Characterization, identification, and detection of aerosol particles in their native atmospheric states remain a challenge. Recently, optical trapping-Raman spectroscopy (OT-RS) has been developed ...and demonstrated for characterization of single, airborne particles. Such particles in different chemical groups have been characterized by OT-RS in recent years and many more are being studied. In this work, we collected single-particle Raman spectra measured using the OT-RS technique and began construction of a library of OT-RS fingerprints that may be used as a reference for potential detection and identification of aerosol particles in the atmosphere. We collected OT-RS fingerprints of aerosol particles from eight different categories including carbons, bioaerosols (pollens, fungi, vitamins, spores), dusts, biological warfare agent surrogates, etc. Among the eight categories, spectral fingerprints of six groups of aerosol particles have been published previously and two other groups are new. We also discussed challenges, limitations, and advantages of using single-particle optical trapping-Raman spectroscopy for aerosol-particle characterization, identification, and detection.
Ag-doped TiO2 nanotubes (TNTs) were fabricated by ion implantation and anodization. The surface morphology, phase components and chemical composition of pure and implanted TNTs were characterized by ...SEM, XRD and XPS respectively. All the implanted samples kept stable releasing of silver ions within a long term. No Ag nanoparticles were observed on the surface of TNTs. In view of the potential clinical applications, Staphylococcus aureus was used to estimate the antimicrobial effects of Ag ions implanted TNTs. All the implanted samples exhibited excellent bacteriostatic effect compared to pure TNTs. The bactericidal ratio increased with increasing the dose of implanted ions. This study provides new insight to optimize the surface design of Ti-based implants to acquire more effective antimicrobial surfaces to meet clinical applications.
•Silver ions were doped by the method of ion implantation.•Ag ions implantation is befit to the formation of TNTs.•Long term and stable antibacterial ability of implanted TNT was found.
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•Implanted TiO2 films with excellent antibacterial and photocatalytic ability was prepared.•Bactericidal effect of released Ag ions was confirmed using VC as radical ...scavenger.•Excitation of TiO2 to visible region is attributed to subtitutional Ag.•Synergetic effect of Ag3+ and Ag+ accounts for the enhanced ability of TiO2.
TiO2 thin films were deposited by spin coating method. Silver ions were implanted into the films using a Metal Vapor Vacuum Arc implanter. The antibacterial ability of implanted films was tested using Escherichia coli removal under fluorescent irradiation and in the dark. The concentration of E. coli was evaluated by plating technique. The photocatalytic efficiency of the implanted films was studied by degradation of methyl orange under fluorescent illumination. The surface free energy of the implanted TiO2 films was calculated by contact angle testing. Vitamin C was used as radical scavengers to explore the antibacterial mechanism of the films. The results supported the model that both generation of reactive oxygen species and release of silver ions played critical roles in the toxic effect of implanted films against E. coli. XPS experimental results demonstrated that a portion of the Ag(Ag3+) ions were doped into the crystalline lattice of TiO2. As demonstrated by density functional theory calculations, the impurity energy level of subtitutional Ag was responsible for enhanced absorption of visible light. Ag ion-implanted TiO2 films with excellent antibacterial efficiency against bacteria and decomposed ability against organic pollutants could be potent bactericidal surface in moist environment.
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•Optically-trapped, chemically-purposed, micron-sized, single-particle reactor (SPR) in air.•Heterogeneous reaction of solid-state Hg(II) halides on the surface SPR.•A new platform ...for the study of surface and heterogeneous chemistry of aerosol particles in air.
We created a micron-sized, single-particle reactor (SPR) freely levitated in air using optical trapping of a single particulate-bound mercury particle formed by mixing HgCl2, HgBr2, or HgBrCl (HgX2, X = Cl, Br) with single-walled carbon nanotubes. Position- and time-resolved, single-particle Raman spectra show clear evidence of reactions of solid-state HgX2 in the presence of excessive O3 under the illumination of 532-nm light. We propose a reaction mechanism: Hg(II)X2 (solid) + O → Hg(I)X + XO, XO + O → O2 + X on the surface of the SPR. This exploratory study demonstrates that the SPR is a new tool for the study the surface and heterogeneous chemistry of mercury at atmospherically relevant surfaces, e.g., aerosols.
Single particles trapped in an optical trap may experience temperature elevation, yet direct measurement of temperature and its distribution inside the optical trap of several to hundreds of microns ...in size remains a big challenge. We introduce a method that can measure the temperature inside a universal optical trap (UOT) using Raman spectroscopy of single trapped particles of high thermal conductivity. We measured temperature and temperature distributions inside the UOT using Raman shifts of single-walled carbon nanotubes (SWCNTs) and micron-sized diamonds (MSDs), which are heated by trapping laser beams directly or indirectly, depending on the location of the particle in the trap. We show that the temperature at the center of the UOT is much lower than the temperature along the hollow beams that form a hollow, cage-shaped UOT. In the range of the trapping laser power of 200–2950 mW, the surface temperature of particles trapped at the center of a UOT changes from 322 K to 830 K, correspondingly. This result gives a heating rate as a high thermal-absorbing particle trapped in the center of the UOT with 18.3 ± 0.4 °C/100 mW. In addition, the temperature gradient outside the UOT was also characterized by trapping SWCNT particles outside the UOT. Results show that when a light-absorbing particle is trapped for the study of material property, phase transitions, surface equilibrium process, chemical reactions, etc., this method can be used to measure temperature distribution and its variations in the trap and its surroundings.
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Sea-spray aerosols (SSAs) contribute to atmospheric loading, bringing toxic compounds like mercury (Hg) to the atmosphere, affecting the climate and human health. Despite their importance, the ...investigation into surface modification, including heterogeneous chemical and photochemical reactions of SSAs, is limited. In this work, we studied the heterogeneous chemistry and photochemistry of a single suspended SSA particle and a SSA containing Hg( ii ) in a reactive environment using optical trapping – Raman spectroscopy. The experiments are focused on the study of hygroscopicity, heterogeneous chemical reaction with ozone (O 3 ), photochemical reaction with UVC radiation of an optically suspended single SSA particle, and photo-reduction of Hg( ii ) in SSAs under UVC radiation. Results show different Raman signal responses of a single SSA particle when it is optically trapped in air under varying relative humidity conditions as the aerosol particle uptakes and loses liquid water from the surrounding environment. The state and size of the aerosol are determined through the on-time images and different single-particle Raman spectral features. Results also show that the formation of chlorate (ClO 3 − ) is a reaction product of the heterogeneous reaction between the SSA particle and O 3 . The photochemical reaction products, as the SSA particle suspended in air under UVC radiation, are ClO 3 − and perchlorate (ClO 4 − ). Further, we observed that these reactions occur only on the surface of the SSA particle. Based on the results, we hypothesize that Hg( ii ) can be photo-reduced to Hg( i ) in SSAs through UVC radiation, and the amount of Hg( i ) in SSAs is minor and balanced between the photo-oxidation and photo-reduction reactions.
We applied a time-resolved, optical trapping-Raman spectroscopy (OT-RS) technique to characterize single, trapped bioaerosol particles under well-controlled reactive conditions that mimic the native ...state of particles in the atmosphere. We measured Raman spectra of seven different fungus samples using an OT-RS system, in which single fungal aerosol particles of tens of microns in size are trapped without photo-damage while relative humidity and ozone concentration around the particle are well controlled. We initially obtained Raman spectral fingerprints of seven different single-trapped fungal aerosol particles in air. We then measured time-resolved Raman spectra of the fungal aerosol particles trapped in air over a period of 40 minutes and characterized the temporal behavior of the trapped particles in terms of Raman band structure and intensity. We also measured time-resolved Raman spectra of the fungal aerosol particles exposed to ozone in a controlled concentration and relative humidity and compared the spectral features with those obtained when the single fungal aerosol particles were exposed to air. Results show that we not only observed time variations of the physical and chemical properties of single-trapped particles, but also specified several individual chemical function groups such as lipids and proteins that undergo chemical reactions with ozone. This work demonstrated that OT-RS is a powerful technology for characterization of physical, chemical, and biological properties of single bioaerosol particles in simulated atmospheric conditions and for potential detection of single bioaerosol particles in the atmosphere using Raman spectral fingerprints.
We applied a time-resolved, optical trapping-Raman spectroscopy (OT-RS) technique to characterize single, trapped bioaerosol particles under well-controlled reactive conditions that mimic the native state of particles in the atmosphere.
•Welan gum production using cane molasses by Alcaligenes sp. ATCC31555 was explored.•The process was optimized by molasses pretreatment, agitation control and addition of additives.•Welan gum ...production and yield obtained in the optimal process were highest so far.•Welan gum from molasses displayed similar physical properties to that from glucose.•Cane molasses may be a suitable substrate for welan gum production on industrial scale.
Welan gum production by Alcaligenes sp. ATCC31555 from cane molasses was studied in batch fermentation to reduce production costs and enhance gum production. The pretreatment of cane molasses, agitation speed and the addition of supplements were investigated to optimize the process. Sulfuric acid hydrolysis was found to be the optimal pretreatment, resulting in a maximum gum concentration of 33.5g/L, which is 50.0% higher than those obtained from the molasses’ mother liquor. Agitation at 600rpm at 30°C and addition of 10% n-dodecane following fermentation for 36h increased the maximum gum production up to 41.0±1.41g/L, which is 49.1% higher than the greatest welan gum concentration in the literature so far. The welan gum product showed an acceptable molecular weight, similar rheological properties and better thermal stability to that obtained from glucose. These results indicate that cane molasses may be a suitable and inexpensive substrate for cost-effective industrial-scale welan gum production.
In this work, silver nitrate, thiourea, bisphenol A diglycidyl ether (BADGE), and propylene glycol methyl ether (PM) were selected for designing a silver(I)-complex to trigger the deposition of ...inductance coil on PET film through electroless copper plating. The most stable silver(I)-complex structure is formed when the ratio of thiourea molecules and silver ions is 3 to 1 by quantum chemical calculations based on density functional theory (DFT). Meanwhile, XRD test demonstrates that the white precipitate crystallized from PM solution of thiourea and silver nitrate is Ag(SC(NH
2
)
2
)
3
NO
3
, which is consistent with theoretical calculations. The cross section of PET film with copper patterns and interconnection holes characterized by metallurgical microscope proves that the silver(I)-complex is able to initiate copper deposition on the surface and through hole wall of PET film. The measured inductance values at operating frequency from 1 to 50 MHz indicate that the fabricated flexible inductor is capable of being integrated into flexible electronics when the bending angles are within 45°. Additionally, the inductor can also be utilized as an angel sensor when the bending angles are in the range of 60° to 180° at 10 MHz.
During breast cancer progression, there is typically increased collagen deposition resulting in elevated extracellular matrix rigidity. This results in changes to cell-matrix adhesion and cell ...migration, impacting processes such as the epithelial-mesenchymal transition (EMT) and metastasis. We aim to investigate the roles of cell-matrix adhesion and cell migration on breast tumor growth and progression by studying the impacts of different types of extracellular matrices and their rigidities. We embedded MCF7 spheroids within three-dimensional (3D) collagen matrices and agarose matrices. MCF7 cells adhere to collagen but not agarose. Contrasting the results between these two matrices allows us to infer the role of cell-matrix adhesion. We found that MCF7 spheroids exhibited the fastest growth rate when embedded in a collagen matrix with a rigidity of 5.1 kPa (0.5 mg/mL collagen), whereas, for the agarose matrix, the rigidity for the fastest growth rate is 15 kPa (1.0% agarose) instead. This discrepancy is attributable to the presence of cell adhesion molecules in the collagen matrix, which initiates collagen matrix remodeling and facilitates cell migration from the tumor through the EMT. As breast tumors do not adhere to agarose matrices, it is suitable to simulate the cell-cell interactions during the early stage of breast tumor growth. We conducted further analysis to characterize the stresses exerted by the expanding spheroid on the agarose matrix. We identified two distinct MCF7 cell populations, namely, those that are non-dividing and those that are dividing, which exerted low and high expansion stresses on the agarose matrix, respectively. We confirmed this using Western blot which showed the upregulation of proliferating cell nuclear antigen, a proliferation marker, in spheroids grown in the 1.0% agarose (≈13 kPa). By treating the embedded MCF7 spheroids with an inhibitor or activator of myosin contractility, we showed that the optimum spheroids' growth can be increased or decreased, respectively. This finding suggests that tumor growth in the early stage, where cell-cell interaction is more prominent, is determined by actomyosin tension, which alters cell rounding pressure during cell division. However, when breast tumors begin generating collagen into the surrounding matrix, collagen remodeling triggers EMT to promote cell migration and invasion, ultimately leading to metastasis.
