There is an increase in bombing assaults in recent years in our country. Determining the explosive material used in these cases by the quick and correct analysis of the evidence obtained after the explosions, is an important starting point for the investigations which are done to reach the perpetrators. The forensic chemistry investigations have to be correct, exact and rapid in order to reach the right criminal. In this study, the Gas Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography-Thermal Energy Analyser (GC-TEA) methods which are being used for the determination of the explosive materials&rsquo / residues used in bombing attacks are optimized with the standard solutions of 2,4,6-Trinitrotoluene (TNT) and 1,3,5-trinitro-1,3,5-triazocyclohexane (RDX) and standard mixture solution. The two methods were compared by analysing the postexplosion soil samples. Also an efficient and applicable sample preparation procedure was developed. The results showed that both methods are efficient and sensitive for the postexplosion investigations. It is seen that GC-TEA has lower detection limit and simple chromatograms due to its selectivity against only nitro group containing explosives. However it is concluded that there is a need for a reliable and sensitive method like GC-MS which provides identification and library search, for the determination of the organic components which can not be identified with GC-TEA

No / A novel dispersive system operating at 1064-nm excitation and coupled with transfer electron InGaAs photocathode and electron bombardment CCD technology has been evaluated for the analysis of drugs of abuse and explosives. By employing near-IR excitation at 1064-nm excitation wavelength has resulted in a significant damping of the fluorescence emission compared to 785-nm wavelength excitation. Spectra of street samples of drugs of abuse and plastic explosives, which usually fluoresce with 785-nm excitation, are readily obtained in situ within seconds through plastic packaging and glass containers using highly innovative detector architecture based upon a transfer electron (TE) photocathode and electron bombarded gain (EB) technology that allowed the detection of NIR radiation at 1064nm without fluorescence interference. This dispersive near-IR Raman system has the potential to be an integral part in the armoury of the forensic analyst as a non-destructive tool for the in-situ analysis of drugs of abuse and explosives. Copyright (c) 2015 John Wiley & Sons, Ltd.

In the last few years, considerable efforts have been given to develop sensitive and effective sensors for explosive materials and to generate systems which exhibit high luminescence in both solution and solid-state. The increasing number of terrorist activities around the world have prompted scientists to design effective ways to detect and disarm even the trace amount of explosives. The nitroaromatics (NACs) are the common constituents of most of the explosives due to high explosive velocity and ease of availability. The NACs were extensively used as the main constituents in landmines until World War II. Apart from their explosive behavior, the NACs are well-known environmental pollutants. The industrial waste and the leakages from unexploded landmines are the major contributors towards the soil and ground water contamination. Presently for effective detection of trace amount of explosives, skilled canines and metal based detectors are commonly used. The canines are trained for a specific type of explosives which limit their ability to detect different types of substrates. The chemical sensors that work on the principle of colorimetric and/or fluorimetric detection techniques have emerged as suitable alternative due to cheap production cost, portability and sensitivity. Different types of materials including conjugated polymers, metal-organic frameworks (MOFs), and quantum-dots have been reported as efficient chemosensors for NACs. However, poor solubility in the common organic solvents, low solid-state fluorescence, very high molecular weight and lack of signal amplification have restricted the application of these material for in-field testing. Renewed interests have been invested in small molecule based systems; and metal-organic discrete molecular architectures due to precise control over their photophysical properties and the supramolecular interaction among neighboring molecules that facilitates energy migration among the molecular backbone. On the other hand, recently post-synthetic modification of different molecular systems including MOFs and polymers has emerged as a potential technique to incorporate desired functional groups into the system and to tune their properties with the retention of basic structures. Reports on the post-synthetic modification of discrete metal-organic architectures are rare due to the delicate nature of the metal-organic bonds that ruptures on mild environmental changes. Therefore, post-synthetic functionalization of discrete molecular systems using mild reaction conditions will open up a myriad of possibilities to generate new systems with desired characteristics. Chapter 1 of the thesis will briefly discuss the history of different explosive materials including different detection methodologies that are widely used. It will also include a brief discussion on different small molecular systems with high solid-state luminescence. In Chapter 2, design and synthesis of triphenylamine-based two Platinum(Pt)(II) molecules functionalized with carboxylic acid and ester groups including their organic analogues have been discussed. The triphenylamine core was chosen due its unique non-planarity and luminescence. On the other hand, Pt(II) center was incorporated to increase intermolecular spacing in solid-state that can induce high luminescence. Scheme 1. Schematic representation of fluorescence quenching using small molecules. All the four molecules were found to be highly sensitive towards NACs including picric acid and dinitrophenol. Although the molecules exhibited similar sensitivity in solution, the carboxylic acid analogues demonstrated superior sensitivity in solid-state. Careful observation of the crystal structures of the systems revealed the acid analogues were oriented in a 2-D grid-like pattern that facilitated energy migration among neighboring molecules (Scheme 1.). Chapter 3 describes design, synthesis, and NACs sensing behavior of anthracene-based four purely organic small molecules. The molecules exhibited high selectivity towards picric acid only. All the molecules were found to be highly emissive in both solution and solid-state due to the vinylanthracene backbone (Scheme 2.). Scheme 2. Schematic representation of fluorescence quenching and solid-state sensing behavior. Chapter 4 discusses the strategy to develop mechano-fluorochromic and AIE active triphenylamine-based Pt(II) complex and its organic analogue. The twisted triphenylamine backbone restricted molecular close packing in solid-state; and weak C-H-- interactions were utilized to hinder the motion of the phenyl rings. As a result, the molecules were highly emissive in solid-state. Grinding disrupted the intermolecular interactions and thus mechano-fluorochromic behavior was observed. Due to twisted backbone, the molecules were also found to be AIE active. Both the systems containing terminal aldehyde groups were finally utilized for selective detection of biomolecule cysteine (Scheme 3.). Scheme 3. Mechano-fluorochromic and AIE behavior of the triphenylamine based Pt(II) complex. In Chapter 5 vinylanthracene-based linear donor was used in combination with carbazole-based 90° and triphenylamine-based 120° Pt(II) acceptors to generate (4+4) and (6+6) molecular squares and hexagons, respectively. The vinylanthracene backbone imparts high solution and solid-state luminescence to the system as well as made them AIE active. The molecules were further investigated for the solution and solid-state sensing for NACs and found to be effective for trinitrotoluene (TNT) and dinitrotoluene (DNT) (Scheme 4.). Scheme 4. Schematic representation of AIE active molecular square and its NACs sensing. Chapter 6 describes the formation of Pd3 self-assembled molecular trinuclear barrels containing triphenylamine imidazole donors and Pd(II) acceptors. Using Knoevenagel condensation the aldehyde group present in the barrel was post-synthetically functionalized with Meldrum’s acid. From spectroscopic characterization, it was proved that the structural integrity remained intact after the post-modification treatment (Scheme 6.). Surprisingly, pre-synthetic modification of the donor alone with Meldrum’s acid followed by self-assembly treatment with the Pd(II) ion did not yield trigonal barrel 6.8. Scheme 6. Post-synthetic functionalization of trinuclear barrels using Knoevenagel condensation.(For colour pictures pl see the abstract pdf file)