As
a potential risk to human and environmental health, radio frequency
(RF) radiation should be studied due to the higher frequencies and
larger bandwidths that may be employed. Electromagnetic interference
(EMI) shielding materials can prevent exposure to RF radiation, but
most of them are visibly opaque. In this work, we propose and fabricate
visibly transparent EMI shielding materials using an ultrathin silver
layer sandwiched by oxides (SLSO) as building blocks. The samples
with a double-sided SLSO (D-SLSO) structure exhibit the highest EMI
shielding effectiveness (SE) of 70 dB at 27.6 GHz (>62 dB on average
at 4–40 GHz) and a transmittance close to 90% at a visible
wavelength of 550 nm, which is comparable with those of polyethylene
terephthalate (PET) and glass substrates. The D-SLSO structure plays
a dual role: it suppresses optical reflections as antireflection coatings
and enhances EMI shielding via Fabry–Pérot interference.
In addition, we discuss the origin of the extraordinary frequency
dependence of SE, which monotonically increases, contrary to that
of conventional metallic mesh. This report describes SLSO-based transparent
EMI shielding materials with record-high SE and visible transmittance
that provide optoelectronic applications with robust safety and reliability
under RF radiation with high and broad frequencies.
As a key enzyme regulating postprandial blood glucose, α-Glucosidase is considered to be an effective target for the treatment of diabetes mellitus. In this study, a simple, rapid, and effective method for enzyme inhibitors screening assay was established based on α-glucosidase catalyzes reactions in a personal glucose meter (PGM). α-glucosidase catalyzes the hydrolysis of maltose to produce glucose, which triggers the reduction of ferricyanide (K3[Fe(CN)6]) to ferrocyanide (K4[Fe(CN)6]) and generates the PGM detectable signals. When the α-glucosidase inhibitor (such as acarbose) is added, the yield of glucose and the readout of PGM decreased accordingly. This method can achieve the direct determination of α-glucosidase activity by the PGM as simple as the blood glucose tests. Under the optimal experimental conditions, the developed method was applied to evaluate the inhibitory activity of thirty-four small-molecule compounds and eighteen medicinal plants extracts on α-glucosidase. The results exhibit that lithospermic acid (52.5 ± 3.0%) and protocatechualdehyde (36.8 ± 2.8%) have higher inhibitory activity than that of positive control acarbose (31.5 ± 2.5%) at the same final concentration of 5.0 mM. Besides, the lemon extract has a good inhibitory effect on α-glucosidase with a percentage of inhibition of 43.3 ± 3.5%. Finally, the binding sites and modes of four active small-molecule compounds to α-glucosidase were investigated by molecular docking analysis. These results indicate that the PGM method is feasible to screening inhibitors from natural products with simple and rapid operations.
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