Various chemicals and molecules have been employed for decontamination in healthcare settings and for disinfection within the respiratory system. Recently, aerosolised delivery methods have been incorporated into decontamination and disinfection protocols to enhance antibacterial and antiviral efficacy. In this review, we discuss the current applications of aerosolised small molecules and chemicals, and other common techniques such as plasma activated products and gaseous agents, for respiratory system disinfection and environmental decontamination. We also highlight the advantages and limitations of these techniques, along with health and safety considerations of chemical and biological decontamination in CBRN (Chemical, Biological, Radiological, and Nuclear) contexts. Ultimately, we will examine if a common effective agent exists that can bridge environmental decontamination and in vivo respiratory disinfection which would be suitable for rapid deployment.
A chemical kinetic model for formation of (KCl)n clusters and initial particles from gas-phase KCl has been developed. Geometries and vibrational frequencies for (KCl)n were calculated by density functional theory (B3LYP) with the 6-31G(2df) basis set for n = 1–18, with single-point energies from DLPNO-CCSD(T)/def2-TZPPD theory. Correlations were derived for enthalpy, entropy, and heat capacity as functions of n, allowing estimation of data for n > 18. It was shown that formation of (KCl)n clusters up through n = 4 proceeds without a barrier. Kinetic modeling predictions for the behavior during cooling (100–1000 K/s), assuming all cluster growth reactions to be barrierless with rate constants similar to NaCl dimerization, indicated that the early stages of particle formation were thermodynamically limited. Cluster growth for n > 4 proceeded through both monomer and dimer addition, rather than step-wise addition of a monomer, as assumed in classical nucleation theory (CNT). The predicted temperature for onset of particle formation, controlled by the thermochemistry of the KCl clusters, was about 100 K lower than estimated by CNT from bulk properties of the liquid.
Aerosol volatility regulates the gas-particle partitioning of compounds and is directly linked to particle composition. To clarify volatility dynamics in polluted megacities and support future clean air strategies, we measured size-dependent volatility shrink factors (VSF) of ambient fine aerosols (40–300 nm) at 80, 150, 200, and 300 °C using a volatility tandem differential mobility analyzer (VTDMA) in urban Beijing during winter and summer. The applied heating temperatures were used as an operational probe to distinguish aerosol components with different volatility ranges. Then, the VSF was linked to key inorganic and organic components for targeted pollution mitigation. Winter observations revealed that aerosol volatility decreased with particle size across all temperatures, with particles more volatile at midnight and noon than during morning and evening rush hours. Aitken-mode particles (40, 80 nm) were less volatile in polluted periods than in clean periods, while accumulation-mode particles (110, 150, 200, 300 nm) showed no such difference, highlighting the need for size-specific control of primary pollutants in winter. In contrast, summer aerosols exhibited higher overall volatility: at 300 °C, 300 nm particles showed an ensemble-mean VSF of ∼0.4 in summer, compared with ∼0.6 in winter, driven by reduced primary emissions and dominant volatile secondary components. Component-specific analysis showed that higher nitrate fractions were associated with lower VSF, with nitrate mass fractions increasing from ∼15% to ∼30% as VSF decreased from 0.9 to 0.5 at 300 °C, identifying nitrate-rich particles as an important contributor to volatile secondary pollution. Sulfate was associated with higher VSF due to its low volatility, while ammonium covaried with nitrate, consistent with their common occurrence as ammonium nitrate. For organic aerosols (OA), more oxidized oxygenated OA (MO-OOA) enhanced volatility resistance, whereas less oxidized oxygenated OA (LO-OOA) was more volatile, indicating that the OA effect depends on oxidation degree. An empirical parameterization model, VSF = 0.54MFOrg+0.25MFNO3+0.71MFSO4+0.14MFNH4+0.5MFBC+0.08ln(Dp/100)+0.15, was further established to represent the combined effects of aerosol composition and particle size on VSF at 300 °C. This study advances understanding of urban aerosol volatility by disentangling size, seasonal, and pollution effects, providing actionable insights for mitigating fine particle pollution in megacities.
A plasma-near-passage unipolar aerosol charger (PNP charger) was developed for high-efficiency charging of sub-10 nm particles, and for the first time, an extrinsic charging efficiency eta(extr)>0.7 was demonstrated for 10 nm particles. The key feature of this device is that particles are passed for a very short time through the high ion concentration region near the plasma , enabling a large nt-product (n is the ion concentration, t is the residence time in the charging region) while minimizing t as much as possible. Analysis based on diffusion charging theory suggested that, at 3.0 L/min, the aerosol particles were exposed to a very high effective, path-averaged ion concentration of 1.1 & times;10(16) m(-3) for only 4.2 ms. This approach reduced diffusion loss of sub-10 nm particles and enabled highly efficient charging. Furthermore, the charged particle generation rate was the highest among previous studies for all particles below 10 nm. These results have the potential to reduce material loss and improve production throughput in device fabrication processes utilizing aerosol particles.
