More Like this

1. Fueling a Hot Debate on the Application of TiO2 Nanoparticles in Sunscreen

   https://doi.org/10.3390/ma12142317  

   Sharma, Shweta; Sharma, Rohit K.; Gaur, Kavita; Cátala Torres, José F.; Loza-Rosas, Sergio A.; Torres, Anamaris; Saxena, Manoj; Julin, Mara; Tinoco, Arthur D. (July 2019, Materials)

   Titanium is one of the most abundant elements in the earth’s crust and while there are many examples of its bioactive properties and use by living organisms, there are few studies that have probed its biochemical reactivity in physiological environments. In the cosmetic industry, TiO2 nanoparticles are widely used. They are often incorporated in sunscreens as inorganic physical sun blockers, taking advantage of their semiconducting property, which facilitates absorbing ultraviolet (UV) radiation. Sunscreens are formulated to protect human skin from the redox activity of the TiO2 nanoparticles (NPs) and are mass-marketed as safe for people and the environment. By closely examining the biological use of TiO2 and the influence of biomolecules on its stability and solubility, we reassess the reactivity of the material in the presence and absence of UV energy. We also consider the alarming impact that TiO2 NP seepage into bodies of water can cause to the environment and aquatic life, and the effect that it can have on human skin and health, in general, especially if it penetrates into the human body and the bloodstream. 

   more » « less
2. Review of Oxidative Dissolution and Sulfidation of Select Nanoparticles in the Environment: Impact on Applications

   https://doi.org/10.1021/acsanm.3c06227  

   O’Keefe, Tana L.; Haynes, Christy L. (April 2024, ACS Applied Nano Materials)

   Nanoparticles (NPs) are increasingly being used in medical, electronic, energy, and agricultural applications due to their unique properties that often arise due to the high surface area-to-volume ratio. However, this characteristic along with the high reactivity of NPs make these materials highly dynamic in environmental settings. Thus, several transformations can take place when these materials enter the environment that determines their transport, toxicity, and fate of them in our environment. These transformations, and more specifically oxidative dissolution and sulfidation, are directly impacted by the characteristics that a NP has in addition to the surrounding environmental conditions. Therefore, this review aims to summarize how NP characteristics (size, coatings, etc.) and other important environmentally relevant conditions (oxic/anoxic waters, natural organic matter, etc.) impact the oxidative dissolution and sulfidation of several metal and metal oxide NPs. The impact of these factors is crucial to understanding and predicting the environmental risks of these materials in a wide range of applications. 

   more » « less
3. Fluorogenic Reaction Probes Defect Sites on Titanium Dioxide Nanoparticles

   Zuo, Li; Hossain, Mohammad Akter; Dubadi, Rabindra; Kist, Madelyn M.; Farhana, Fatiha; Chen, Jiao; Jaroniec, Mietek; Shen, Hao (May 2024, ChemNanoMat)

   Charlotte Liu (Ed.)

   Titanium dioxide nanoparticles (TiO2 NPs) have traditionally been utilized as industrial catalysts, finding widespread application in various chemical processes due to their exceptional stability and minimal toxicity. However, quantitatively assessing the reactive sites on TiO2 NPs remains a challenge. In this study, we employed a fluorogenic reaction to probe the apparent reactivity of TiO2 NPs. By manipulating the number of defect sites through control of hydrolysis speed and annealing temperature, we determined that the Ti(Ⅲ) content is positively correlated with the reactivity of TiO2 NPs. Additionally, these Ti(Ⅲ) sites could be introduced by reducing commercial TiO2 NPs using NaBH4. Our findings suggest that fluorogenic oxidation of Amplex Red is an effective method for probing defect site densities on TiO2 NPs. Utilizing single-molecule fluorescence imaging, we demonstrated the ability to map defect site density within TiO2 nanowires. Achieving sub-nanoparticle spatial resolution, we observed significant intraparticle and interparticle variations in the defect site distribution, leading to substantial reactivity heterogeneity. 

   more » « less
4. Size-tunable silver nanoparticle synthesis in glycerol driven by a low-pressure nonthermal plasma

   https://doi.org/10.1088/1361-6463/ac9ce9  

   Xu, Chi; Andaraarachchi, Himashi P; Xiong, Zichang; Eslamisaray, Mohammad Ali; Kushner, Mark J; Kortshagen, Uwe R (November 2022, Journal of Physics D: Applied Physics)

   Abstract Silver nanoparticles (NPs) are extensively used in electronic components, chemical sensors, and disinfection applications, in which many of their properties depend on particle size. However, control over silver NP size and morphology still remains a challenge for many synthesis techniques. In this work, we demonstrate the surfactant-free synthesis of silver NPs using a low-pressure inductively coupled nonthermal argon plasma. Continuously forming droplets of silver nitrate (AgNO 3 ) precursor dissolved in glycerol are exposed to the plasma, with the droplet residence time being determined by the precursor flow rate. Glycerol has rarely been studied in plasma-liquid interactions but shows favorable properties for controlled NP synthesis at low pressure. We show that the droplet residence time and plasma power have strong influence on NP properties, and that improved size control and particle monodispersity can be achieved by pulsed power operation. Silver NPs had mean diameters of 20 nm with geometric standard deviations of 1.6 under continuous wave operation, which decreased to 6 nm mean and 1.3 geometric standard deviation for pulsed power operation at 100 Hz and 20% duty cycle. We propose that solvated electrons from the plasma and vacuum ultraviolet (VUV) radiation induced electrons produced in glycerol are the main reducing agents of Ag + , the precursor for NPs, while no significant change of chemical composition of the glycerol solvent was detected. 

   more » « less
5. Electrochemical Manufacturing Routes for Organic Chemical Commodities

   https://doi.org/10.1146/annurev-chembioeng-101121-090840  

   Mathison, Ricardo; Ramos Figueroa, Alexandra L.; Bloomquist, Casey; Modestino, Miguel A. (June 2023, Annual Review of Chemical and Biomolecular Engineering)

   Electrochemical synthesis of organic chemical commodities provides an alternative to conventional thermochemical manufacturing and enables the direct use of renewable electricity to reduce greenhouse gas emissions from the chemical industry. We discuss electrochemical synthesis approaches that use abundant carbon feedstocks for the production of the largest petrochemical precursors and basic organic chemical products: light olefins, olefin oxidation derivatives, aromatics, and methanol. First, we identify feasible routes for the electrochemical production of each commodity while considering the reaction thermodynamics, available feedstocks, and competing thermochemical processes. Next, we summarize successful catalysis and reaction engineering approaches to overcome technological challenges that prevent electrochemical routes from operating at high production rates, selectivity, stability, and energy conversion efficiency. Finally, we provide an outlook on the strategies that must be implemented to achieve large-scale electrochemical manufacturing of major organic chemical commodities. Expected final online publication date for the Annual Review of Chemical and Biomolecular Engineering, Volume 14 is June 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates. 

   more » « less