Carbonaceous nanoparticle layers prepared using candle soot by direct- and spray-based depositions

To investigate the properties and structures of soot particles derived from candle combustion, two deposition routes were performed. In “Route-1,” the aerosol (soot) particles were collected by direct exposure of a substrate in a chamber with controlled airflows. In "Route-2,” deposited soot nanoparticles was transferred into suspension and subsequently, the deposition of particles on to the substrate was achieved by an electrospray. Raman spectral analysis has shown the difference of G-band intensity relative to D-band between hydrophobic and hydrophilic particle layers obtained from different collection regions of the candle flame. It also reveals the effect of airflows during the collection to the ratio of the D to G peak. Meanwhile, the Raman spectra of the particles seem invariant to the preparation methods of suspension and electrospray deposition process. From the curve gradient of spectroscopy (190–2500 nm) results, the electrospray-deposited particle layers (Route-2) show higher absorbance in the near-infrared region compared to direct-deposited particle layers (Route-1). This change in the spectrum may due to the change in morphology of nanoparticle layers formed by each route

Shinyei based sensor with added roof enhanced detection of indoor particulate matter

Commercially available monitoring systems in the market are expensive and rather challenging to maintain, had prompted researchers to invent low-cost monitoring system as alternative. New cost-effective, portable and user-friendly prototypes have been proposed using Shinyei PPD42NS sensor for PM10 monitoring. The performances of the original and roofed prototype were tested by measuring indoor PM10 concentrations. The roofed prototype showed a higher reading of PM10 (822 μgm-3) detected at minutes 16 compared to the original prototype (0 μgm-3) due to the presence of a roof decreased the velocity of particulate matter and accumulate before entered the Shinyei sensor inlet. CFD analysis of the roofed prototype illustrated lower air velocity of 0.3 ms-1 compared to original prototype having a velocity of 0.4 ms-1. The original prototype exhibit comparable performance to the reference instrument (GRIMM) in detecting PM10 concentration. Shinyei PPD42NS inside the original prototype showed high sensitivity by detecting higher concentration of PM10 with readings of 79 μgm-3. The prototypes were successfully developed by detecting the presence of PM10 and addition of roof showed increase efficiency in detecting particulate matter in the air

Detachment of submicron particles from substrates using the suspension-assisted ultrasonic method

A protocol for the detachment of solid samples deposited on flat substrates and their collection in aqueous samples is proposed based on a suspension-assisted ultrasonic method. As samples, combustion-synthesized magnesium oxide aggregates in the submicron size range were deposited in the gas phase onto three kinds of substrates: a silicon wafer and coarse and fine alumina-coated resin sheets. To enhance the sample particle detachment, a solid–liquid suspension made of candle combustion soot particles was selected as an ultrasound propagation medium, which is different from the usual liquid medium, such as water, a surfactant solution, or a solvent. Preliminary detachment experiments were performed using low-power (42 kHz and 35 W) ultrasonication, and the substrates and suspensions were analyzed using scanning electron microscopy (SEM) images and particle size distributions based on dynamic light scattering, respectively. The detachment efficiency, defined as the fraction of cleaned area on a substrate, was determined from the SEM images and indicates that the detachment using the medium with soot had a higher efficiency compared to that without soot, and there was an optimum soot concentration for particle detachment for all three substrates. The suspension particle size distribution after ultrasonication showed good dispersion of the sample particles in the soot suspension