Utilization of waste beverages for achieving carbon-based core-shell nanostructures of high visible light photocatalytic performance.

Waste beverages are utilized as resources in various valuable, albeit energy-consuming, waste-to-energy processes. There is a growing need for alternative cost-effective methods to harness their potential. This study explored the feasibility of employing waste beverages as feedstock for the counterpart component of a TiO2-based composite photocatalyst. Several commonly available carbonated soft drinks from the Japanese market have been investigated to achieve this goal. The investigation revealed that a mild hydrothermal treatment condition could transform all examined beverages into carbonaceous materials suitable for fabricating a core-shell structure with TiO2, resulting in a remarkably efficient visible light active photocatalyst. Notably, a pH-adjusted photocatalyst derived from Coca Cola® exhibited superior visible light photodegradability toward dye molecules and enhanced bactericidal efficacy compared to the counterpart derived from pure sucrose. The heightened visible light photocatalytic activity can be attributed to the distinctive carboxy-rich surface functional groups, based on the findings of experimental analyses and density functional theory calculations. The bidentate-type bonding of these groups with TiO2 induces a modified interfacial bond structure that facilitates the efficient transfer of photoexcited carriers. This study presents a novel avenue for the effective utilization and recycling of waste beverages, and adds value under environmentally benign conditions.

Performance and stability improvement of perovskite solar cells using a nanopillar conductive polymer formed via electropolymerisation.

BF4--doped poly(3-methylthiophene) (P3MT) was formed using electropolymerisation as a hole transport material for inverted perovskite solar cells. The controlled nanopillar morphology of P3MT enables void-less uniform perovskite formation and exhibits conversion efficiency of 11.11%. The P3MT-based cells exhibited superior stability in ambient air to poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid)-based cells.

Development of a high-speed bioaerosol elimination system for treatment of indoor air.

We developed a high-speed filterless airflow multistage photocatalytic elbow aerosol removal system for the treatment of bioaerosols such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Human-generated bioaerosols that diffuse into indoor spaces are 1-10 µm in size, and their selective and rapid treatment can reduce the risk of SARS-CoV-2 infection. A high-speed airflow is necessary to treat large volumes of indoor air over a short period. The proposed system can be used to eliminate viruses in aerosols by forcibly depositing aerosols in a high-speed airflow onto a photocatalyst placed inside the system through inertial force and turbulent diffusion. Because the main component of the deposited bioaerosol is water, it evaporates after colliding with the photocatalyst, and the nonvolatile virus remains on the photocatalytic channel wall. The residual virus on the photocatalytic channel wall is mineralized via photocatalytic oxidation with UVA-LED irradiation in the channel. When this system was operated in a 4.5 m3 aerosol chamber, over 99.8% aerosols in the size range of 1-10 µm were removed within 15 min. The system continued delivering such performance with the continuous introduction of aerosols. Because this system exhibits excellent aerosol removal ability at a flow velocity of 5 m/s or higher, it is more suitable than other reactive air purification systems for treating large-volume spaces.

Aqueous mechano-bactericidal action of acicular aragonite crystals.

Nanoneedle structures on dragonfly and cicada wing surfaces or black silicon nanoneedles demonstrate antibacterial phenomena, namely mechano-bactericidal action. These air-exposed, mechano-bactericidal surfaces serve to destroy adherent bacteria, but their bactericidal action in the water is no precedent to report. Calcium carbonate easily accumulates on solid surfaces during long-term exposure to hard water. We expect that aragonite nanoneedles, in particular, which grow on TiO2 during the photocatalytic treatment of calcium-rich groundwater, exhibit mechano-bactericidal action against bacteria in water. Here, we showed that acicular aragonite modified on TiO2 ceramics prepared from calcium bicarbonate in mineral water by photocatalysis exhibits mechanical bactericidal activity against E. coli in water. Unmodified, calcite-modified and aragonite-modified TiO2 ceramics were exposed to water containing E. coli (in a petri dish), and their bactericidal action over time was investigated under static and agitated conditions. The surfaces of the materials were observed by scanning electron microscopy, and the live/dead bacterial cells were observed by confocal laser scanning microscopy. As a result, the synergistic bactericidal performance achieved by mechano-bactericidal action and photocatalysis was demonstrated. Aragonite itself has a high biological affinity for the human body different from the other whisker-sharpen nanomaterials, therefore, the mechano-bactericidal action of acicular aragonite in water is expected to inform the development of safe water purification systems for use in developing countries.

Effect of dissolved silica on photocatalytic water purification with a TiO2 ceramic catalyst.

If photocatalytic water purification technologies will find practical applications, the impact of total dissolved solids in the source water on the activity of the photocatalyst must be evaluated. In this study, we evaluated the effects of SiO32- in water on a TiO2 ceramic photocatalyst; specifically, we determined the effects of SiO32- on the rate of photocatalytic degradation of formic acid (as a model contaminant) and on the rate of photocatalytic inactivation of Escherichia coli in an aqueous solution. Both the rate of formic acid degradation and the sterilization rate decreased with increasing SiO32- concentration. On the other hand, at a given SiO32- concentration, the activity of the photocatalyst did not decrease over the course of 120 h, and the surface structure of the photocatalyst did not change (i.e., no precipitate formed on the surface). The decreases in photocatalytic activity due to the presence of SiO32- could be recovered by flushing the experimental apparatus with distilled water. These results show that the reason for the lower photocatalytic activity in the presence of SiO32- than in its absence was due to adsorption of SiO32- onto the surface of the TiO2 photocatalyst and that SiO32- adsorption was an equilibrium process in water.

Physicochemical Evaluation of Micellar Solution and Lyotropic Phases Formed by Self-Assembled Aggregates of Morpholinium Geminis.

The micellar solution and the lyotropic liquid crystalline phases formed by gemini surfactants containing morpholinium headgroups are investigated for their self-aggregation and physicochemical properties in water. These gemini surfactants demonstrated good surface activity because they are able to undergo micellization at lower concentration and form nanosized micellar aggregates in dilute aqueous solution. The binary mixture of the morpholinium gemini surfactant-water system is investigated over a wide range of concentrations. The micellar solution of the morpholinium gemini surfactants demonstrated Newtonian fluidlike behavior between 10 and 50 wt % as the observed viscosities were independent of the applied shear rate. At higher concentration, morpholinium geminis formed self-assembled lyotropic phases in water. These liquid crystalline phases were characterized by small-angle X-ray scattering and polarized optical microscopy techniques.

Self-aggregation and liquid crystalline behavior of new ester-functionalized quinuclidinolium surfactants.

A new type of ester-based cationic surfactant having a quinuclidinolium headgroup has been synthesized starting from linear fatty alcohols and has been characterized using spectroscopic techniques. The self-aggregation and thermodynamic properties of these surfactants have been investigated by pendant-drop surface tensiometry and conductivity measurements. The liquid crystalline behaviors of these surfactants were investigated by small-angle X-ray scattering (SAXS) technique. The quinuclidinolium headgroup demonstrated a unique ability to interlock among themselves thus affecting the physicochemical properties of surfactants in aqueous solution. The current research finding supports the new concept of headgroup interlocking which is supported by 1D and 2D NMR studies.

[Effectiveness of oral vitamin B12 therapy for pernicious anemia and vitamin B12 deficiency anemia].

We investigated the efficacy of oral vitamin B12 (B12) therapy in patients with B12-deficiency anemia. Between June 1994 and June 2000, 17 patients, who were diagnosed as having B12-deficiency anemia and gave their informed consent, were enrolled in this study. Of these patients, 7 were further treated with a maintenance dose of methylcobalamin (1,500 micrograms daily for 7 days every 1-3 months). Correction of hematological and neurological abnormalities was prompt. The hemoglobin level and serum concentration of B12 were normalized within two months after starting the treatment. Recovery from neurological disturbance was observed within one month. To maintain a normal serum concentration of B12, a 7-day regime of administration was needed every month in 3 patients, every 2 months in 3 patients, and every 3 months in 1 patient. These results demonstrate the effectiveness of oral cobalamin therapy, and also that oral intermittent therapy is useful for maintaining a normal serum B12 concentration. Oral cobalamin therapy might be as effective as conventional injection therapy, and useful for long-term treatment.