The optical responses of DNA-wrapped single-walled carbon nanotubes (DNA-SWNTs) caused by the addition of epigallocatechin gallate (EG) and tannic acid (TA) were investigated. Near infrared absorbance and photoluminescence spectra of pre-oxidized DNA-SWNTs were measured with and without EG and TA. Since both EG and TA have antioxidant abilities, the near infrared spectra changed after the addition of the chemicals. While detection of the antioxidant abilities of EG by DNA-SWNT hybrids has been previously reported, TA was employed for the first time. The changes in the absorbance caused by the addition of TA were found to saturate at 0.33 µM TA, although saturation was not observed even at 3.3 µM with the addition of EG. Oxidation of DNA-SWNT was suppressed by addition of TA or EG. The effects of TA were much greater than those of EG on the absorbance. The photoluminescence did not appear to saturate at 3.3 µM for either EG or TA. photoluminescence had a larger measurement capacity than NIR absorbance. Interestingly, the photoluminescence change caused by EG was much larger than that of TA at 3.3 µM, although the antioxidant property of TA was stronger at 0.33 and 0.033 µM, suggesting that the optical responses were not simple redox reactions. Peak shifts in the absorbance/photoluminescence spectra revealed unique differences according to the chirality of the SWNTs and the types of chemicals used. This suggests that the combination of absorbance/photoluminescence and peak intensity/peak shifts could detect multiple types of chemical information, not only redox reaction. A direct comparison between EG and TA was demonstrated for the first time in this novel study. In addition, sensing of EG and TA by near infrared spectra was made available using not only changes in intensity but also a variety of peak shifts of SWNTs.

Alkali-activated cements prepared from aluminosilicate powders, such as blast furnace slag and fly ash, are rapidly attracting attention as alternatives to cement because they can significantly reduce CO2 emissions compared to conventional cement concrete. In this study, we investigated the relationship between the physical and chemical changes by accelerated carbonation conditions of alkali-activated cements. Alkali-activated cements were prepared from binders composed of blast furnace slag and fly ash as well as alkali activators sodium silicate and sodium hydroxide. Physical changes were analyzed from compressive strength, pH, and neutralization depth, and chemical changes were analyzed from XRD, TG-DTG, and 29Si MAS NMR. The C–(N)–A–S–H structure is noted to change via carbonation, and the compressive strength is observed to decrease. However, in the case of Na-rich specimens, the compressive strength does not decrease by accelerated carbonation. This work is expected to contribute to the field of alkali-activated cements in the future.

DNA-wrapped single-walled carbon nanotubes (DNA-SWCNTs) in stable dispersion are expected to be used as biosensors in the future, because they have the property of absorption of light in the near infrared (NIR) region, which is safe for the human body. However, this practical application requires the understanding of the DNA-SWCNTs’ detailed response characteristics. The purpose of this study is to predict, in detail, the response characteristics of the absorption spectra that result when the antioxidant catechin is added to oxidized DNA-SWCNTs, from a small amount of experimental data. Therefore, in the present study, we predicted the characteristics of the absorption spectra of DNA-SWCNTs using the Bayesian regularization backpropagation neural network (BRBPNN) model. The BRBPNN model was trained with the catechin concentration and initial absorption peaks as inputs and the absorption spectra after catechin addition as outputs. The accuracy of the predicted absorption peaks and wavelengths after the addition of catechin, as predicted by the BRBPNN model, was within 1% of the error of the experimental data. By inputting the catechin concentrations under hundreds of conditions into this BRBPNN model, we were able to obtain detailed prediction curves for the absorption peaks. This method has the potential to help to reduce the experimental costs and improve the efficiency of investigating the properties of high-cost materials such as SWCNTs.

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