Yi-Tao Long

Recent developments and applications of screen-printed electrodes in environmental assays--a review.

Screen-printed electrodes (SPEs), which are used as economical electrochemical substrates, have gone through significant improvements over the past few decades with respect to both their format and their printing materials. Because of their advantageous material properties, such as disposability, simplicity, and rapid responses, SPEs have been successfully utilised for the rapid in situ analysis of environmental pollutants. This critical review describes the basic fabrication principles, the configuration designs of SPEs and the hybrid analytical techniques based on SPEs. We mainly overview the electrochemical applications of SPEs in environmental analysis over the past 3 years, including the determination of organic compounds, heavy metals and gas pollutants.

Quantized plasmon quenching dips nanospectroscopy via plasmon resonance energy transfer

We observed quantized plasmon quenching dips in resonant Rayleigh scattering spectra by plasmon resonance energy transfer (PRET) from a single nanoplasmonic particle to adsorbed biomolecules. This label-free biomolecular absorption nanospectroscopic method has ultrahigh molecular sensitivity.

New starburst sensitizer with carbazole antennas for efficient and stable dye-sensitized solar cells

A new starburst organic sensitizer (I) with carbazole units as antennas and the corresponding dyes (II and III) with starburst triphenylamine or one triphenylamine moiety (for the purpose of comparison) were designed and synthesized, in which carbazole or triphenylamine moieties were used as the electron donor, thiophene units as the π-conjugated bridge, and a cyanoacrylic acid group as the electron acceptor. The photophysical and electrochemical properties of the dyes were investigated by UV-vis spectrometry and cyclic voltammetry. Electrochemical measurement data indicate that the tuning of the HOMO and LUMO energy levels can be conveniently accomplished by alternating the donor moiety. Photovoltaic devices with carbazole dye I showed a maximum monochromatic incident photon to current efficiency (IPCE) of 89% and an overall conversion efficiency of 4.4% under full sunlight (AM 1.5G, 100 mW cm−2) irradiation. The dyes were also tested in quasi-solid-state devices and showed good efficiencies. The stability of devices was performed over 1200 h in full sunlight and at 50 °C. The sensitizer I with carbazole antennas exhibited good stability, retaining 95% of its initial efficiency, while dyes II and III retained 82% and 46% after 1200 h of irradiation, respectively. This result means that carbazole is a photostable hole-transporting moiety for use in dye-sensitized solar cells.

Design of a gold nanoprobe for rapid and portable mercury detection with the naked eye.

A gold nanoprobe that can respond colorimetrically to Hg(2+) is designed and coupled with a power-free PDMS device; the system can be used for rapid and visual detection of low micromolar Hg(2+) in real environmental samples.

Bithiazole-bridged dyes for dye-sensitized solar cells with high open circuit voltage performance

Five new metal-free organic dyes (T1–T5) containing bithiazole moieties were synthesized and used for dye-sensitized solar cells (DSSCs). Their absorption spectra, electrochemical and photovoltaic properties were fully characterized. Electrochemical measurement data indicate that the tuning of the HOMO and LUMO energy levels can be conveniently accomplished by alternating the donor moiety. All of these dyes performed as sensitizers for the DSSC test, and the photovoltaic performance data of these bithiazole-bridged dyes showed higher open circuit voltages (745–810 mV). Among the five dyes, T1 showed the best photovoltaic performance: a maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 83.8%, a short-circuit photocurrent density (Jsc) of 11.78 mA cm−2, an open-circuit photovoltage (Voc) of 810 mV, and a fill factor (ff) of 0.60, corresponding to an overall conversion efficiency of 5.73% under standard global AM 1.5 solar light condition, which reached 93% with respect to that of an N719-based device fabricated under similar conditions. The result shows that the metal-free dyes based on bithiazole π-conjugation are promising candidates for improvement of the performance of DSSCs.

Nanopore-Based Sequencing and Detection of Nucleic Acids

Nanopore-based techniques, which mimic the functions of natural ion channels, have attracted increasing attention as unique methods for single-molecule detection. The technology allows the real-time, selective, high-throughput analysis of nucleic acids through both biological and solid-state nanopores. In this Minireview, the background and latest progress in nanopore-based sequencing and detection of nucleic acids are summarized, and light is shed on a novel platform for nanopore-based detection.

Recent progress in surface enhanced Raman spectroscopy for the detection of environmental pollutants

AbstractSurface enhanced Raman spectroscopy (SERS) has emerged as one of the most promising analytical tools in recent years. Due to advantageous features such as sensitivity, specificity, ease of operation and rapidity, SERS is particularly well suited for environmental analysis. We summarize here some considerations with respect to the detection of pollutants by SERS and provide an overview on recent achievements in the determination of organic pollutants, heavy metal ions, and pathogens. Following an introduction into the topic and considering aspects of sensitivity, selectivity, reproducibility and portability, we are summarizing applications of SERS in the detection of pollutants, with sections on organic pollutants (pesticides, PAHs and PCBs, explosives), on heavy metal ions, and on pathogens. In addition, we discuss current challenges and give an outlook on applications of SERS in environmental analysis. Contains 174 references. FigureThe application of surface enhanced Raman spectroscopy (SERS) for the detection of environmental pollutants.

Ultrasensitive determination of cysteine based on the photocurrent of nafion-functionalized CdS-MV quantum dots on an ITO electrode.

As a fundamental building block for functional and structural components of many proteins and enzymes, cysteine, a sulfur-containing nonessential amino acid, plays a critical role in many biological processes. [ 1 ] This critical residue helps to fold and maintain a stable structure of protein, contributes towards enzymatic reactions and detoxifi cation processes, and participates in numerous posttranslational modifi cations. [ 2 ]

Single Gold Nanoparticles as Real‐Time Optical Probes for the Detection of NADH‐Dependent Intracellular Metabolic Enzymatic Pathways

Plasmonics, is an emerging subfield of nanophontonics, and it attracts increasing attention because of its potential applications in controlling and manipulating light at nanoscale dimensions. The advent of dark-field microscopy (DFM) has enabled the study of plasmonic nanoparticles, especially the coinage metals and the effects of their size, shape, composition as well as the local environment, which further facilitate its use in biological-labeling and detection. DFM provides a direct means to probe chemical reactions, real-time optical sensing with high sensitivity, and the in vivo imaging of cancer cells. Recently, redox reactions were directly monitored on single gold nanocrystals using DFM. Actually, every individual nanoparticle (NP) in the assembly could potentially act as an independent probe. Single-nanoparticle sensing platforms offer advantages since they are readily implemented in multiplex detection. Single nanoparticle probes offer improved absolute detection limits and also enable higher spatial resolution. Single nanoparticles have promising applications for measurements in vitro and in vivo events that are non-reachable by fixed solid array. However, the use of plasmonic nanoparticles for the detection of biomolecules or biological processes is still scarce. Nicotinamide adenine dinucleotide/reduced nicotinamide adenine dinucleotide (NAD/NADH) plays an important role as cofactor in numerous biocatalyzed processes, including energy metabolism, mitochondrial responses, immunological functions, aging and cell death. The catalytic deposition of copper on gold nanoparticles (AuNPs) by the NADH cofactor has been applied for the optical and electrochemical detection of NADH and NAD-dependent biocatalytic processes. Herein, we describe a novel method to detect enzymatic activity at the single particle level inside and outside cells by DFM. To our knowledge, it is the first time to monitor the intracellular metabolism and the effect of anticancer drugs on the cell metabolism using copper growth on the AuNP probes. To investigate the application of single Au@Cu nanoparticles for nano-sensing, the plasmon resonance Rayleigh scattering (PRRS) spectra lmax of a single particle was used to probe the gold-catalyzed reduction of Cu ions on AuNPs by NADH or by NAD-cofactor-dependent enzyme/substrate system that generates NADH (Scheme 1). Compared with the scattering spectra in the absence of NADH, the scattering spectra acquired with NADH exhibit a distinct peak shift

Facile On-Site Detection of Substituted Aromatic Pollutants in Water Using Thin Layer Chromatography Combined with Surface-Enhanced Raman Spectroscopy

A novel facile method for on-site detection of substituted aromatic pollutants in water using thin layer chromatography (TLC) combined with surface-enhanced Raman spectroscopy (SERS) was explored. Various substituted aromatics in polluted water were separated by a convenient TLC protocol and then detected using a portable Raman spectrometer with the prepared silver colloids serving as SERS-active substrates. The effects of operating conditions on detection efficacy were evaluated, and the application of TLC-SERS to on-site detection of artificial and real-life samples of aromatics/polluted water was systematically investigated. It was shown that commercially available Si 60-F(254) TLC plates were suitable for separation and displayed low SERS background and good separation efficiency, 2 mM silver colloids, 20 mM NaCl (working as aggregating agent), 40 mW laser power, and 50 s intergration time were appropriate for the detection regime. Furthermore, qualitative and quantitative detection of most of substituted aromatic pollutants was found to be readily accomplished using the developed TLC-SERS technique, which compared well with GC-MS in terms of identification ability and detection accuracy, and a limit of detection (LOD) less than 0.2 ppm (even at ppb level for some analytes) could be achieved under optimal conditions. The results reveal that the presented convenient method could be used for the effective separation and detection of the substituted aromatic pollutants of water on site, thus reducing possible influences of sample transportation and contamination while shortening the overall analysis time for emergency and routine monitoring of the substituted aromatics/polluted water.