Optimization of TiO2-P25 photocatalyst dose and H2O2 concentration for advanced photo-oxidation using smartphone-based colorimetry

Emerging Roles of Microrobots for Enhancing the Sensitivity of Biosensors

To meet the increasing needs of point-of-care testing in clinical diagnosis and daily health monitoring, numerous cutting-edge techniques have emerged to upgrade current portable biosensors with higher sensitivity, smaller size, and better intelligence. In particular, due to the controlled locomotion characteristics in the micro/nano scale, microrobots can effectively enhance the sensitivity of biosensors by disrupting conventional passive diffusion into an active enrichment during the test. In addition, microrobots are ideal to create biosensors with functions of on-demand delivery, transportation, and multi-objective detections with the capability of actively controlled motion. In this review, five types of portable biosensors and their integration with microrobots are critically introduced. Microrobots can enhance the detection signal in fluorescence intensity and surface-enhanced Raman scattering detection via the active enrichment. The existence and quantity of detection substances also affect the motion state of microrobots for the locomotion-based detection. In addition, microrobots realize the indirect detection of the bio-molecules by functionalizing their surfaces in the electrochemical current and electrochemical impedance spectroscopy detections. We pay a special focus on the roles of microrobots with active locomotion to enhance the detection performance of portable sensors. At last, perspectives and future trends of microrobots in biosensing are also discussed.

GO-TiO2 as a Highly Performant Photocatalyst Maximized by Proper Parameters Selection

The synthesis and characterization of novel graphene oxide coupled to TiO₂ (GO-TiO₂) was carried out in order to better understand the performance of this photocatalyst, when compared to well-known TiO₂ (P25) from Degussa. Thus, its physical-chemical characterization (FTIR, XRD, N₂ isotherms and electrochemical measurements) describes high porosity, suitable charge and high electron mobility, which enhance pollutant degradation. In addition, the importance of the reactor set up was highlighted, testing the effect of both the irradiated area and distance between lamp and bulb solution. Under optimal conditions, the model drug methylthioninium chloride (MC) was degraded and several parameters were assessed, such as the water matrix and the catalyst reutilization, a possibility given the addition of H₂O₂. The results in terms of energy consumption compete with those attained for the treatment of this model pollutant, opening a path for further research.

Eco-friendly synthesis of cobalt-zinc ferrites using quince extract for adsorption and catalytic applications: An approach towards environmental remediation

Cobalt-zinc ferrite nanoparticles were synthesized using environmentally friendly approach with quince extract as a reducing agent. Crystal structure and morphology of the obtained materials were studied by XRD, SEM-EDS, Mössbauer and IR spectroscopy. The synthesized nanoparticles have a cubic spinel structure and crystallite size ranging from 5 to 9 nm. The infrared spectra contain characteristic absorption bands for the M_A-O (∼560 cm^-1) and M_B-O bonds (∼420 cm^-1). Force constants were calculated for both tetrahedral and octahedral bonds. As the Co content increases, the force constant for the tetrahedral bond increases and the force constant for the octahedral bond decreases. The obtained ferrite nanoparticles have good magnetization as shown by VSM (in the range from 36 to 67 emu/g). Magnetic nanoparticles Co_xZn_1-xFe₂O₄ were also tested for induction heating with electromagnetic field. The sample with x (Co) = 0.4 has the highest specific absorption rate. The synthesized samples were tested as adsorbents using the Congo Red dye as model pollutant. The best adsorbent was pure zinc ferrite with the adsorption capacity of 24.7 mg/g. The catalytic activity of the obtained ferrites for the decomposition of H₂O₂ was studied as well. The most active catalyst was pure cobalt ferrite. Probably, the active centers are octahedral cobalt ions. Thus, the obtained magnetic nanoparticles can be used for the adsorptive removal of pollutants, catalytic decomposition of the H₂O₂ and low-frequency hyperthermia.

Hydrogenated Amorphous Titania with Engineered Surface Oxygen Vacancy for Efficient Formaldehyde and Dye Removals under Visible-Light Irradiation

Hydrogenated crystalized TiO_2−x with oxygen vacant (O_V) doping has attracted considerable attraction, owing to its impressive photoactivity. However, amorphous TiO₂, as a common allotrope of titania, is ignored as a hydrogenated templet. In this work, hydrogenated amorphous TiO_2−x (HAm-TiO_2−x) with engineered surface O_V and high surface area (176.7 cm² g⁻¹) was first prepared using a unique liquid plasma hydrogenation strategy. In HAm-TiO_2−x, we found that O_V was energetically retained in the subsurface region; in particular, the subsurface O_V-induced energy level preferred to remain under the conduction band (0.5 eV) to form a conduction band tail and deep trap states, resulting in a narrow bandgap (2.36 eV). With the benefits of abundant light absorption and efficient photocarrier transportation, HAm-TiO_2−x coated glass has demonstrated superior visible-light-driven self-cleaning performances. To investigate its formaldehyde photodegradation under harsh indoor conditions, HAm-TiO_2−x was used to decompose low-concentration formaldehyde (~0.6 ppm) with weak-visible light (λ = 600 nm, power density = 0.136 mW/cm²). Thus, HAm-TiO_2−x achieved high quantum efficiency of 3 × 10⁻⁶ molecules/photon and photoactivity of 92.6%. The adsorption capabilities of O₂ (−1.42 eV) and HCHO (−1.58 eV) in HAm-TiO_2−x are both largely promoted in the presence of subsurface O_V. The surface reaction pathway and formaldehyde decomposition mechanism over HAm-TiO_2−x were finally clarified. This work opened a promising way to fabricate hydrogenated amorphous photocatalysts, which could contribute to visible-light-driven photocatalytic environmental applications.

Study of photocatalytic activity of green synthesized nickel oxide nanoparticles in the degradation of acid orange 7 dye under visible light

Environmental pollution is one of the most important problems that human beings face. Today, nanotechnology has played an important role in green chemistry and the use of nanoparticles in the removal of environmental pollutants is one of the newest methods of removing pollutants in the world. So, in this study, Nickel oxide nanoparticles (NiO NPs) of this work were successfully synthesized via a green method by the usage of nickel nitrate hexahydrate as the source of metal and Biebersteinia multifida extract as the stabilizing agent throughout different annealing temperatures. The physicochemical properties of the obtained NiO NPs were characterized through the application of scanning electron microscopy (SEM), energy dispersive X-ray (EDX), powder X-ray diffraction (PXRD), ultraviolet visible (UV-vis), and Raman analysis. According to the results of SEM and PXRD, the prepared product contained a satisfying distribution and very fine cubic structure with minimal accumulation. The average crystal size of prepared nanoparticles was obtained 54-58 nm. The energy band gap of synthesized NiO NPs was calculated 3-3.7 using Tauc equation. The photocatalytic performance of NiO NPs was investigated under visible light through the decolourization reaction of acid orange 7 (AO7) dye in aqueous solution. Being composed at 300 °C of annealing temperature, these nanoparticles exhibited excellent adsorption and photocatalytic activity (90.2%) toward AO7 dye. Therefore, it can be indicated that the synthesized NiO NPs demonstrated an excellent dispersion in dye solution, as well as considerable photocatalytic activity.

Effects of pollution on hydrogeochemistry and water quality of the Damietta branch (Nile River, Egypt)

Currently, different sources of contamination threaten water quality in Damietta, Egypt. The aim of this study was to assess the pollution, hydrogeochemistry and suitability for use in agriculture of water collected atseven stations along the Damietta branch of the Nile River. In addition to pH, temperature, dissolved oxygen (DO), and electrical conductivity (EC), levels of Mg²⁺, Ca²⁺, K⁺, Na⁺, Cl^-, HCO₃^-, SO₄^2- and CO₃^2- were measured. From the highest to the lowest, the concentrations of cations were Na⁺ > Ca²⁺ > Mg²⁺ > K⁺, whereas those of anions were HCO₃^- > SO₄^2- > Cl^- in water samples collected at seven stations along the Damietta branch. Moreover, water quality indexes, such as sodium percentage (Na%) ranged between 21.6 and 71.4, Kelly's ratio from 0.37 to 3.85, sodium adsorption ratio (SAR) varied from 1.73 to 61.8, residual sodium carbonate (RSC) found to be in range of 0.2 to 3.8. Also, the potential salinity (PS) and permeability index (PI), magnesium hazard (MH), were calculated. Most samples (71%) belonged to the Mg-Ca-Na-HCO₃ watertype. Fertilization wastes were identified as the main contributors of alkaline earth metals, whereas ion exchange was the main source of alkali metals. This work also provides information on distinguishing geochemical behaviors and the pollution of water samples.