Integrated Nanophotonic Waveguide-Based Devices for IR and Raman Gas Spectroscopy

On-chip devices for absorption spectroscopy and Raman spectroscopy have been developing rapidly in the last few years, triggered by the growing availability of compact and affordable tunable lasers, detectors, and on-chip spectrometers. Material processing that is compatible with mass production has been proven to be capable of long low-loss waveguides of sophisticated designs, which are indispensable for high-light-analyte interactions. Sensitivity and selectivity have been further improved by the development of sorbent cladding. In this review, we discuss the latest advances and challenges in the field of waveguide-enhanced Raman spectroscopy (WERS) and waveguide infrared absorption spectroscopy (WIRAS). The development of integrated light sources and detectors toward miniaturization will be presented, together with the recent advances on waveguides and cladding to improve sensitivity. The latest reports on gas-sensing applications and main configurations for WERS and WIRAS will be described, and the most relevant figures of merit and limitations of different sensor realizations summarized.

Catalyst displacement assay: a supramolecular approach for the design of smart latent catalysts for pollutant monitoring and removal

Latent catalysts can be tuned to function smartly by assigning a sensing threshold using the displacement approach for targeted analytes. Three cyano-bridged bimetallic complexes were synthesized as "smart" latent catalysts through the supramolecular assembly of different metallic donors [FeII(CN)6]4-, [FeII(tBubpy)(CN)4]2-, and FeII(tBubpy)2(CN)2 with a metallic acceptor [CuII(dien)]2+. The investigation of both their thermodynamic and kinetic properties on binding with toxic pollutants provided insight into their smart off-on catalytic capabilities, enabling us to establish a threshold-controlled catalytic system for the degradation of pollutants such as cyanide and oxalate. With these smart latent catalysts, a new catalyst displacement assay (CDA) was demonstrated and applied in a real wastewater treatment process to degrade cyanide pollutants in both domestic (level I, untreated) and industrial wastewater samples collected in Hong Kong, China. The smart system was adjusted to be able to initiate the catalytic oxidation of cyanide at a threshold concentration of 20 μM (the World Health Organization's suggested maximum allowable level for cyanide in wastewater) to the less harmful cyanate under ambient conditions.

Molecularly Imprinted Sol-Gel-Based QCM Sensor Arrays for the Detection and Recognition of Volatile Aldehydes

The detection and recognition of metabolically derived aldehydes, which have been identified as important products of oxidative stress and biomarkers of cancers; are considered as an effective approach for early cancer detection as well as health status monitoring. Quartz crystal microbalance (QCM) sensor arrays based on molecularly imprinted sol-gel (MISG) materials were developed in this work for highly sensitive detection and highly selective recognition of typical aldehyde vapors including hexanal (HAL); nonanal (NAL) and bezaldehyde (BAL). The MISGs were prepared by a sol-gel procedure using two matrix precursors: tetraethyl orthosilicate (TEOS) and tetrabutoxytitanium (TBOT). Aminopropyltriethoxysilane (APT); diethylaminopropyltrimethoxysilane (EAP) and trimethoxy-phenylsilane (TMP) were added as functional monomers to adjust the imprinting effect of the matrix. Hexanoic acid (HA); nonanoic acid (NA) and benzoic acid (BA) were used as psuedotemplates in view of their analogous structure to the target molecules as well as the strong hydrogen-bonding interaction with the matrix. Totally 13 types of MISGs with different components were prepared and coated on QCM electrodes by spin coating. Their sensing characters towards the three aldehyde vapors with different concentrations were investigated qualitatively. The results demonstrated that the response of individual sensors to each target strongly depended on the matrix precursors; functional monomers and template molecules. An optimization of the 13 MISG materials was carried out based on statistical analysis such as principle component analysis (PCA); multivariate analysis of covariance (MANCOVA) and hierarchical cluster analysis (HCA). The optimized sensor array consisting of five channels showed a high discrimination ability on the aldehyde vapors; which was confirmed by quantitative comparison with a randomly selected array. It was suggested that both the molecularly imprinting (MIP) effect and the matrix effect contributed to the sensitivity and selectivity of the optimized sensor array. The developed MISGs were expected to be promising materials for the detection and recognition of volatile aldehydes contained in exhaled breath or human body odor.

Synthesis, spectral, thermal, crystal structure, Hirschfeld analysis of [bis(triamine)Cadimium(II)][Cadimum(IV)tetra-bromide] complexes and their thermolysis to CdO nanoparticles

Background

The coordination chemistry of cadmium(II) with diamine ligands is of particular interest. The most common structure around cadmium(II) center in their complexes is tetrahedral, that is due the octet rule obeyed. Nevertheless, five and six-coordinated complexes are also well known. Now a day, many cadmium(II) complexes with chelate ligands were synthesized for their structural or applications properties. Antibacterial activities and DNA binding affinity of this class of cadmium complexes have attracted considerable interest.

Results

Cadmium(II) complexes in dicationic form with general formula [Cd(dien)₂]CdBr₄ complex 1 (dien = diethylenetriamine) and [Cd(dipn)₂]CdBr₄ complex 2 (dipn = diproylenetriamine) were prepared and elucidated there chemical structures by elemental analysis, UV–Vis, IR, TG and NMR, additionally complex 1 structure was solved by X-ray diffraction study. The Cd(II) cation is located in a slightly distorted octahedral geometry while Cd(IV) anion is in tetrahedral geometry. High stability of the synthesized complexes confirmed by TG. Thermolysis of complex 1 revealed the formation of pure cubic nanoparticles CdO which was deduced by spectral analysis. The average size of CdO nanoparticles was found to be ~60 nm.

Conclusions

Two new Cd(II) complexes of general formula [Cd(N₃)₂]CdBr₄ were made available. The structure of [Cd(dien)₂]CdBr₄ was confirmed by X-ray diffraction. Thermal, electro and spectral analysis were also investigated in this study. The direct thermolysis of such complexes formed a cubic CdO regular spherical nanoparticle with the ~60 nm average particle size.Graphical abstract

Gated Silica Mesoporous Materials in Sensing Applications

Silica mesoporous supports (SMSs) have a large specific surface area and volume and are particularly exciting vehicles for delivery applications. Such container-like structures can be loaded with numerous different chemical substances, such as drugs and reporters. Gated systems also contain addressable functions at openings of voids, and cargo delivery can be controlled on-command using chemical, biochemical or physical stimuli. Many of these gated SMSs have been applied for drug delivery. However, fewer examples of their use in sensing protocols have been reported. The approach of applying SMSs in sensing uses another concept-that of loading pores with a reporter and designing a capping mechanism that is selectively opened in the presence of a target analyte, which results in the delivery of the reporter. According to this concept, we provide herein a complete compilation of published examples of probes based on the use of capped SMSs for sensing. Examples for the detection of anions, cations, small molecules and biomolecules are provided. The diverse range of gated silica mesoporous materials presented here highlights their usefulness in recognition protocols.

An electrochemical impedimetric sensor based on biomimetic electrospun nanofibers for formaldehyde

Herein, simple molecular recognition sites for formaldehyde were designed on electrospun polymer nanofibers.

Detection of copper(ii) and aluminium(iii) by a new bis-benzimidazole Schiff base in aqueous media via distinct routes

Synthesis and characterization of a bis-benzimidazole appended Schiff base ligand, 2-(3,5-bis(1H-benzimidazole-2-yl)-phenyliminomethyl)phenol (H3L) displaying excellent selectivity towards Cu²⁺and Al³⁺in mixed aqueous media.

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011

Herein, we present a survey of the literature covering the development of molecular imprinting science and technology over the years 2004-2011. In total, 3779 references to the original papers, reviews, edited volumes and monographs from this period are included, along with recently identified uncited materials from prior to 2004, which were omitted in the first instalment of this series covering the years 1930-2003. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by sections describing fundamental aspects of molecular imprinting including the development of novel polymer formats. Thereafter, literature describing efforts to apply these polymeric materials to a range of application areas is presented. Current trends and areas of rapid development are discussed.

Towards chemical communication between gated nanoparticles

The design of comparatively simple and modularly configurable artificial systems able to communicate through the exchange of chemical messengers is, to the best of our knowledge, an unexplored field. As a proof-of-concept, we present here a family of nanoparticles that have been designed to communicate with one another in a hierarchical manner. The concept involves the use of capped mesoporous silica supports in which the messenger delivered by a first type of gated nanoparticle is used to open a second type of nanoparticle, which delivers another messenger that opens a third group of gated nanoobjects. We believe that the conceptual idea that nanodevices can be designed to communicate with one another may result in novel applications and will boost further advances towards cooperative systems with complex behavior as a result of the communication between simple abiotic individual components.

Chemodosimetric analysis in food-safety monitoring: design, synthesis, and application of a bimetallic Re(i)–Pt(ii) complex for detection of dimethyl sulfide in foods

Detection of neutral biogenic sulfides plays a crucial role in food safety. A new heterobimetallic Re(i)–Pt(ii) donor–acceptor chemodosimeter—[Re(biq)(CO)₃(CN)]–[Pt(DMSO)(Cl)₂] (1, biq = 2,2′-biquinoline)—was synthesized and characterized.

X-ray lithography and small-angle X-ray scattering: a combination of techniques merging biology and materials science

The advent of micro/nanotechnology has blurred the border between biology and materials science. Miniaturization of chemical and biological assays, performed by use of micro/nanofluidics, requires both careful selection of the methods of fabrication and the development of materials designed for specific applications. This, in turn, increases the need for interdisciplinary combination of suitable microfabrication and characterisation techniques. In this review, the advantages of combining X-ray lithography, as fabrication technique, with small-angle X-ray scattering measurements will be discussed. X-ray lithography enables the limitations of small-angle X-ray scattering, specifically time resolution and sample environment, to be overcome. Small-angle X-ray scattering, on the other hand, enables investigation and, consequently, adjustment of the nanostructural morphology of microstructures and materials fabricated by X-ray lithography. Moreover, the effect of X-ray irradiation on novel materials can be determined by use of small-angle X-ray scattering. The combination of top-down and bottom-up methods to develop new functional materials and structures with potential in biology will be reported.