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Graphene quantum dots (GQDs) are attractive materials for use as highly selective and sensitive chemical sensors, owing to their simple preparation and affordability. GQDs have been successfully deployed as sensors for toxic metal ions, which is a significant issue due to the ever-increasing environmental contamination from agricultural and industrial activities. Despite the success of GQDs in this area, the mechanisms which underpin GQD-metal ion specificity are rarely explored. This lack of information can result in difficulties when attempting to replicate published procedures and can limit the judicious design of new highly selective GQD sensors. Furthermore, there is a dearth of GQD examples which selectively detect biologically relevant alkali and alkaline earth metals. This review will present the current state of GQDs as metal ion sensors for harmful contaminants, highlighting and discussing the discrepancies that exist in the proposed mechanisms regarding metal ion selectivity. The emerging field of GQD sensors for biorelevant metal ion species will also be reviewed, with a perspective to the future of this highly versatile material. Refereed/Peer-reviewed

Powdered activated carbon (PAC) is an economical sorbent for removing micropollutants from water, but it generates hazardous dust that is flammable and a respiration hazard. Additionally, the fine particles of PAC can cake and block filters and membranes, complicating its use in continuous processes. In this study, we present a sulfur polymer support for PAC that overcomes these problems. The blend of the sulfur polymer and PAC generates low dust and it does not block filters. The utility of the sorbent is demonstrated in the remediation of water contaminated with perflurooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS)—persistent micropollutants that currently threaten water safety worldwide. Fundamental discoveries of PFOA self-assembly are also reported, as well as testing on a field sample of contaminated surface water. Refereed/Peer-reviewed

Lipid droplets (LDs) are found in most eukaryotic cells and in addition to serving as lipid reservoirs, these highly dynamic organelles play fundamental roles in cell metabolism and growth. The study of LDs and their interactions with other cellular compartments provides new insights into normal cell biology and disease processes such as virus packaging, metabolic disorders, and cancer progression. Here we report the synthesis and comprehensive evaluation of two readily prepared, low molecular weight 3,4-dimethoxy-1,8-naphthalimides, as selective LD stains. The newly synthesised 1,8-naphthalimide derivative (DMN-LD), demonstrated impressive versatility compared to currently available options, by staining LDs in both live and fixed cells, as well as a three-dimensional spheroid, using both single and two-photon excitation. This new imaging agent has the potential to further unravel the complex biology of LDs, which are essential to cell survival, and when altered, underpin many disease states. Refereed/Peer-reviewed

Functionalized nanoparticles have played a major role in the field of targeted therapy, owing to their ability to control the release and for the selective delivery of entrapped materials to tumours. In this work, we described the loading capacity and in vitro release kinetics of mesoporous silica nanoparticles (MSNs), functionalized with Poly-L-Histidine and Tamoxifen. The model drug Doxorubicin (DOX) was successfully encapsulated into MSN-based systems, using the technique of solvent immersion. A post-surface grafting loading method was investigated on functionalized systems, with DOX loading content determined using HPLC. Dialysis bag diffusion was employed to investigate the release kinetics of DOX-loaded-systems at pH 7.4 and 5. The amount of DOX released from native MSNs systems over a 72 h period at pH 5 was approximately 40%, and at pH 7.4 ≈ 30%. A moderate pH dependent release behaviour was observed with both our functionalized systems: DOX@MSN-PLH and DOX@MSN-PLH-TAM, with approximately 5% of DOX released from DOX@MSN-PLH-TAM at pH 7.4 and about 9% released at pH 7.4 over 72 h. The maximal cumulated release of DOX molecules from DOX@MSN-PLH after 72 h was ≈ 18% at pH 7.4 and ≈ 23% at pH 5, respectively. The outcome of this work offers a promising contribution towards building future stimuli-responsive nano-drug delivery systems.

The Buchwald–Hartwig cross-coupling reaction between 4-methylumbelliferone-derived nonaflates with amides, carbamates, and sulfonamides is described. A wide variety of N-substituted 7-amino coumarin analogues was prepared in good to excellent yields. The photophysical properties of aqueous-soluble derivatives were determined, and they displayed auxochrome-based variations. Gram-scale synthesis provided an acrylamide analogue, which was used to fabricate a fluorescent poly(2-hydroxylethyl methacrylate) (pHEMA) hydrogel that was resistant to leaching in ultrapure H2O. We envisage that our reported protocol to access 7-amino-4-methylcoumarin derivatives will find use toward the development of new fluorescent coumarin-based probes by researchers in the field. usc Refereed/Peer-reviewed

A porous silicon rugate filter (pSiRF) insulin biosensor has been constructed and systematically optimised by investigating the effects of specific experimental parameters. The pSiRF biosensor is based on an optical sensing platform using interferometric reflectance spectroscopy (IRS) to monitor insulin binding to a surface-anchored insulin binding aptamer (IBA) within the pores. The aim of this study was to determine the optimal fabrication to elicit the maximum sensor response, lowest limit of detection (LOD) and fastest response time. Thermal hydrosilylation with undecylenic acid was used as a base surface modification, with IBA attached through formation of an amide bond. The following pSiRF fabrication conditions were investigated; porous film thickness and IBA concentration in the conjugation solution. The effect of solution flow speed over the pSiRF during insulin biosensing was also investigated in an effort to improve the performance. The optimised pSiRF biosensor was successfully applied for the detection of insulin secreted from human islets on stimulation with glucose.Finally, as a proof of concept, insulin sensing in the presence of human islets on the pSiRF surface was performedto demonstrate the robust performance of the biosensor and the potential for in-situ insulin biosensing. Refereed/Peer-reviewed

The widespread uptake and use of emissive metal ion complexes for investigating cellular structure, composition and function, is evidence of the effectiveness and vast potential for this type of imaging probe. Metal ion complexes provide significant advantages over their organic fluorophore counterparts, including long emission lifetime, resistance to photobleaching and the capacity to readily modify their peripheral chemistry to target specific organelles, signalling pathways and individual molecules. This review will discuss recent progress in the development and use of metal ion complexes, specifically for studying metabolic diseases at the cellular level. Advanced metal ion complexes for organelle imaging and the detection of biorelevant species, to elaborate complexes for understanding cellular mechanisms and recent therapeutic applications will be reviewed. To align with the special issue, Coordination Chemistry Reviews: Coordination Chemistry in Australia, the work of Australian researchers actively engaged in this field is featured prominently, along with key developments from the global research community. Refereed/Peer-reviewed

A robust and accurate chemical sensor for dissolved iron has been developed, based on highly fluorescent graphene quantum dots (GQDs). This work describes the construction of a GQD embedded hydrogel that displays strong fluorescence emission from the bulk structure. The hydrogel is made from poly(2-hydroxyethyl methacrylate) (pHEMA) and crosslinked by ethylene glycol dimethacrylate to form a water permeable, flexible and transparent material. Polymerisation in the presence of the GQDs physically entraps the fluorescent nanoparticles within the hydrogel. The fluorescence properties of the GQD-pHEMA hydrogels have been thoroughly characterised, including by confocal microscopy in the first reported use of this technique for a GQD composite material. Sensing of dissolved Fe(III) by the GQD-pHEMA hydrogels has been demonstrated, whereby the Fe(III) quenches the GQDs fluorescence emission. The GQD-pHEMA hydrogels were selective to Fe(III) and showed a linear response for concentrations in the range of 10-200 μM. Refereed/Peer-reviewed

Due to the favorable properties of graphene quantum dots (GQDs), there has been a rapid development of sensors, devices, and composite materials, which incorporate this 0D nanomaterial. GQDs provide a means to instill superior optical, electronic, mechanical, and adsorptive properties to various platforms and have found use as biosensors, photovoltaic devices, polymer composites,and drug delivery vehicles. One of the key factors to successfully integrating GQD technology is the intelligent choice of synthetic chemical pathways to fabricate, modify, and instill functionality in the developed platform. GQDs are decorated with a variety of functional groups that are amenable to traditional synthetic chemistry transformations; however, the technology for post-synthetic modifications is only in its infancy. Herein, a comprehensive analysis of the chemistry available for modifying GQDs is provided; starting from methods for GQD fabrication and synthetic chemical pathways for producing functional GQDs, to the advantages, disadvantages, and challenges of specific chemistries,and finally techniques for the appropriate characterization of these functional materials. This review is meant for researchers considering entering the GQD field, as well as those more experienced, providing a practical guide on how to prepare, modify, and characterize GQDs for a broad range of applications. Refereed/Peer-reviewed

Porous silicon microparticles (pSi MPs) functionalized with fluorescent dyes (lissamine and carboxy-5-fluorescein) and intrinsically luminescent pSi MPs were explored as novel fingerprint dusting powders. The versatility of luminescent pSi MPs is demonstrated through time-gated imaging of their long-lived (lifetime>28μs) near-IR emission, and mass spectrometry analysis of fingerprints dusted with luminescent pSi MPs to provide further information on exogenous small molecules present in latent fingerprints. Refereed/Peer-reviewed

A label-free porous silicon (pSi) based, optical biosensor, using both an antibody and aptamer bioreceptor motif has been developed for the detection of insulin. Two parallel biosensors were designed and optimised independently, based on each bioreceptor. Both bioreceptors were covalently attached to a thermally hydrosilylated pSi surface though amide coupling, with unreacted surface area rendered stable and low fouling by incorporation of PEG moieties. The insulin detection ability of each biosensor was determined using interferometric reflectance spectroscopy, using a range of different media both with and without serum. Sensing performance was compared in terms of response value, response time and limit of detection (LOD) for each platform. In order to demonstrate the capability of the best performing biosensor to detect insulin from real samples, an in vitro investigation with the aptamer-modified surface was performed. This biosensor was exposed to buffer conditioned by glucose-stimulated human islets, with the result showing a positive response and a high degree of selectivity towards insulin capture. The obtained results correlated well with the ELISA used in the clinic for assaying glucose-stimulated insulin release from donor islets. We anticipate that this type of sensor can be applied as a rapid point-of-use biosensor to assess the quality of donor islets in terms of their insulin production efficiency, prior to transplantation. Refereed/Peer-reviewed

Interfacing mammalian cells with single-walled carbon nanotubes (SWCNTs) has been considered a potential route for various bioengineering applications. Here, the interaction between human neuroblastoma cell line, SK-N-SH, with catalyst-free SWCNT-decorated porous silicon (pSi) substrates is investigated. SWCNT-decorated surfaces were fabricated by chemically attaching carboxy-functional SWCNTs to pSi functionalized via an amino silane. SWCNT attachment was confirmed by atomic force microscopy and Raman spectroscopy. Patterning of the amino silane on pSi by photolithography permitted the creation of patterned SWCNT-decorated pSi substrates. The number of cells attaching to the SWCNT decorated surface was observed to correlate with SWCNT density, implying that vertically aligned SWCNTs allowed the capture of cells. By incorporating a low fouling PEG silanization surface modification into the procedure, cell patterning was achieved on the fabricated SWCNT patterns. These SWCNT-decorated pSi substrates could potentially find application in lab-on-chip devices, particularly as platforms for the electrical stimulation of neuronal cells. Refereed/Peer-reviewed

Porous silicon (pSi) surfaces have been chemically patterned via a UV initiated hydrosilylation reaction of an alkene through a photomask, introducing chemical functionality in the exposed surface areas. A secondary, UV initiated hydrosilylation reaction with a second alkene of different functionality is performed to backfill the silicon hydride terminated regions on the surface, thereby affording patterned porous films with dual, surface chemistry. UV initiated hydrosilylations were performed using the alkene undecylenic acid N-hydroxysuccinimide (NHS) ester, and the pSi surfaces were stabilized by a second hydrosilylation reaction with a polyethylene glycol (PEG) appended alkene. NHS ester and PEG functionalized surfaces were used for the selective immobilization of the cell adhesion mediator protein fibronectin (FN), in the NHS-functional regions. Matrix-assisted laser desorption/ionization mass spectrometry imaging on the protein functionalized pSi surface confirmed the patterned conjugation of the FN to the NHS functionalized regions. Mammalian cells cultured on these surfaces showed attachment that was confined to the patterned areas of FN on the pSi surface.

This paper describes a novel transducer principle converting biomolecular binding events into changes in porous silicon structural colour. An enzyme-catalysed reaction, horseradish peroxidase (HRP) mediated oxidation of 3,3 ,5,5 -tetramethylbenzidine (TMB), induced an amplified optical detection signal on an antibody-functionalised porous silicon film, which manifested as significant changes in the Fabry–Pérot fringe pattern. Exposing porous silicon to non-oxidised TMB and oxidised TMB products and measuring the resulting effective optical thickness (EOT) changes of the porous silicon layer, an amplified signal from porous silicon was found, caused by an intermediate radical cation produced during the enzymaticcatalysed oxidation of TMB. Finally, it was shown that this system could be used to detect a human immunoglobulin (IgG) at 0.2 g/ml. This work may lead to the development of new biosensors where porous silicon acts as the sensing matrix and transducer element. Refereed/Peer-reviewed

We report on the synthesis of two carboxy-functional alkene compounds as modifiers of porous silicon (pSi) surface chemistry by means of thermal hydrosilylation. Both alkene compounds have hydrophobic, aliphatic carbon segments, with terminal carboxylic acid functionality appended through a thioether linkage. In one of the alkene linkers, we incorporated a short oligoethylene glycol (OEG) moiety to explore its low-fouling properties when attached to porous silicon. We examined surface stability of the surface-modified porous silicon in aqueous milieu. Albumin and fibronectin were adsorbed and, using carbodiimide chemistry, covalently immobilised to linker-modified porous silicon, and the propensity for mammalian cells to attach to these surfaces investigated. Surface chemistry was characterised by infrared spectroscopy and the stability of porous silicon in an aqueous milieu was investigated by interferometric reflectance spectroscopy (IRS). Surfaces functionalised with the alkene linker containing OEG displayed greater resistance to the adsorption of albumin. This linker also facilitated higher levels of covalent protein immobilisation to the functionalised pSi surface. Higher levels of cell attachment were observed on pSi surfaces with fibronectin covalently immobilised onto the OEG linker, than for fibronectin covalently immobilised on the non-OEG linker. Refereed/Peer-reviewed

Advanced biosensors in future medicine hinge on the evolvement of biomaterials. Porous silicon (pSi), a generally biodegradable and biocompatible material that can be fabricated to include environment-responsive optical characteristics, is an excellent candidate for in vivo biosensors. However, the feasibility of using this material as a subcutaneously implanted optical biosensor has never been demonstrated. Here, we investigated the stability and biocompatibility of a thermally-hydrocarbonised (THC) pSi optical rugate filter, and demonstrated its optical functionality in vitro and in vivo. We first compared pSi films with different surface chemistries and observed that the material was cytotoxic despite the outstanding stability of the THC pSi films. We then showed that the cytotoxicity correlates with reactive oxygen species levels, which could be mitigated by pre-incubation of THC pSi (PITHC pSi). PITHC pSi facilitates normal cellular phenotypes and is biocompatible in vivo. Importantly, the material also possesses optical properties capable of responding to microenvironmental changes that are readable non-invasively in cell culture and subcutaneous settings. Collectively, we demonstrate, for the first time, that PITHC pSi rugate filters are both biocompatible and optically functional for lab-on-a-chip and subcutaneous biosensing scenarios. We believe that this study will deepen our understanding of cell-pSi interactions and foster the development of implantable biosensors. Refereed/Peer-reviewed

Here, we report a novel surface modification for porous silicon (pSi). Hydroxyl-terminated pSi surfaces are modified with a hydrosilane via Si–H activation using the Lewis acid catalyst tris(pentafluorophenyl) borane. This surface reaction is fast and efficient at room temperature, and leads to a surface stabilised against hydrolytic attack in aqueous media. The resulting surface shows promise as a substrate for surface-assisted laser desorption/ionisation mass spectrometry Refereed/Peer-reviewed

To ensure the availability of clean water for humans into the future, efficient and cost-effective water purification technology will be required. The rapidly decreasing quality of water and the growing global demand for this scarce resource has driven the pursuit of high-performance purification materials, particularly for application as point-of-use devices. This review will introduce the main types of natural and artificial contaminants that are present in water and the challenges associated with their effective removal. The efficiency and performance of recently developed materials for water purification, with a focus on activated carbon, carbon nanotubes and graphene will be discussed. The recent advances in water purification using these materials is reviewed andtheir applicability as point-of-use water purification systems discussed. Refereed/Peer-reviewed

In the quest for solutions to meeting future energy demands, solar fuels play an important role. A particularly promising example is photocatalysis since even incremental improvements in performance in this process are bound to translate into significant cost benefits. Here, we report that semiconducting and high surface area 3D silicon replicas prepared from abundantly available diatom fossils sustain photocurrents and enable solar energy conversion. Refereed/Peer-reviewed

The ability to monitor glucose levels in chronic wound fluid of diabetic patients is a promising theranostic approach in chronic wound healing. Phenylboronic acid polymers are glucose- and pH-responsive materials. In the presence of glucose, these polymers reversibly form cyclic boronate esters, changing the properties of the polymer and forming the basis of glucose sensing. In this report, poly(4-vinylphenylboronic acid) (PVPBA) was covalently grafted to the pores of porous silicon (pSi) films (pSi-PVPBA). Polymer switching in response to changing pH and glucose concentration was monitored by means of interferometric reflectance spectroscopy (IRS). We observed that a shift of the boronic acid equilibrium between the neutral and anionic form in the polymer translated into refractive index changes that could be detected as a variation of the effective optical thickness (EOT) of the pSi-PVPBA film. The pSi/polymer composite was further investigated as a platform for the detection of glucose. Using this sensing platform, we were able to detect glucose in a buffer solution as low as 0.15 mM and also in a wound fluid sample without encountering interferences. Refereed/Peer-reviewed

The fabrication of chemically patterned porous silicon (pSi) photonic crystals towards their use as an internally referenced organic vapour sensor is reported. The sensor fabrication technique involves photoresist patterning and surface silanisation of pSi photonic crystals to produce patterns of hydrophobic and hydrophilic regions. The photonic response to the presence of organic vapour is monitored at the interface of these regions. Refereed/Peer-reviewed

Porous silicon (pSi) surfaces were chemically micropatterned through a combination of photolithography and surface silanization reactions. This patterning technique produces discretely defined regions on a pSi surface functionalized with a specific chemical functionality, and the surrounding surface displays a completely different functionality. The generated chemical patterns were characterized by a combination of IR microscopy and the conjugation of two different fluorescent organic dyes. Finally, the chemically patterned pSi surface was used to direct the attachment of neuronal cells to the surface. This patterning strategy will be useful for the development of high-throughput platforms for investigating cell behavior. Refereed/Peer-reviewed

We describe the fabrication of arrays of porous silicon spots by means of photolithography where a positive photoresist serves as a mask during the anodization process. In particular, photoluminescent arrays and porous silicon spots suitable for further chemical modification and the attachment of human cells were created. The produced arrays of porous silicon were chemically modified by means of a thermal hydrosilylation reaction that facilitated immobilization of the fluorescent dye lissamine, and alternatively, the cell adhesion peptide arginine-glycine-aspartic acid-serine. The latter modification enabled the selective attachment of human lens epithelial cells on the peptide functionalized regions of the patterns. This type of surface patterning, using etched porous silicon arrays functionalized with biological recognition elements, presents a new format of interfacing porous silicon withmammalian cells. Porous silicon arrays with photoluminescent properties produced by this patterning strategy also have potential applications as platforms for in situ monitoring of cell behavior. Refereed/Peer-reviewed

The control of protein binding into nanostructured porous surfaces is highly relevant to the development of advanced biosensors and other biodevices. Here, an investigation of the covalent immobilisation of a model protein (albumin) onto porous silicon (pSi) films was conducted using a new alkene linker, the synthesis of which was developed. This alkene linker contained both hydrophobic and hydrophilic (oligoethylene glycol) sections and terminated in a protected thiol. The alkene was attached to freshly etched porous silicon via thermal hydrosilylation, where further surface reactions resulted in the attachment of a maleimido N-hydroxysuccinimidyl (NHS) heterobifunctional crosslinker. Albumin was then covalently immobilised on the porous silicon layer through reaction of the protein's amine groups and the NHS functional group of the crosslinker. Surface modification reactions were monitored by infrared spectroscopy and interferometric reflectance spectroscopy. Protein binding was monitored by infrared spectroscopy, fluorescence imaging and atomic force microscopy.