Mohammad Vaseem

Wide Linear-Range Detecting Nonenzymatic Glucose Biosensor Based on CuO Nanoparticles Inkjet-Printed on Electrodes

Inkjet-printed copper oxide nanoparticles (CuO NPs) on silver electrodes were used to fabricate the nonenzymatic glucose biosensor. The inkjet-printed CuO NPs electrodes produced high and reproducible sensitivity of 2762.5 μAm M(-1) cm(-2) at an applied potential of +0.60 V with the wide linear-detecting range of 0.05-18.45 mM and the detection limit of ~0.5 μM (S/N = 3). The long-term stability and reproducibility of sensor in glucose electro-oxidation resulted from the chemical stability of CuO NPs and pore-like structure formed on Ag surface, which prevented the CuO NPs from conglomeration and the interference of oxygen in the air. Significantly, the effect of interfering species, such as AA, UA, and DA were negligible, whereas sugar derivatives (lactose, fructose, and mannose) show insignificant interference. Finally, the electrode was applied to analyze glucose concentration in human serum samples.

Inkjet Printed Fractal-Connected Electrodes with Silver Nanoparticle Ink

The development of a simple and reliable method for nanoparticles-based ink in an aqueous solution is still a challenge for its inkjet printing application. Herein, we demonstrate the inkjet printing of fractal-aggregated silver (Ag) electrode lines on substrates. Spherical, monodisperse Ag nanoparticles have been synthesized using silver nitrate as a precursor, ethylene glycol as a reducing agent, and polyvinyl pyrrollidone as a capping agent. As-synthesized pure Ag nanoparticles were well dispersed in water-ethylene glycol mixture, which was directly used as an ink for inkjet printing. Using this ink, the Ag electrodes of fractal-connected lines were printed on Si/SiO2, glass, and polymer substrates. The fractal-connected Ag lines were attributed to the diffusion-limited aggregation of Ag nanoparticles and the effect of annealing on conductivity was also examined.

Robust Design of a Particle-Free Silver-Organo-Complex Ink with High Conductivity and Inkjet Stability for Flexible Electronics.

Currently, silver-nanoparticle-based inkjet ink is commercially available. This type of ink has several serious problems such as a complex synthesis protocol, high cost, high sintering temperatures (∼200 °C), particle aggregation, nozzle clogging, poor shelf life, and jetting instability. For the emerging field of printed electronics, these shortcomings in conductive inks are barriers for their widespread use in practical applications. Formulating particle-free silver inks has potential to solve these issues and requires careful design of the silver complexation. The ink complex must meet various requirements, such as in situ reduction, optimum viscosity, storage and jetting stability, smooth uniform sintered films, excellent adhesion, and high conductivity. This study presents a robust formulation of silver-organo-complex (SOC) ink, where complexing molecules act as reducing agents. The 17 wt % silver loaded ink was printed and sintered on a wide range of substrates with uniform surface morphology and excellent adhesion. The jetting stability was monitored for 5 months to confirm that the ink was robust and highly stable with consistent jetting performance. Radio frequency inductors, which are highly sensitive to metal quality, were demonstrated as a proof of concept on flexible PEN substrate. This is a major step toward producing high-quality electronic components with a robust inkjet printing process.

Copper oxide quantum dot ink for inkjet-driven digitally controlled high mobility field effect transistors

Copper oxide (CuO) quantum dots (QDs) having a diameter of 5–8 nm were synthesized by a simple solution process. The as-synthesized QDs showed a highly crystalline monoclinic phase of CuO with a bandgap of ∼1.75 eV. The CuO QDs were further formulated as an ink for inkjet printing of CuO field effect transistors (FETs). The ink-jetting behavior of the as-formulated ink samples showed that the CuO concentration and digitally controlled number of over-prints are important factors for optimizing the uniformity and thickness of printed films with smooth edge definition. To examine the electrical properties, CuO FETs were fabricated based on inkjet-printed line and dot patterns. The inkjet-printed CuO FETs showed a p-type semiconducting nature with a high carrier mobility of 16.4 cm2 V−1 s−1 (line-pattern) and 16.6 cm2 V−1 s−1 (dot-pattern). Interestingly, when microwave-assisted annealing was applied the FET showed ∼2 times higher mobility (i.e., 28.7 for line-pattern and 31.2 cm2 V−1 s−1 for dot-pattern), which is the best among the p-type inorganic based FETs.

Thermoelectric properties of SrTiO3 nano-particles dispersed indium selenide bulk composites

We investigated the thermoelectric properties of the InSe, InSe/In4Se3 composite, and SrTiO3 (STO) nano-particles dispersed InSe/In4Se3 bulk composites. The electrical conductivity of the InSe/In4Se3 composite with self-assembled phase separation is significantly increased compared with those of InSe and In4Se3–δ implying the enhancement of surface conductivity between grain boundaries. The thermal conductivity of InSe/In4Se3 composite is decreased compared to those of InSe. When the STO nano-particle dispersion was employed in the InSe/In4Se3 composite, a coherent interface was observed between nano-particle precipitates and the InSe bulk matrix with a reduction of the thermal conductivity.

Green chemistry of glucose-capped ferromagnetic hcp-nickel nanoparticles and their reduced toxicity

Well-designed multifunctional D-(+) Glucose capped nickel nanoparticles (G-Ni NPs) with reduced toxicity was synthesized via green chemistry using D-(+) Glucose and ammonia in water. Here, glucose serves as a reducing and capping agent, resulting in highly stable and well-dispersed G-Ni NPs in the solution. The temperature and field dependent magnetization (M–H) showed a typical magnetic behavior for the G-Ni NPs. In zero field cooled (ZFC) curve, the peak was observed at ∼15 K, attributed to the blocking temperature (TB). At room temperature, the saturation magnetization (Ms), remanent magnetization (Mr), and coercivity (Hc) were found to be 35.57 emu/g, 11.77 emu/g, and 161 Oe, respectively. Interestingly, a dosage of 50 μg ml−1 G-Ni NPs were found to be well-tolerated by the cells with more than 50% cell viability. Hence, these smartly designed the G-Ni NPs can be envisioned as a future potential biomaterial for various applications.

Synthesis and characterisation of ZnO structures containing the nanoscale regime

Synthesis of ZnO nanorods assembled in flower-shaped spherical morphologies have been grown via solution process by using zinc nitrate hexahydrate (Zn(NO3)2. 6H2O) and sodium hydroxide (NaOH) at low-temperature of 100°C in eight hours. The grown ZnO structures were characterised in terms of their structural and optical properties. The detailed structural characterisations demonstrated that the synthesised products are single crystalline with the wurtzite hexagonal phase and grown along the [0001], c-axis direction. A strong absorption band at 480 cm−1 was observed in Fourier transform infra red (FTIR) spectrum which was related with the ZnO. The optical property of the grown ZnO structures was observed by using UV-visible studies. Only a sharp peak at 371 nm was observed in the UV-vis. spectrum which is a characteristic band for the wurtzite hexagonal pure ZnO. Moreover, systematic time-dependent reactions were also performed to know the detailed growth process for the synthesised ZnO nanostructures.

Structural, optical and field emission properties of ZnO nanowires grown by non-catalytic thermal evaporation process

Well-crystallised vertically aligned ZnO nanowires have been synthesised on silicon substrate via simple thermal evaporation process without the use of metal catalysis or additives at 750°C by using metallic zinc powder and oxygen gas as source materials for zinc and oxygen, respectively. The X-ray diffraction (XRD) pattern of the grown nanowires reveals that the grown structures are well-crystalline and possessing a wurtzite hexagonal phase. The room-temperature PL spectrum exhibited a sharp and strong UV emission with a broad green emission confirming good optical properties for the as-grown ZnO nanowires. The field emission characterisation exhibited that a turn-on field for the vertically aligned ZnO nanowires was 3.7 V/μm and the emission current density reached to 0.014 mA/cm² at an applied electrical field of ∼5.5 V/μm and shows no saturation. Moreover, the ZnO nanowire based field emission device exhibited a uniform light emission.