Filter-based surface-enhanced Raman spectroscopy for rapid and sensitive detection of the fungicide ferbam in water

<p>Surface-enhanced Raman spectroscopy (SERS) has been widely applied for rapid and sensitive detection of various chemical and biological targets. Here, we incorporated a filter syringe system into the SERS method to detect the fungicide ferbam in water. Silver nanoparticles (Ag NPs) were aggregated by sodium chloride (NaCl) to form nanoclusters that could be trapped in the pores of the filter membrane to from the SERS-active membrane. Then samples were filtered through the membrane. After capturing the target, the membrane was taken out and air dried before measuring by a Raman instrument. After optimisation of various parameters, the developed filter SERS method was able to detect the fungicide ferbam as low as 2.5 μg/L and had a good quantitative capability. The developed method was successfully applied in three water samples, including double-distilled water, tap water, and pond water. The test can be carried out on site using a portable Raman instrument. This study shows that the filter-based SERS method improves the detection capability in water samples, including the sensitivity and portability, and could be applied in the detection of various toxins in real-world water samples.</p

Rapid detection of TiO₂ (E171) in table sugar using Raman spectroscopy

<p>The potential toxic effects of titanium dioxide (TiO₂) to humans remain debatable despite its broad application as a food additive. Thus, confirmation of the existence of TiO₂ particles in food matrices and subsequently quantifying them are becoming increasingly critical. This study developed a facile, rapid (< 30 min) and highly reliable method to detect and quantify TiO₂ particles (E171) from food products (e.g., table sugar) by Raman spectroscopy. To detect TiO₂ particles from sugar solution, sequential centrifugation and washing procedures were effectively applied to separate and recover 97% of TiO₂ particles from the sugar solution. The peak intensity of TiO₂ sensitively responded to the concentration of TiO₂ with a limit of detection (LOD) of 0.073 mg kg^–1. In the case of sugar granules, a mapping technique was applied to directly estimate the level of TiO₂, which can be potentially used for rapid online monitoring. The plot of averaged intensity to TiO₂ concentration in the sugar granules exhibited a good linear relationship in the wide range of 5–2000 mg kg^–1, with an LOD of 8.46 mg kg^–1. Additionally, we applied Raman spectroscopy to prove the presence of TiO₂ in sugar-coated doughnuts. This study begins to fill in the analytical gaps that exist regarding the rapid detection and quantification of TiO₂ in food, which facilitate the risk assessment of TiO₂ through food exposure.</p

A Triple Functional Approach To Simultaneously Determine the Type, Concentration, and Size of Titanium Dioxide Particles

The large-scale manufacturing and use of titanium dioxide (TiO₂) particles in food and consumer products significantly increase the likelihood of human exposure and release into the environment. We present a simple and innovative approach to rapidly identify the type (anatase or rutile), as well as to estimate, the size and concentration of TiO₂ particles using Raman spectroscopy and surface-enhanced Raman spectroscopy (SERS). The identification and discrimination of rutile and anatase were based on their intrinsic Raman signatures. The concentration of the TiO₂ particles was determined based on Raman peak intensity. Particle sizes were estimated based on the ratio between the Raman intensity of TiO₂ and the SERS intensity of myricetin bound to the nanoparticles (NPs), which was proven to be independent of TiO₂ nanoparticle concentrations. The ratio that was calculated from the 100 nm particles was used as a cutoff value when estimating the presence of nanosized particles within a mixture. We also demonstrated the practical use of this approach when determining the type, concentration, and size of E171: a mixture that contains TiO₂ particles of various sizes which are commonly used in many food products as food additives. The presence of TiO₂ anatase NPs in E171 was confirmed using the developed approach and was validated by transmission electron micrographs. TiO₂ presence in pond water was also demonstrated to be an analytical capability of this method. Our approach shows great promise for the rapid screening of nanosized rutile and anatase TiO₂ particles in complex matrixes. This approach will strongly improve the measurement of TiO₂ quality during production, as well as the survey capacity and risk assessment of TiO₂ NPs in food, consumer goods, and environmental samples

Pressure Regulations on the Surface Properties of CeO₂ Nanorods and Their Catalytic Activity for CO Oxidation and Nitrile Hydrolysis Reactions

Surface properties of nanoscale CeO₂ catalysts in terms of the surface Ce³⁺ fraction and concentration of oxygen vacancy can affect their catalytic performance significantly. Continual adjustment on surface properties of CeO₂ with the morphological preservation has not been realized by synthetic methods. The revisited studies show that surface properties of CeO₂ nanorods can be effectively regulated by synthetic pressures while the rodlike morphology is well-preserved. Such phenomena are ascribed to the contact possibility between Ce³⁺ species and dissolved O₂, which is balanced by the rapidly increased and gradually saturated dissolution/recrystallization rate of Ce­(OH)₃ and linearly increased concentration of dissolved O₂ with the increase of total air pressure or partial pressure of O₂. Surface-property-dependent catalytic activity of CeO₂ nanorods synthesized under various pressures was also demonstrated in two benchmark reactionscatalytic oxidation of CO and hydrolysis of nitrile. Such a finding of the pressure regulation on the reducible metal oxides provides an effective approach to rationally design novel catalysts for specific reactions, where ceria are supports, promoters, or actives

Construction of Natural Polysaccharide-Based pH-Responsive Gold Nanorods for Combined Photothermal Therapy and Immunotherapy

Photothermal therapy and immunotherapy are emerging strategies for treating tumors. The combination of these two therapies can effectively leverage their advantages, thereby enhancing the therapeutic efficacy. Based on this premise, the natural polysaccharide was prepared from the edible Rosa roxburghii fruit and applied to coat gold nanorods (GNRs). The antitumor nanorods, designated as RRP-MPBA-GNRs, were developed to combine photothermal therapy and immunotherapy. This system employed 4-mercaptophenylboronic acid (MPBA) as the connecting unit. The hydroxy groups of RRP formed dynamic borate ester bonds with MPBA, and this conjugated bonds exhibited pH-responsive properties. The RRP-MPBA was immobilized on the surface of GNRs through sulfur–gold bonds, enhancing the stability and preserving the photothermal effects of GNRs. In vivo experiments have demonstrated that RRP-MPBA-GNRs reduced the number of cancer cells at the transplant site and inhibited metastasis. Further investigation revealed that the photothermal effects of RRP-MPBA-GNRs can increase reactive oxygen species (ROS) levels in cancer cells and induce apoptosis. RRP released from RRP-MPBA-GNRs can induce an antitumor immune response by promoting the maturation of dendritic cells and up-regulating the expression of surface marker molecules. The results suggested that RRP-MPBA-GNRs can effectively integrate photothermal therapy and immunotherapy for tumor treatment

Alteration of the Nonsystemic Behavior of the Pesticide Ferbam on Tea Leaves by Engineered Gold Nanoparticles

A model system consisting of a nonsystemic pesticide (ferbam), engineered gold nanoparticles (AuNPs) and a plant tissue (tea leaves) was investigated using surface enhanced Raman spectroscopy (SERS). Ferbam has no ability by itself to penetrate into tea leaves. When AuNPs were placed with ferbam onto the surface of tea leaves, however, the SERS signal of the ferbam-AuNPs complex was observed inside of the tea leaves. Within 1 h, the ferbam-AuNPs complex rapidly penetrated into the leaf to a depth of approximately 190 μm, about ¹/₃ to ¹/₂ of the leaf’s thickness. The rate of penetration was dependent on the size of AuNPs, with 30 nm AuNPs-ferbam penetrating more rapidly when compared with complexes made with the 50 and 69 nm AuNPs. These results clearly demonstrated an alteration of the nonsystemic behavior of ferbam in the combined presence with AuNPs. This finding might lead to the development of some new pesticide formulations. Conversely, new toxicity issues may arise as the behaviors and fate of pesticides are altered significantly upon interaction with engineered NPs in the pesticide formulation or environment

Ratiometric Indicator Based on Vibration-Induced Emission for in Situ and Real-Time Monitoring of Gelation Processes

Monitoring specific processes such as gelation in a ratiometric and visual manner is of scientific value and has practical implications but remains challenging. Herein, an innovative fluorescent low-molecular-weight gelator (DPAC-CHOL) capable of revealing and self-revealing the gelation processes in situ and in real time via the ratiometric fluorescence change from orange-red to blue has been developed. By virtue of its vibration-induced emission attribute, the gelation point, critical gelation concentration, and the internal stiffness of the gel networks of DPAC-CHOL and other gelation systems could be facilely evaluated in a ratiometric and naked-eye-observable fashion. Noteworthily, the DPAC-CHOL-doped gelation system Ph-CHOL can quantitatively identify the environmental temperature in a daily-concerned range (i.e., 20–55 °C). This work not only provides a versatile advanced material but also opens up a new avenue for the investigation of gelation systems

Ratiometric Indicator Based on Vibration-Induced Emission for in Situ and Real-Time Monitoring of Gelation Processes

Monitoring specific processes such as gelation in a ratiometric and visual manner is of scientific value and has practical implications but remains challenging. Herein, an innovative fluorescent low-molecular-weight gelator (DPAC-CHOL) capable of revealing and self-revealing the gelation processes in situ and in real time via the ratiometric fluorescence change from orange-red to blue has been developed. By virtue of its vibration-induced emission attribute, the gelation point, critical gelation concentration, and the internal stiffness of the gel networks of DPAC-CHOL and other gelation systems could be facilely evaluated in a ratiometric and naked-eye-observable fashion. Noteworthily, the DPAC-CHOL-doped gelation system Ph-CHOL can quantitatively identify the environmental temperature in a daily-concerned range (i.e., 20–55 °C). This work not only provides a versatile advanced material but also opens up a new avenue for the investigation of gelation systems

Ratiometric Indicator Based on Vibration-Induced Emission for in Situ and Real-Time Monitoring of Gelation Processes

Monitoring specific processes such as gelation in a ratiometric and visual manner is of scientific value and has practical implications but remains challenging. Herein, an innovative fluorescent low-molecular-weight gelator (DPAC-CHOL) capable of revealing and self-revealing the gelation processes in situ and in real time via the ratiometric fluorescence change from orange-red to blue has been developed. By virtue of its vibration-induced emission attribute, the gelation point, critical gelation concentration, and the internal stiffness of the gel networks of DPAC-CHOL and other gelation systems could be facilely evaluated in a ratiometric and naked-eye-observable fashion. Noteworthily, the DPAC-CHOL-doped gelation system Ph-CHOL can quantitatively identify the environmental temperature in a daily-concerned range (i.e., 20–55 °C). This work not only provides a versatile advanced material but also opens up a new avenue for the investigation of gelation systems