Multiplexed DNA-functionalized graphene sensor with artificial intelligence-based discrimination performance for analyzing chemical vapor compositions.

This study presents a new technology that can detect and discriminate individual chemical vapors to determine the chemical vapor composition of mixed chemical composition in situ based on a multiplexed DNA-functionalized graphene (MDFG) nanoelectrode without the need to condense the original vapor or target dilution. To the best of our knowledge, our artificial intelligence (AI)-operated arrayed electrodes were capable of identifying the compositions of mixed chemical gases with a mixed ratio in the early stage. This innovative technology comprised an optimized combination of nanodeposited arrayed electrodes and artificial intelligence techniques with advanced sensing capabilities that could operate within biological limits, resulting in the verification of mixed vapor chemical components. Highly selective sensors that are tolerant to high humidity levels provide a target for "breath chemovapor fingerprinting" for the early diagnosis of diseases. The feature selection analysis achieved recognition rates of 99% and above under low-humidity conditions and 98% and above under humid conditions for mixed chemical compositions. The 1D convolutional neural network analysis performed better, discriminating the compositional state of chemical vapor under low- and high-humidity conditions almost perfectly. This study provides a basis for the use of a multiplexed DNA-functionalized graphene gas sensor array and artificial intelligence-based discrimination of chemical vapor compositions in breath analysis applications.

Effect of Extrinsic Disorder on the Magnetoresistance Response of Gated Single-Layer Graphene Devices.

Analogous to the case of classical metal oxide semiconductor field-effect transistors, transport properties of graphene-based devices are determined by scattering from adventitious charged impurities that are invariably present. The presence of charged impurities renders experimental graphene samples "extrinsic" in that their electrical performances also depend on the environment in which graphene operates. While the role of such an extrinsic disorder component has been studied for conventional charge transport in graphene, its impact on the magnetotransport remains unexplored. Here, we show that single-layer graphene transistors with a low density of extrinsic disorder feature a larger magnetoresistance (MR) than those with a high density. Importantly, in gated single-layer devices with a low density of charged impurities, we find that MR peaks at gate voltage values far from the charge neutrality point not only at a low temperature but also at room temperature; in particular, MR approaches 800% at room temperature and 1400% at 50 K in such devices. In addition, dynamic measurements of MR on devices with a low degree of extrinsic disorder lead to stable and reliable single-layer graphene magnetosensors endowed with an ultralow power consumption of 2.5 nW. Our work indicates that the initial value of the minimum conductivity σ0 at room temperature along with carrier mobility must be looked at to select the most promising devices for magnetosensing.

Graphene-Iodine Nanocomposites: Highly Potent Bacterial Inhibitors that are Bio-compatible with Human Cells.

Graphene-composites, capable of inhibiting bacterial growth which is also bio-compatible with human cells have been highly sought after. Here we report for the first time the preparation of new graphene-iodine nano-composites via electrostatic interactions between positively charged graphene derivatives and triiodide anions. The resulting composites were characterized by X-ray photoemission spectroscopy, UV-spectroscopy, Raman spectroscopy and Scanning electron microscopy. The antibacterial potential of these graphene-iodine composites against Klebsiella pneumonia, Pseudomonas aeruginosa, Proteus mirobilis, Staphylococcus aureus, and E. coli was investigated. In addition, the cytotoxicity of the nanocomposite with human cells [human white blood cells (WBC), HeLa, MDA-MB-231, Fibroblast (primary human keratinocyte) and Keratinocyte (immortalized fibroblast)], was assessed. DGO (Double-oxidizes graphene oxide) was prepared by the additional oxidation of GO (graphene oxide). This generates more oxygen containing functional groups that can readily trap more H(+), thus generating a positively charged surface area under highly acidic conditions. This step allowed bonding with a greater number of anionic triiodides and generated the most potent antibacterial agent among graphene-iodine and as-made povidone-iodine (PVP-I) composites also exhibited nontoxic to human cells culture. Thus, these nano-composites can be used to inhibit the growth of various bacterial species. Importantly, they are also very low-cytotoxic to human cells culture.

Static and Dynamic Performance of Complementary Inverters Based on Nanosheet α-MoTe2 p-Channel and MoS2 n-Channel Transistors.

Molybdenum ditelluride (α-MoTe2) is an emerging transition-metal dichalcogenide (TMD) semiconductor that has been attracting attention due to its favorable optical and electronic properties. Field-effect transistors (FETs) based on few-layer α-MoTe2 nanosheets have previously shown ambipolar behavior with strong p-type and weak n-type conduction. We have employed a direct imprinting technique following mechanical nanosheet exfoliation to fabricate high-performance complementary inverters using α-MoTe2 as the semiconductor for the p-channel FETs and MoS2 as the semiconductor for the n-channel FETs. To avoid ambipolar behavior and produce α-MoTe2 FETs with clean p-channel characteristics, we have employed the high-workfunction metal platinum for the source and drain contacts. As a result, our α-MoTe2 nanosheet p-channel FETs show hole mobilities up to 20 cm(2)/(V s), on/off ratios up to 10(5), and a subthreshold slope of 255 mV/decade. For our complementary inverters composed of few-layer α-MoTe2 p-channel FETs and MoS2 n-channel FETs we have obtained voltage gains as high as 33, noise margins as high as 0.38 VDD, a switching delay of 25 µs, and a static power consumption of a few nanowatts.

Phosphorus-Doped Graphene Oxide Layer as a Highly Efficient Flame Retardant.

A simple and easy process has been developed to efficiently dope phosphorus into a graphene oxide surface. Phosphorus-doped graphene oxide (PGO) is prepared by the treatment of polyphosphoric acid with phosphoric acid followed by addition of a graphene oxide solution while maintaining a pH of around 5 by addition of NaOH solution. The resulting materials are characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The as-made PGO solution-coated cloth exhibits excellent flame retardation properties. The PGO-coated cloth emits some smoke at the beginning without catching fire for more than 120 s and maintains its initial shape with little shrinkage. In contrast, the pristine cloth catches fire within 5 s and is completely burned within 25 s, leaving trace amounts of black residue. The simple technique of direct introduction of phosphorus into the graphene oxide surface to produce phosphorus-doped oxidized carbon nanoplatelets may be a general approach towards the low-cost mass production of PGO for many practical applications, including flame retardation.