A poly(methylene blue)-modified glassy carbon electrode (PMB/GCE) was fabricated by electropolymerisation of methylene blue on a GCE and further utilized to investigate the electrochemical determination of 4-nitrophenol (4-NP) by cyclic voltammetry (CV), differential pulse voltammetry and chronocoulometry. The morphology of the PMB on GCE was examined using a scanning electron microscope (SEM). An oxidation peak of 4-NP at the PMB modified electrode was observed at 0.28 V, and in the case of bare GCE, no oxidation peak was observed, which indicates that PMB/GCE exhibits a remarkable effect on the electrochemical determination of 4-NP. Due to this remarkable effect of PMB/GCE, a sensitive and simple electrochemical method was proposed for the determination of 4-NP. The effect of the scan rate and pH was investigated to determine the optimum conditions at which the PMB/GCE exhibits a higher sensitivity with a lower detection limit. Moreover, kinetic parameters such as the electron transfer number, proton transfer number and standard heterogeneous rate constant were calculated. Under optimum conditions, the oxidation current of 4-NP is proportional to its concentration in the range of 15-250 nM with a correlation coefficient of 0.9963. The detection limit was found to be 90 nM (S/N = 3). The proposed method based on PMB/GCE is simple, easy and cost effective. To further confirm its possible application, the proposed method was successfully used for the determination of 4-NP in real water samples with recoveries ranging from 97% to 101.6%. The interference due to sodium, potassium, calcium, magnesium, copper, zinc, iron, sulphate, carbonate, chloride, nitrate and phosphate was found to be almost negligible.

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Gd 2 (SO 4 ) 3 ·8H 2 O , Gd 2 O 2 SO 4 , and Gd 2 O 2 SO 4 :Eu 3+ nanoparticles have been synthesized in the presence of Gd 3+ ion and sodium dodecyl sulphate (SDS) by the simple complexationthermal decomposition (CTD) method. The structural analysis, growth mechanism and optical properties of the Gd 2 (SO 4 ) 3 ·8H 2 O, and Gd 2 O 2 SO 4 is described by diffraction pattern, functional group analysis, Raman, morphology, elemental analysis, and absorbance spectra. The most intriguing future was that the Gd 2 O 2 SO 4 nanoplates are in the range of 42-50 nm without adding any external stabilizer. The study results revealed that the Gd 2 O 2 SO 4 nanoparticles with orthorhombic structure are having a band gap of 3.12 eV. Furthermore, Gd 2 O 2 SO 4 shows an intense red photoluminescence associated with the 5 D 0 → 7 F 2 transition in the presence of Eu 3+ .The results suggest that the Gd 2 O 2 SO 4 :Eu 3+ nanophosphors, may have a beneficial approach in the field of biomedical application as luminescent probe/labels.

Various hollow manganese oxide (bixbyite Mn 2 O 3 and hausmannite Mn 3 O 4 ) nanoparticles (NPs) with different morphologies were obtained from a single precursor, manganese oxalate IJMnC 2 O 4 ). To synthesize a Mn 3 O 4 stacked nanostructure rather than coral-like Mn 2 O 3 nanospheres, as synthesized MnC 2 O 4 was thermally decomposed at 700°C in the presence of Gd 3+ , through the oriented arrangement mechanism. The formation process and structural variation arising from varying the thermal treatment (450°C and 700°C) and the cationic dopant Gd 3+ were analyzed by FTIR, TGA, and XRD. The unexpected size reduction, and significant physicochemical properties were analyzed using various techniques such as FESEM coupled with EDAX, HR-TEM, DRS-UV-vis, EPR, EIS and VSM. The addition of gadolinium induces particle size reduction and a phase transition from cubic Mn 2 O 3 to tetragonal Mn 3 O 4 , which leads to the suppression of the electrical conductivity, and changes in the optical band gap. The prepared Mn 3 O 4 nanocrystals exhibit ferromagnetic behavior below T c ≈ 45 K and weak paramagnetic behavior at room temperature.

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