James B. Murowchick

Electronic waste, or e-waste, is one of the fastest-growing waste streams as electronic gadgets become increasingly prevalent and short-lived. E-waste contains a significant amount of precious metal gold (Au), whose retrieval offers substantial financial and environmental benefits. We have previously developed triazine-crosslinked polyethyleneimines (TCPEIs) that can capture Au(III) with high capacity, high selectivity, and fast kinetics. Herein, to better understand the underlying mechanisms, we studied the gold adsorption on crosslinked polyethyleneimines (CPEIs) with rigid crosslinkers of varying lengths and a different PEI type. Specifically, a triazine (2,4,6-trichloro triazine, TCT) and a piperazine-bridged triazine dimer (1,4-di(4,6-dichloro-1,3,5-triazine-2-yl)piperazine, DTP) were used to crosslink linear PEIs to generate CPEIs − lTCPEI and lDCPEI, respectively. lDCPEI, with a longer rigid crosslinker, consistently showed faster adsorption kinetics across all three tested initial gold concentrations than lTCPEI, and the lower the gold concentration, the more pronounced the difference in their adsorption rates. At 20 ppm, a gold concentration that is relevant to the acidic leaching solution of electronic waste, lDCPEI exhibited a gold adsorption rate constant (K2 = 0.5837 g mg−1 min−1) that is more than twice as high as that of lTCPEI (K2 = 0.2231 g mg−1 min−1). The gold recovery efficiency of lDCPEI is also significantly higher than that of lTCPEI at this concentration. The maximum adsorption capacities of the lDCPEI and lTCPEI as determined by Langmuir isotherm analysis are, however, comparable, and are 2777 and 2857 mg g−1, respectively. X-ray diffraction analysis indicated that the predominant mechanism of initial adsorption is electrostatic interactions, followed by the reduction of Au(III) ions. In the presence of competing metal ions of even higher concentrations, lDCPEI was able to recover 99% of the gold. Moreover, the desorption study showed that 99% of the adsorbed gold could be recovered within 30 s. This simple approach to e-waste recycling offers sustainable benefits for both the circular economy and environmental protection.

Earth‐abundant, low‐cost, and highly active bifunctional electrocatalysts are of significant importance to the large‐scale production of hydrogen from water electrolysis. Herein, it is reported that novel FeNi₃/NiFeO_x nanohybrids display high electrocatalytic activities in both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). These FeNi₃/NiFeO_x nanohybrids are obtained with the unique hydrogenation treatment of NiFeO_x nanosheets. Small onset potentials of ≈20 and 240 mV are obtained for HER and OER, respectively, benefited from the synergistic effect of FeNi₃ and NiFeO_x. Only a small voltage of 1.55 V is needed to reach a current density of 10 mA cm⁻² for the overall water splitting in an alkaline electrolyzer when using FeNi₃/NiFeO_x as both cathode and anode catalysts. This is one of the best performance of electrocatalysts for HER and OER, shining the bright future for earth‐abundant, low‐cost bifunctional electrocatalysts for large‐scale production of hydrogen from water electrolysis.

Hydrogenated MnMoO₄exhibited excellent supercapacitive properties and high catalytic activity towards the hydrogen evolution reaction.

Purpose It is hypothesized that sodium acetate (SA) can be used for in situ coating of drug loaded chitosan NPs for improved physico-chemical properties. Methods Tenofovir (TFV) is used as a model drug. Uncoated chitosan NPs are prepared by ionic gelation. SA is generated in situ from half neutralization of acetic acid with sodium hydroxide, and coats chitosan NPs during freeze-drying. The NPs' physico-chemical properties [e.g., particle mean diameters (PMD) zeta potential (ζ), EE%, drug release profile, morphology] are characterized by dynamic light scattering, spectrophotometry, Korsmeyer-Peppas model, transmission electron microscopy (TEM), respectively. Melting point (MP), non-aqueous titration, Fourier transform infrared (FTIR) analysis, and powder X-ray diffractometry (XRD) pattern evaluate the SA coated chitosan NPs. The NPs' cytotoxicity on macrophages Raw 264.7 is assessed by neutral red, resazurin, nitrite oxide (NO) and cytokines assays. Results Collectively, FTIR, ζ, XRD, MP, and TEM data confirm that SA coats chitosan NPs. The PMD range is 136–348 nm (uncoated) and 171–379 nm (coated NPs). The ζ values range is +24.3–28.5 mV (uncoated) and 0.1–3.1 mV (coated NPs). The EE% ranges from 5.5 to 11.7% (uncoated NPs) and increased up to 86.3-92.7%(8-17-fold) after coating. The SA also prevents NPs aggregation during the freeze-drying and aqueous dispersion. The core-shell NPs exhibited a sustain release of TFV following anomalous transport mechanism (R² ~ 0.99). The coated NPs are non-cytotoxic (cell viability ~100%) and without any proinflammatory response. Conclusions This SA coating chitosan NPs mechanism may be useful for (i) efficient encapsulation, (ii) stabilizing colloidal dispersions, (iii) controlling the release and solubility of bioactive agents.

Hydrogenation largely improves the microwave absorbing efficiency of BaTiO₃ nanoparticles.

Electromagnetic interactions in the microelectronvolt (μeV) or microwave region have numerous important applications in both civil and military fields, such as electronic communications, signal protection, and antireflective coatings on airplanes against microwave detection. Traditionally, nonmagnetic wide-bandgap metal oxide semiconductors lack these μeV electronic transitions and applications. Here, we demonstrate that these metal oxides can be fabricated as good microwave absorbers using a 2D electron gas plasma resonance at the disorder/order interface generated by a hydrogenation process. Using ZnO and TiO₂ nanoparticles as examples, we show that large absorption with reflection loss values as large as −49.0 dB (99.99999%) is obtained in the microwave region. The frequency of absorption can be tuned with the particle size and hydrogenation condition. These results may pave the way for new applications for wide bandgap semiconductors, especially in the μeV regime.