Holey MoS2-based electrochemical sensors for simultaneous dopamine and uric acid detection.

In this study, two-dimensional holey MoS2 (h-MoS2) nanosheets were used to develop electrochemical sensors for simultaneous detection of dopamine (DA) and uric acid (UA). The holes were created on MoS2 layers using hydrogen peroxide (H2O2) in the presence of Bovine Serum Albumin (BSA). h-MoS2 was characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, dynamic light scattering (DLS), and ultraviolet-visible spectroscopy (UV-vis). Electrochemical dopamine and uric acid sensors were prepared by drop-casting h-MoS2 on a glassy carbon electrode (GCE). The electroanalytical performance of the sensors was evaluated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) methods. The sensors revealed linear ranges between 50-1200 µM and 200-7000 µM with a limit of detection (LOD) of 4.18 µM and 5.62 µM for DA and UA, respectively. Furthermore, the h-MoS2-based electrochemical sensors showed high stability, sensitivity, and selectivity. The reliability of the sensors was elucidated in human serum. Recoveries ranging between 100.35% and 102.48% were calculated from real sample experiments.

Ni/NiO/Ni-B/graphene heterostructure-modified electrodes and their electrochemical activities towards acetaminophen.

The surface of graphene was decorated with nickel/nickel oxide/nickel-boron particles to develop high-performance electrochemical sensors. The nanohybrid structures were prepared via a one-step reduction method under an oxygen-rich atmosphere to obtain an oxide phase besides metallic nickel nanoparticles. In addition, the use of NaBH4 as the reducing agent enabled simultaneous formation of Ni-B species on the graphene surface. XRD, XPS, TEM, Raman, and TGA analyses were implemented to characterize the samples. The XRD and XPS results revealed the presence of Ni/NiO/Ni-B on the surface of graphene. The electroanalytical performance of the nanocomposite was investigated against acetaminophen, which is an extensively exploited antipyretic and analgesic drug. The analytical performance results showed that the Ni/NiO/Ni-B/Gr-based sensors had a very wide working window between 10 µM and 2500 µM (y (µA) = 10.706x (mM) + 0.3151 (R2 = 0.9993)). The excellent storage stability, selectivity, and recovery results along with the high analytical performance make the novel Ni/NiO/Ni-B/Gr hybrid systems promising materials for the development of novel sensor platforms.

SERS-active linear barcodes by microfluidic-assisted patterning.

Simple, low-cost, robust, and scalable fabrication of microscopic linear barcodes with high levels of complexity and multiple authentication layers is critical for emerging applications in information security and anti-counterfeiting. This manuscript presents a novel approach for fabrication of microscopic linear barcodes that can be visualized under Raman microscopy. Microfluidic channels are used as molds to generate linear patterns of end-grafted polymers on a substrate. These patterns serve as templates for area-selective binding of colloidal gold nanoparticles resulting in plasmonic arrays. The deposition of multiple taggant molecules on the plasmonic arrays via a second microfluidic mold results in a linear barcode with unique Raman fingerprints that are enhanced by the underlying plasmonic nanoparticles. The width of the bars is as small as 10 µm, with a total barcode length on the order of 100 µm. The simultaneous use of geometric and chemical security layers provides a high level of complexity challenging the counterfeiting of the barcodes. The additive, scalable, and inexpensive nature of the presented approach can be easily adapted to different colloidal nanomaterials and applications.