy for rapid pathogen detection has proposed and has a high potential application value in the early diagnosis of infections causes by virus or bacteria. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Nanostructured sensing platforms based on a 2D-MoS 2 ternary complex. • Modified electrode with a persistent catalytic activity towards hydrazine oxidation. • Application to the determination of hydrazine in tap and river water samples. A new strategy to modify screen-printed graphene electrodes (SPGrEs) with two-dimensional molybdenum disulfide (2D-MoS 2) nanosheets is described. The nanomaterial confined on the electrode surface is further modified forming a ternary complex with the redox mediator hematein (HM), using Al3+ salts as mordant. The formation of this ternary complex, HM-Al3+-(2D-MoS 2), gives rise to new nanostructures that can be visualized by scanning electron microscopy (SEM). The resulting nanostructured platform has been characterized by electrochemical techniques. It exhibits a strong electrocatalytic activity towards hydrazine oxidation mainly due to the presence of quinone/hydroquinone moieties from the hematein and a good stability. The large value calculated for the electrocatalytic kinetic constant, (8.1 ± 0.1) x104 M−1 s−1, suggests that the presence of 2D-MoS 2 nanosheets significantly improves the properties of hematein as an electron donor/acceptor. The catalytic current showed a linear dependence with the hydrazine concentration, which has allowed the development of a hydrazine sensor based on HM-Al3+-(2D-MoS 2)/SPGrEs with detection and quantification limits of 1.05 μM and 3.48 μM, respectively. The presence of different interfering compounds such as glucose, urea and others did not significantly affect the response of the proposed hydrazine sensor. This sensor has been used for the determination of hydrazine in tap and river waters. [ABSTRACT FROM AUTHOR]

This work focuses on the combination of molybdenum disulfide (MoS 2) and à la carte functionalized carbon nanodots (CNDs) for the development of DNA biosensors for selective and sensitive detection of pathogens. MoS 2 flakes prepared through liquid-phase exfoliation, serves as platform for thiolated DNA probe immobilization, while thionine functionalized carbon nanodots (Thi-CNDs) are used as electrochemical indicator of the hybridization event. Spectroscopic and electrochemical studies confirmed the interaction of Thi-CNDs with DNA. As an illustration of the pathogen biosensor functioning, DNA sequences from InIA gen of Listeria monocytogenes bacteria and open reading frame sequence (ORF1ab) of SARS-CoV-2 virus were detected and quantified with a detection limit of 67.0 fM and 1.01 pM, respectively. Given the paradigmatic selectivity of the DNA hybridization, this approach allows pathogen detection in the presence of other pathogens, demonstrated by the detection of Listeria monocytogenes in presence of Escherichia coli. We note that this design is in principle amenable to any pathogen for which the DNA has been sequenced, including other viruses and bacteria. As example of the application of the method in real samples it has been used to directly detect Listeria monocytogenes in cultures without any DNA Polymerase Chain Reaction (PCR) amplification process. • New à la carte functionalized carbon nanodots (CNDs) synthesis. • MoS 2 and à la carte CNDs for the development of DNA biosensors for Listeria monocytogenes and SARS-CoV-2 detection. • Direct detection of Listeria monocytogenes in real samples without any DNA and PCR amplification process. [ABSTRACT FROM AUTHOR]