L-Glutamine-assisted synthesis of ZnO oatmeal-like/silver composites as an electrochemical sensor for Pb2+ detection.

We report a green synthesis of oatmeal ZnO/silver composites in the presence of L-glutamine as an electrochemical sensor for Pb2+ detection. The synthesis was performed via the direct reduction of Ag+ in the presence of L-glutamine in NaOH. X-ray diffraction indicated that the Ag+ was completely reduced to metallic Ag. The field emission scanning electron microscopy (FESEM) and energy dispersive X-ray results confirmed an oatmeal-like morphology of the ZnO with the presence of Ag. The FESEM images showed the effect of L-glutamine on the ZnO morphology. The EIS results confirmed a significant decrease in the charge transfer resistance of the modified glassy carbon electrode due to the presence of Ag. From the differential pulse voltammetry results, a linear working range for the concentration of Pb2+ between 5 and 6 nM with LOD of 0.078 nM (S/N = 3) was obtained. The sensitivity of the linear segment is 1.42 µA nM-1 cm-2. The presence of L-glutamine as the capping agent and stabilizer decreases the size of Ag nanoparticles and prevents the agglomeration of ZnO, respectively. Graphical abstract ᅟ.

Experimental and Theoretical Study of Enhanced Photocatalytic Activity of Mg-Doped ZnO NPs and ZnO/rGO Nanocomposites.

A systematic experimental and theoretical study of the origin of the enhanced photocatalytic performance of Mg-doped ZnO nanoparticles (NPs) and Mg-doped ZnO/reduced graphene oxide (rGO) nanocomposites has been performed. In addition to Mg, Cd was chosen as a doping material for the bandgap engineering of ZnO NPs, and its effects were compared with that of Mg in the photocatalytic performance of ZnO nanostructures. The experimental results revealed that Mg, as a doping material, recognizably ameliorates the photocatalytic performance of ZnO NPs and ZnO/graphene nanocomposites. Transmission electron microscopy (TEM) images showed that the Mg-doped and Cd-doped ZnO NPs had the same size. The optical properties of the samples indicated that Cd narrowed the bandgap, whereas Mg widened the bandgap of the ZnO NPs and the oxygen vacancy concentration was similar for both samples. Based on the experimental results, the narrowing of the bandgap, the particle size, and the oxygen vacancy did not enhance the photocatalytic performance. However, Brunauer-Emmett-Teller (BET) and Barret-Joyner-Halenda (BJH) models showed that Mg caused increased textural properties of the samples, whereas rGO played an opposite role. A theoretical study, conducted by using DFT methods, showed that the improvement in the photocatalytic performance of Mg-doped ZnO NPs was due to a higher electron transfer from the Mg-doped ZnO NPs to the dye molecules compared with pristine ZnO and Cd-doped ZnO NPs. Moreover, according to the experimental results, along with Mg, graphene also played an important role in the photocatalytic performance of ZnO.

Effects of annealing atmosphere and rGO concentration on the optical properties and enhanced photocatalytic performance of SnSe/rGO nanocomposites.

The photocatalytic properties of SnSe nanostructures (NSs) and SnSe/graphene nanocomposites with different graphene concentrations (5, 10, and 15 wt%/v) were investigated. The products were synthesized by a simple and cost-effective co-precipitation method. The samples obtained demonstrated that graphene concentration at an optimum amount was an important factor in enhancing the photocatalytic performance of the products. The graphene source was graphene oxide (GO) sheets and several characterization results indicated, which were used to remove Methylene blue (MB) dye, that the GO sheets were changed into reduced graphene oxide (rGO) sheets during the synthesis process. The optical properties of the products were studied using a room temperature photoluminescence (PL) spectrometer and it was observed that the near-band-edge (NBE) position of the samples was at the end of the red region between 729 and 756 nm of the electromagnetic spectrum, which was confirmed by a UV-vis spectrometer. The PL spectra of the samples also demonstrated three emissions from the violet, green, and orange regions of the visible spectrum, which were from different defects. The samples were annealed in a hydrogen and air atmosphere at 300 °C and it was found that defect concentrations were increased by annealing for the SnSe/rGO nanocomposites. The photocatalyst studies of the post-annealed samples revealed that the photocatalytic performance of the products was enhanced by annealing in hydrogen, while it was reduced by annealing in air. In addition to MB, the photocatalytic performance of the products for the degradation of phenol as a colorless pollutant was examined. It was observed that rGO in this process also had a significant role in the enhancement of photocatalytic performance. In fact, the electron spin resonance (ESR) test showed the role of rGO in photocatalytic activity very well.

COMPARISON OF THE EFFECTS OF PREEMPTIVE INTRAVENOUS AND RECTAL ACETAMINOPHEN ON PAIN MANAGEMENT AFTER INGUINAL HERNIORRHAPHY IN CHILDREN: A PLACEBO-CONTROLLED STUDY.

BACKGROUND: Postoperative pain management is a critical concern in pediatric surgery. Acetaminophen is the safest and most widely used analgesic in children. The present study compared the analgesic efficacy of intravenous (IV) and rectal acetaminophen versus placebo in children undergoing inguinal herniorrhaphy. METHODS: A total of 120 children, who were candidate for elective surgical repair of unilateral inguinal hernia, were enrolled and randomly allocated to four groups of 30 patients each to receive IV acetaminophen, acetaminophen suppository, IV placebo, and placebo suppository during surgery. Postoperative pain scores, measured on the Face, Legs, Activity, Cry, and Consolability (FLACC) scale, were recorded and compared. RESULTS: The four groups had no significant differences in the mean age, weight, length of stay in the recovery room, and duration of operation. The frequency of postoperative vomiting was significantly lower in the IV and rectal acetaminophen groups compared to the two placebo groups (P = 0.04). The mean pain scores of the two acetaminophen groups were similar during the first two hours after surgery. These scores were significantly lower than the scores of the placebo groups. However, the four groups were not significantly different in terms of pain scores at the fourth, sixth, and 12th postoperative hours. During the first hour after surgery, IV acetaminophen had the largest analgesic effect. Moreover, among all four groups, the IV acetaminophen group had the highest sedation level in the recovery room. CONCLUSION: Both IV and rectal acetaminophen were more effective than placebo in pain relief after inguinal hernia repair in children. They were also associated with lower frequencies of postoperative vomiting. The greatest analgesic efficacy of both forms was observed during the first two hours after surgery.

Synthesis and characterization of Co3O4 ultra-nanosheets and Co3O4 ultra-nanosheet-Ni(OH)2 as non-enzymatic electrochemical sensors for glucose detection.

The present study examines the synthesis of Co3O4 ultra-nanosheets (Co3O4 UNSs) and Co3O4 ultra-nanosheet-Ni(OH)2 (Co3O4 UNS-Ni(OH)2) via solvothermal process and their application as non-enzymatic electrochemical sensors for glucose detection. X-ray diffraction and transmission electron microscopy results confirmed the Co3O4 UNS deposition on Ni(OH)2 surface. The presence of Co3O4 UNSs on Ni (OH) 2 surface improved the sensitivity of glucose detection, from the increase of glucose oxidation peak current at the Co3O4 UNS-Ni(OH)2/glassy carbon electrode (current density: 2000µA·cm(-2)), compared to the Co3O4 UNSs. These results confirmed that Ni(OH)2 on glassy carbon electrode is a sensitive material for glucose detection, moreover the Co3O4 UNSs can increase the interaction and detection of glucose due to their high surface area. The estimated limit of detection (S/N=3) and limit of quantification (S/N=10) of the linear segment (5-40µM) are 1.08µM and 3.60µM respectively. The reproducibility experiments confirmed the feasibility of Co3O4 UNS-Ni(OH)2 for the quantitative detection of certain concentration ranges of glucose.

Graphene oxide electrocatalyst on MnO2 air cathode as an efficient electron pump for enhanced oxygen reduction in alkaline solution.

Graphene oxide (GO) was deposited on the surface of a MnO2 air cathode by thermal evaporation at 50°C from a GO colloidal suspension. Fourier transformed infrared spectroscopy and field emission scanning electron microscopy confirmed the presence of GO on the MnO2 air cathode (GO-MnO2). Voltammetry and chrono-amperometry showed increased currents for the oxygen reduction reaction (ORR) in 6 M KOH solution for GO-MnO2 compared to the MnO2 cathode. The GO-MnO2 was used as an air cathode in an alkaline tin-air cell and produced a maximum power density of 13 mW cm(-2), in contrast to MnO2, which produced a maximum power density of 9.2 mW cm(-2). The electrochemical impedance spectroscopy results suggest that the chemical step for the ORR is the rate determining step, as proposed earlier by different researchers. It is suggested that the presence of GO and electrochemically reduced graphene oxide (ERGO) on the MnO2 surface are responsible for the increased rate of this step, whereby GO and ERGO accelerate the process of electron donation to the MnO2 and to adsorbed oxygen atoms.

Sonochemical synthesis of hierarchical ZnO nanostructures.

This work is about fabrication of ZnO nanostructures (ZnO-NS) via a simple sonochemical method. The chemicals used for the synthesis of various shaped ZnO are Zn salt, sodium hydroxide and ammonia solution without other structure directing agent or surfactant needed. This method is feasible and green, as it does not require high temperature and/or highly toxic chemicals. The shape of the ZnO-NS can be tuned by adjusting the ultrasound energy dissipated via varying the ultrasonication time from 5 to 60 min. It was found that uniform ZnO nanorods with diameter around 50 nm were formed after 15 min of ultrasonication while flowerlike ZnO-NS was formed after 30 min. This method produces high quality ZnO-NS with controllable shapes, uniformity, and purity.