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4 figures, 2 tables.-- Supplementary information available., Two cellulose nanocrystals/single-walled carbon nanotube (CNC/SW) hybrids, using two cellulose polymorphs, were evaluated as electrochemical transducers: CNC type I (CNC-I/SW) and CNC type II (CNC-II/SW). They were synthesized and fully characterized, and their analytical performance as electrochemical sensors was carefully studied. In comparison with SWCNT-based and screen-printed carbon electrodes, CNC/SW sensors showed superior electroanalytical performance in terms of sensitivity and selectivity, not only in the detection of small metabolites (uric acid, dopamine, and tyrosine) but also in the detection of complex glycoproteins (alpha-1-acid glycoprotein (AGP)). More importantly, CNC-II/SW exhibited 20 times higher sensitivity than CNC-I/SW for AGP determination, yielding a LOD of 7 mg L−1.These results demonstrate the critical role played by nanocellulose polymorphism in the electrochemical performance of CNC/SW hybrid materials, opening new directions in the electrochemical sensing of these complex molecules. In general, these high-active-surface hybrids smartly exploited the preserved non-oxidized SW conductivity with the high aqueous dispersibility of the CNC, avoiding the use of organic solvents or the incorporation of toxic surfactants during their processing, making the CNC/SW hybrids promising nanomaterials for electrochemical detection following greener approaches., Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This work has been financially supported by the TRANSNANOAVANSENS program from the Community of Madrid (P2018/NMT-4349), and the Spanish Ministry of Economy and Competitiveness (CTQ2017-86441-C2-1-R). Additional funding support was from Spanish MINEICO/MICINN under project with references ENE2016-79282-C5-1-R (AEI/FEDER/UE), PID2019-104272RB-C51/AEI/10.13039/501100011033, and PID2020-120439RA-I00. Funding support from Gobierno de Aragón (Grupo Reconocido T03_20R) is also acknowledged.

Janus micromotors encapsulating transition metal dichalcogenides (TMDs) and modified with a rhodamine (RhO)-labeled affinity peptide (RhO-NFMESLPRLGMH) are used here for Salmonella enterica endotoxin detection. The OFF–ON strategy relies on the specific binding of the peptide with the TMDs to induce fluorescence quenching (OFF state); which is next recovered due to selectively binding to the endotoxin (ON state). The increase in the fluorescence of the micromotors can be quantified as a function of the concentration of endotoxin in the sample. The developed strategy was applied to the determination of Salmonella enterica serovar Typhimurium endotoxin with high sensitivity (limits of detection (LODs) of 2.0 µg/mL using MoS2, and 1.2 µg/mL using WS2), with quantitative recoveries (ranging from 93.7 ± 4.6 % to 94.3 ± 6.6%) in bacteria cultures in just 5 min. No fluorescence recovery is observed in the presence of endotoxins with a similar structure, illustrating the high selectivity of the protocol, even against endotoxins of Salmonella enterica serovar Enteritidis with great similarity in its structure, demonstrating the high bacterial specificity of the developed method. These results revealed the analytical potential of the reported strategy in multiplexed assays using different receptors or in the design of portable detection devices. Graphical abstract

The aim of this conceptual review is to cover recent developments of light-propelled micromotors for analytical (bio)-sensing. Challenges of self-propelled light-driven micromotors in complex (biological) media and potential solutions from material aspects and propulsion mechanism to achieve final analytical detection for in vivo and in vitro applications will be comprehensively covered. Graphical abstract.

The authors describe tailor-designed electrodes based on the use of films of carbonaceous nanomaterials with demostrated conductivitiy at the microscale. These represent a unique conductive material for deposition on adaptable nonconductive substrates. Single-walled and multi-walled carbon nanotubes as well as graphene scaffold film electrodes (SFEs) were designed, and their electroanalytical performance was evaluated by using two different designs. The first is a 3-electrode configuration for off-chip detection, and the second is one for on-chip detection of the biomarkers dopamine and catechol at +0.70 V detection potential (vs. Ag/AgCl). The SFEs were fabricated by filtration of conducting carbon nanomaterials using a tailored template. In our perception, they pave the way for a wide field of opportunities in off-chip and microfluidic electrochemistry because of their reliability, ease of fabrication and remarkable performance that is based on the exclusive use of the carbon nanomaterial transducers.

Single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT) and graphene have been tested as carbon allotropes for the modification of carbon screen-printed electrodes (CSPEs) to simultaneously determine melatonin (MT) and serotonin (5-HT). Two groups of CSPEs, both 4 mm in diameter, were explored: The first includes commercial SWCNT, MWCNT and graphene, the second includes SWCNT, MWCNT, graphene oxide nanoribbons and reduced nanoribbons that were drop casted on the electrodes. The carbon nanomaterials enhanced the electroactive area in the following order: CSPE

We report on a microfluidic system for the electrochemical determination of inulin. It is making use of electro-synthesized catalytically active nanowires (NWs; made from nickel or copper; 6 μm long and 300 nm wide) capable of detecting inulin at a working voltage of +0.70 V (vs. Ag/AgCl) and a pH value of 12.0 with a sensitivity that is 40 times better than that for fructose (its monomer). The copper nanoelectrodes were characterized by field emission scanning electron microscopy and photoelectron spectroscopy which revealed a random distribution of copper NWs. Their core is found to be metallic while the outer few atomic layers (

We demonstrate that the formation of gold nanoparticles (AuNPs) can be exploited in a well-defined and reliable electron-transfer assay for antioxidant capacity (AOxC). The AOxC of a sample usually is due to the presence of polyphenols, and a good correlation exists between the production of AuNPs and the concentration of polyphenols. The results obtained by this method correlate well with the established AOxC assays (FRAP and FC; p < 0.05). HPLC analysis revealed that the AOxC is driven by the overall quantitative levels of polyphenolic antioxidants. UV characterization and TEM confirm the formation of stabilized AuNPs of well-defined size (all