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A new type of photosensitizer, made from Rose Bengal (RB)-decorated silica (SiO2–NH2–RB) nanoparticles, was developed to inactivate gram-positive bacteria, including Methicillin-resistant Staphylococcus aureus (MRSA), with high efficiency through photodynamic action. The nanoparticles were characterized microscopically and spectroscopically to confirm their structures. The characterization of singlet oxygen generated by RB, both free and immobilized on a nanoparticle surface, was performed in the presence of anthracene-9,10-dipropionic acid. The capability of SiO2–NH2–RB nanoparticles to inactivate bacteria was tested in vitro on both gram-positive and gram-negative bacteria. The results showed that RB-decorated silica nanoparticles can inactivate MRSA and Staphylococcus epidermidis (both gram-positive) very effectively (up to eight-orders-of-magnitude reduction). Photosensitizers of such design should have good potential as antibacterial agents through a photodynamic mechanism.

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We show the experimental observation of SERS inside metal nanoshells for the first time. Giant enhancement, solely due to the electromagnetic enhancement in the near field and on the order of 10(11) to 10(14), can be consistently and reproducibly achieved. The results provide new insights to the SERS effect and pave the way for a new design of nanostructures to be used as SERS-tags for Raman-based assays and imaging.

Water and soil repellency is one of the most desirable properties for textile fabrics. A surface with a water contact angle higher than 150° is considered to be a practically nonwettable superhydrophobic surface. In this research, we studied the formation of highly hydrophobic surfaces on cotton and polyester fabrics using silica sol formed by hydrolysis and subsequent condensation of tetraethoxysilane under alkaline conditions followed by hydrophobization using hydrolyzed hexadecyltrimethoxysilane (HDTMS). The textile fabrics thus treated showed excellent water repellency with a water contact angle as high as 155° on cotton and 143° on polyester. The high hydrophobicity of the treated fabrics is due to the presence of hydrophobic HDTMS as well as the increase in roughness by silica sol on the surfaces of the treated fabrics. The morphology of the cotton and polyester fabrics were characterized by scanning electron microscopy. We also found that the treated cotton and polyester are resistant to hydrolysis of multiple washing cycles.

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