Room-temperature chlorine gas sensor based on CdSnO_(3) synthesized by hydrothermal process

The perovskite-structure CdSnO_(3) was obtained by calcinating CdSnO_(3)·3H_(2)O precursor at 550℃,which was synthesized by hydrothermal process at 170℃for 16 h.The phase and microstructure of the obtained CdSnO_(3) powders were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The CdSnO_(3) powders exhibit uniformly cubic structure with side length of about 100 nm.The effects of working temperature and concentration of detected gas on the gas response were studied.The selectivity of chlorine gas against other gases and response-recovery time of the sensor were also investigated.The results reveal that the CdSnO_(3) gas sensor has enhanced sensing properties to 1-10 ppm chlorine gas at room temperature;the value of gas response can reach 1338.9 to 5 ppm chlorine gas.Moreover,the sensor shows good selectivity and quick response behavior(23 s)to chlorine gas,indicating its application in detecting chlorine gas at room temperature in the future.

Chlorine gas sensors using hybrid organic semiconductors of PANI/ZnPcCl_(16)

PANI/ZnPcCl_（16）（polyaniline doped with sulfosalicylic acid/hexadecachloro zinc phthalocyanine） powders were vacuum co-deposited onto Si substrates,where Pt interdigitated electrodes were made by micromachining.The PANI/ZnPcCl_（16） films were characterized and analyzed by SEM,and the influencing factors on its intrinsic performance were analyzed and sensitivities of the sensors were investigated by exposure to chlorine（Cl_2） gas.The results showed that powders prepared with a stoichiometric ratio of（ZnPcCl_（16））_（0.6）（PANI）_（0.4） had a preferential sensitivity to Cl_2 gas, superior to those prepared otherwise;the optimal vacuum co-deposition conditions for the films are a substrate temperature of 160℃,an evaporation temperature of 425℃and a film thickness of 75 nm;elevating the operation temperature （above 100℃） or increasing the gas concentration（over 100 ppm） would improve the response characteristics,but there should be upper levels for each.Finally,the gas sensing mechanism of PANI/ZnPcCl_（16） films was also discussed.

Effects of Chlorine Dioxide Gas on Postharvest Physiology and Storage Quality of Green Bell Pepper (Capsicum frutescens L.var.Longrum)

The effects of treatment of chlorine dioxide （C1Oz） gas on postharvest physiology and preservation quality of green bell peppers were studied. Green bell peppers were collected in bags and treated with 0, 5, 10, 20, and 50 mg L^-1 ClO2 gas at 10±0.5℃ for over 40 d, and the changes in postharvest physiology and preservation quality of the peppers were evaluated during the storage. The inhibition of rot of the peppers was observed for all the tested ClO2 gas treatments. The rot rates of the treated samples were 50% lesser than those of the control after day 40 of storage. The highest inhibitory effect was obtained after 50 mg L^-1 ClO2 gas treatment, where the peppers did not decay until day 30 and showed only one-fourth of the rot rate of the control at day 40 of storage. The respiratory activity of the peppers was significantly （P〈0.05） inhibited by 20 and 50 mg L^-1 ClO2 treatments, whereas no significant effects on respiratory activity were observed with 5 and 10 mg L^-1 ClO2 treatments （P〉0.05）. Except for 50 mg L^-1 ClO2, malondialdenyde （MDA） contents in the peppers treated with 5, 10, or 20 mg L^-1 ClO2 were not significantly （P〉0.05） different from those in the control. Degradation of chlorophyll in the peppers was delayed by 5 mg L-1ClO2, but promoted by 10, 20, or 50 mg L^-1 ClO2. The vitamin C content, titratable acidity, and total soluble solids of the peppers treated by all the tested ClO2 gas did not significantly change during the storage. The results suggested that ClO2 gas treatment effectively delayed the postharvest physiological transformation of green peppers, inhibited decay and respiration, maintained some nutritional and sensory quality, and retarded MDA accumulation.

Research on the explosion characteristics of chlorine dioxide gas

The explosion characteristics of chlorine dioxide gas have been studied for the first time in a cylindrical exploder with a shell capacity of 201. The experimental results have indicated that the lower concentration limit for the explosive decomposition of chlorine dioxide gas is 9.5% （[ClO2]/[air]）, whereas there is no corresponding upper concentration limit. The maximum pressure of explosion relative to the initial pressure was measured as 0.024 MPa at 10% ClO2 and 0.641 MPa at 90% ClO2. The induction time （the time from the moment of sparking to explosion） at 10% ClO2 was 2195 ms, but at 90% ClO2 the induction time was just 8 ms. The explosion reaction mechanism of ClO2 is of a degenerate chain-branching type involving the formation of a stable intermediate （Cl2O3）, from which the chain branching occurs.

Virucidal Activity of Chlorine Dioxide Gas for Reduction of Coronavirus on Surfaces and PPE

A coronavirus (SARS-CoV-2) has caused a global pandemic and associated morbidity and mortality resultant from COVID-19. As a result of efforts to control direct (person to person) and indirect (contaminated objects, surfaces, indoor air) transmission of the virus, various interventions have been evaluated. Studies were conducted to evaluate the efficacy of commercially available chlorine dioxide (CD) products to reduce viral loads on PPE (face masks) and surfaces using a novel dry gas release intervention. The efficacy of CD slow release 30-day sachets was tested on N95 face masks inoculated with human coronavirus OC43 in suspension. One sachet was placed with an inoculated mask in plastic resealable bags. Three trials were completed using the original sachet where a mask and sachet were placed into a plastic bag for 13 hours per sachet age of 1 day, 14 days, and 30 days. The amount of CD generated during a 13-hour treatment period was 0.30 mg. The nominal concentration of CD was estimated to be 317 mg/m3. All three tests demonstrated at least a 99.91% reduction of viral loading in the mask versus a non-treated control. Efficacy of CD dry gas fast releasing pods (Ultrashok) for fumigation was also tested in a 1344 ft3 closed room. Two pods were placed in the space and CD surface virucidal efficacy was tested in three locations of the room after 1 hour and 2 hours of dwell time. The estimated nominal peak concentration was 15 ppmv in the room. The one-hour exposure saw a >99.91% OC43 reduction on surfaces and the two-hour exposure resulted in a >99.997% OC43 reduction on surfaces versus a non-treated control. These results indicate dry CD is highly effective against human coronavirus. CD was 99.91% effective for eliminating human coronavirus OC43 in both sachet and capsule fumigant form using both fast and slow release mechanisms. Rapid fumigant application is suitable for contaminated rooms, ambulances, emergency vehicles, and many types of PPE, most particularly porous PPE materials. The gaseous state of CD allows for rapid diffusion and transfer of the virucidal stable free radical to all surfaces of PPE and indoor areas that would favor virus survival. Additionally, this work suggests CD can be effective at levels with significant margins of safety (little to no exposure and rapid degradation of residuals) providing minimal public health risks associated with the use of CD.

Decontamination of Bacillus subtilis var. niger spores on selected surfaces by chlorine dioxide gas

Objective： Chlorine dioxide （CD） gas has been used as a fumigant in the disinfection of biosafety labo- ratories. In this study, some experiments were conducted to assess the inactivation of spores inoculated on six ma- terials [stainless steel （SS）, painted steel （PS）, polyvinyl chlorid （PVC）, polyurethane （PU）, glass （GS）, and cotton cloth （CC）] by CD gas. The main aims of the study were to determine the sporicidal efficacy of CD gas and the effect of prehumidification before decontamination on sporicidal efficacy. Methods： Material coupons （1.2 cm diameter of SS, PS, and PU; 1.0 cmx1.0 cm for PVC, GS, and CC） were contaminated with 10 IJI of Bacillus subtilis var. niger（ATCC 9372） spore suspension in mixed organic burden and then dried in a biosafety cabinet for 12 h. The spores were recovered by soaking the coupons in 5 ml of extraction liquid for 1 h and then vortexing the liquid for 1 min. Results： The log reductions in spore numbers on inoculated test materials exposed to CD gas [0.080% （volume ratio, v/v） for 3 h] were in the range of from 1.80 to 6.64. Statistically significant differences were found in decontamination efficacies on test material coupons of SS, PS, PU, and CC between with and without a 1-h prehumidification treatment. With the extraction method, there were no statistically significant differences in the recovery ratios between the porous and non-porous materials. Conclusions： The results reported from this study could provide information for developing decontamination technology based on CD gas for targeting surface microbial contamination.

Sensitive properties of In-based compound semiconductor oxide to Cl_2 gas

Aiming at detecting Cl2 gas, this study was made on how to make In-based compound semiconductor oxide gas sensor. The micro-property and sensitivity of In-based gas sensing material were analyzed and its gas sensitive mechanism was also discussed. Adopting constant temperature chemical coprecipitation, the compound oxides such as In-Nb, In-Cd and In-Mg were synthesized, respectively. The products were sintered at 600 ℃ and characterized by the Scanning Electron Microscope （SEM）, showing the grain size almost about 50-60 nm. The test results show that the sensitivities of In-Nb, In-Cd and In-Mg materials under the concentration of 50 × 10^-6 in Cl2 gas are above 100 times, 4 times and 10 times, respectively. The response time of In-Nb, In-Cd and In-Mg materials is about 30, 60 and 30 s, and the recovery time less than 2, 10 and 2 min, respectively. Among them, the In-Nb material was found to have a relatively high conductivity and ideal sensitivity to Cl2 gas, which showed rather good selectivity and stability, and could detect the minimum concentration of 0.5 × 10^-6 with the sensitivity of 2.2, and the upper limit concentration of 500 × 10^-6. The power loss of the device is around 220 mW under the heating voltage of 3 V.

Using highly concentrated chloride solutions to leach valuable metals from cathode-active materials in spent lithium-ion batteries

This study focused on the extraction of valuable metals from the cathode-active materials in spent lithiumion batteries using a high-concentration chloride solution.The effects of the concentrations of ammonium chloride(NH4 Cl),hydrochloric acid(HCl),and reductants such as hydrogen peroxide(H_(2)O_(2))and urea(CO(NH_(2))_(2))on metal extraction and chlorine production were studied experimentally.The leaching mechanism was analyzed,and a leaching model was established.It was found that the addition of solid NH4 Cl to an HCl solution significantly improved the metal extraction capability of the latter and reduced the formation of chlorine gas by 96.0%compared to that only using HCl.The activation energies for leaching Li,Ni,Co,and Mn were determined to be 30.4,38.5,30.6,and 38.2 kJ·mol^(-1),respectively.This study demonstrates an environmentally friendly method for recycling metal resources from cathode-active materials and furthers understanding of how NH4 Cl inhibits chlorine production when leaching with mixed solutions of HCl and NH4 Cl.