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The Feature highlights Electron Paramagnetic Resonance (EPR) spectroscopy as an indispensable tool to understand the excited state reactivity of organic molecules.

Disposable sensors are inexpensive, user-friendly sensing tools designed for rapid single-point measurements of a target. Disposable sensors have become more and more essential as diagnostic tools due to the growing demand for quick, easy-to-access, and reliable information related to the target. Dopamine (DA), a prevalent catecholamine neurotransmitter in the human brain, is associated with central nervous system activities and directly promotes neuronal communication. For the sensitive and selective estimation of DA, an enzyme-free amperometric sensor based on polyaniline-doped multi-walled carbon nanotubes (PANI-MWCNTs) drop-coated disposable screen-printed carbon electrodes (SPCEs) was fabricated. This PANI-MWCNTs-2/SPCE sensor boasts exceptional accuracy and sensitivity when working directly with ex vivo mouse brain homogenates. The sensor exhibited a detection limit of 0.05 μM (S/N = 3), and a wide linear range from 1.0 to 200 μM. The sensor's high selectivity to DA amidst other endogenous interferents was recognized. Since the constructed sensor is enzyme-free yet biocompatible, it exhibited high stability in DA detection using ex vivo mouse brain homogenates extracted from both Parkinson's disease and control mice models. This research thus presents new insights into understanding DA release dynamics at the tissue level in both of these models. [ABSTRACT FROM AUTHOR]

Melatonin (MT), a pineal gland hormone, regulates the sleep/wake cycle and is a potential biomarker for neurodegenerative disorders, depression, hypertension, and several cancers, including prostate cancer and hepatocarcinoma. The amperometric detection of MT was achieved using a sensor customized with ruthenium-incorporated carbon spheres (Ru–CS), possessing C- and O-rich catalytically active Ru surfaces. The non-covalent interactions and ion–molecule adducts between Ru and CS favor the formation of heterojunctions at the sensor–analyte interface, thus accelerating the reactions towards MT. The Ru–CS/Screen-printed carbon electrode (SPCE) sensor demonstrated the outstanding electrocatalytic oxidation of MT owing to its high surface area and heterogeneous rate constants and afforded a lower detection limit (0.27 μM), high sensitivity (0.85 μA μM −1 cm−2), and excellent selectivity for MT with the co-existence of crucial neurotransmitters, including norepinephrine, epinephrine, dopamine, and serotonin. High concentrations of active biomolecules, such as ascorbic acid and tyrosine, did not interfere with MT detection. The practical feasibility of the sensor for MT detection in pharmaceutical samples was demonstrated, comparable to the data provided on the product labels. The developed amperometric sensor is highly suitable for the quality control of medicines because of its low cost, simplicity, small sample size, speed of analysis, and potential for automation. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor based on Cu-loaded carbon nanospheres (Cu–CNSs) was designed and fabricated. Initially, the CNSs were synthesized using a natural or inexpensive carbon source (dark brown sugar), and Cu was loaded to enhance the electrocatalytic properties of the material. Subsequently, the synthesized Cu–CNSs were modified onto a screen-printed carbon electrode (SPCE), termed Cu–CNS/SPCE, to simultaneously detect the biomarkers dopamine (DA) and melatonin (MT) through differential pulse voltammetry. The surface characterization of the Cu–CNSs confirmed the formation of carbon spheres and Cu nanoparticles covering the spheres. Electrochemical studies showed that the Cu–CNS/SPCE had a high selectivity and sensitivity toward DA and MT, with a significant peak separation of 0.502 V. The two linear ranges of DA were 0.125–20 μM and 20–100 μM and the linear range of MT was 1.0–100 μM, with corresponding detection limits of 0.34 μM and 0.33 μM (S/N = 3), respectively. The quantification limits for DA and MT were 2.19 and 1.09 μM (S/N = 10), respectively. The sensor performance is attributed to the high conductivity and large, electrochemically active surface area of the Cu–CNS. In human serum samples, the Cu–CNS/SPCE exhibited good selectivity and satisfactory reproducibility for the simultaneous determination of DA and MT. [ABSTRACT FROM AUTHOR]

A detailed understanding of the photoluminescence (PL) from silicon nanocrystals (SiNCs) is convoluted by the complexity of the decay mechanism, including a stretched-exponential relaxation and the presence of both nanosecond and microsecond time scales. In this publication, we analyze the microsecond PL decay of size-resolved SiNC fractions in both full-spectrum (FS) and spectrally resolved (SR) configurations, where the stretching exponent and lifetime are used to deduce a probability distribution function (PDF) of decay rates. For the PL decay measured at peak emission, we find a systematic shift and narrowing of the PDF in comparison to the FS measurements. In a similar fashion, we resolve the PL lifetime of the ‘blue’, ‘peak’, and ‘red’ regions of the spectrum and map PL decays of different photon energy onto their corresponding location in the PDF. A general trend is observed where higher and lower photon energies are correlated with shorter and longer lifetimes, respectively, which we relate to the PL line width and electron-phonon coupling.

The expected worldwide demand for agriculture, energy, and manufactured products will result in a supply chain that is increasingly dependent on exported rural products (e.g., livestock, cereal grains, fossil fuel, and biofuel). Rural areas such as the northern Great Plains are net exporters of food and energy, essentially “mining” valuable water and nutrient resources to do so. Rural areas are the foundation of supply chains; thus, to achieve sustainability, one must begin focusing at the source of the supply chain– with the farm, ranch, mine, or well. There are many knowledge gaps within the food–energy–water nexus in rural areas that shroud regional sustainability thresholds. Research and legislation are needed to address these critical issues.

Bacterial infections in marine fishes are linked to mass mortality issues; hence, rapid detection of an infection can contribute to achieving a faster diagnosis using point-of-care testing. There has been substantial interest in identifying diagnostic biomarkers that can be detected in major organs to predict bacterial infections. Aspartate was identified as an important biomarker for bacterial infection diagnosis in olive flounder (Paralichthys olivaceus) fish. To determine aspartate levels, an amperometric biosensor was designed based on bi-enzymes, namely, glutamate oxidase (GluOx) and aspartate transaminase (AST), which were physisorbed on copolymer reduced graphene oxide (P-rGO), referred to as enzyme nanosheets (GluOx-ASTENs). The GluOx-ASTENs were drop casted onto a Prussian blue electrodeposited screen-printed carbon electrode (PB/SPCE). The proposed biosensor was optimized by operating variables including the enzyme loading amount, coreactant (α-ketoglutarate) concentration, and pH. Under optimal conditions, the biosensor displayed the maximum current responses within 10 s at the low applied potential of −0.10 V vs. the internal Ag/AgCl reference. The biosensor exhibited a linear response from 1.0 to 2.0 mM of aspartate concentrations with a sensitivity of 0.8 µA mM−1 cm−2 and a lower detection limit of approximately 500 µM. Moreover, the biosensor possessed high reproducibility, good selectivity, and efficient storage stability. [ABSTRACT FROM AUTHOR]