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Phenotyping of bacteria with vibrational spectroscopy has caught much attention in bacteria-related research. It is known that many factors could affect this process. Among them, solution pH maintenance is crucial, yet its impact on the bacterial SERS spectra is surprisingly neglected. In this work, we focused on two situations related to pH maintenance: the effect of the same buffer on the SERS spectra of bacteria under different pH values, and the influence of different buffers on the SERS spectra of bacteria under the same pH value. Specifically, Britton-Robison (BR) buffer was used to evaluate the effect of pH value on bacteria SERS spectra thanks to its wide pH range. Four different buffers, namely BR buffer, acetate buffer, phosphate buffer, and carbonate buffer, were used to illustrate the impact of buffer types on SERS spectra of bacteria. The results showed that the intensity and number of characteristic peaks of the SERS spectra of Gram-negative (G -) bacteria changed more significantly than Gram-positive (G +) bacteria with the change of pH value. Furthermore, compared with phosphate buffer and carbonate buffer, BR buffer could bring more characteristic SERS bands with better reproducibility, but slightly inferior to acetate buffer. In conclusion, the influence of the pH and types of the buffer on the SERS spectra of bacteria are worthy of further discussion.

Surface-enhanced Raman scattering (SERS) is a powerful tool for constructing biomolecular fingerprints, which play a vital role in differentiation of bacteria. Due to the rather subtle differences in the SERS spectra among different bacteria, artificial intelligence is usually adopted and enormous amounts of spectral data are required to improve the differentiation efficiency. However, in many cases, large volume data acquisition on bacteria is not only technical difficult but labour intensive. It is known that surface modification of SERS nanomaterials can bring additional dimensionality (difference) of the SERS fingerprints. Here in this work, we show that the concept could be used to improve the bacteria differentiation efficiency. Ag NPs were modified with 11-mercaptoundecanoic acid, 11-mercapto-1-undecanol, and 1-dodecanethiol to provide additional dimensionality. The modified NPs then were mixed with cell lysate from different strains of Bacillus cereus (B. cereus). Even by applying a simple PCA process to the resulting SERS spectra data, all the three modified Ag NPs showed superior differentiation results compared with bare Ag NPs, which could only separate Staphylococcus aureus (S. aureus) and B. cereus. It is believed that the multidimensional SERS could find great potential in bacteria differentiation.

Surface-enhanced Raman spectroscopy (SERS) stands out in the field of microbial analysis due to its rich molecular information, fast analysis speed, and high sensitivity. However, achieving strain-level differentiation is still challenging because numerous bacterial species inevitably have very similar SERS profiles. Here, a method inspired by the black-box theory was proposed to boost the spectral differences, where the undifferentiated bacteria was considered as a type of black-box, external environmental stress was used as the input, and the SERS spectra of bacteria exposed to the same stress was output. For proof of the concept, three types of environmental stress were explored, i.e., ethanol, ultraviolet light (UV), and ultrasound.

This study synthesized UiO-66 (Zr) in situ on wood via a one-step solvothermal method. UiO-66/wood was successfully prepared and its catalytic performance for the ofloxacin (OFX) photodegradation under simulate sunlight was also explored. UiO-66/wood exhibited a better catalytic performance, and its degradation rate constant was about 1.2 and 1.5 times than that of UiO-66 and wood, respectively. The effects of solution initial concentration, pH of the system and dosage of the photocatalyst were explored. Additionally, the active species trapping experiments and UV–vis diffused reflectance spectra measurements were conducted to investigated the photocatalytic mechanism of the UiO-66/wood composite, superoxide radical (O2•–) and hydroxyl radical (•OH) were the main reactive species. In addition, the possible degradation pathways of OFX were analyzed by LC-MS. Meanwhile, the UiO-66/wood showed outstanding stability and reusability after 4 cycles experiments. The removal performance of UiO-66/wood towards real samples showed it has potential in actual application .

CTAC modified N-doped carbon dots (N-CDs–CTAC) were designed through a post-modification strategy as a highly selective fluorescent sensor for Cr(vi) detection based on the dynamic quenching mechanism.

Organophosphorus flame retardant (OPFRs) is a new type of environmental pollutant, and the rapid and sensitive detection of OPFRs is a very important job. A new experimental phenomenon was found that TCEP, a kind of organophosphorus flame retardant, can effectively enhance the signal of the luminol-H2 O2 chemiluminescence (CL) system. Combined with the controllability of flow injection analysis, a rapid, stable, and sensitive CL method was established. The CL intensity responded linearly to the concentration of TCEP in the range 0.5 μg/L to 100 μg/L (R2 = 0.999) with a low detection limit of 33 ng/L. The relative standard deviation (R.S.D.) was 2.2 % (n= 7, c= 100 μg/L). The water samples were labeled and recycled with RSDs of 1.1 % - 5.7 % and recoveries of 88.7 % - 116.1 %. Based on this, this study established a new CL detection method for environmental pollutant TCEP.

The adverse reactions caused by 6-thioguanine (6-TG) in anti-cancer treatment are closely related to the dose, leading to the urgent need for clinical monitoring of its concentration. In this work, a highly reproducible free-standing liquid membrane (FLM) surface-enhanced Raman spectroscopy (SERS) substrate was developed to detect 6-TG in human urine and serum quantitatively. Briefly, a prepared sample was adjusted to pH 2 and mixed with concentrated core–shell bimetallic nanoparticle (AgcoreAushell NP) suspension. The Au/Ag ratio of the AgcoreAushell NPs was optimized. Then the mixture was formed into an FLM using a custom mold. The relative standard deviation (RSD) of the experimental results can be stabilized below 10% (n ≥ 10). The R2 of the calibration curve in the range of 10 ~ 100 μg kg−1 was 0.988. In addition, the limit of detection (LOD) (3σ/k) of 6-TG was 5 μg kg−1. The FLM SERS platform has been successfully applied to the rapid and reliable analysis of 6-TG spiked in body fluids.

Trace explosive detection has become one of the hottest topics in scientific communities because homeland security is one of the top priorities for countries all around the world. In this work, Ag NPs prepared with different reducing reagents were modified with various halogen ions for the SERS detection of nitroaromatic explosives (2,4-DNT and 2,4,6-TNT). It was proposed that halogen ions probably replaced the surface adsorbates on Ag NPs

Surface-enhanced Raman scattering (SERS) has been widely used in various fields due to high sensitivity, but it is hindered by its low repeatability. Here, we explored a highly reproducible free-standing liquid-state platform (FSM) for monitoring norfloxacin (NOR) in the environmental field. After optimizing the types of nanoparticles (NPs) and pH value in NOR solution, the relative standard deviation (RSD) of FSM SERS analysis can be stabilized below 10% (n ≥ 8), and the R2 of the calibration curve in the range of 20 µg/L–100 µg/L was 0.995. In addition, the results showed that the limit of detection (LOD) (3σ/k) of NOR was 1.3 µg/L. Moreover, the NOR in the spiked samples was successfully quantified by FSM, and the recovery rate exceeded 95%. The proposed method has the potential for rapid analysis of drug residues in environmental samples.

Tetracycline (TC) represents a broad-spectrum antibiotic to treat bacterial infections. In this study, a ratiometric fluorescence (FL) probe was developed for the detection of TC in water samples by using waste printing paper extract as a FL indicator. In this ratiometric probe, the emission of printing paper extract at 436 nm gradually decreased and the emission of mixed solution at 538 nm significantly increased with the sequential addition of TC upon being excited at 390 nm, coupled with a remarkable FL color change from bright blue to faint yellow. Thus, a ratiometric F538 /F436 FL probe was created for TC detection by simply mixing the printing paper extraction and TC. Under the optimized conditions, the linear range from 1-100 μM and a detection limit of 0.48 μM (S/N = 3) for TC were obtained. Importantly, the FL probe can be easily prepared with rapid response, high sensitivity, and good selectivity. The application of the waste printing paper extract for the detection of TC in environmental water samples was demonstrated.

Tetracycline (TC) is widely detected in the environment because of its abuse and persistence. There is an urgent need to efficiently treat TC due to its potential threat to the ecosystem and human health. In this study, microscale Fe/Cu bimetallic particles' (mFe/Cu) catalysis enhanced by H2O2 was proposed to remove TC in an aqueous solution. Based on the pre-experiment, the effect of theoretical Cu mass loading (TMLCu) and some key operating parameters on the TC removal efficiency were investigated thoroughly. The degradation rates of TC by mFe/Cu with different TMLCu followed the pseudo-first-order kinetics model, and the optimal TMLCu (0.34 g Cu/g Fe) was obtained. The optimal operating parameters of mFe/Cu dosage, concentration of H2O2, initial concentration of TC, stirring speed and operating temperature were 5 g/L, 50 mM, 50 ppm, 400 r/min, and 55°C, respectively. Compared with the control system, the system of mFe/Cu catalysis enhanced by H2O2 (mFe/Cu-H2O2) presented excellent performance due to its synergistic effect. Also, the fresh and reacted mFe/Cu was characterized by scanning electron microscope, which showed the surface of mFe/Cu was rougher after reaction, indicating mFe/Cu participated in the degradation reaction. Besides, with the presence of inorganic anions, the degradation of TC in mFe/Cu-H2O2 system did not change much. And mFe/Cu presented good stability and recyclability after 10 repeated tests. Therefore, mFe/Cu-H2O2 system had a great potential for cost-effective removal of antibiotics in wastewater.

As a result of the rise in network technology, information security has become particularly important. Digital images play an important role in network transmission. To improve their security and efficiency, a new color image encryption algorithm is proposed. The proposed algorithm adopts a classical scrambling–diffusion framework. In the scrambling stage, the dynamic block Zigzag transformation is designed by combining the chaotic sequence with the standard Zigzag transformation, which can dynamically select the transformation range and the number of times. It is used to scramble the pixel positions in the R, G, and B components. In the diffusion stage, the six-sided star model is established by combining the chaotic sequence and the six-sided star structure characteristics, which can store the 24 bits of the pixel in a defined order to realize bit-level diffusion operation. Experimental analyses indicate that our algorithm has the characteristics of high key sensitivity, large key space, high efficiency, and resistance to plaintext attacks, statistical attacks, etc.

Rapid ultrasensitive detection of trace polycyclic aromatic hydrocarbons (PAHs) is essential and significant for pollution control due to their hazard, persistence, and the wide distribution in the environment. Therefore, rapid detection of PAHs is critical for controlling pollution and protecting the ecology. Considering the advantages of surface-enhanced Raman spectroscopy (SERS), a simple and reliable SERS method was proposed in this work for detecting PAHs in water. Three chemicals, namely NaCl, KBr, and KI, were chosen to modify Ag nanoparticles (NPs) for phenanthrene (Phe) detection, and Ag NPs modified with KBr (Ag-Br NPs) showed the best SERS response. The mixing sequence and the concentration of KBr were optimized. The addition order of mixing KBr and Ag NPs before Phe solution was the best sequence, and the optimal concentration of KBr was 20 mM. Under optimal conditions, the limits of quantification for Phe, pyrene (Pyr), and anthracene (Ant) were 10

Here, the advanced one-dimensional convolutional neural network (1D-CNN) approach was applied to accurately identify the surface-enhanced Raman scattering (SERS) spectral signature of industrial wastewaters for source tracing. The silver nanoparticles (Ag NPs) were prepared as the label-free SERS substrate, and 66,000 SERS spectra were acquired from wastewaters of 22 facilities across 10 industrial categories at three excitation wavelengths after data augmentation. The superiority of SERS spectra in capturing the wastewaters’ characteristics can be intuitively reflected by the principal component analysis (PCA). Moreover, the 1D-CNN model consisting of three convolutional units was built to achieve effective feature extract of SERS spectra. The pre-trained 1D-CNN can distinguish the effluents with a 100% recognition accuracy rate at each excitation wavelength. In comparison, random forest (RF) and support vector machine (SVM), more common classification techniques, achieve averaged accuracies of 54.08% and 72.39%, respectively. As a proof-of-concept, the multi-mixed wastewater samples were used to simulate the practical pollution scenarios, and the identification accuracy rate of the wastewater tracing model can reach 97.33% at 638 nm. The results suggest that the SERS combined with the 1D-CNN model can achieve rapid classification and accurate identification of industrial wastewaters even in complex environments, exhibiting a significant application potential in pollution source tracing.

Three-dimensional (3D) titanium dioxide – graphene aerogels (TA-TiO2-GA) with network architectures and in-situ growth of TiO2 NPs onto its surface were facilely self-assembled via one-step hydrothermal treatment by employing tannic acid (TA). TA as the reducing agent and linker promoted a strong coupling between the graphene and TiO2. The TA-TiO2-GA exhibited good photocatalytic performance and reusability in the degradation of typical organic contaminants: upon 3 h simulated solar irradiation, the removal rate of tetracycline, methylene blue and rhodamine B reached 43.2%, 77.8%, and 91.9%, respectively; nearly no deactivation of the TA-TiO2-GA was observed after reuse of over10 cycles. Mechanistic studies indicated that the synergy of adsorption and photocatalysis played an important role, and superoxide radical anions and hydroxyl radicals are the major reactive oxidative species. To conclude, this study provides a novel alternative to fabricate 3D TA-TiO2-GA which has great potential in solar light-driven environmental applications.

A novel method was developed for the sensitive and visual detection of p-phenylenediamine (PPD) via immobilizing the target specie PPD on dialdehyde cellulose membrane (DCM) followed by the reaction with salicylaldehyde. The obtained solid fluorescent membrane (S-PPD-DCM) emitted yellow fluorescence under 365 nm UV light. DCM was not only used as a solid matrix but also played a vital role in the enrichment of PPD. Experimental variables influencing the fluorescence signal were investigated and optimized. Under the optimum conditions, a detection limit of 5.35 μg L−1 was obtained and two linear ranges were observed at 10–100 and 100–1000 μg L−1, respectively. Moreover, the fluorescence of the resultant membrane can still be visualized by naked eye when PPD concentration was 50 μg L−1. The detection of PPD was hardly affected by the coexistence of 1 mg L−1 of o-phenylenediamine, m-phenylenediamine or p henylamine , exhibiting good selectivity. The developed method involved in a two-step Schiff base reaction and enhanced the fluorescence emission via blocking nonradiative intramolecular rotation decay of the excited molecules. It was applied to determine the PPD in spiked hair dye with satisfactory results.

Poor reproducibility has long been one of the major limitations for quantitative surface-enhanced Raman scattering (SERS) analysis. Historically, plasmonic nanoparticles (NPs) have been assembled o...

2,4,6-trinitrotoluene (TNT) sensing on surfaces and in solution is an important issue in sensor fabrication for homeland security and environmental protection. Herein, Play-Doh, a modeling material popular for kids, was proposed as a versatile sensor for on-site fluorescent (FL), visual FL (VFL), and colorimetric detection of TNT both on surfaces and in solution after being doped with -NH2 through a one-step approach. Play-Doh exhibits FL emission due to the main ingredient of flour. After -NH2 doping, amino-Play-Doh (APD) was utilized to construct a FL sensor based on FL resonance energy transfer and inner filter effect for TNT detection. The advantage of APD was that no additional fluorophore was needed compared with the traditional sensors for FL and VFL analysis. The orange complex visible to the naked eye was also recorded for smartphone-based colorimetric detection of TNT. In both cases, the APD demonstrated good analytical performance for TNT. Finally, APD was successfully utilized for TNT sensing on fingerprints, luggage, and in environmental water samples, respectively. Play-Doh might be a potential sensor for future on-site detection of TNT owing to the merits of being cost-effective and versatile.

On-site identification and quantification of chemicals is critical for promoting food safety, human health, homeland security risk assessment, and disease diagnosis. Surface-enhanced Raman spectroscopy (SERS) has been widely considered as a promising method for on-site analysis due to the advantages of nondestructive, abundant molecular information, and outstanding sensitivity. However, SERS for on-site application has been restricted not only by the cost, performance, and portability of portable Raman instruments, but also by the sampling ability and signal enhancing performance of the SERS substrates. In recent years, the performance of SERS for on-site analysis has been improved through portable Raman instruments, SERS substrates, and other combined technologies. In this review, popular commercial portable Raman spectrometers and the related technologies for on-site analysis are compared. In addition, different types of SERS substrates for on-site application are summarized. SERS combined with other technologies, such as electrochemical and microfluidics are also presented. The future perspective of SERS for on-site analysis is also discussed.

Organophosphorus flame retardants (OPFRs) are new types of environmental pollutants, therefore the rapid and sensitive detection of OPFRs is a very important objective. A new experimental phenomenon was found in which tris(2-chloroethyl)phosphine (TCEP), a type of OPFR, could effectively enhance the signal of the luminol-H

In this study, a novel alkali-modified biochar prepared from ginkgo leaves was produced by simply one-step pyrolysis and was investigated as an adsorbent for the removal of Pb, Cd, and Cu from aqueous solutions. After modified by alkali, ginkgo leaves biochar exhibited abundant surface functional groups and large porosity, resulting in high adsorption capacities for Pb (589.32 mg·g−1), Cd (563.55 mg·g−1), and Cu (81.7 mg·g−1). Simulation results showed that pseudo-second-order model and Langmuir model were better fitted to analyze the heavy metals adsorption process by alkali-BC, indicating that multilayer adsorption was the main reason for heavy metals removal. Besides, effect of pH and coexisting cations on adsorption of Pb, Cd, and Cu by alkali-BC was studied. Moreover, competitive adsorption of the three heavy metal ions by alkali-BC in binary system was also explored. Finally, the removal mechanism of Pb, Cd, and Cu in aqueous solution was analyzed and summarized. Due to the good performance in a wider pH range and high absorption capacity, alkali-BC would be an efficient adsorbent for heavy metals in real environmental samples.

In this work, we report a simple and rapid surface-enhanced Raman scattering (SERS) method for the screening of pesticide residues on fruit peels using a portable Raman spectrometer. Adhesive tapes were used as the sampling media; the effectiveness of different tape brands was examined. Collection efficiencies were found to be 60.2 ± 7.6%, 54.3 ± 5.0%, and 52.3 ± 9.0% on glass, aluminum foil, and fruit peels, respectively. SERS was achieved by applying silver nanoparticles (Ag NPs) to the surface of the tape after analyte collection. Preparation of the Ag NPs was optimized for pesticide detection. The limit of detection of triazophos on apple peels was 25 ng/cm2 with the portable Raman spectrometer. Considering the least favorable conditions, the calculated detection limit was 0.0225 mg/kg, which is an order of magnitude less than the maximum residue limit (MRL, 0.2 mg/kg) in China. The method is sufficiently sensitive for use in field analysis.