The citrate reduction method for the synthesis of gold nanoparticles (GNPs) has known advantages but usually provides the products with low nanoparticle concentration and limits its application. Herein, we report a facile method to synthesize GNPs from concentrated chloroauric acid (2.5 mM) via adding sodium hydroxide and controlling the temperature. It was found that adding a proper amount of sodium hydroxide can produce uniform concentrated GNPs with low size distribution; otherwise, the largely distributed nanoparticles or instable colloids were obtained. The low reaction temperature is helpful to control the nanoparticle formation rate, and uniform GNPs can be obtained in presence of optimized NaOH concentrations. The pH values of the obtained uniform GNPs were found to be very near to neutral, and the pH influence on the particle size distribution may reveal the different formation mechanism of GNPs at high or low pH condition. Moreover, this modified synthesis method can save more than 90% energy in the heating step. Such environmental-friendly synthesis method for gold nanoparticles may have a great potential in large-scale manufacturing for commercial and industrial demand.

Introduction. Formic acid decomposes upon contact with strong acids producing carbon monoxide. Carbon monoxide poisoning from such a source, however, is extremely rare. Case Report. A 26-year-old man committed suicide by mixing 2.5 L of formic acid and 2.5 L of sulfuric acid in three beakers and staying in a closed room. The 53-year-old father performed cardiopulmonary resuscitation on his son but soon lost consciousness. In hospital, he initially manifested coma, hypoxemia, metabolic acidosis, and a carboxyhemoglobin level of 45.8%. He was treated with hyperbaric oxygen but developed acute respiratory distress syndrome on day four despite an early improvement. He was successfully weaned from the ventilator on day 8. The 53-year-old mother felt dizziness, headache and had a carboxyhemoglobin level of 23.0%. Her symptoms improved after oxygen therapy. Discussion and Conclusions. Formic acid is a highly fatal source of carbon monoxide poisoning when mixed with sulfuric acid. In addition to the toxicities of carbon monoxide, concomitant inhalation of formic acid fumes can cause severe lung injury, which may complicate the management of carbon monoxide poisoning.

Photonic crystals (PCs) are periodic dielectric structures with photonic bandgaps and they can be used to control and manipulate photons effectively. Novel photonic crystal materials with tunable bandgaps can be prepared by changing the refractive index of the dielectric or lattice parameters under external stimuli, while using temperature to adjust the photonic band gap is a simple and convenient method. In this paper, silica PCs having different pseudo-gaps in the range of 450–750 nm were prepared with colloidal SiO₂ spheres of different sizes. Thermo-sensitive PNIPAM hydrogel was then infiltrated into the PCs to obtain PNIPAM-PCs, whose pseudo-gap blue-shifted when the temperature was changed from 24 to 34 °C and exhibited good reversibility. The PCs with tunable bandgaps are significant for the development of integrated photonic devices, sensors, and in detection and other technologies.